Functional Foods: Benefits, Concerns and Challenges

During the first 50 years of the 20th century, scientific focus was on the identification of essential elements, particularly vitamins, and their role in the prevention of various dietary deficiency diseases. This emphasis on nutrient deficiencies or “undernutrition” shifted dramatically, however, during the 1970s when diseases linked to excess and “overnutrition” became a major public health concern. Thus began a flurry of public health guidelines, including the Senate Select (McGovern) Committee's Dietary Goals for the United States (1977), the Dietary Guidelines for Americans (1980, 1985, 1990, 1996, 2000— a joint publication of the USDA and the Department of Health and Human Services), the Surgeon General's Report on Nutrition and Health (1988), the National Research Council's Diet and Health (1989) and Healthy People 2000 and 2010 from the U.S. Public Health Service. All of these reports are aimed at public policy and education emphasizing the importance of consuming a diet that is low in saturated fat, and high in vegetables, fruits, whole grains and legumes to reduce the risk of chronic diseases such as heart disease, cancer, osteoporosis, diabetes and stroke.

All foods are functional to some extent because all foods provide taste, aroma and nutritive value. However, foods are now being examined intensively for added physiologic benefits, which may reduce chronic disease risk or otherwise optimize health. It is these research efforts that have led to the global interest in the growing food category now recognized as “functional foods.” Functional foods have no universally accepted definition. The concept was first developed in Japan in the 1980s when, faced with escalating health care costs, the Ministry of Health and Welfare initiated a regulatory system to approve certain foods with documented health benefits in hopes of improving the health of the nation's aging population (1). These foods, which are eligible to bear a special seal, are now recognized as Foods for Specified Health Use (FOSHU).3 As of July 2002, nearly 300 food products had been granted FOSHU status in Japan.

In the United States, functional foods have no such regulatory identity. However, several organizations have proposed definitions for this new food category. In 1994, the National Academy of Sciences' Food and Nutrition Board defined functional foods as “any modified food or food healthcare ingredients that may provide a health benefit beyond the traditional nutrients it contains” (2). The International Life Sciences Institute defines them as “foods that, by virtue of the presence of physiologically-active components, provide a health benefit beyond basic nutrition” (3). In a 1999 position paper, the American Dietetic Association defined functional foods as foods that are “whole, fortified, enriched, or enhanced,” but more importantly, states that such foods must be consumed as “… part of a varied diet on a regular basis, at effective levels ” for consumers to reap their potential health benefits (4).Claims linking the consumption of functional foods or food advanced health ingredients with health outcomes require sound scientific evidence and significant scientific agreement. The Food and Drug Administration (FDA) outlined the criteria for “significant scientific agreement” in a guidance document released on December 22, 1999 (7). As summarized in the schematic shown in Figure 1, there is a clear discrepancy between “emerging evidence” (characterized by in vitro or animal studies, uncontrolled human studies, as food additives, now on the market including L. johnsonii La1, L. reuteri, L. GG, and L. casei Shirota. A recent Scientific Status Summary on probiotics from the Institute of Food Technologists summarized the scientific support for the therapeutic and/or preventive use of these functional ingredients for various health concerns including cancer, intestinal tract function, immune function, allergy, stomach health, urogenital health, cholesterol lowering and hypertension (17). The review emphasizes that the future success of probiotics will require strong support from medical and nutrition scientists and that studies documenting these effects in humans are limited.

Functional foods of plant origin (Natural Plant Extract)

Numerous plant foods or physiologically active ingredients, such as pharmaceuticals, derived from plants have been investigated for their role in disease prevention and health. However, only a small number of these have had substantive clinical documentation of their health benefits. An even smaller number have surpassed the rigorous standard of “significant scientific agreement” required by the FDA for authorization of a health claim, which will be discussed in further detail below. Those plant foods currently eligible to bear an FDA-approved health claim include oat soluble (β-glucan) fiber (26), soluble fiber from psyllium seed husk (27), soy protein (28) and sterol- and stanol-ester–fortified margarine (29).Although there is evidence that certain functional foods or food ingredients can play a role in disease prevention and health promotion, safety considerations should be paramount. Safety concerns have recently been raised, particularly with regard to the seemingly indiscriminate addition of botanicals to foods. A plethora of “functional” bars, beverages, cereals and soups are being enhanced with botanicals, some of which may pose a risk to certain consumers. The safety issues related to herbs are complex