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.
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.
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.