More than 20 prospective studies have addressed components of diet and the risk of heart disease.

The type of fat consumed appears to be more important than the amount of total fat.

Trans fatty acids increase risk of heart disease while polyunsaturated and monounsaturated fats decrease risk.

There is controversy about whether it is optimal to substitute saturated fats with carbohydrate. An increase in carbohydrate tends to reduce the level of good high density lipoprotein (HDL) cholesterol in addition to total and low density lipoprotein (LDL) cholesterol. Thus, the reduction in heart disease risk may be less than predicted by the reduction of saturated fat alone.

Observational studies have consistently shown that individuals consuming diets high in vegetables and fruits (which are rich in antioxidant vitamins) had a reduced risk of heart disease.

Results of a number of randomized trials are now available and show largely no significant clinical benefits of antioxidant vitamins on heart disease.

Supplemental vitamin C, E, and beta carotene cannot be recommended in the primary prevention of CHD.

Taking supplements without clinical benefits could, in theory, increase the risk if individuals mistakenly avoid therapeutic lifestyle changes or drug therapies with proven benefits.