tag:theconversation.com,2011:/us/topics/lactose-26825/articlesLactose – The Conversation2023-06-22T13:38:35Ztag:theconversation.com,2011:article/2073832023-06-22T13:38:35Z2023-06-22T13:38:35ZFull-fat or low-fat cheese and milk? A dietitian on which is better<figure><img src="https://images.theconversation.com/files/532750/original/file-20230619-1823-uf7sp3.jpg?ixlib=rb-1.1.0&rect=16%2C114%2C5447%2C3522&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Are low-fat dairy products really better for us?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/young-woman-slice-cheese-her-hand-2056001120">Bernardo Emanuelle/Shutterstock</a></span></figcaption></figure><hr>
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<p>When it comes to dairy products do you tend to buy full-fat or low-fat products? For many people, going for low-fat options can seem like the “healthier” choice. </p>
<p>Indeed, a <a href="https://foodinsight.org/consumer-survey-purchasing-behaviors-eating-decisions-and-health-perceptions-of-dietary-fats-and-oils/">2020 survey</a> in the US found that out of 1,000 people questioned, one in three sought out “low fat” or “reduced fat” foods or drinks, with dairy being the most common food category for low–fat options. But is low-fat milk, cheese, yoghurt and butter really any better for us?</p>
<p>Many governments and public health bodies recommend dairy as a <a href="https://journals.lww.com/nutritiontodayonline/fulltext/2008/11000/Role_of_Dairy_Foods_in_the_Dietary_Guidelines.3.aspx?casa_token=y8APLahFjikAAAAA:fDX-SfWQ2mxKll7omZN0CYiSEwE04-DmCt43jks8deC_VCsPXRoRWiKDTyR_xK43yM9T2aVeW7f_djSoG0xkvu-MH1w">key part</a> of a healthy diet (although it’s perfectly possible to be healthy without it, as many people around the world are). And many people opt for low-fat options as part of this. </p>
<p>Low-fat milk is made by removing or skimming the cream off the milk. So you can get whole or full-fat milk (3.5% fat), semi-skimmed or half-fat milk (1.8% fat) or fully skimmed milk (0.1%-0.3% fat). </p>
<p>The same process can be used to make lower-fat cheeses and yoghurts. However, removing fat can affect how cheese dries and how flavours develop during maturing.</p>
<p>Most relevant dietary guidelines encourage the consumption of low-fat dairy foods, except for in very young children. But a recent <a href="https://academic.oup.com/advances/article/11/4/928/5760740?login=false">review</a> of the available research found that children who consumed full-fat dairy foods were healthier and leaner than those who consumed reduced-fat versions. </p>
<p>It could be that families who tend to have a history of living with health issues relating to diet or higher body weight may be more likely to eat low-fat products. An alternative view is that full-fat dairy products might be more filling and help with the regulation of appetite, meaning people eat less overall. </p>
<p>Either way, these observations in children have also been seen in <a href="https://academic.oup.com/advances/article/10/5/917S/5569504?login=false">adults</a>. </p>
<h2>Explaining the science</h2>
<p>It’s not just that low-fat dairy foods may not be better for our health. There is increasing evidence that some of the fatty acids found in dairy fats might actually reduce our risk of developing <a href="https://link.springer.com/article/10.1007/s11883-018-0724-z">heart disease</a> and <a href="https://www.sciencedirect.com/science/article/pii/S0261561421002934">type 2 diabetes</a>. </p>
<p>Indeed, it seems that higher intakes of <a href="https://link.springer.com/article/10.1007/s00394-017-1556-2">fermented dairy products</a> like unsweetened full-fat yoghurt and some cheeses might be associated with lower risks of heart disease and type 2 diabetes.</p>
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<img alt="Low-fat milk pile in supermarket" src="https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/532753/original/file-20230619-23-ztdomo.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Could low-fat be worse for you than whole milk?</span>
<span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/los-angeles-california-united-states-09012020-1814166020"> The Image Party/Shutterstock</a></span>
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<p>When it comes to the recommendation to eat reduced-fat dairy foods, the Australian guidelines seem to be based on a <a href="https://www.health.gov.au/sites/default/files/australian-dietary-guidelines.pdf">mathematical decision</a> around how calories add up to meet the recommended calorie intake for an average adult. </p>
<p>It’s unclear if this is the same for the guidelines in other countries, as elsewhere the detailed evidence has not been published in the same way. But it may well be that other recommendations to use lower-fat dairy products are based more on maths than science. </p>
<p>It’s also worth noting that the potential health benefits linked to dairy foods do not extend to butter and possibly not milk either, but are largely linked to intakes of <a href="https://link.springer.com/article/10.1007/s00394-017-1556-2">yoghurt and some types of cheese</a>.</p>
<p>There’s also <a href="https://twitter.com/KenDBerryMD/status/1086679359719698433">a myth</a> that low-fat milk and cheese can lead to weight gain, but this is false. It appears to be based on historical farming practices that used leftover <a href="https://library.dpird.wa.gov.au/cgi/viewcontent.cgi?article=3923&context=journal_agriculture4">skimmed milk from making cream to fatten piglets</a>.</p>
<h2>Low-fat v full-fat</h2>
<p>So, given the minimal evidence, why do so many healthy eating guidelines – including in the <a href="https://www.nhs.uk/live-well/eat-well/food-guidelines-and-food-labels/the-eatwell-guide/">UK</a>, <a href="https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf">US</a> and <a href="https://www.eatforhealth.gov.au/guidelines/australian-guide-healthy-eating">Australia</a> – recommend that we choose low-fat or reduced-fat versions of dairy products? </p>
