John Bryson writes: "Eating less of one amino acid might lengthen your life. There have been lots of previous studies showing that many species live long on highly restricted calories, but a lot of this benefit may be possible by only restricting one amino acid. Amino acids that have shown this have been tryptophan and methionine. A recent study, published online December 2 in Nature, a highly respected journal, may help explain some of the health benefits of restricted-calorie diets. Grandison, R.C., Piper, M.D.W., and Partridge, L. 2009. Amino-acid imbalance explains extension of lifespan by dietary restriction in Drosophila. Nature, published online Dec. 2. doi:10.1038/nature08619"