Oxidation and Glycation
When you leave a banana unpeeled for very long, or bite into an apple and wait, what happens? That brown color begins to appear. This is oxidation.
What happens after sugar is heated and melts in a pan, or when vegetables are pan fried? The brown that occurs in these cases is a result of caramelization, which is a chemical change involving internal rearrangement of sugar molecules. The physiological term for this is glycation. It is a similar chemical change that turns paper yellow over time.
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Hmm,
ReplyDeleteSome damaging evidence against the oxidative theory of ageing came out in the last decade; only 1 of 18 genetic manipulations of antioxidant enzymes (up or downregulation) has a significant effect on rat lifespan. Previous research was only associative (lifespan and oxidative stress). It clearly needs more research before we tell people that antioxidants are the solution.
Other areas that support this conclusion are the large antioxidant vitamin trials which are finding no effect on disease outcomes.
Also, I recommend searching medline on hormetic theory. Hormesis suggests that subtoxic exposure to ROS induce adaptations which upregulate endogenous antioxidants and induce signaling networks which in fact may be the reason exercise, calorie restriction, and phytochemicals have health and longevity benefits. Essentially free radicals are how we adapt to handle stress. Also some "anti"oxidants may actually be prooxidant in vivo, which may in fact be why they are beneficial. There are also studies which suggest that antioxidant vitamins may diminish the beneficial effects of exercise (eg mitochondrial biogenesis) in large doses.
It is all quite fascinating.