<p>Research has found that higher intakes of saturated fatty acids are linked to an increased risk of <a href="https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/fats/saturated-fats#:%7E:text=The%20American%20Heart%20Association%20recommends,of%20saturated%20fat%20per%20day.">heart disease</a>, type 2 diabetes and <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1140705/#:%7E:text=The%20Chicago%20study%20reported%20the,by%202%20to%203%20times.">dementia</a>. </p>
<p>But this research looks at saturated fatty acids in general and not specifically saturated fatty acids found in dairy products, which have been shown in both <a href="https://academic.oup.com/advances/article/11/4/928/5760740?login=false">children</a> and <a href="https://academic.oup.com/advances/article/11/3/533/5697079?login=false">adults</a> to be potentially beneficial for our health. This is thought to be to do with the way these foods are fermented. </p>
<p>So these recommendations may come as part of suggestions to limit overall fat intake more broadly, rather than because full-fat dairy is “bad” for us.</p>
<p>Switching from full-fat milk to semi-skimmed milk in tea (up to five cups a day) is likely to save the average person less than 50kcal per day. This means, even when considering calories and energy, the effect of <a href="https://theconversation.com/dietary-guidelines-dont-work-heres-how-to-fix-them-68803">reducing fat is minimal</a>. </p>
<p>So if you consume dairy products, it’s likely that there’s no need to worry too much about the fat content. This is especially the case when it comes to unsweetened yoghurt and cheese, which when consumed in their full-fat form do seem to come with potential health benefits.</p><img src="https://counter.theconversation.com/content/207383/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Duane Mellor is a member of the British Dietetic Association</span></em></p>A recent evidence review found children who ate full-fat dairy were healthier and leaner.Duane Mellor, Lead for Evidence-Based Medicine and Nutrition, Aston Medical School, Aston UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1144122019-04-11T10:43:52Z2019-04-11T10:43:52ZCan changing the microbiome reverse lactose intolerance?<figure><img src="https://images.theconversation.com/files/267689/original/file-20190404-123426-11oj065.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Reversing lactose intolerance might make it possible for adults to enjoy a milkshake again.</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/drinking-milk-cocktail-father-daughter-together-1302644437?src=utJIocy_CFUrDAZ21kndJA-1-4">YAKOBCHUK VIACHESLAV / Shutterstock.com</a></span></figcaption></figure><p>After childhood, about two-thirds of the world’s human population <a href="http://doi.org/10.1007/s00439-008-0593-6">loses the ability to digest milk</a>. As far as we know, 100% of nonhuman mammals also lose this ability after weaning. The ongoing ability to digest lactose, the main sugar in milk, into adulthood is a biological abnormality.</p>
<p>Lactose cannot be directly absorbed in the intestinal tract and must, instead, be broken down into its two smaller component sugars by an enzyme called lactase. Normally, the activity of the gene that produces lactase, LCT, declines after infancy. New evidence suggests that this decline occurs not because the genetic code is changed, but because the DNA is <a href="http://doi.org/10.1038/nsmb.3227">chemically modified</a>
so that the <a href="http://doi.org/10.1038/s41598-018-23957-4">lactase gene is switched off</a>. Such modifications that affect gene activity while leaving the DNA sequence intact are called epigenetic. The epigenetic modification that <a href="http://doi.org/10.1038/nsmb.3227">turns off the lactase gene</a> does not happen in <a href="http://doi.org/10.1038/s41598-018-23957-4">lactose-tolerant individuals</a>. This new finding gives an important insight into how lactose intolerance develops with age or after trauma to the intestinal tract.</p>
<p><a href="https://biology.indiana.edu/about/faculty/foster-patricia.html">I’m a microbiologist</a>, and I became interested in the causes of lactose intolerance because it afflicts a close friend. He is of Norwegian descent and, like most Norwegians, is genetically lactose tolerant. But, he became permanently <a href="https://www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance">lactose intolerant</a> at the age of 45 after a long regimen of antibiotics. </p>
<p>There are other cases of people who should be able digest lactose because of their genetics, but lose that ability late in life, either spontaneously or when <a href="https://www.mayoclinic.org/diseases-conditions/lactose-intolerance/symptoms-causes/syc-20374232">the small intestine is damaged by disease or other traumas</a>. In most cases, the lactose intolerance goes away when the underlying cause is treated, but some people become permanently lactose intolerant.</p>
<p>It seems possible, even probable, that such trauma to the digestive tract can trigger the same epigenetic change that normally turns off the lactase gene in childhood. Scientists have found other cases of such <a href="http://doi.org/10.1146/annurev-publhealth-040617-014629">environmentally induced epigenetic changes</a>, although more research is needed to establish the persistence and consequences of these alterations.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=219&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=219&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=219&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=276&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=276&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267868/original/file-20190405-180010-1dua2bh.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=276&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The lactase enzyme breaks down the sugar lactose into two smaller sugars that can be absorbed in the small intestine.</span>
<span class="attribution"><a class="source" href="http://www.evo-ed.com">http://www.evo-ed.com</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
