In the developed world, nutritional research has its roots in recognition of the role of environmental factors in the origins of disease and the need for measures to improve the health of the public. Early emphasis was placed on the role of governments in public health matters, largely by removing the threats of foul air, poor hygiene in food preparation, and inadequate sanitation. Only much later, for reasons of food safety, did government interest turn to food. By 1900, a consensus had emerged that public health matters were the responsibility of government, whereas doctors were responsible for the health of the individual patient. Recruitment of poorly nourished conscripts into the army during the Great War (1914-1918) became a national concern when it was recognized that many young men were malnourished and that, without remedial steps, the war might be lost. Victory brought its own problems as advocates of the eugenics movement argued that the upper classes would be overwhelmed by the more fecund lower classes, whose gene pool was weakened through loss of the ''cream of the generation'' in the war. This view was once widely held but soon countered in the United Kingdom (but not Germany) through research that showed the ill
Handbook of Models for Human Aging
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health and short stature of poor people to be caused not by genetics but by the malnourishment of poverty. Nutritional research energized many social reformers who ensured that by 1933, U.K. school children could receive free meals and milk. Cod liver oil was soon added to prevent rickets. The discovery of vitamins by then had made a huge impact in clinical medicine and reinforced the view that public action to improve diet should be aimed at meeting minimal requirements for promoting growth through addition of meat, milk, fruit, and vegetables to a poor diet.
These issues were at the fore in the United Kingdom during the Second World War (1939-1945) when fear of ''starvation into submission" was high: over 50% of U.K. food came from the United States and Canada at a time when German submarines sank huge numbers of Allied ships. This threat produced a food strategy informed by nutritional research. For the first time in U.K. history, a generation of children were able to consume a diet sufficient not only in energy but in necessary proteins and vitamins. These policies met with international acclaim after the war when it was recognized that scientific advice had produced an effective system of rationing, governments had devised efficient distribution and pricing policies, and nutritional education was well directed. Thereafter, the same policies shaped U.S. food aid to a devastated Europe only to be slowly replaced, as Europe recovered, by policies of self-reliance and commercial investment in the industrialization of food supply. These successful policies have produced the enormous food surpluses of today. Sadly, these policies have also destabilized food supply in underdeveloped countries and caused massive, and not necessarily healthy, changes in Western dietary habits. Monocultural farming systems have reduced the cost of raising cattle, pigs, and chickens so much that the usual diets in Western Europe and urban United States now comprise a great deal of what was once regarded as luxury food. These changes are now being extended as former Eastern bloc countries reflect their growing affluence and perception that freedom of choice should include choice of food as well as democracy.
In post-war Europe, the notion became widespread that the days of malnutrition were over and that the role of governments should be to regulate food safety rather than its nutrient value which, it was felt, could be confidently assumed and, anyway, was a matter of personal choice in a free society. The nutritional content of foodstuffs was inspected from the standpoint of minimum content to protect the consumer against the adulteration of foods but not to ensure nutrient value. The present situation is now hugely complex, with many more new food products widely available through the growth of supermarkets to replace traditional distribution systems of local foods. Returns on these massive investments can be assured only by adding advertising and other overhead to the costs of food.
In these circumstances, it is unsurprising that processed foods now comprise over 70% of the modern Western diet: more potatoes are eaten in processed form than in their freshly cooked state. Likewise, sugar is added widely to foods, as is salt, to enhance taste, so much so that most of the salt consumed in the Western diet is now derived from processed foods over which the consumer has no control. Many commentators are aware of the health risks associated with modern energy-dense but nutrient-poor diets and advocate change. Too often, these remedies repeat the lessons of nutritional education that had been so effective in the early part of the last century but are no longer appropriate. Modern consumers are encouraged to believe that their diets are deficient in specific ways much as those earlier diets were deficient in energy, protein, or vitamins. Addition of missing ingredients to modern diets is the most often proposed remedy when there is a much better case to adopt radical changes in eating patterns. Healthy eating provides less energy, less sugar and salt, and more fruit and vegetables. Nutritional gerontology is thus faced with a complex set of problems. Probably to a greater extent than at any other point in human history, there is greater diversity in diet within and between populations. In some older individuals, dietary preferences established in youth can persist into late life: meals are prepared following traditional routines. In others, greater reliance on prepared foods has been acquired, sometimes with regular supplementation with specific foods, complementary or alternative medicines. Younger individuals, in contrast, may have insufficient interest (and often little time) to prepare foods and rely heavily on convenience foods.
Research designs in nutritional gerontology are influenced by these historical considerations. At the simplest level, sampling subjects for studies in nutritional gerontology takes account of the problem that between birth cohorts (say, 1915-1919 and 1935-1939) there are often very large differences in early life dietary histories. These may be sufficient to account for differences that might otherwise be attributed to aging. At a more complex level (set out later in the final sections on gene-nutrient programming of developmental plasticity), there is good evidence that maternal/fetal exposures to different nutritional environments can modify the risk of late-onset diseases. Inclusion of historical dietary data in studies of this type requires some knowledge of prevailing dietary exposures during relevant epochs. Carpenter (2003a, b, c, d) has provided an excellent overview of the history of nutritional science.
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