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Scientific Advances in Animal Nutrition: Promise for the New Century, Proceedings of a Symposium 3 Designing Foods: Feeding Animals to Reduce Human Health Risks BRUCE A. WATKINS Center for Enhancing Foods to Protect Health Purdue University The public is concerned about how diet impacts health and risk for disease, but they are often confused when presented with conflicting reports in the news media. It is sometimes difficult for media reporters and writers to evaluate scientific and clinical studies; thus, important messages may be overlooked, misinterpreted, or down-played. Designing foods—feeding animals to create nutritionally modified food products that improve health or reduce human health risks for disease—is an increasingly important aspect of animal nutrition. The food industry has been driven to take the lead in designing animal products because of the increasing role that foods and food ingredients play in disease prevention. Also, consumers have become more interested in self-medication. An interest in improving the quality of life of the growing aging population and reducing the amount of money spent on health care costs and treating disease have further contributed to the development of designed foods.
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Scientific Advances in Animal Nutrition: Promise for the New Century, Proceedings of a Symposium EARLY IMPROVEMENT IN FOODS One of the first nutrients altered by the food industry was fat, because of its implications in cardiovascular disease, stroke, and cancer. Food scientists and human nutritionists introduced low-fat foods, which led to a decline in saturated fat intake. The composition of beef, pork, and poultry products has been altered through genetic selection—selecting animals that have less fat and are more efficient at converting nutrients to lean mass—and through the identification of nutrition requirements by the National Research Council’s Committee on Animal Nutrition. Milk was improved with the introduction of low fat varieties and by fortification with vitamin D, which increased the bioavailability of calcium. IMPACTS OF MODIFIED PROCESSED FOODS Unfortunately these low fat foods are not decreasing the incidence of obesity, which has been on the rise in the United States. Eating less animal fat and more plant oil has increased the ratio of n-6 to n-3 polyunsaturated fatty acids in the human diet, which, when based on biochemical data, favors inflammatory responses that contribute to cardiovascular disease, some cancers, and bone disease. Processed foods and hydrogenated vegetable oils also contain less n-3 (omega-3) fatty acids and may contribute to these inflammatory processes. In support of these concerns, a direct correlation is evident when the incidence of cardiovascular disease is plotted relative to fat intake. However, the relationship between dietary fat and chronic disease indicates that both total fat and fat type influence risk for disease. POTENTIAL DISADVANTAGES OF REDUCED INTAKE OF ANIMAL-DERIVED FOODS Reduced consumption of animal products may actually be harmful because they supply a variety of important vitamins, high quality proteins, and minerals for growing children and elderly who have problems achieving adequate nutrition. Animal fats are an important source of arachidonic acid for children because they cannot synthesize this fatty acid, which is essential for growth and development. Docosahexaenoic and eicosapentaenoic acids, also provided in some fish oils, are important in modulating eicosanoid production and act as direct agonists of inflammatory compounds. Current animal diets contain a limited number of different types of ingredients for simplicity and cost efficiency. Previously, poultry were fed fishmeal and other food animals were fed fish byproducts. Without these ingredients, omega-3 fatty acid concentrations decreased in animal products. Omega-3 fatty acid levels can now be restored in meat, eggs, and fish by feeding small amounts of newly developed products, such as algae-derived omega-3 fatty acids and other sources.
