diet food and drink regularly consumed for nourishment. Nutritionists generally recommend eating a wide variety of foods; however, some groups of people survive on a very limited diet. The traditional Eskimo diet, for example, depended heavily on meat, but Eskimos ate nearly all of the animal; organ meats are rich in vitamins and minerals. Vegetarians exclude meat (and sometimes by extension dairy products) from their diet, often for philosophical reasons. Others exclude only red meat, but eat poultry and dairy products. To maintain a healthy diet, vegetarians need to eat a wide variety of plants whose nutrients complement each other, providing a balance of amino acids and vitamins.

Cultural, Regional, and Practical Factors

Until the advent of refrigeration , the most important factor in a person's diet was availability; diets varied according to animal migrations and the growing seasons of fruits, nuts, and vegetables. Another factor in food selection can be religion. Muslims, for example, are forbidden to drink alcohol.

Diets vary throughout the world. North Africa, with many Muslims, and the Middle East have similar diets. A starchy food (see starch ), such as rice, boiled and pounded yam mush, or cassava, is often accompanied by a spicy stew of fish or chicken with vegetables. Other popular dishes include curries, kebabs (marinated meat threaded on a stick and roasted), couscous (steamed wheat semolina), falafel (a spiced fritter), and yogurt. Many Asian diets are based on rice, which is often served with bite-size vegetables and meats accompanied by spicy seasoning. In Europe, bread is often the main starch, but Italy is noted for pasta , a nutritious noodle made from wheat and usually topped with a sauce, such as a small serving of cooked tomatoes garnished with cheese. In Scandinavia, fish in general, and herring in particular, are main staples of the diet.

Food has always been subject to cross-cultural influences, often as a result of colonization and migration of people. Thus, French influences can be seen throughout Asia, particularly in Japan and Indochina; Dutch influences in Indonesia and South Africa; and Indian influences throughout the Commonwealth of Nations. Certain foods, such as dumplings, are found in slightly different forms in all cultures. North American cuisine is an amalgam of Native American foods, such as corn-on-the-cob, and immigrant cuisines, including that of Africans.

Diet in the Twentieth Century

In the 20th cent. diets have been transformed by refrigeration, improved and faster transportation, advances in food preservation , and new farming methods that prolong the growing season and increase the yield per acre. As a result, foods are available more regularly, items purchased in one season can be frozen and consumed in another, and prices have become more competitive. After World War II, increased advertising, particularly on television, and the growing number of households in which all adults are employed, contributed to an increased consumption of unhealthy fast foods. Efforts in the 1980s and 90s by health experts to educate the public about the importance of a healthy diet has had some impact. People are eating more fruits, grains, and vegetables, and less red meat, and are aware of the need to control their weight. The latter has given rise to many ineffective, and sometimes dangerous, fad diets that do not provide all of the necessary daily nutrients. Successful weight control requires a carefully planned regimen of exercise combined with a diet based on the nutrition information supplied by the U.S. Dept. of Agriculture's Food Guide Pyramid (see food pyramid ).

Bibliography

See D. and P. Von Welanetz, The Von Welanetz Guide to Ethnic Ingredients (1982); J. Newman, Melting Pot: An Annotated Bibliography and Guide to Food and Nutrition Information for Ethnic Groups in America (1986); S. Quandt and C. Ritenbaugh, Training Manual in Nutritional Anthropology (1986); B. Griggs, The Food Factor: An Account of the Nutrition Revolution (1988).

diets A diet is a pattern of food consumption which is followed by a population or an individual. The diets of populations are affected by local factors including geography, climate, food availability, culture, and religion, whereas the diets of individuals within populations are further influenced by factors such as socio–economic status, personal preference, and health considerations. To maintain life, all diets must supply the essential amounts of energy, protein, essential fatty acids, vitamins, and minerals, but these needs can be met by a wide variety of diets, each of which will be sufficient for growth, survival, and reproduction but may also have obvious or subtle effects on the long-term state of health.

Traditional diets

The traditional diets of populations around the world vary greatly. The diet of Inuit hunters in the Arctic is composed almost entirely of meat and fish, but most hunter-gatherers in other parts of the world obtain more food from gathering plants than from hunting animals. Pastoralists keep different animals according to where they live, varying from reindeer in the north to camels in hot arid areas, but they always have a diet rich in animal foods such as milk, meat, and blood. Peasant agriculturalists grow different staple crops according to local conditions, but usually have diets composed largely of plant foods with only small amounts of animal foods.

