Humans live longer when they exercise, eat lots of fruits and vegetables, keep body fat low, and restrict excess calories, meat and protein. The latest research show that restricting a certain protein building block called methionine may be more effective in prolonging life than restricting calories or proteins.
Caloric restriction with adequate intake of nutrients prolongs life in fruit flies, roundworms, and mice by increasing insulin sensitivity and heart function, and decreasing inflammation and the muscle wasting of aging. In humans, calorie restriction helps to prevent diabetes, heart disease and cancer. However, getting all of the nutrients you need while restricting calories is very difficult.
Anything that increases cell growth and increases production of new cells in your body appears to shorten lifespan. Your cells are programmed so that when food is scarce, cells lie dormant in an attempt to conserve energy to help you survive. However, when food is plentiful, extra calories stimulate new cell growth which ultimately shortens lifespan. Researchers have identified a protein in cells called TOR (Target Of Rapamycin) which promotes cell growth. Blocking TOR increases lifespan in yeast, worms, flies and mice (Aging Cell, September 2010). Caloric restriction and a drug called rapamycin block TOR to decrease cell growth and prolong life (Nature, July 8, 2009). However, rapamycin is not safe because it suppresses immunity to increase infections and it also markedly increases blood levels of triglycerides to increase risk of heart attacks.
The most potent dietary activators of TOR are amino acids, the building blocks of protein. Restricting protein lowers TOR and another major promoter of cell growth called Insulin-like Growth Factor-1 (Rejuvenation Research, October 2007). Restricting just one amino acid, methionine, extends the life of flies and mice as much as caloric restriction does (Medical Hypotheses, February 2009). Methionine is found primarily in animal products, and is very low in foods that come from plants. Eating a diet high in fruits and vegetables and low in meat and dairy products markedly restricts intake of methionine. Furthermore, this diet is much easier to follow than one that restricts calories.