Prof Patrick Holford makes a basic error about antioxidant side effects

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.



Filed under antioxidants, Holford, patrick holford, supplements, vitamin c

20 responses to “Prof Patrick Holford makes a basic error about antioxidant side effects

  1. Can we vote for our favourite antioxidant side-effects?
    I’m sure excess Beta Carotene turns yours skin orange – it might not be dangerous but it would certainly be unsightly and may scare some people who might think their yellow-orange skin was a sign of jaundice.
    I’m not sure if Selenium and Zinc qualify as actual antioxidants – but as the alties claim them as antioxidants, I think I’ll vote for anaemia and weakening of the bones for Zinc and selenosis, a condition that in its mildest form can lead to loss of hair, skin and nails, for Selenium.
    Info on Zn/Se is from:

  2. Er, that should have been ‘your skin’.
    Beta Carotene features here in a BBC story on Sunny Delight and here on wrong diagnosis dot com.

  3. Not sure it’s a favourite, but desquamation after vitamin A overdose sounds like the least fun.

  4. Dudes, you’re in The Telegraph. That’s excellent!

  5. Thank you, Coracle. That was a nice shout-out from Damian Thompson.

  6. Thanks Coracle :) Posted on the article here

  7. koo

    Selenium has fantastic health benefits and has solved a lot of my health problems. It attaches itself to heavy metals in the body such as mercury and aluminum and flushes them out.

    Without it I am a victim of night sweats and hot flushes with it they disappear altogether

    Thank god for selenium.

    It is found in the body naturally and we are supossed to get adequaute amounts of it through the food we consume but because soil is so depleted of it we do not get what we need.

    Please look up depleted selenium content of soil and see for yourselves

  8. koo

    Oh and yes you can take up to 200 mg per day anything more then that is not good, its not to difficult to understand, its like knowing a bottle of wine is probably going to give you a horrible hangover in the morning as opposed to a mere glass. Most of us are quite sensible and don’t need to be treated like supplement overdose idiots

  9. Koo – are you really claiming that up to 200mg per day of Selenium is OK and following that claim with the remark “most of us are quite sensible and don’t need to be treated like supplement overdose idiots”?

    Taking 200mg per day of Selenium is most certainly not OK – the FSA’s Expert group on Vitamins and Minerals set a Safe Upper Level of 0.45mg for total intake and in the 1989 study by Yang et al, 0.91mg was the mean intake at which marginal selenium toxicity occurred. Are you sure you didn’t mean ‘micrograms’ (µg) rather than ‘milligrams’ (mg)?

  10. Wulfstan

    Most of us are quite sensible and don’t need to be treated like supplement overdose idiots

    Of course not. But maybe people who don’t understand the difference between milligrams and micrograms could do with some assistance. Especially if there are concerns that large doses might be co-carcinogenic. Patient UK has some useful information.

    Koo – it would be reassuring to know that you don’t give nutritional advice to anyone who would heed you.

  11. LeeT

    “Over-supplementation with selenium is risky because the difference between safe and toxic does is relatively small. Safe upper levels are set for adults at no more than 450 micrograms per day. Toxic effects are seen at levels as low as 900 micrograms per day. In China, nutritionists linked doses as high as 5 milligrams of selenium a day (90 times the RNI) to thickened but fragile nails, hair loss, and perspiration with a garlicky odour.” (Nutrition for Dummies, John Wiley & Sons, p.140)

    Brazil nuts are a good soucre of selenium – you need only TWO of them to get the recommended RNI.

  12. koo

    0.45mg of selenium has no beneficial effects on the human body at all, none.

    These new safe upper limits are a nonesence
    note there is no safe upper limit imposed on aspartame

    Selenium is a very efficient anti carcinogenic

    I don’t need you guys to tell me that the selenium I take at the levels that I take it in are doing me harm because I see and feel nothing but benefits. This particular supplement has transformed my life.

    Your ‘safe upper limits’ do not take into account that everybody’s chemistry is different and some need more then others…………………..

    Your safe upper limits are part of the Codex standards that are being introduced in 2009 and I know what the motivation behind it is, its a shame you don’t but maybe one day you will figure it out.