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<h2>Lactose intolerance is mostly due to your genes</h2>
<p>While the ability to produce the lactase enzyme persists into adulthood in only about 35% of adults worldwide, this <a href="http://doi.org/10.1146/annurev-genom-091416-035340">proportion varies widely among ethnic groups</a>. In the U.S., the proportion of lactose-tolerant people is about <a href="http://doi.org/10.1016/S2468-1253(17)30154-1">64%</a>, reflecting the mixture of ethnic groups that populate the country. </p>
<p>The ability of adults to digest lactose appeared in humans relatively recently. Specific genetic changes – known as single-nucleotide polymorphisms, SNPs – conveying lactase-persistence arose independently in various populations around the same time as their domestication of dairy animals. None of these SNPs are in the lactase gene itself, but instead are in a nearby region of the DNA that <a href="http://doi.org/10.1007/s00439-017-1847-y">control its activity</a>. Scientists have been trying to figure out how these changes exert their influence over this gene’s behavior.</p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=740&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=740&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=740&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=931&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=931&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267869/original/file-20190405-180036-1uyi5b6.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=931&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">This SNP, located 13910 base pairs in front of the lactase gene, has the DNA base pair C:G replaced by a T:A. The change apparently prevents the DNA from being methylated at this site, and so the lactase gene stays active.</span>
<span class="attribution"><a class="source" href="http://www.evo-ed.com">http://www.evo-ed.com</a>, <a class="license" href="http://creativecommons.org/licenses/by-nc/4.0/">CC BY-NC</a></span>
</figcaption>
</figure>
<p>Recently researchers have shown that one of the SNPs changes the level of <a href="http://doi.org/10.1038/s41598-018-23957-4">epigenetic modification</a> of the DNA in <a href="http://doi.org/10.1038/nsmb.3227">the lactase gene control regions</a>. Specifically, the SNP prevents small chemical units, called methyl groups (which consist of one carbon and three hydrogen atoms) from being attached to the DNA. Methyl groups are especially important in regulating gene activity because when they are added to the DNA, they turn off the gene. </p>
<p>These studies imply that after early childhood, the lactase gene is usually shut off by DNA methylation. The SNPs that alter the DNA sequence in the control region, however, prevent this methylation from happening. This, in turn, results in the production of lactase because the gene is kept on.</p>
<p>To date, <a href="http://doi.org/10.1007/s00439-017-1847-y">five different SNPs have been strongly associated</a> with lactase persistence, and another 10 or so have been found in isolated populations. The estimated times of appearance of these SNPs in different cultures range from <a href="http://doi.org/10.1146/annurev-genom-091416-035340">3,000 (Tanzania) to 12,000 (Finland) years ago</a>. That the trait persisted and spread in these populations indicates that the ability to digest milk beyond infancy had a significant selective advantage.</p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=358&fit=crop&dpr=1 600w, https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=358&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=358&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=450&fit=crop&dpr=1 754w, https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=450&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/267634/original/file-20190404-123431-he5wvi.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=450&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Lactic acid bacteria can digest the sugar lactose and produce lactic acid as a byproduct.</span>
<span class="attribution"><a class="source" href="https://upload.wikimedia.org/wikipedia/commons/8/86/Lactobacillus_paracasei.jpg">Dr. Horst Neve, Max Rubner-Institut</a>, <a class="license" href="http://creativecommons.org/licenses/by-sa/4.0/">CC BY-SA</a></span>
</figcaption>
</figure>
<h2>Your microbiome and lactose intolerance</h2>
<p>The symptoms of <a href="https://www.niddk.nih.gov/health-information/digestive-diseases/lactose-intolerance">lactose intolerance</a> include diarrhea, stomach pain, cramps, bloating and flatulence, all of which result from failure to break down lactose in the small intestine. As undigested lactose moves into the large intestine, water enters to reduce the lactose concentration, producing diarrhea. The lactose is eventually eaten by microorganisms in the large intestine, producing, as byproducts, various gases that cause bloating, cramping and flatulence.</p>
<p>Recent studies have shown that the <a href="http://doi.org/10.1007/s12602-018-9507-7">symptoms of lactose intolerance can be relieved</a> in some people by <a href="http://doi.org/10.1073/pnas.1606722113">changing the population of their intestinal microbes</a>, called the microbiome, to encourage lactose-digesting bacteria. Specifically, bacteria, called “lactic acid bacteria,” eat the lactose but produce the byproduct lactic acid instead of gas. While lactic acid has no nutritional value, it does not produce the unpleasant symptoms of lactose intolerance. This <a href="http://doi.org/10.1073/pnas.1813608115">adaptation of the intestinal microbiome</a> may be how some ancient pastoral populations with no genetic evidence of lactase persistence tolerated a dairy-rich diet.</p>
<p><a href="http://doi.org/10.1007/s12602-018-9507-7">Ingesting lactic acid bacteria as a probiotic</a> can alleviate the symptoms of lactose intolerance, but these bacteria may not persist in the colon. A promising new strategy is to “feed” the lactic acid bacteria a complex sugar that they can digest but humans cannot. In initial clinical trials, subjects using this “prebiotic” reported <a href="http://doi.org/10.1186/1475-2891-12-160">improved lactose tolerance</a> and had a corresponding <a href="http://doi.org/10.1073/pnas.1606722113">shift in their intestinal microbiome</a>. <a href="https://www.clinicaltrials.gov/ct2/show/NCT03597516?term=NCT03597516&rank=1">Larger clinical trials are in progress</a>. </p>
