Numerous foods and natural products are reputed to have lifespan-extending or other anti-aging benefits. For example, genistein (soy), gingerol (ginger) and curcumin (turmeric) have been shown to inhibit carcinogenesis in multiple tissues. A great deal of attention has been paid to resveratrol, the compound in grape skins (and therefore red, but not white, wine) that activates sirtuins and extends lifespan in model organisms, possibly by mimicking calorie restriction.

Each of these claims requires evidence, of course, from a more reputable and less biased source than the label on the side of a “nutraceutical” bottle (don’t get me started about the ethics of this industry). And this is why I always note papers like the following, and tuck them away in a corner of my mind — as well as in a folder in my desk, because someday (I fantasize) I’m going to sit down with all two hundred papers, do a meta-analysis, and figure out just how much candied ginger and soy milk I need to add to my green tea every day in order to reap the maximum benefit.

In the recent issue of Biogerontology, Unno et al. demonstrate that oral administration of catechin, a compound found in green tea (it’s in black tea too; there’s just less) delays neurodegeneration in a mouse model:

Almost all elderly people show brain atrophy and cognitive dysfunction, even if they are saved from illness, such as cardiac disease, malignancy and diabetes. Prevention or delay of brain senescence would therefore enhance the quality of life for older persons. Because oxidative stress has been implicated in brain senescence, we investigated the effects of green tea catechin (GT-catechin), a potential antioxidant, in senescence-accelerated (SAMP10) mice. The mouse is a model of brain senescence with short life span, cerebral atrophy and cognitive dysfunction. … We found that daily consumption of GT-catechin prevented memory regression and DNA oxidative damage in these mice. GT-catechin did not prolong the lifetime of SAMP10 mice, but it did delay brain senescence. These findings suggest that continued intake of GT-catechin might promote healthy ageing of the brain in older persons.

Caveats: these particular mice carry multiple genetic modifications that make them short-lived and prone to early cognitive decline. Labs routinely use senescent-accelerated mice in order (mostly) to save time; I used to frown on the practice until I realized that many human sufferers of age-related disease are also carriers of mutations that make them prone to early onset of the conditions in question.

One question that studies of this kind raise for me is whether the anti-oxidant function of the compound in question is responsible for the observed effect. Lots of compounds are anti-oxidants, though some are stronger than others, but just because a molecule can reduce reactive oxygen species doesn’t mean that this is the cause of all effects it might have on the body.

A good example is resveratrol, which is (chemically speaking) an antioxidant, but whose life-extension potency is thought to derive from its activation of sirtuins.

The reason why this is important: If any old antioxidant will do, then we should be looking for the strongest anti-oxidants that are orally bioavailable, non-toxic, and able to target all parts of the cell (water-soluble compounds like ascorbate/vitamin C are good in the aqueous/proteinaceous cytosol, wherease lipid-soluble compounds like tocopherol/vitamin E are better in the greasy mitochondrial matrix). Furthermore, there’s likely a point of diminishing returns, where antioxidant supplementation is doing the theoretically best job of dealing with endogenous oxidative stress. In other words, at some point one is just taking too many pills.

On the other hand, if these natural products that happen to be anti-oxidants protect against age-related diseases (or aging itself) in other ways, then it’s possible that they’ll act on multiple pathways and have synergistic effects in combination. This makes the optimization problem more complex, certainly, but no one ever said this was going to be easy.

I’m going to have some turmeric-garlic broccoli stir fry now, mostly because it’s delicious.

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