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Monday’s medical myth: eating carrots will improve your eyesight

Getting enough vitamin A is important for healthy eyes. And carrots are a rich and natural source of this vitamin, which is basically a group of chemicals made up of retinal (the active form of vitamin…

In the developed world, where vitamin A deficiency isn’t an issue, eating carrots won’t help you see more clearly. Nerdcoregirl

Getting enough vitamin A is important for healthy eyes. And carrots are a rich and natural source of this vitamin, which is basically a group of chemicals made up of retinal (the active form of vitamin A) and carotenes such as beta-carotene (which gives carrots their distinctive colour).

But a diet overloaded with carrots – and vitamin A – won’t leave you with healthier eyes.

To understand where vitamin A fits in, I’ll first explain a little about the process of vision. When we look at something, light from that object enters the eye and is focused onto the inside back surface of the eyeball, which is lined by a thin layer of cells. This is called the retina.

The retina is responsible for catching light and turning this into a neural signal, which is then sent up to the brain for further processing. In order to perform this wondrous action, the retina has specialised cells, called photoreceptors, each of which is packed with light-catching pigments.

Joost J. Bakker IJmuiden

The predominant pigment in the retina is rhodopsin, a major part of which is retinal (vitamin A). When the retinal reacts with light, it induces a cascade of biochemical events and shape changes in the rhodopsin molecule. In turn, this creates an electrical signal. This whole process is known as phototransduction, and this is really where vision begins.

Humans are unable to synthesise vitamin A afresh and, therefore, must take it in through their diet to maintain normal visual function. Vitamin A can be found in a range of meats and vegetables – the most notable being the carrot, though the best source is probably liver.

For most people living in developed countries, adequate vitamin A intake is not an issue, so eating more carrots will make no noticeable difference. This is because our diets contain enough vitamin A and we are able to store it, unlike other nutrients, such as vitamin B.

If you have a healthy diet, it’s likely you’re already getting enough vitamin A. Flickr/f1uffster (Jeanie)

In fact, well-nourished pregnant women should avoid supplementing their diet with vitamin A when their total daily intake is around 3,000 IU because too much vitamin A (well above 10,000 IU per day) can cause birth defects. But vitamin A-rich foods are safe so you can still munch on a bag of carrots without doing any harm (provided you don’t mind your skin turning orange from the carotenes!).

In the developing world, however, an estimated half a million children become blind each year as a consequence of dietary vitamin A deficiency. But carrots aren’t the answer, as they are not easily grown and don’t last long enough to be distributed. World food programs are instead trialling vitamin A-rich bananas and sweet potatoes as a source of nutrition to improve eye health.

While there is still much to be done to prevent vitamin A deficiency in the developing world, to those reading this article, carrots will make very little difference to your eyesight.

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7 Comments sorted by

  1. Russell Hamilton

    Librarian

    Very brave, Harrison, to post anything on diet or health!

    So what's wrong with this contribution?

    The headline is 'Monday's medical myth: eating carrots will improve your eyesight', but what Harrison writes is "But a diet overloaded with carrots – and vitamin A – won’t leave you with healthier eyes."

    Well, no, one has claimed that a diet 'overloaded' with carrots will improve your eyesight. But a carrot, compared with, say, a chocolate bar or a bag of hot chips, is likely to be better for your eyes, so it hardly seems a good idea to put about the idea that carrots being good for you is a 'medical myth'. Aren't Australians meant to be eating more vegetables? And if so, is it wise to destroy the humble carrot's reputation as 'a good thing'?

    If you're not eating enough vegetables, carrots included, then you will probably do your eyes a favour by eating more carrots. Harrison's attack on the status of the carrot is surely unhelpful.

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    1. Harrison Weisinger

      Foundation Director of Optometry Studies at Deakin University

      In reply to Russell Hamilton

      Thanks for reading Russell.

      Of course, I didn't mean to attack poor carrots - I was just attempting to debunk the myth that carrots are (always) good for your eyes. I have actually had patients tell me that they dutifully devour a bag of carrots a day!!! Nor did I mean to divert people from the fruit and veg section to the lollies aisle. I trust my article won't have that effect. As for being brave, I'll take that as a compliment! Cheers, H

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    2. Russell Hamilton

      Librarian

      In reply to Harrison Weisinger

      Hi Harrison,

      No worries, we expect at least 100 critical comments on any diet related post ..... just making my contribution.

      When you say you've had patients 'dutifully devour a bag of carrots a day!!!' I'm not surprised, since I did it myself: decades ago when juicers were invented I got one and tried different things (pineapple comes out nice and creamy) but my favourite was carrots. I just loved the taste of it and was drinking it every day. Eventually I did in fact turn orange, and when friends started advising me to change soap etc I cut back on the carrot juice. And you're right - my eyes didn't improve any.

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    3. Sean Alexander

      Jack of all

      In reply to Russell Hamilton

      Well, I'd rather actually know the truth. Yes, there are bigger world problems, but there should be nothing wrong with giving people the *right* information so they can make informed choices. Gone are the days when we just listened to the "words of wisdom" from our elders. Now we have all sorts of reputable sources of information, as opposed to parents who just spouted what they were told.

      There were once 5 monkeys in a cage...

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    4. Doug Cotton

      logged in via Facebook

      In reply to Harrison Weisinger

      Harrison - I do find it a bit surprising that someone in your position would appear to have little liaison with the US Government's National Eye Institute which has been involved in the studies I mentioned above. You surely don't dispute their findings, nor consider the eyes of Australians are likely to be particularly different - then again, perhaps they are - being blinded to international research.

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  2. Geoff Russell

    Computer Programmer, Author

    I kind of agree with Russell (no relation). There are so many potent nutritional myths in Australia that eating "extra" carrots is harmless at
    worst.

    Why don't you tackle something tough? ... its now the official position of the NHMRC dietary guidelines evidence report that dairy products don't reduce your risk of hip fracture. ... so the relevant myth is that bone mineral density is a good measure of bone health ... if it doesn't even correlate with actual damage, then its not much of a measure.

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  3. Doug Cotton

    logged in via Facebook

    This is yet another ill-informed article. Note the inclusion of beta carotene (precursor to vitamin A) in this study carried out by the National Eye Institute.

    The large, multicenter study explored the use of zinc and antioxidant oral supplements containing above the recommended daily requirements to prevent advanced AMD. It examined 3,640 persons aged 55 to 80, who had a high risk of developing advanced AMD, already had it, or had been blinded in one eye by the condition. These participants…

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