NUTRACEUTICALS. There are many ways to think about food. In the simplest sense, food is fuel. Food provides the energy needed to perform daily functions and maintain normal metabolic processes. But we all know that food is more than fuel. Food contains nutrients that are essential to prevent diseases. For example, scurvy will occur if vitamin C is not continually present in the human diet. Similarly, blindness can occur where diets are deficient in vitamin A. The "essential nutrients"—those that are needed to prevent specific diseases—have been a major focus of human nutrition research for the past century. Through this research we have determined the amount of each essential nutrient required to prevent disease in populations of various ages, cultures, and genetic predispositions. What is interesting, however, is that the link between diet and disease, or more important, diet and health, cannot be entirely explained by the absence or presence of the various essential nutrients in our diets. And so today, a multitude of components that are found in foods are being investigated to determine what, if any, role they play in maintaining health and reducing the risk of disease. Numerous phytochemicals (plant chemicals) that occur in fruits and vegetables are taking center stage in this research, as more evidence accumulates regarding their health-promoting properties (Beecher, 1999).

Human Nutrition Research

Concurrent with these new activities in nutrition research is a reevaluation of the medicinal practices of past and present cultures. These traditional medicines are based largely on the use of plant materials. Chinese medicine, which predates modern medicine by thousands of years, employs a vast array of botanical materials for the treatment of disease and the maintenance of health. Similarly, East Indian Ayurvedic medicine, early European folk medicine, and native North American medicine are based largely on the use of plant materials.

Health-Promoting Foods

Today the exploration and exploitation of the diseasefighting properties of a multitude of phytochemicals found in both food and nonfood plants have created a renaissance in human health and nutrition research. At the same time, many opportunities for the development of novel dietary products have been created. With all new fields of study come new terms. "Nutraceuticals" and "functional foods" are two new terms used to describe health-promoting foods or their extracted components. Although debate continues regarding the exact meaning of these terms, it is convenient to consider nutraceuticals as healthful products that are formulated and taken in dosage form (for example, capsules, tinctures, or tablets). Functional foods, on the other hand, are products that are consumed as foods, and not in dosage form.

The beneficial role of many nutraceuticals and functional foods may relate to their protective effects against degenerative diseases, such as cancer and cardiovascular disease. Typically the active ingredient(s) in the food or supplement is believed to help the body combat metabolic processes that lead to degenerative conditions. In this way, supplementing the diet with beneficial phytonutrients may reduce the risk of degenerative diseases during aging. These concepts are well illustrated by the example of dietary antioxidants.

There is overwhelming evidence to suggest that oxygen and its highly reactive by-products are responsible for oxidative damage ("rust") to biomolecules in our bodies. Oxidative damage to biomolecules is believed by many to be a significant factor in the etiology of many degenerative diseases and the aging process itself. Oxidative damage to cellular DNA is an underlying element in the initiation of cancer. Similarly, oxidative damage to low-density lipoprotein in the blood is a causal agent in the development of atherosclerotic plaque in cardiovascular disease. It has been suggested and supported by various types of evidence that consuming antioxidants may provide greater protection against the deleterious effects of oxidative damage (Ames et al., 1993).

Several groups of plant phytochemicals, including carotenoids, tocopherols, and polyphenolics, are extremely effective antioxidants; these antioxidants are found at various levels in fruits, vegetables, and nonfood plants. Thus, with respect to the terms "nutraceutical" and "functional foods," a fresh or processed fruit or vegetable that is particularly high in antioxidant phytochemicals could be considered a functional food. The high antioxidant level may be a normal characteristic of the plant, or may be due to phytochemical fortification during manufacture of a processed food product. A nutraceutical may be an antioxidant phytochemical concentrate, having been extracted from raw materials and formulated as a standardized capsule or tablet (Hasler, 1998).

Challenges and Opportunities

The field of nutraceuticals and functional foods is new, and many gaps exist in the knowledge base. For example, it is widely accepted that the health-promoting properties of foods are not necessarily due to single components, but rather a few or several active ingredients. This creates a significant paradigm shift from the pharmaceutical model, which is based on the efficacy of single agents. Many of the bioactive phytochemicals under investigation have long been ignored, thus methods for their handling and measurement are lacking. Manufacturers wish to make specific claims of health benefits on their product labels. Clearly such claims must be based on solid scientific evidence, which to date is often lacking. Government regulatory bodies also face challenges in this new category of health products, which lies between foods and drugs. However, all parties share the desire to improve personal and public health through diet modification, to reap the consequent social and economic benefits.

The field of nutraceuticals and functional foods is at times confused, or at least lumped together with the field of biotechnology and genetic modification. The two areas are distinctly different, although there is some potential for overlap. Techniques in genetic modification may be applied to enhance the phytochemical content of food and nonfood plants. Although the complex series of biochemical reactions used by plants to synthesize specific phytochemicals is often not well understood, there is tremendous potential to harness the plant's sophisticated biochemical machinery to synthesize valuable compounds and ultimately enhance human health.

See also Antioxidants; Biotechnology; Crop Improvement; Dietary Assessment; Dietary Guidelines; Ethnobotany; Ethnopharmacology; Functional Foods; Genetic Engineering; Vitamins.

Wilhelmina Kalt