In the wake of more attention being drawn to the general ineffectiveness of ingested antioxidants as even a marginal tool for health and longevity, Randall Parker remarks in passing:
Biogerontologist Aubrey de Grey makes what to to my mind is a persuasive argument against the expectation that antioxidants will deliver large health benefits: The metabolic cost of making and retaining antioxidants in the body is pretty low. If antioxidants could deliver benefits as large as some of their advocates claim then natural selection would long ago have selected for mutations that boost body antioxidant levels. So why expect consumed antioxidants to deliver a big benefit?
So (I hear you asking) why wouldn't the body make more detoxifying enzymes even in the absence of foods consumed that up-regulate detoxifying enzymes? My guess is that those enzymes are more metabolically expensive to keep around.
Human metabolism certainly isn't the most effective possible from a perspective of longevity, but one would expect that any easily attainable and practical change that benefits health in youth would already have been selected over the generations. On the other side of the coin, simple changes that benefit health in old age and extend longevity do in fact exist, and have not been selected for - for example, mutations to boost the level of naturally occuring antioxidants in the mitochondria:
The catalase soaks up some portion of free radicals before they can attack your vulnerable mitochondrial DNA. Damage to this [DNA] leads to an unfortunate chain of events that causes entire cells to rabidly produce damaging free radicals and export them throughout the body. But stop a fraction of the original mitochondrial free radicals from attacking their birthplace, and you have slowed the rate at which one cause of aging happens - you have slowed down aging, and extended healthy life.
Evolution cares not for your old age - if you're past the point of reproductive fitness, you're on your own. So mutations that might help your longevity, but have little benefit in youth, are unlikely to have prospered and spread in the dark days of cave living, disease, parasites and short, brutish lives.
It seems there is something to be done with antioxidants and advanced biotechnology in combination, given the evidence to date of the effectiveness of targeting to the mitochondria via gene therapy or other clever science. But the salesmen of the "anti-aging" marketplace - those folk energetically waving pills and potions in your face today - are most likely sitting on a pile of junk and nonsense rather than any even marginally effective product.