A study has found a potential link between a common amino acid and lifespan, with some research suggesting that reducing intake of this amino acid may increase lifespan in animals. The amino acid in question is also used as an ingredient in some supplements, and there is evidence that it may have both positive and negative effects on health, including potentially reducing brain plaques in animal models of Alzheimer's disease. The impact of this amino acid on human lifespan, particularly in men, is still being explored.