=biology =food =health
Linus Pauling was
a chemist who won a Nobel Prize in Chemistry in 1954. He later became
well-known for advocating large doses of Vitamin C.
I've heard that
advocacy referred to as a cautionary tale, but I've long had a bit of
sympathy for Linus, and I'm writing this post to explain how and why.
mainstream nutrition
One reason for my sympathy for Linus is that I've heard him used as an
example of why you shouldn't go off on your own instead of trusting
mainstream views in a field, yet his advice, while not particularly helpful,
caused much less harm than contemporary "mainstream nutritional advice",
such as:
- the food
pyramid
- "partially hydrogenated vegetable oil is healthier than
butter"
- "a very-low-fat diet is healthy"
- "eating very little salt
is healthy"
I certainly wouldn't suggest trying to independently compete with the conceptual framework of, say, semiconductor physics or structural engineering, but when a field is rotten enough (nutrition, psychology, education, and economics come to mind) history indicates to me that someone smart from another field is often more correct than specialists on that topic, when they have an interest in it.
my view of Vitamin C
To be clear, I'm not advocating for the very high doses of Vitamin C
that Linus did. I do think the World Health Organization's RDA (45 mg/day)
is a bit low, but the RDA of Japan and the EU (~100 mg/day) seems entirely
reasonable to me.
Amounts above that generally don't have much effect
on blood levels of Vitamin C, because it's absorbed less and the excess is
expelled. Thus, some people have advocated administering it by IV, but one
has to consider the possibility that there's a good reason for a specific
level being naturally maintained.
Research since Linus first
advocated for Vitamin C megadoses has supported oxidative stress being a
major cause of aging. It's associated with many problems (Alzheimer's comes
to mind) and there's a good theoretical basis (DNA I-compounds) for its
long-term harms. We've also seen that previous suggestions for Vitamin D
doses were much too low, so there's also precedent for that.
Where,
then, did Linus go wrong?
Vitamin C is an antioxidant, but it's
also a
pro-oxidant. It can reduce iron and copper, which can then react with
hydrogen peroxide or oxygen to form hydroxyl radicals or peroxide ions. It
can also form some complexes with metal ions that could conceivably have
some harmful catalytic effects. (Its ability to interact with metal ions in
certain ways is the main reason it's used in cells rather than some other
compound: it's a cofactor.) The normal levels of free Fe and Cu ions are
low, but my view is that the natural blood level of Vitamin C is a
compromise set by pro-oxidant effects.
When an infection happens that
causes hypochlorite production by immune cells, it's logical that the
optimal level of Vitamin C would be higher. And indeed, there's evidence
that extra Vitamin C during infections (especially bacterial infections)
helps somewhat. But the main antioxidant in mammals seems to be
glutathione rather
than Vitamin C, and it has to be used in combination with superoxide
dismutase.
So, Linus was one the right track. He was trying to solve
the right problem, and he found a reasonable solution to it, but he
overlooked some complicated side effects. That's a mistake I consider
forgivable. He should have realized that there was a reason for homeostasis
of Vitamin C levels, but the ideology of his time was that biological
regulatory systems were so ineffective that any deliberate management by
people would be better. There were, thus, people optimizing the balance of
purified starch/fat/protein diets they fed rats, and being puzzled when the
rats kept dying. Then, as soon as they discovered essential vitamins and the
rats weren't dying anymore, they immediately declared victory and
recommended people follow their new scientific diet.
conclusion
Different antioxidants are not fungible. Some are enzyme cofactors, there
are different side effects, there are membrane-bound antioxidants, specific
enzymes some antioxidants need to be used with, and so on. But when I see
people even today pushing quinoa or "raw water" or burnt food or fad diets,
I can't blame Linus Pauling too much for not having understood that.