Food for thought

Vegetables, and not carbohydrates, should be the diet mantra of Americans

Published: Wednesday 31 March 2004

-- us citizens need beneficial dietary guidance, indicates a 30-year-long study of the us Centres for Disease Control and Prevention. As per the research, calorie intake of the nation has increased manifolds -- in 1971 women ate 1,542 calories a day, compared with today's 1,877, while men went from 2,450 calories to 2,618. The numbers dwarf government's recommendations of 1,600 calories a day for women and 2,200 for men. Cookies, soda and other carbohydrates are being blamed for the epidemic of bulging waistlines, which has increased the risk of heart diseases, diabetes and cancer.

It is still unclear whether the findings would influence a revision of the food pyramid (guidelines) of the us agriculture department (usda), which emphasises a low-fat diet rich in breads. " usda pyramid offers scientifically unsound advice," argues Walter Willett, chairperson of the department of nutrition at the Harvard School of Public Health. In his book, Eat, drink, and be healthy: the Harvard Medical School Guide to Healthy Eating, he propagates a food pyramid based on the largest long-term dietary survey ever undertaken in the us: the 121,700-participant nurses' health study begun in 1976 by Harvard Medical School professor Frank Speizer, with dietary analysis done by Willett.

Willett found that the usda diet mantra is a prescription for portliness. The problem with overeating carbohydrates such as white flour is that amylase, an enzyme, quickly converts them into simple sugar glucose. That goads the pancreas to overproduce insulin, the substance that guides glucose into the cells. But excessive sugar is toxic to cells, so after years of glucose and insulin overload, the cells can become insulin-resistant and may no longer allow insulin to easily push glucose inside them. That keeps blood glucose levels high, forcing the pancreas to make even more insulin in a desperate attempt to jam the stuff through cell membranes. The high blood glucose levels can lead to obesity, and type-2 diabetes can be one result of the increased insulin levels.

Willett's food pyramid aims to even out the glucose roller coaster through an emphasis on foods with low glycemic loads -- foods like whole grains, plant oils and vegetables, which convert to glucose slowly. This keeps blood glucose levels relatively constant, sparing the pancreas from overwork. Steady blood glucose also helps keep the appetite in check, which makes maintaining a healthy weight easier, says Willett. "My food pyramid is not severely restrictive. It does not mean that one cannot eat high-carbohydrates food, but rather they should be de-emphasised," he says. Even the renowned nutrition expert has a little chocolate now and then.

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