<p>So there is hope for lactose-intolerant people that real ice cream may be on the menu again.</p><img src="https://counter.theconversation.com/content/114412/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Patricia L. Foster receives funding from the US Army Research Office. She is a member of the Union of Concerned Scientists and Concerned Scientists at Indiana University. </span></em></p>You may think that your milk-drinking, ice cream-licking days are behind you as you battle the discomfort of lactose intolerance. But there maybe be a way to reverse the situation.Patricia L. Foster, Professor Emerita of Biology, Indiana UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1020842018-08-29T10:15:20Z2018-08-29T10:15:20ZThe surprising role cheese played in human evolution<figure><img src="https://images.theconversation.com/files/234042/original/file-20180829-195298-c94cey.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><span class="source">shutterstock</span></span></figcaption></figure><p>A solid white mass found in a broken jar in an Ancient Egyptian tomb has turned out to be the <a href="https://www.bbc.co.uk/news/world-africa-45233347">world’s oldest example</a> of solid cheese. </p>
<p>Probably made mostly from sheep or goats milk, the cheese was found several years ago by archaeologists in the <a href="http://time.com/5371503/ancient-egypt-tomb-old-cheese/">ancient tomb of Ptahmes</a>, who was a high-ranking Egyptian official. The substance was identified after the archaeology team carried out <a href="https://pubs.acs.org/doi/10.1021/acs.analchem.8b02535">biomolecular identification of its proteins</a>.</p>
<p>This 3,200-year-old find is exciting because it shows that the Ancient Egyptian’s shared our love of cheese – to the extent it was given as a funerary offering. But not only that, it also fits into archaeology’s growing understanding of the importance of dairy to the development of the human diet in Europe. </p>
<h2>Dairy in diets</h2>
<p>About two-thirds of the world’s population <a href="https://www.karger.com/Article/PDF/360136">is lactose intolerant</a>. So although dairy products are a daily part of the diet for many living in Europe, Northern India and North America, drinking milk in adulthood was only possible from <a href="https://depot.ceon.pl/bitstream/handle/123456789/13155/nature14507.pdf?sequence=2">the Bronze Age</a>, over the last 4,500 years. </p>
<p>For most of human history, adults lost the ability to consume milk after infancy – and the same is true of people who are lactose intolerant today. After weaning, people with lactose intolerance can no longer produce <a href="https://www.karger.com/Article/PDF/360136">the enzyme lactase</a>. This is necessary to break down the lactose sugars in fresh milk into compounds that can be easily digested. People with lactose intolerance experience unpleasant symptoms if they consume dairy products such as bloating, flatulence and diarrhoea. </p>
<p><a href="https://depot.ceon.pl/bitstream/handle/123456789/13155/nature14507.pdf?sequence=2">Ancient DNA analysis</a> on human skeletons from prehistoric Europe places the earliest appearance of the gene lactase gene (LCT) – which keeps adults producing lactase – to 2,500BC. But there is plenty of evidence from the Neolithic period (around 6,000-2,500BC in Europe) that milk was being consumed. </p>
<p>This is not totally surprising though, as the Neolithic marks the start of farming in most regions of Europe – and the first time humans lived closely alongside animals. And although they were unable to digest milk, we know that Neolithic populations were processing milk into substances they could consume. </p>
<h2>Archaeological evidence</h2>
<p>Using a technique called “<a href="https://www.nature.com/articles/nature07180">lipid analysis</a>”, sherds of ancient pottery can be analysed and fats absorbed into the clay identified. This then allows archaeologists to find out what was cooked or processed inside them. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/234044/original/file-20180829-195325-gf7shx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">We have ancient ancestors to thank for the cheese we eat today.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
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</figure>
<p>Although it is not yet possible to identify the species of animal, dairy fats can be distinguished. It is also challenging to determine what techniques were being used to make dairy products safe to consume, with many potential options. Fermenting milk, for example, breaks down the lactose sugar into lactic acid. Cheese is low in lactose because it involves separating curd (from which cheese is made) from whey, in which the majority of the lactose sugars remain. </p>
<p><a href="https://www.nature.com/news/archaeology-the-milk-revolution-1.13471">Clay sieves from Poland</a>, similar to modern cheese sieves, have been found to have dairy lipids preserved in the pores of clay, suggesting that they were being used to separate curds from the whey. Whether the curds were then consumed or attempts made to preserve them by pressing into a harder cheese is unknown. Fermentation of milk was also possible to our ancestors, but harder to explore with the techniques currently available to archaeology. </p>
<h2>Early cheese making</h2>
<p>While the techniques from bioarchaeology have provided this fantastic detail on Neolithic diets, where the science stops, experimental archaeology can explore what was possible. </p>
<p><a href="https://www.youtube.com/watch?v=jVx-O9ZYa3A">We have been making cheese</a> using the <a href="http://www.prehistoricsociety.org/files/PAST_84_for_web.pdf">utensils, plants and techniques</a> available to Neolithic farmers. The aim of the experiments is not to faithfully recreate early cheeses, but to begin to capture some of the decisions available to early cheese makers – and the experiments have thrown up some interesting results. </p>
