Despite the general low standard of responses to the recent Cochrane review on antioxidants and mortality, Holford characteristically manages to stand out from the crowd. Aside from errors already discussed on this site, Professor Patrick Holford of Teesside University makes a very striking error about antioxidant side effects: he claims that
“there are no known or reported short-term side effects of antioxidants”.
This is simply wrong, at a very basic level. It is well-known that relatively high doses of vitamin C can have short-term side effects: this can cause an irritated stomach, diarrhoea and so forth. And, we should not overlook hypervitaminosis A and hypervitaminosis D. What constitutes a high dose for one person might be within bounds for someone else: e.g., women who take particular types of oral contraception may be warned not to take a multivitamin with vitamin A because the hormones might promote hypermetabolism or greater absorption of available sources.
This is a very odd mistake for a Professor to make. It is also somewhat worrying if the Head of Science and Education at the supplement company Biocare gets things wrong about the side effects of certain supplements because it might lead people to ignore signs that they are taking too high a dose and, prior belief that supplements have no side-effects can lead people not to mention them to medical advisers. While the side effects of vitamin C are generally relatively mild, they can still be unpleasant – if a proper or want-to-be healthcare professional tells me to take something that can cause diarrhoea, I would want advance warning! – and they are potentially serious in people whose health is otherwise compromised. Interestingly, of course, as the redoutable Catherine Collins recently detailed in a Radio 5 item, there is no mechanism for reporting side-effects from herbal medicines or supplements (see the recent example from the New York Times: Potential for harm in dietary supplements).
Did I mention that Holford is a Professor at Teesside? One does wonder what type of example he is setting the students there…
Update 30 April: some comments about selenium compel us to add a note to state something that will be very obvious to some of our readers but may be life-saving information to others.
Milligrams are a unit of mass equal to one-thousandth of a gram.
Micrograms are a unit of mass equal to one-millionth of a gram.
Confusing the two can literally be lethal for some substances, like selenium.