Wednesday, 13 February 2013

The antioxidant myth


A recent Scientific American article challenges the myth of antioxidants being associated with ageing. This is not the first time SciAm has covered this topic (here, here and here). The article challenges current perceived wisdom, not only regarding the effectiveness of anti-oxidants but of the underlying theory that oxidative damage causes ageing.  The current evidence tells us that antioxidant supplementation is not only ineffective, it is harmful. The sorry story of antioxidants should really be one of my “Lessons from History” blogs, except that it has not yet been relegated to history. But the story still provides lessons.

The Decline Effect
The science behind the association between oxidative damage and ageing is a classic example of the Decline Effect. The initial studies showing an association between decreased life expectancy in worms and damage from oxygen free radicals have not been adequately replicated. Later studies showed no such association and more recent studies showed the opposite effect: longer life span and evidence of free radicals triggering cellular repair. In other words, the initial findings “declined” over time.

The clinical research is also against antioxidants. The balance of evidence shows that anti-oxidant supplements (such as vitamin A and vitamin E) are associated with an increase in the rate of early death (JAMA review, Cochrane review).

Those reviews were from 2007/8. The pervasive nature of these myths, and our wish to believe them (our lack of scepticism) is responsible for the fact that antioxidants are still being advertised as useful, despite being the opposite.

Outsmarting nature?
I think this is also an example of trying to outsmart nature. While it is established that eating fresh fruit and vegetables is healthy, when we try to get clever and reckon we know the one magic ingredient responsible for the benefit, everything falls down. It is a measure of our hubris that we believed that we could explain the cause of ageing so simply. As usual, things are more complicated than we thought, and there are always unintended consequences of any treatment.

The bottom line
Instead of trying to guess and extract a single magic ingredient from fresh fruit and vegetables, doesn’t it make more sense to just eat the fruit and vegetables? It’s probably cheaper, and it certainly tastes better.

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