Paracelsus' poison

Toxic vitamins

Vitamins, not as toxic as some people make out. Ian Musgrave

While I have been distracted with other things, there have been a number of internet articles relating to toxicology that have come and gone, but are still interesting to talk about. There was an article called “Eight Foods That We Eat in The US That Are Banned in Other Countries” the article went viral, but it has been superbly eviscerated by Derek Lowe and Allison Aubery.

Another recent one was “Your Vitamins may be doing you more harm than good”, I was expecting a discussion of the evidence that high-dose fat-soluble antioxidant vitamins not only do not improve health outcomes, but actually may be (slightly) harmful. Or perhaps a discussion of this paper on how high doses of vitamin E and C reduce the lifespans of voles.

But no, I should have known, what I found was a farrago of confusion, misinformation and a decided lack of appreciation of the concept that “the dose makes the poison”.

If there is anything guaranteed to drive someone with a chemistry education wild, it is confusion of the terms organic, inorganic, natural and synthetic. This article mixes them all up in a brain-hurting confabulation.

To someone with chemistry knowledge, “organic” is almost every compound that contains carbon. In the organic food industry, it’s any food that has been produced without the use of inorganic fertilisers or synthetic pesticides. Okay, it’s a bit more complicated than that, but it explains all the chemists snarkily replying to people purveying “organic” food, that they have never seen inorganic food.

Be that as it may, the “Toxic vitamins” article actually sometimes uses the organic/inorganic distinction in the chemists way, and other times in the alternate food way. Its use of natural and synthetic is unrecognisable, the author thinks a compound being in its salt form makes it synthetic (who knew table salt was a synthetic form of sodium). And of course, there is the persistent idea that if something is toxic at one concentration, it is toxic at all concentrations.

If we were to take this concept seriously, then we would have to eschew most vitamins. While essential for health, many vitamins are toxic at high concentrations. Australian Antarctic explorer Douglas Mawson experienced a life threatening overdose of vitamin A, and people have died from too much beta-carotene.

Selenomethionine. Ian Musgrave, visulalised in JMol

The authors list of “toxic vitamins” will evoke a groan from qualified nutritionists. I’ll take as my starting point their treatment of selenite. Selenium, as they correctly claim, is toxic. But it is also an essential mineral.

We encounter selenium in a variety of forms in our diet. The commonest form is one where selenium replaces sulphur in the amino acid methionine. Selenomethionine is identified in the article as organic selenium, which it is in the chemists sense (that is, it a carbon containing compound), and we mostly get it from plants. We also consume inorganic forms of selenium, mostly selenate and selenite, both of which we mostly get from drinking water.

Selenate and selenite are incorrectly identified as “synthetic” by the article; they are all natural.

Crucially, selenomethionine, selenate and selenite are all toxic at high enough concentrations. Seleniomethionine is more effectively incorporated into the body’s essential selenoproteins, but the inorganic forms can be incorporated as well. While low concentrations of these compounds are essential to provide us with the antioxidant selenoproteins we require for health, and might even produce some protection from cancer, if you push the concentration high enough you will have toxicity.

But if you are worried about your vitamins, large meta-analyses of selenium supplement intake, even at the mega-doses that are beloved of the alternative nutrition fraternity, have failed to show any adverse effects of selenium from this source. Of course, they have shown no benefit either.

The same tactic is used to claim a whole range of micro-nutrients are toxic. Cobalt, chromium, magnesium, manganese are all required in small doses, but will cause toxicity at higher doses. Just as wholly natural vitamins E and A will be toxic at higher doses than required for health.

The article is mightily concerned about the salts of various trace elements and vitamins. But the salt form doesn’t make something synthetic. To be synthetic the entire chemical must be made from much simpler components by humans. As I said above, sodium chloride is a salt, but we get it from natural sources like the sea.

Not that being synthetic matters, it’s been shown that natural vitamins and synthetic vitamins are identical when it comes to fulfilling dietary needs.

The best source of vitamins and minerals for healthy people is a balanced diet with plenty of fresh fruit and vegetables. But if you are taking vitamin tablets, you can be assured the selenium is not poisoning you when taken as directed.