    Codex is a trade commission not a health commission it is there to protect the interests of the pharms not individuals health

  13. gimpy

    koo, before you embarrass yourself further I have to point out that there is an order of magnitude difference between a microgram (µg) and milligram (mg). Such confusion is lethal with regards to selenium dosage. I pray to the great Dawkins that you are not taking such vast amounts nor telling other people to and that your statement merely represents a staggering scientific ignorance rather than actual clinical practice.

  14. Wulfstan

    You still can’t acknowledge that you don’t understand the difference between milligrams and micrograms? Do you even vaguely comprehend that you are advocating the consumption of 200,000 micrograms?

    Go on, Koo – post a picture of the bottle of supplements you are taking with a close up of the nutrient information label. Name the manufacturer and the product. State the number of pills that you take.

    Denial is a powerful and dangerous state. Once again.

    Koo – it would be reassuring to know that you don’t give nutritional advice to anyone who would heed you.

    You do realise that if somebody took you seriously you could kill them? Do you even vaguely comprehend the enormity of your error?

  15. gimpy

    Ooops! That should be three orders of magnitude not ‘an order of magnitude’. I just didn’t proof read my post. I do know the difference.

  16. Woobegone

    Koo, if you don’t believe us, believe BioCare :

    Even they don’t recommend more than 200 ug (0.2 mg) per day.

  17. Koo – re your throwaway line about there being no limit on aspartame: JECFA, SCF and COT established an Acceptable Daily Intake (ADI) of 40 mg/kg body weight/day and the English regulations on sweeteners set limits for sweeteners (including aspartame) in different types of food.
    SCF report on aspartame:
    The Sweeteners in Food Regulations 1995:

    You seem to have ignored my earlier reference to ‘micrograms’ (µg) and ‘milligrams’ (mg). Perhaps you will take note of Gimpy: “Such confusion is lethal with regards to selenium dosage”

  18. koo

    you seemed to of misplaced my reply

    anything to do with saying that the FDA and FSA are corrupt?

    or was it because I mentioned how in a normal day it was impossible to tot up the amount of aspartame you were consuming

    or was it because I mentioned aspartame seems to be an essential ingredient in pharms

    either way this is sedition, you know what you are doing

  19. Wulfstan

    Ooh, let’s see. What’s the more plausible explanation. HW have censored one of your ludicrous messages or you have somehow made a mistake.

    Well, we can see plenty of evidence of your comments getting through.

    We can see plenty of evidence of asinine mistakes that you make on a regular basis that you won’t acknowledge and blame others for.

    That wasn’t hard.

    Whatever your warblings about aspartame, jdc325 gave you some good information. It just seems like you are as incapable of understanding that as you are why you were advocating lethal doses of selenium. Whoever cultivated that over-blown sense of self-esteem in you, they did you no favours.

    With whatever remains of your sentient life, drag yourself along to Adult Ed. and acquire the skill of reading and learning plus some basic maths – in your case, it may literally save your life.

  20. Koo wondered why a post hadn’t got through: “was it because I mentioned how in a normal day it was impossible to tot up the amount of aspartame you were consuming”
    Quoting from the SCF report (my italics) –
    The available estimates of intake
    of aspartame by mean and high level consumers are fairly consistent among European
    countries, even though different approaches were used for the assessment. They show
    that intakes in high level consumers, including adults, children, and diabetics of all
    ages, range up to 10 mg/kg bw/day and thus are unlikely to exceed the current ADI
    for aspartame of 40 mg/kg bw established by the SCF (1985, 1989)

    “aspartame seems to be an essential ingredient in pharms” –
    Erm, as opposed to natural products like vitamins and minerals? Check out the chewable vitamin tablets and capsules available – many contain one or more of the following intensive sweeteners: aspartame, acesuflame K, sodium cyclamate. Aspartame is very common indeed in food supplements. Why focus on its presence in pharmaceuticals?

    “the FDA and FSA are corrupt” –
    Do you have evidence for this or is this just another baseless, paranoid assertion?

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