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Scientific Advances in Animal Nutrition: Promise for the New Century, Proceedings of a Symposium EXAMPLES OF CONTEMPORARY DESIGNED FOODS Animal products that have been enriched with different types of fatty acids and fortified with vitamin E, simply by feeding sources of these nutrients to the animal, have been successfully marketed in the United States, Canada, and Australia (Table 3-1). Moreover, these designer foods are beginning to change the way people eat. One company, claiming to have one percent of the market, produces eggs that have 25 percent more vitamin E than do conventional eggs. Another company is marketing docosahexaenoic (DHA) -enriched eggs. And still another company has a line of nutrient-modified eggs. Dairy products that have active microbial cultures, such as probiotics in yogurt and acidophilus milk, have been quite successful in Europe. Because these dairy products also make health claims, they comprise 65 percent of the functional food market in Europe (1.37 billion U.S. dollars), which is a small amount when compared with the overall food market, but a successful one in the area of designed foods. Fatty Acids Most recently, conjugated linoleic acid (CLA) found predominately in dairy products and meat from ruminants, has generated great interest in TABLE 3-1. Status of designed foods. Nutrient/Health Protectant Target Food Statusa Long-chain omega-3 fatty acids (20:5n-3, 22:6n-3) Poultry Eggs A Chicken and Turkey Meat R, D Pork R Fish: Perch, Salmon, Trout R Beef R Dairy: Milk R Conjugated linoleic acids Poultry: Eggs, Meat R Pork R Fish: Perch, Striped Bass R Dairy: Milk, Cheese R Tocopherols, carotenoids, lycopene, phytochemicals Poultry: Eggs A, D Beef R Pork R aStatus: A = available, R = research, D = commercialization development
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Scientific Advances in Animal Nutrition: Promise for the New Century, Proceedings of a Symposium polyunsaturated fatty acid research. CLA is a derivative of linoleic acid. The two double bonds in CLA are connected in contrast to linoleic acid, which has a methylene carbon separating the double bonds in the hydrocarbon chain. CLA will not substitute for the essential fatty acid, linoleic acid, but does have potent effects on enzyme systems, eicosanoid production, and growth and development of animals that may, in the future, benefit human health. CLA seems to be important in modulating biochemical and physiologic processes in the body that may reduce the risk of cancer, heart disease, and other types of inflammatory responses with observed pathology. Phytochemicals Interest in creating designed foods derived from plants has risen because of the phytochemicals in plants that may reduce lipid peroxidation and protect the body from free radical damage. Phytochemicals, including carotenoids, tocopherols, phenolics, and flavonoids, are found in a variety of plants. Soybeans, garlic, cabbage, ginger, licorice, carrots, celery and flaxseed have received the greatest amount of research attention. Methods to change the composition of phytochemicals in plants, determine how they are delivered, and the nutritional quality of the final product, are being investigated. Antioxidants Another important area in designed foods research is in antioxidants. Antioxidants are important in lowering oxidative stress and risk of cardiovascular disease, cancers, and possibly joint disease and inflammatory arthritis. For instance, beef that has been produced with high levels of tocopherols, such as vitamin E, has increased shelf life and may contribute significantly to the health of the consumer by lowering risk of chronic disease. FUTURE RESEARCH Dietary fats, phytochemicals, and antioxidants have been identified as having potential properties for reducing the risk of cancer and heart disease. The real issue now is to identify how these nutrients can potentially act as modulators of tyrosine kinases, cyclooxygenase 2, signal transduction systems, oxidative stress, and transcription factors at the cellular level. Tyrosine kinases influence many activities of cells including proliferation and apoptosis. Cyclooxygenase 2, an inducible enzyme that was fully characterized in the human system 2 years ago, is responsible for the inflammatory process associated with various cancers and joint disease. Opportunities exist to use designed foods to modulate the activity of this enzyme.
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Scientific Advances in Animal Nutrition: Promise for the New Century, Proceedings of a Symposium CONCLUSIONS Modifying the fatty acid composition of animal products can be accomplished. Designed foods include animal products that contain a modified nutrient or health protectant content that directly benefits human health. However, it is not clear how these health protectants impact cell activity and influence disease risk. More research is needed so that in the future health benefit labeling claims can be made and supported for the health protectants and nutraceuticals used to make these new foods. Some of the first designed foods created could restore the omega-3 fatty acids to the human diet to balance the ratio of n-6 to n-3 fatty acids. Perhaps in the near future CLA will be better understood, and dairy products and red meat CLA levels will be increased to reduce human risk for cancer, heart disease, osteoporosis, and inflammatory diseases. Future designed foods will also involve examining raw materials and modification of nutritionally fortified processed animal products containing new health protectants.
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