Saw this discussed in comments and thought it deserved a real question. Antioxidants are hyped in nearly every news story from "green tea cures cancer!" to "blueberries do your taxes!" But others say they aren't so great and may even by poison.
Avoid or enjoy?
I don't think vitamins and other plant nutrients are healthy because they are antioxidants (with a possible exception for GI tract cancers, where there is direct contact with at-risk tissue). To help prove the point, see the following study showing people on flavinoid free diets don't show markers for increased oxidation (see the study here).
However, polyphenols/flavinoids have other effects than just their capacity to reduce oxidation. Many are anti-inflammatories. Many affect cellular nuclear receptors and thus have a direct impact on gene expression.
I agree that the antioxidant theory is bankrupt, but fruits and vegetables offer so much more than just antioxidants.
This is the best take on it I've read: Cooling Inflammation
Every time a plant product has an impact on a disease it seems to be attributed to its antioxidant activity. Plant products are active, because they bind to proteins. They bind to lots of different proteins.
And Stephan's comment
I remember seeing a presentation on curcumin and alzheimer's at a conference, I think it was by Dr. Greg Cole. I can't seem to find the notes right now, but the jist was that the effect was not due to its antioxidant properties, but to its drug-like effect on signaling pathways.
Polyphenols don't contribute significantly to the antioxidant potential of serum. Our serum antioxidants are primarily uric acid, vitamin C and vitamin E, with little to no contribution from these supposedly wonderful vegetable antioxidants. The increase in serum antioxidant capacity seen after ingesting certain plant foods is actually the result of increased serum uric acid! Often it's due to the fructose. You can get the same effect by drinking a Pepsi.
It's salesmanship. There is no direct evidence that supplementing antioxidant vitamins above what you can get from a nutritious diet is healthy. In fact, there's evidence that it's ineffective and even outright harmful in certain cases. Ironically, big doses of antioxidants can actually increase oxidation under certain circumstances. Furthermore, the whole concept that oxidation is a bad thing that we need to eliminate is incorrect. Excessive oxidation is a problem, but the body uses oxidation in a number of ways that are normal and beneficial.
I think this question on Rooibos tea inspired the current question.
Original post from Stephan of Whole Health Source touching on polyphenols similar to Acton's quote.
Conventional wisdom claims that there is strong evidence that fruit and vegetables are great for health and by association polyphenols. Don at Primal Wisdom does a good job showing how weak this evidence is.
As research on antioxidants has often been underwhelming (noted in the other posts), more attention is being directed towards anti-inflammatory compounds. This is the "sweet spot" of the paleo lifestyle. Neolithic foods cause inflammation, and eating "real foods" reduces inflammation. An oft-repeated aphorism is that "D is the new C." By being here, most of us probably believe this is truth and not just a fashion statement. Anti-inflammatory foods, and supplements such as vitamin D3, fish oil and niacin, are more effective for health and disease prevention than pharmacologic doses of antioxidants. Even statins are believed to lower cardiac events because of anti-inflammatory activity, not because they lower cholesterol. That said, I believe that you need to avoid deficiencies of antioxidant cofactors such as vitamin C to remain healthy. For example, adequate intake of selenium is essential for the function of the glutathione system, one of the most important antioxidant systems in the body ( http://ajpregu.physiology.org/cgi/content/full/291/3/R704 ). I believe that we should enjoy "real food" antioxidants in vegetables, berries, fruits and nuts as part of our diet, but we should not go out of our way to take mass quantities of antioxidant supplements.
Interesting post on the subject by Dr. Eades:
From Loren Cordain, Ph.D., Professor latest Paleo Diet Email
Epigenetics is defined as the science studying changes in phenotype or gene expression by mechanisms other than changes in DNA nucleotide sequence1. The phenotype is someone's appearance which it's determined by the genotype (stable and heritable) and the environment (nutrition and other lifestyle factors) which give place to the epigenotype (heritable, labile and rapid)1. Epigenetic changes are controlled, among other mechanisms, by methylation and histone modification. Altered methylation pattern and histone modification may lead to increased susceptibility to disease. E.G. cancer is associated to generalized hypomethylation and localized promoters hypermethylation1. Histone manipulation may also increase or decrease disease susceptibility2.
Both, methylation and histone manipulation are under the control of dietary substances. For example, methylation depends on SAMe availability, which in turn is influenced by vitamin B6, vitamin B12 and folate intake3, and long chain polyunsaturated fatty acids such as DHA4. On the other hand, certain substances such as garlic, horseradish, fiber, blueberries, apple, onion, nuts, berries, red grapes, broccoli, etc. are known nutrients involved in histone modification2.
The Paleo Diet is rich is all of these nutrients5, hence it may exert positive effects upon epigenetics machinery leading to decreased disease susceptibility. Decreased availability of micronutrients is associated to disease severity, probably, through complex epigenetic mechanisms, and supplementation could improve those symptoms3. Improved epigenetic is influenced by metabolic programming during foetal and early life. These two periods are crucial for the developing newborn and future adult's health. Hence, The Paleo Diet may confer protection against several diseases improving the epigenetic programming.
We have unique detoxification systems (liver P450 enzymes) and other routes... we are all so different! Bruce Ames in some unique studies showed that just deficiency in one dietary component e.g. vitamin B6 or folate, etc was associated with just as DNA damage from radiation.
If food cannot be complete for a variety of reasons (no compost, no fertilization, non-organic, lack of soil minerals) then it would be prudent to supplement in same way if silent damage is occurring... for optimal enzyme, protein, hormone and neurotransmitter synthesis and maintenance. The S.A.D. and environmental pollutants are tough opponents for those for whatever reason are susceptible... (like me).