Most systems included positive nutrients, that is, the nutrients that should be encouraged because of health benefits and shortfalls in the average diet of the population. However, the evidence for effects on health is less clearly known for positive than for negative nutrients.
One exception is fiber, which has a role in body weight regulation (Howarth, Saltzman, & Roberts, 2001), helps prevent type 2 diabetes (Salmerón et al., 1997), reduces total and LDL cholesterol (Queenan et al., 2007), and is associated with reduced risk of CHD (Truswell, 2002). FDA has evaluated the scientific evidence for fiber, particularly soluble fiber, and risk of CHD and issued health claim regulation for soluble fiber and risk of CHD (Code of Federal Regulations, 2008 amended-b). In the United States, the recommended intake of fiber is 14 g per 1,000 kcal consumed (Food and Nutrition Board. Institute of Medicine, 2002).
Evidence for single vitamins or minerals in chronic disease risk is less well established. Calcium and vitamin D have a critical role in bone development and prevention of osteoporosis. FDA has issued food labeling regulation to allow a health claim for calcium, vitamin D, and osteoporosis (Code of Federal Regulations, 2008 amended-a). Folate prevents neural tube defects, and FDA has issued regulations for health claims (Code of Federal Regulations, 2000 amended) and fortification (Code of Federal Regulations, 1996). Contradictory studies have confused the scientific community and the public, for example, with regard to vitamin E in heart disease and beta-carotene in cancer prevention. It is not possible to include in this report a full review of the literature on the role of micronutrients and disease risk.
A large number of potential positive nutrients could be included in a summary system, and the content of these nutrients (e.g., vitamins and minerals) varies greatly in foods. Some foods are good sources of particular vitamins or minerals but are low in other nutrients. Most threshold systems that include criteria for positive nutrients do not require that the food be a good source of all of the positive nutrients specified, but they do require that one or two of the nutrients are provided in a specified amount (e.g., ≥10% of the daily recommended value). In comparison to icon or rating systems, summary score systems apply criteria for positive nutrients to all foods rather than only foods that meet thresholds. Therefore, summary systems can test the impact of including specific positive nutrients to determine the overall nutritional quality of foods. Summary scoring systems can also test how the ratings of the foods related to overall diet quality. Most systems cap positive nutrients at a certain level or include only the nutrients intrinsic to the food (not added via fortification). The reasons for capping positive nutrients include to prevent the score from being overly influenced by a large quantity of a single nutrient and to prevent over-fortification by food manufacturers to meet a system's criteria.
Many systems base their inclusion of positive nutrients on those that the population consumes in less than recommended amounts, as reported in the DGA report (U.S. Department of Health and Human Services & U.S. Department of Agriculture, 2005). Although these nutrients are essential for health and their consumption should be promoted, some may question whether an FOP system is the appropriate method to encourage consumption.