These are some notes I’ve collected which I place here while collecting my thoughts to write something longer.
Most will be familiar with the phenomenon of calorie restriction (CR) and the fact that it dramatically increases both mean and maximum lifespan in many different species of animals, from yeast to mammals.
It turns out that CR usually also amounts to protein restriction, and that is the true driver of the CR effect on longevity. Furthermore, recent research has determined that the restriction of only one amino acid is responsible for the increasing longevity seen in CR, and that is methionine. See this abstract for an explanation. (Interesting to note that a great deal of this work has been done in Spain, ranked 9th in the world in scientific output.)
Methionine restriction works through several pathways, such as increasing insulin sensitivity, decreasing visceral fat, and lowering IGF-1 levels, as well as decreasing the production of oxygen radicals by mitochondria. Methionine restriction also increases blood glutathione levels – that’s a good thing.
A number of humans are attempting calorie restriction; however, it appears that until now they’ve been blowing it, at least partially, because they increased their protein intake, or didn’t change it, and while they have received benefits in the form of lower blood pressure and better cardiovascular disease markers, their serum IGF-1 levels did not decrease, thus denying them full benefits. But (same paper), when protein levels were restricted, IGF-1 levels plummeted within weeks.
All this is interesting because calorie restriction, though it might bring huge health benefits for humans, is something that only highly disciplined people can carry out. But restricting protein ought to be pretty easy – no need to go hungry.
Which diet is lowest in protein? Score one for the vegans. (That’s from my favorite journal.)
On the other hand, it’s pretty clear that restricting carbohydrates in the diet is also a good strategy for health, and vegans usually have a high carb intake. (CR research has shown that neither carbohydrate restriction nor fat restriction is responsible for CR longevity effects.) It seems that a good strategy for those desiring to pursue both protein and carbohydrate restriction might be the Kwasniewski or “Optimal” diet.
From an evolutionary point of view, it’s thought that CR works because in conditions of food scarcity, it allows an animal to “survive and fight another day”. Methionine, the protein constituent which appears to be the driver of CR, is an essential amino acid in humans, found most abundantly in meat. Methionine scarcity – and I’m speculating here – appears to be an indication of scarcity in general; it would be the first dietary element to disappear when conditions of scarcity begin; so it makes sense that its restriction causes CR longevity effects.