The traditional diets of populations have been followed for hundreds or thousands of years and, except in times of severe food shortage, are certainly compatible with the maintenance of health sufficient for the survival and growth of infants and children, and for successful reproduction. However, traditional diets are sometimes far from optimal and may be accompanied by serious nutritional disorders, from which the people may have suffered for many generations. For example, approximately one-fifth of the population of the world is at significant risk for developing iodine deficiency disorders; pellagra was formerly common in populations subsisting largely on maize due to deficiency in the vitamin niacin and the amino acid tryptophan; and high blood pressure and stroke are common in populations with a diet high in salt.

‘Western’ diets

The diets of affluent Western populations changed very rapidly during the twentieth century. In comparison with the diets of peasant agriculturalists, Western diets are usually much higher in animal protein and fat and much lower in starch and dietary fibre, and ample food is available throughout the year. It is well known that Westernization of the diet is usually associated with increases in the rates of some diseases, such as ischaemic heart disease, large bowel cancer, and obesity, but it should also be appreciated that Westernization is generally accompanied by an increase in overall life expectancy and by decreases in the rates of some diet-related diseases such as stomach cancer, as well as decreases in the incidence of most infectious diseases.

Diets for health

Within Western populations, the word ‘diet’ is commonly used to refer to patterns of food consumption which are followed for reasons of health or for ethical or religious reasons (vegetarian and vegan diets are discussed in separate entries). A good diet is of profound importance for the maintenance of good health; nutritional deficiencies severe enough to cause obvious diseases such as scurvy and pellagra are now very rare in Western societies, but diet is a major determinant of the risk for developing many of the commonest fatal diseases, including ischaemic heart disease, stroke, and cancers of the large bowel and stomach.

The commonest type of diet followed for health reasons is one intended to cause weight loss in the treatment of overweight, and the term dieting is often assumed to refer to a weight-reduction diet. Numerous types of weight-reducing diets have been marketed. Most will cause some initial weight loss, but this is difficult to maintain because obesity is associated with the typical Western lifestyle of low physical activity and constant availability of highly palatable, energy-dense foods.

After obesity, the most common reason for requiring dietary changes is a high blood cholesterol concentration and associated ischaemic heart disease. The blood cholesterol concentration is increased by diets high in saturated fat and cholesterol. Reducing the intake of these factors causes a reduction in blood cholesterol, but most individuals find it difficult to change their diet sufficiently to have more than a small effect. Other diets followed for health reasons include low salt diets for the reduction of raised blood pressure and gluten-free diets for individuals with coeliac disease.

High-fibre diets have become popular since the work of Denis Burkitt and others in the early 1970s. Fibre is now defined as non-starch polysaccharides, and is supplied by unrefined cereals, vegetables, and fruits. Fibre has several benefits, including the prevention of constipation and probably reducing the risk for coronary heart disease and cancer of the large bowel.

The topic of diet and health is covered extensively by the media and many people are confused as to what constitutes a healthy diet. Government bodies in many countries now make dietary recommendations. In Britain, the Committee on Medical Aspects of Food Policy (COMA) reviews various aspects of the relationship of diet with health. In their recent report on nutritional aspects of cardiovascular disease, COMA made several recommendations for adults, including that total fat and saturated fat should provide no more than 35% and 10% respectively of food energy, that average salt intake should be reduced to 6 g per day, and that the consumption of vegetables, fruit, potatoes, and bread should be increased by at least 50%. These recommendations reflect a growing consensus that a healthy diet should be based on starch-rich foods such as cereals and should include generous quantities of fruit and vegetables. This type of diet is also rich in dietary fibre and many vitamins, and the emphasis is on supplying these nutrients from ordinary foods rather than from special high-fibre foods or vitamin supplements.

Future needs — more science in the choice of diets for populations and individuals

Traditional diets have evolved out of necessity, to be sufficient for life, but are often far short of ideal. Western diets have come from traditional roots but have been radically changed by affluence, developments in agriculture and food processing, advertising, fashion, etc. Most people now eat a diet determined by a mixture of tradition, availability, convenience, taste, and peer pressure. The health effects of the resulting mix are themselves mixed, with some diet-related health problems decreasing and others increasing. We already have sufficient knowledge to do much better than this, and need to introduce more science into all the components of society which affect food consumption, including agricultural policy and the education of children, caterers, and politicians. Evidence from sound scientific studies should be continually fed into society with the aim of producing improvements in the health of the population and in the optimal use of land and other resources.

Tim Key

Bibliography

Report of the Cardiovascular Review Group Committee on Medical Aspects of Food Policy (1994). Nutritional aspects of cardiovascular disease. HMSO, London.

diet (dy-ĕt) n. the mixture of foods that a person eats. balanced d. a diet that contains the correct proportions of all the nutrients.