Only recently has there been a lab study where underfeeding did not increase life span. The only difference between this study and others was the sources of the foods consumed. Typically, after establishing diet criteria, one uses the cheapest food available, but this study followed a procedure close to what the CRONies did, choosing foods by nutrient density and this change seems to be important.
Reductio ad absurdum
I decided to find the foods with the fewest calories that would have all the nutrients necessary (using my current age and weight for a reference, where that would make a difference). I could do it on 1168 calories, in a diet that does not look particularly appetizing:
1/4 tsp. iodized salt
3.2 oz. can Atlantic sardines
1 c. cooked spinach
1/4 c. raw sunflower seeds
1 1/2 c. raw (medium firm) tofu
1 1/2 c. raw cremini/portobello mushrooms
4 shiitake mushrooms
1 c. cooked lentils
1 c. raw (green) bell pepper
2/3 c. sun-dried tomatoes
1/2 c. wheat bran
This diet turns out to get 34% of its calories from protein and 43% from fat. A very large percentage of the carbohydrates are fiber. This makes it an extremely low carb diet. [For reference in the following discussion, this diet contains 1900 mg. of methionine]
It may be the method of obtaining "optimum nutrition" that made the difference in this study, as the amount of fat and protein is much higher and the amount of carbohydrate is much smaller than in the other studies. As those societies studied who live longest had only 10-15% of their calories from protein and 10-15% from fat, the CRON group may have chosen the wrong foods. It is not the calorie restriction itself that seem to be important, but restriction of some nutrient, for increased longevity.
Which nutrient(s) might be crucial? The difference between the studies suggested that it was one or two of the 9 essential amino acids and the leading candidates were methionine and tryptophan. A quick survey of foods shows that restricting one of these is indistinguishable from restricting the other. One questionable animal study has recently shown that it is methionine restriction that is crucial for lifespan extension. Interestingly, methionine restriction is sometimes used with cancer patients to starve rapidly growing tumors.
A very BIG "however"
It is essential to ingest methionine in order to live. The challenge, then, is to find a diet that supplies adequate, but minimal, methionine (the exact amount is debatable, but 600 mg/day is definitely too low and 1200mg/day is probably too high), and has everything else in abundance. Here's food groups ranked by methionine content:
very high: meats, fish, poultry, eggs, milk and dairy products
high: grains and legumes
very low: fruit
The reason for the long-lived groups mentioned in part 1 having near-vegan diets suddenly becomes apparent in this context. If one tries to create a diet that is low in methionine, one starts with fruit and one quickly discovers that some nutrients are very difficult to get in adequate amounts, such as calcium, zinc, riboflavin and linoleic and linolenic acids. Adding foods that are high in these creates a new problem: excessive copper and (especially) manganese.
A 2000 calorie diet that meets the requirements:
11 cups of water
1/4 tsp. iodized salt
1/4 oz sunflower seeds
1 Tbsp. (whole) sesame seeds
2 tsp. flax seeds
1/2 oz. almond
1 Tbsp. sunflower or safflower oil
3/4 c. cooked beans (lentils, black beans, pinto beans)
1/2 c. raw onion
1c raw asparagus (or other green vegetable: cucumber, bell pepper, celery, endive)
2 Tbsp. tomato paste
1/2c. canned turnip greens (or collard or mustard greens)
2 oz. (dry measure) brown rice
1 1/2 c. cooked white rice
2 Tbsp dark molasses (Brer brand)
1/2 c. cooked white button mushrooms
banana (7 inch)
1 oz. dried apricots
apple (3-3.5 in.)
1/2 c. raw firm tofu
1 c. raw broccoli
1 oz. oats
baked potato with skin (2 1/4-3 1/4 inch)
Vitamin B-12 supplement
Vitamin D supplement
This diet is remarkably similar to the one suggested by Mark Fuhrman in his book "Super Immunity," though he came about it in a completely different way, starting with antioxidant content (he would avoid the white rice, molasses, oil and probably the potato and supplements, though I couldn't do that without obtaining dangerous amounts of manganese).
The diet above is about 20% fat and only 10% protein, which is probably the absolute bare minimum of protein possible. It has 900 mg. of methionine.
The thing not being considered here, however, is exercise (animals that are underfed tend not to move very much). That will be the focus of the next part of this series.
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