As for tryptophan, the body can't make it, so diet must supply this chemical, which is found poultry, meat, cheese, yogurt, fish, and eggs.

A diet that contains animal products, however, also supplies cholesterol to the body.

The body can't make it, so diet must supply tryptophan.

The diet does not supply adequate amounts of the vitamins and minerals the body needs.

"Probably they contain some trace elements our present diet is not supplying," Joe suggested.

For instance, a recommended 1,200 calorie diet would supply about 660 calories from carbohydrates, 180 from protein, and 360 from fat.

The body cannot manufacture some of these; therefore the diet must supply these.

The body does not manufacture certain fatty acids and the diet must supply these.

In general, a healthy diet typically supplies enough vitamin B6.

The diet of many people in poorer areas of the world does not supply enough protein.