<p>By using these ancient techniques, we have discovered that a wealth of different means of curdling the milk would have been possible, each producing different forms, tastes and amounts of cheese. </p>
<p>And such specialist knowledge may have been akin to the spread of bronze smelting at the end of the Neolithic. Dairy may have had a special status among foodstuffs. For example, at the major late <a href="https://www.cambridge.org/core/journals/antiquity/article/feeding-stonehenge-cuisine-and-consumption-at-the-late-neolithic-site-of-durrington-walls/E60784FB3D83BFF8ED22A2E9393B5B3E">Neolithic feasting site of Durrington Walls</a>, not far from and contemporary with Stonehenge, dairy residues were found in a particular kind of pottery vessel and concentrated in the area around a timber circle – a form of Late Neolithic monument. </p>
<p>From the Bronze Age, however, lactase persistence offered an advantage to some people who were able to pass this on to their offspring. It also seems that this advantage was not solely because of increased calorie and nutrient intake alone – but because of the special status dairy foods may have had. The development of this biological adaption to fresh milk took place after humans had already found ways to safely include dairy products in the diet. </p>
<p>This shows that humans are not only able to manipulate their food to make it edible, but that what we consume can also lead to new adaptations in our biology.</p><img src="https://counter.theconversation.com/content/102084/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Penny Bickle receives funding from the AHRC. </span></em></p>Archaeologists have discovered the world’s oldest cheese, and it reveals how our ancestor’s cooking methods helped the human diet adapt.Penny Bickle, Lecturer in Archaeology, University of YorkLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/942952018-05-24T20:04:03Z2018-05-24T20:04:03ZPlain, Greek, low-fat? How to choose a healthy yoghurt<figure><img src="https://images.theconversation.com/files/218000/original/file-20180508-46353-4spjww.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">With all the different types of yogurt on offer, making a decision on which one to buy can be difficult.</span> <span class="attribution"><span class="source">from shutterstock.com</span></span></figcaption></figure><p>Yoghurt is one of the oldest fermented dairy foods in the world. Its origins date back to the <a href="https://academic.oup.com/nutritionreviews/article/73/suppl_1/4/1819293">dawn of civilisation</a>. When humans began domesticating animals for milk production, milk’s short shelf life required solutions for storing it. </p>
<p>The word “yoghurt” itself <a href="https://www.elsevier.com/books/tamime-and-robinsons-yoghurt/tamime/978-1-84569-213-1">comes from Turkish</a>, meaning something like “curdled” or “thickened milk”, which is pretty much what happens to milk during yoghurt production.</p>
<p>Like milk, yoghurt is a rich source of calcium and protein. And it <a href="https://academic.oup.com/ajcn/article/99/5/1243S/4577504">provides other nutrients</a> such as iodine, vitamins D, B2 and B12, and zinc. </p>
<p>But yoghurt is actually more nutritious than milk. The main reason is that the fermentation process makes it easier to digest, so the nutrients can be absorbed more easily into the body.</p>
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Read more:
<a href="https://theconversation.com/from-bulgaria-to-east-asia-the-making-of-japans-yogurt-culture-76598">From Bulgaria to East Asia, the making of Japan's yogurt culture</a>
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<p>Yet with all the various types, like Greek and liquid yoghurts, and ones with added fruits and probiotics, how do you know which one is healthiest?</p>
<h2>Making yoghurt</h2>
<p>Yoghurt is made by introducing certain bacteria into fresh milk – typically <em>Streptococcus thermophilus</em> and <em>Lactobacillus delbrueckii subsp. bulgaricus</em>. </p>
<p>Usually, both these bacteria are present in yoghurt and form the yoghurt starter culture. Their synergistic relationship is a key factor in the consistency of the final product. These cultures may also provide some health benefits, such as reducing the <a href="https://www.ncbi.nlm.nih.gov/pubmed/14627358">severity and duration of diarrhoea</a>. </p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=397&fit=crop&dpr=1 600w, https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=397&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=397&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=499&fit=crop&dpr=1 754w, https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=499&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/217999/original/file-20180508-46364-gsqsl6.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=499&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Yoghurt is made by introducing a starter culture of bacteria into milk.</span>
<span class="attribution"><a class="source" href="https://www.flickr.com/photos/inthe-arena/10372695863/in/photolist-gNAM6R-a41WoE-axxDjL-a2qdFb-cJ4KiQ-zaiG5-9Y5u1V-bwktpH-dZ1WpZ-axxESN-PFwbv-9e57PA-6aaynh-quG5pa-4pQyL1-6Y4eiy-9ZSM8P-9AXD83-6LMsD4-aavUZL-oejucg-axxD3s-axuXvv-axuYuR-6LRBJL-axuXQx-6DnSyf-QDWHf4-6o6EZa-QGLYwE-axxDAj-5hSCbx-GmBLc-7A5ypG-dRGUct-7Szc93-8bhcPt-6eHCk5-29yKSq-7TwfT5-9v9n8t-SBbdNf-dtoEBA-buwu2p-9WgKAp-aoxrax-8ZFTF-eyrRok-9Deo3D-nZqQc">Andrew Seaman/Flickr</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The bacteria ferment the naturally occurring milk sugar (lactose) for energy and growth. During this process, lactose becomes lactic acid. The acidity development leads to the main milk protein, casein, breaking down and losing some of its elementary structure. </p>
<p>This partial breakdown results in the semi-solid, gel-like structure we know as yoghurt. The lactic acid is also responsible for yoghurt’s sour flavours, as well as helping it stay fresher for longer than milk. </p>
