effort to inform the public about the likelihood of certain risks and the possible benefits of dietary modification and (2) the use of technological and other means (e.g., production of leaner meat) to facilitate dietary change.
The process of arriving at dietary recommendations, rather than the recommendations themselves, previously has received little attention. One relevant attempt is the development of the Public Health Objectives for the Nation by the Office of Disease Prevention and Health Promotion of the U.S. Department of Health and Human Services (DHHS, 1983). That office proposed 17 priority objectives for improving nutrition during the 1990s as well as an implementation plan for meeting these objectives. A midcourse review of the status of these objectives documented the process of developing the objectives and suggested that substantial progress has been made in achieving certain nutrition-related objectives (DHHS, 1986). The logic, criteria, and philosophy for formulating dietary recommendations are also discussed in reports by the Health Education Council in the United Kingdom (NACNE, 1983), the American Heart Association in its Dietary Guidelines for Healthy American Adults (AHA, 1986), the National Research Council's Committee on Diet, Nutrition, and Cancer (NRC, 1982), and a Food and Nutrition Board report entitled Toward Healthful Diets (NRC, 1980b).
Several individual attempts to define or analyze the process of developing dietary recommendations also provide insights into the philosophy underlying recommendations issued in different countries (e.g., Grobstein, 1983; Langsford, 1979; Molitor, 1979; Palmer, 1983). The committee hopes to contribute to this nascent field through the discussions that follow.
A special feature of the present study is its attempt to develop recommendations and strategies for risk reduction across the entire spectrum of major diet-related chronic diseases. Several factors were considered in this process: risks and benefits; the advantages of making recommendations by nutrient, by food, or by dietary pattern; the basis for proposing quantitative as opposed to qualitative recommendations; recommendations for individuals as opposed to populations; and the feasibility of implementation. These are discussed in the following sections.
To develop dietary recommendations for reducing the overall risk of diet-related chronic diseases, it is essential to analyze and compare recommendations pertaining to individual diseases. For example, recommendations to increase calcium intake to provide possible protection against osteoporosis might in isolation be viewed as conflicting with recommendations for coronary heart disease (CHD) prevention, because dairy productswhich contribute the most calcium to the U.S. dietare also major sources of saturated fatty acids (SFAs), which are known to increase plasma cholesterol levels and CHD risk. Thus, recommendations for maintaining adequate bone mass and for preventing CHD would both have to stress consumption of low-fat dairy products.
Other important considerations are dietary interactions and their synergistic or antagonistic effects. For example, the potential benefits of enhanced trace element intake for certain cancers might be offset by increasing the intake of vegetables and cereals in an attempt to reduce risk for colon cancer, because such foods are also high in fiber, which could in principle initially inhibit intestinal absorption of certain trace elements.
As exemplified systematically at the end of this chapter, the committee considered such potential risks as well as dietary interactions and dose-response relationships in assessing the probable impact of dietary modification on risk factors across the range of chronic diseases. To some extent, this task was simplified by the inherent concordance in dietary risk and protective factors. For example, a recommendation to lower fat intake would be consistent with evidence that low-fat intake may reduce the risk of certain cancers and with stronger evidence that decreased SFA and cholesterol intakes reduce cardiovascular disease risk.
The committee discussed whether to base its recommendations on individual nutrients, single foods or food groups, or the overall pattern of dietary intake. Nutrient-based recommendations (e.g., fluoridation of water for the general population or iron fortification to reduce the risk of iron deficiency) might be easy for public health personnel to interpret and implement (e.g., through supplementation or food fortification); however, they may fail to take into account needs that arise from interactions among nutrients (e.g., increased selenium requirements for those on a high-vitamin C diet or enhanced iron absorption in the presence of vitamin C). Furthermore, such recommenda-