Sunday, October 13, 2013

THE DEVELOPMENTAL ORIGINS THEORY

The British researcher David J. Barker first proposed the developmental origins theory in the 1980s to explain a puzzling paradox: as British prosperity increased, so did heart disease; yet geographically, the most heart disease was found in the poorest places in Britain. Barker found geographical associations of heart disease with infant mortality, but not with smoking or dietary fat. Yet even infant mortality had declined over the course of the century, just as prosperity had gone up. When he accounted for a time lag between cause and effect of more than 50 years, however, the paradox was resolved—something was determining the risk of disease at or near birth, not late in life when the disease develops.58
Barker and his team of researchers then studied the birth weight of individuals born between 1911 and 1930 in Hertfordshire, UK. This allowed them to study the association at the level of individuals rather than local districts. Infants carried to term with birth weights between 8.5 and 9.5 pounds had a 45 percent lower risk of heart disease than infants carried to term weighing less than 5.5 pounds; they had a similarly lower risk of stroke, a nearly 70 percent lower risk of insulin resistance, and a slightly lower blood pressure in the seventh decade of life. The risk declined steadily and evenly between 5.5 and 9.5 pounds and began increasing thereafter. Later, other researchers found similar trends in the United States and southern India.59
Data from the three-month Dutch famine that occurred during World War II suggests that specific types of diseases are associated with specific windows of development during pregnancy. Women who were exposed to this famine during their first trimester gave birth to offspring with an increased risk of cardiovascular disease; women exposed during their second trimester gave birth to offspring with an increased risk of kidney disease; women exposed during their third trimester gave birth to offspring with an increased risk of insulin disorders.60
Developmental origins theorists have offered several explanations for these associations: poor nutrition could alter the development of the pancreas, which secretes insulin, and the liver, which secretes cholesterol and blood clotting proteins; muscle tissue could program itself for insulin resistance in order to spare glucose and amino acids for the brain when the supply of these materials is limited; overgrowth of the left ventricle of the heart—which itself is independently associated with cardiovascular disease—could be a response to the need to supply a greater volume of blood to the brain at the expense of the other tissues.59
Just as Weston Price had associated the skeletal defects that occur because of poor prenatal nutrition with the risk of disease in childhood and adolescence, researchers are now associating the defects of the internal organs that occur due to poor nourishment with the risk of disease in adulthood and old age.

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