A little bit of regular harm does you a lot of good.
If we are going to biofortify foods with extra doses of beneficial chemicals that are not essential nutrients, such as resveratrol found in grapes (see A GM wheat that prevents Alzheimer’s disease, extract below) or with polyphenols that are found in berries, it behooves us to understand what they do to us.
Polyphenols, Hormesis and Disease: Part IIIn the last post, I explained that the body treats polyphenols as potentially harmful foreign chemicals, or “xenobiotics”. How can we reconcile this with the growing evidence that at least a subset of polyphenols have health benefits?
Clues from Ionizing Radiation
One of the more curious things that has been reported in the scientific literature is that although high-dose ionizing radiation (such as X-rays) is clearly harmful, leading to cancer, premature aging and other problems, under some conditions low-dose ionizing radiation can actually decrease cancer risk and increase resistance to other stressors (1, 2, 3, 4, 5). It does so by triggering a protective cellular response, increasing cellular defenses out of proportion to the minor threat posed by the radiation itself. The ability of mild stressors to increase stress resistance is called “hormesis.” Exercise is a common example. I’ve written about this phenomenon in the past (6).
The Case of Resveratrol
Resveratrol is perhaps the most widely known polyphenol, available in supplement stores nationwide. It’s seen a lot of hype, being hailed as a “calorie restriction mimetic” and the reason for the “French paradox.”* But there is quite a large body of evidence suggesting that resveratrol functions in the same manner as low-dose ionizing radiation and other bioactive polyphenols: by acting as a mild toxin that triggers a hormetic response (7). Just as in the case of radiation, high doses of resveratrol are harmful rather than helpful. This has obvious implications for the supplementation of resveratrol and other polyphenols. A recent review article on polyphenols stated that while dietary polyphenols may be protective, “high-dose fortified foods or dietary supplements are of unproven efficacy and possibly harmful” (8).
The Cellular Response to Oxidants
Although it may not be obvious, radiation and polyphenols activate a cellular response that is similar in many ways. Both activate the transcription factor Nrf2, which activates genes that are involved in detoxification of chemicals and antioxidant defense**(9, 10, 11, 12). This is thought to be due to the fact that polyphenols, just like radiation, may temporarily increase the level of oxidative stress inside cells. Here’s a quote from the polyphenol review article quoted above (13):
We have found that [polyphenols] are potentially far more than ‘just antioxidants’, but that they are probably insignificant players as ‘conventional’ antioxidants. They appear, under most circumstances, to be just the opposite, i.e. prooxidants, that nevertheless appear to contribute strongly to protection from oxidative stress by inducing cellular endogenous enzymic protective mechanisms. They appear to be able to regulate not only antioxidant gene transcription but also numerous aspects of intracellular signaling cascades involved in the regulation of cell growth, inflammation and many other processes.
It’s worth noting that this is essentially the opposite of what you’ll hear on the evening news, that polyphenols are direct antioxidants. The scientific cutting edge has largely discarded that hypothesis, but the mainstream has not yet caught on.
Read the rest at The Whole Health Source.
Related stories from the GMO Pundit Archive:
May 12 2006: A GM wheat that prevents Alzheimer’s disease?
…avoid the alcohol intake of wine (and risks of cancer and car accidents) and eat a new GM wheat instead. It is now possible to get the grape chemical resveratrol in a new GM wheat, which should provide the health benefits of red wine without the bother. Grain Biotech Australia, an agbiotech company based in WA , has developed an experimental GM wheat containing resveratrol that protects against cardiovascular disease despite a high-fat diet. This might be away to avoid the side effects of indulging in red wine to gain the benefits of the resveratrol.
June 12 2009: More about the French paradox
March 29 2009: Cooking causes organic vegetables to lose phytochemical advantages and The antioxidant capacity and polyphenol content of organic and conventional retail vegetables after domestic cooking