Patrick Holford On Cell Studies and Antioxidants

August 19, 2010 at 8:50 pm (Nutritionism, Patrick Holford)

Here, Patrick Holford responds to a study that found “antioxidants suppressed DNA damage at low concentrations, but potentiated such damage at higher concentrations”.

Holford told the Irish Independent that he “isn’t convinced” by the Cedars-Sinai study:

“We don’t have the full study available yet and I think it’s significant that it is a cell study, rather than one carried out on humans,” he says. “We have to know that it’s a cell study and may have some limitations. The devil is in the detail.”

Holford says there is existing research to support taking higher doses of antioxidants.

“We already have studies on people taking high dose Vitamin C, for example, and there is data out there on things such as high dose Vitamin C reducing cardiac risk.” [Italics mine.]

So, in this instance at least, Patrick Holford is urging caution in the interpretation of an in vitro study. A study which led the authors to come to conclusions that are rather awkward for an advocate of high doses of antioxidants. Is Mr Holford always so cautious when it comes to the interpretation of cell studies?

In his Optimum Nutrition Bible, Patrick Holford made this statement: “AZT, the first prescribable anti-HIV drug, is potentially harmful, and proving less effective than Vitamin C.” This statement was ‘supported’ by a reference to a paper that described an experiment in HIV-infected T-lymphocytic cell lines. This has been covered by  Ben Goldacre here (with follow-up here and here).

Onto the second point: Holford’s interpretation of the existing research is at odds with mine. While Holford claims that “there is existing research to support taking higher doses of antioxidants”, the best available evidence does not seem to support his advocacy of high doses of antioxidants.

For example, there is the Cochrane review “Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases”.

The reviewers looked at 67 randomised trials and found that in the trials with a low risk of bias, the antioxidant supplements significantly increased mortality (RR 1.05, 95% CI 1.02 to 1.08). Here are the conclusions from the abstract:

We found no evidence to support antioxidant supplements for primary or secondary prevention. Vitamin A, beta-carotene, and vitamin E may increase mortality. Future randomised trials could evaluate the potential effects of vitamin C and selenium for primary and secondary prevention. Such trials should be closely monitored for potential harmful effects. Antioxidant supplements need to be considered medicinal products and should undergo sufficient evaluation before marketing.

If Patrick Holford isn’t convinced by a Cochrane review, it should come as no surprise that a single in vitro study leaves him cold. It seems that for Patrick Holford (and he’s far from alone here) evidence is only convincing when it supports a position you already hold.

Update, 20th August

I only gave one example of Holford’s approach to in vitro studies that have results / conclusions that apparently support his advocacy of vitamin pills. Here’s another…

From a newsletter sent out in 2008: “Of the five gene mutations they found in their volunteers, four could be restored to normal functionality by increasing intracellular levels of folate.” Here’s what HolfordWatch had to say:

…not only did Holford fail to link to the paper, he neglected to mention that the study tested the function of human gene variants by transplanting them into yeast cells – no actual humans were involved in the way that his summary suggested.