Much of the CHD protective effects of diet are mediated through the effects of diet on risk factor levels. The best studied are the effects of diet on lipoprotein levels and blood pressure. With these effects in mind, specific dietary recommendations have been made to reduce CHD rates among healthy Americans. Dietary modification will reduce risk factor levels in the majority of people and will have measurable impact on CHD rates in the nation (Table 9). In the treatment of patients, it is important to distinguish which lipoprotein and blood pressure abnormalities are amenable to diet and which ones require drug therapy. This distinction can be made by understanding the quantitative relationship between dietary intake and risk factor levels that has been presented here and by assessing the current dietary intake of the individual. There must be a significant change in dietary composition to produce a significant change in risk factor level. This point, although it appears obvious when stated, is a common source of confusion concerning the efficacy of diet. For individuals, most nonresponse to dietary change reflects the lack of a dietary change. Poor adherence, in turn, may be the direct result of inadequate diet counseling. Counseling with a registered dietitian may be useful not only in educating the high-risk patient concerning the nutrient content of food, but also in establishing the current dietary intake of the patient. Compliance is not the only cause of nonresponse. For some patients who are already following a CHD prevention diet, additional risk factor reductions may not be evident when minor dietary constituents are altered. Because the majority of the diet effect has already been achieved, this "nonresponse" should not be surprising. The benefit of a change in a minor dietary constituent may not be detectable above the random day-to-day variation in risk factor levels. Lastly, although true nonresponders to diet have been observed, at least for blood cholesterol levels, the prevalence of nonresponse or minimal response is less than 10% of the population. Although the small changes in risk factor levels achieved by diet cannot compare with the greater changes achieved by drug therapy, dietary therapy will always have an important place in altering the health of the United States and its people. For some individuals, dietary and lifestyle modification may be all that is needed for CHD prevention; for others, dietary and lifestyle modifications provide a foundation on which drug therapy can be added for maximum CHD risk reduction.