<h2>What makes yoghurt healthy?</h2>
<p>Yoghurt is easier to digest than milk because enzymes involved in the fermentation process break down substances, such as lactose, into <a href="https://academic.oup.com/ajcn/article/99/5/1243S/4577504">smaller compounds</a>, which can be readily absorbed and used by the body. And certain minerals, such as calcium, phosphorus and iron, are <a href="https://www.sciencedirect.com/science/article/pii/B9780128051344000018">better used by the body</a> when they come from yoghurt.</p>
<p>And because lactose is broken down and converted to lactic acid during fermentation, lactose-intolerant people can consume yoghurt without adverse effects. </p>
<p>Consuming yoghurt is associated with <a href="https://www.elsevier.com/books/yogurt-in-health-and-disease-prevention/shah/978-0-12-805134-4">many health benefits</a>, including maintaining a healthy microbiota (the colony of bacteria in your gut). Yoghurt can feed the good bacteria and help them fight against <a href="https://www.ncbi.nlm.nih.gov/pubmed/26995128">disease-causing microorganisms</a>.</p>
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Read more:
<a href="https://theconversation.com/explainer-what-is-the-gut-microbiota-and-how-does-it-affect-mind-and-body-40536">Explainer: what is the gut microbiota and how does it affect mind and body?</a>
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<p>Yoghurt consumption helps to maintain bone structure and has even been found to reduce the risk of <a href="https://onlinelibrary.wiley.com/doi/full/10.1002/ijc.26193">certain cancers</a> and infectious diseases, as it enhances the immune response. Yoghurt <a href="https://academic.oup.com/ajcn/article/80/2/245/4690304">can help reduce symtpoms of conditions</a> such as constipation, inflammatory bowel disease, infection with a bacterium that can damage the stomach lining (<em>Helicobacter pylori</em>), <a href="http://www.who.int/en/news-room/fact-sheets/detail/diarrhoeal-disease">diarrhoeal diseases</a> and some allergic reactions, such as to certain foods. </p>
<h2>Types of yoghurt</h2>
<p>Cow’s milk is the most widely used raw ingredient for yoghurt manufacturing. But other types, such as sheep and goat milk yoghurt, are available. There are slight differences in the nutritional composition among these milk types. </p>
<p>Although cow’s milk is generally more appealing (as goat and sheep milk may have <a href="https://wakethewolves.com/goats-milk-vs-cows-milk-is-there-a-difference/">unpleasant smells</a>), the latter two may provide additional health benefits. For instance, <a href="https://www.sciencedirect.com/science/article/pii/S0308814612009971">goat’s milk is easier to digest</a> than cow’s milk and is less likely to cause an allergic reaction.</p>
<p>Non-dairy alternatives such as soy and coconut milk yoghurt are becoming increasingly popular too.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/218004/original/file-20180508-46364-qvpfkx.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Goat’s milk is easier to digest than cow’s milk.</span>
<span class="attribution"><span class="source">from shutterstock.com</span></span>
</figcaption>
</figure>
<p>The most commonly known types of yoghurt are plain set yoghurt, flavoured yoghurt, Greek yoghurt, frozen yoghurt and drinking yoghurt.</p>
<p><em>Plain set yoghurt</em> is usually made from dairy ingredients and fermented in the cups or tubs with no sugar or sweeteners.</p>
<p><em>Flavoured yoghurt</em> is made by adding sugar and fruit or other flavourings to plain yoghurt. Often, the milk mixture is fermented in large vats, cooled and then stirred for a creamy texture with various fruits or other flavours. These stirred yoghurts are also known as Swiss-style yoghurts.</p>
<p><em>Greek yoghurt</em> is a thick yoghurt. It’s traditionally prepared by straining the water known as whey from plain yoghurt to make it thicker, richer and creamier. It contains more protein than regular yoghurt and has no added sugar.</p>
<p><em>Frozen yoghurt</em> is frozen ice milk with a typical yoghurt flavour. It tastes more like ice-cream with a hint of yoghurt.</p>
<p><em>Drinking yoghurts</em> are prepared from a yoghurt mix with reduced milk solids. They come in almost every variety and flavour. They’re usually more watery, but some thick varieties are also available. Kefir and lassi are the popular drinking yoghurt types.</p>
<h2>Added ingredients for health purposes</h2>
<p>Many yoghurts contain added ingredients. These include <a href="https://www.benecol.co.uk/our-products/yogurts/garden-fruits?utm_medium=cpc&utm_source=google&utm_term=benecol-yogurt&utm_content=text&utm_campaign=mec---brand---product---yogurt-(b)&gclid=CjwKCAjw2dvWBRBvEiwADllhn7saBYlt7KTGzuaG_kj7emog2j957TlcdEyjB46RLqqdjIfeKp5AzBoCV68QAvD_BwE&gclsrc=aw.ds">cholesterol-lowering compounds</a> (such as stanol and sterol esters) and <a href="https://www.ncbi.nlm.nih.gov/pubmed/26619790">fibre</a> aimed at improving gut health. </p>
<p>Some yoghurts also have added probiotics. These are <a href="http://www.mdpi.com/2311-5637/3/4/67">live microorganisms</a> that can help establish a healthy gut microbiota. The most widely used probiotics are the acidophilus strain, known as <em>Lactobacillus acidophilus</em>, and <em>Bifidobacterium</em>. These could be useful for people who have gastrointestinal problems such as <a href="https://link.springer.com/article/10.1007/s00535-016-1224-y">irritable bowel syndrome (IBS)</a>.</p>
<p>Probiotics can be more effective when <a href="https://www.sciencedirect.com/science/article/pii/S0963996909002749">consumed in yoghurt</a> than through capsules or <a href="https://www.sciencedirect.com/science/article/pii/S096399691300330X">other beverages</a>.</p>
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Read more:
<a href="https://theconversation.com/so-you-think-you-have-ibs-coeliac-disease-or-crohns-heres-what-it-might-mean-for-you-39128">So you think you have IBS, coeliac disease or Crohn’s? Here’s what it might mean for you</a>
