Appetite and social customs are unreliable guides for food choices, contributing to widespread disease.

Original passage

Those foods should be chosen that best supply the elements needed for building up the body. In this choice, appetite is not a safe guide. Through wrong habits of eating, the appetite has become perverted. Often it demands food that impairs health and causes weakness instead of strength. We cannot safely be guided by the customs of society. The disease and suffering that everywhere prevail are largely due to popular errors in regard to diet.