The throughput of the liver for many of the enzymatic reactions that it performs, either for converting harmful chemical compounds into harmless substances, or for generating some conditionally-essential nutrients from precursors present in food, decreases in older people.

Because of this, when older, one should pay more attention to observing a healthy diet, which contains smaller amounts of harmful substances (e.g. alcohol) and enough quantities of all nutrients, including those that can be produced by a human body, but in insufficient quantities in older people (e.g. long-chain omega-3 fatty acids).