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<p>The two bacteria in yoghurt starter culture – <em>S. thermophilus</em> and <em>L. delbrueckii</em> ssp. <em>bulgaricus</em> – are not <a href="https://www.elsevier.com/books/yogurt-in-health-and-disease-prevention/shah/978-0-12-805134-4">natural inhabitants</a> of the intestine and cannot survive the acidic conditions and bile concentrations in the gastrointestinal tract. So they don’t do much to change the microbiota in your gut. In contrast, probiotics can survive and colonise the large intestine.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/218012/original/file-20180508-46359-c4cs2i.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">It’s healthier to add your own fruit to yoghurt than to buy fruity yoghurt.</span>
<span class="attribution"><a class="source" href="https://unsplash.com/photos/MFs_fEGsoqY">Peter Hershey/Unsplash</a></span>
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<p>Regular intake of yoghurt that contains microbial cultures such as probiotic acidophilus has also been found to potentially reduce the risk of coronary heart disease by helping to <a href="https://www.tandfonline.com/doi/abs/10.1080/07315724.1999.10718826">decrease cholesterol absorption</a>. </p>
<h2>Which yoghurt is better for you?</h2>
<p>When whole milk is used to produce plain yoghurts, these may contain 3.5-4.4 grams of fat per 100g. Low-fat yoghurt contains less than 3g of fat per 100g, and non-fat or fat-free yoghurts must contain less than <a href="http://www.legendairy.com.au/%7E/media/Legendairy/Documents/Health/Fact%20sheets/2012%20Proximate%20Composition%20Booklet.ashx">0.15g fat per 100g</a>. </p>
<p>High fat and high sugar in any food can lead to health problems. So, a low-fat and low-sugar yoghurt product, like a low-fat Greek yoghurt, would be ideal if you’re looking to keep healthy.</p>
<p>Yoghurt products incorporating fruit or nuts can provide additional nutritional and health benefits, but many of these can also contain added sugar. Adding fresh fruit or nuts to a yoghurt yourself is a healthier option.</p>
<p>If you would like to have probiotic effects, you can choose a product with acidophilus or bifidobacteria. </p>
<p>You should check the product label as it is a legal requirement to list all the ingredients, cultures and nutritional information in commercial yoghurts. When it comes to probiotic yoghurts, it’s always better to choose a fresh product rather than one closer to the expiry date, as <a href="http://www.mdpi.com/2311-5637/3/4/67">probiotics die during storage</a>.</p><img src="https://counter.theconversation.com/content/94295/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Duane Mellor is a director, council member and spokesperson of the British Dietetic Association</span></em></p><p class="fine-print"><em><span>Nenad Naumovski, Said Ajlouni, and Senaka Ranadheera do not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Consuming yoghurt is associated with many health benefits. But with all the varieties of yoghurt, and added ingredients like fruits and probiotics, it can be hard to know which is best for your health.Senaka Ranadheera, Tutor, The University of MelbourneDuane Mellor, Senior Lecturer, Coventry UniversityNenad Naumovski, Asistant Professor in Food Science and Human Nutrition, University of CanberraSaid Ajlouni, Associate Professor, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/579132016-04-21T14:25:50Z2016-04-21T14:25:50ZBreast milk is a marvel of nature but that doesn’t mean adults should drink it to see off disease<figure><img src="https://images.theconversation.com/files/119440/original/image-20160420-25601-1cxpj2y.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Don't give it to grandad.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&searchterm=breast%20milk&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=271722359">www.shutterstock.com</a></span></figcaption></figure><p>A woman’s claim that she <a href="http://www.dailymail.co.uk/news/article-3542866/Helen-swears-breast-milk-gave-dying-dad-extra-year-life-right.html">extended her father’s life</a> by more than a year by feeding him expressed milk has led many to ask whether human milk can really delay the growth of cancer. The gold standard nutrition for infants, human milk is not, however, a replacement for conventional medicine in the treatment of adult diseases.</p>
<p>Human milk is perfectly composed for babies, including both nutrient and bioactive components that promote growth and development. <a href="http://www.nhs.uk/Conditions/pregnancy-and-baby/Pages/benefits-breastfeeding.aspx">Official guidance</a> in the UK recommends exclusive human milk feeding for the first six months of life. Continued breastfeeding for one to two years or longer is then endorsed by various organisations, <a href="http://www.who.int/topics/breastfeeding/en/">including the WHO</a>.</p>
<h2>Changeable milk</h2>
<p>The composition of human milk varies. <a href="http://www.cell.com/trends/biochemical-sciences/fulltext/S0968-0004%2816%2900045-1">Research</a> shows that it changes within feeds, across the day, across lactation, and between different women. This variability benefits the infant as they grow and develop. </p>
<p>The first fluid produced after delivery is colostrum. It is produced in low quantities and is rich in compounds that boost the immune system (such as leukocytes, secretory immunoglobulin A, and lactoferrin), as well as others that support growth and development (like epidermal growth factor). However, colostrum is relatively low in lactose, potassium, and calcium, leading <a href="http://ssu.ac.ir/cms/fileadmin/user_upload/Mtahghighat/tfood/ARTICLES/milk/Human_Milk_Composition.pdf">researchers</a> to conclude its function is not primarily to provide nutrition. </p>
<p>Within days the composition changes, lactose increases, marking the production of what many call “<a href="http://ajcn.nutrition.org/content/53/5/1197.short">transitional milk</a>”. This change in the milk can be delayed if the baby is delivered preterm or if the mother has a metabolic condition or is obese.</p>
<p>Across the next few weeks, milk production increases rapidly. This is to support the changing nutritional and developmental needs of the growing infant. Within a month to six weeks, the milk becomes fully mature. </p>
<h2>Complex stuff</h2>
<p><a href="http://ssu.ac.ir/cms/fileadmin/user_upload/Mtahghighat/tfood/ARTICLES/milk/Human_Milk_Composition.pdf">Mature milk</a> provides around 65 to 70 calories per 100g, which come from about 4g of fat, 7g of carbohydrate, and 1g of protein. But this composition is constantly changing. The variation in calories is primarily due to differences in fat content. Fat content is significantly lower at night and morning compared with afternoon or evening milk. It also varies within the feed itself. Milk at the end of the feed has <a href="https://www.researchgate.net/profile/Chantal_Lau/publication/12944835_Feeding_strategies_for_premature_infants_Beneficial_outcomes_of_feeding_fortified_human_milk_versus_preterm_formula/links/0deec536d7c743b2d0000000.pdf">higher levels</a> than the initial flow.</p>
<p>The composition of milk also varies with maternal diet, especially the amount and type of fatty acid. Many women in developed countries aren’t getting enough fatty acid – important for infant brain development – in their diet and this affects the composition of their breast milk. For example, low levels of docosahexaenoic acid (DHA) – an omega 3 fatty acid – consumed by North American mothers translates to low levels in their milk. This has led some <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3566653/">researchers</a> to suggest that mothers should take appropriate supplements. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=416&fit=crop&dpr=1 600w, https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=416&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=416&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=523&fit=crop&dpr=1 754w, https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=523&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/119449/original/image-20160420-25615-1udeamm.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=523&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
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<span class="caption">Some mothers might benefit from taking fatty acid supplements.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/cat.mhtml?lang=en&language=en&ref_site=photo&search_source=search_form&version=llv1&anyorall=all&safesearch=1&use_local_boost=1&autocomplete_id=&search_tracking_id=TU9ndqjQrevZ5pNRYs_6nA&searchterm=fish%20oil%20supplement&show_color_wheel=1&orient=&commercial_ok=&media_type=images&search_cat=&searchtermx=&photographer_name=&people_gender=&people_age=&people_ethnicity=&people_number=&color=&page=1&inline=288277154">www.shutterstock.com</a></span>
</figcaption>
</figure>
<h2>More than just nutrition</h2>
<p>But human milk doesn’t just contain nutrition; it contains a variety of compounds with medicinal qualities that are important for the baby’s survival. These “growth factors” are numerous and have wide-ranging effects. For instance, epidermal growth factor is important for the development and repair of the gastrointestinal tract. Insulin-like growth factors are critical in stimulating growth and development, with high levels of some <a href="https://www.researchgate.net/publication/16992978_Immunoreactive_Somatomedin-CInsulin-Like_Growth_Factor_I_and_Its_Binding_Protein_in_Human_Milk">linked</a> to neural, and cochlea development in the ear. There are many growth factors, and they affect many important functions, including the development of the blood vessels, metabolism, intestinal system, nervous system, and endocrine (hormone) system. </p>
<p>Human milk also has important immune impacts, protecting against inflammation and infection. Oligosaccharides (a carbohydrate) encourage the growth of organisms that plays an essential role in early bacterial colonisation of the intestine which have important impacts on gut health and general well-being in later life, while also reducing vulnerability to some pathogens, such as <a href="http://jid.oxfordjournals.org/content/190/10/1850.full">noroviruses</a>.</p>
<h2>Not for sharing</h2>
<p>Containing a variety of <a href="http://www.bbc.co.uk/schools/gcsebitesize/science/21c_pre_2011/disease/diseaseresistancerev4.shtml">white blood cells</a>, human milk stimulates the development of the infant immune system while providing protection from germs. <a href="http://adc.bmj.com/content/84/5/381.full">Research</a> reveals that such transmission, however, opens up the potential for infection with HIV, syphilis, hepatitis and herpes, among other viruses, which can pass along with these cells.</p>
<p>This viral transmission, along with the risk of contamination with bacteria and toxins, creates a need for careful management of milk sharing <a href="http://www.bmj.com/content/350/bmj.h1485">and selling</a>. The nutrient and bioactive compounds are affected by the mother’s consumption of food, drink, medicines and illicit drugs. The presence of toxins and contaminants are introduced by a mother’s environmental exposure, as well as during expression and storage of the milk. Expressing and pasteurising milk <a href="http://ajcn.nutrition.org/content/96/3/544.full.pdf+html">changes its composition</a> which can reduce or even eliminate some bioactive components. </p>
<p>Such impacts make oversight crucial for babies fed with another mother’s milk, but also mean a careful approach is needed by those adults who think human milk might hold medicinal value. While a liquid gold, awareness of the risks as well as the benefits of human milk is crucial, both for adult and infant consumers.</p><img src="https://counter.theconversation.com/content/57913/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Sarah Steele does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Most people are aware of the benefits of breastmilk, but few are aware of the risks.Sarah Steele, Queen Mary University of LondonLicensed as Creative Commons – attribution, no derivatives.