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United States Department of Agriculture

Agricultural Research Service

What you eat can affect your health
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By Hank Lukaski

Comparing the roles of food and medicine in achieving and maintaining health is easy. Food provides nutrients that help maintain health and prevent disease. In contrast, medicine acts to relieve the symptoms of illness and to help sick people regain health.

Thus, food provides nutrients that are the building blocks for health and medicine as a repair that helps to overcome the cause of the illness.

Eating a meal causes the release of many hormones, such as insulin, and other chemicals that influence how cells communicate to produce proteins that impact energy storage and use.

Understanding the complex pathways associated with hormones is a multibillion dollar effort by drug companies. Emerging evidence, however, shows that some of these pathways - particularly those involved in regulating insulin levels after eating - normally are regulated by certain foods, namely carbohydrates.

Insulin regulates the uptake, storage and use of many nutrients, including sugar or glucose and fat after a meal. The composition of a meal, particularly the type of carbohydrate, affects glucose levels in the blood, which influences insulin concentration.

Complex carbohydrates, such as whole grains, delay the increase in blood sugar, but simple carbohydrates, such as table sugar or soda, causes a rapid spike in blood glucose.

Diets may be classified based on their effects on insulin response after eating a meal. High-insulin-response diets elevate insulin levels for prolonged periods of time (four to six hours) after eating. In contrast, low-insulin response meals yield a much lower insulin level that is maintained for long periods of time. High insulin levels are thought to promote obesity by increasing fat storage and decreasing fat use to meet energy needs.

Perhaps not surprisingly, fat tissue below the skin in the abdomen produces unique chemical signals that decrease the effectiveness of insulin in regulating sugar and fat use. Thus, fat or adipose tissue is a target to evaluate the effects of diet on development of obesity and type 2 diabetes.

Insightful study

A recent study provides valuable insight as to how fat cells respond to these types of diets. Overweight and obese women and men with various clinical signs characteristic of pre-diabetes (elevated fasting insulin levels, increased waist circumferences, high blood pressure and increases in certain types of lipids in the blood) consumed diets with either a high- or low-insulin response for three months. Low-insulin response would be from eating bread and pasta made from unprocessed cereal, grains and pasta, and high-insulin response would be from eating bread made from processed oat-wheat-potato flour, bread and potatoes.

The diets had the same amounts of fiber, fat, carbohydrate and protein. As expected, consumption of the low- compared with the high-insulin response diet resulted in important reductions in fasting insulin and glucose after a standardized, high-glucose test meal. This effect, however, occurred without a decrease in body weight, which is the expected change associated with decreases in blood insulin and glucose.

Analysis of small pieces of fat obtained from under the skin at the front of the abdomen revealed some very important changes within these cells. The size of the fat cells decreased with the low- but not the high-insulin response diet. In the fat cells, certain genes that manage the production of proteins that control specific functions were impacted. The low-insulin response diet turned off many genes, specifically those that regulate how insulin affects carbohydrate and fat storage, and regular replacement of cells.

Two other findings are critical. The low-insulin response diet decreased the activity of an enzyme, hormone-sensitive lipase, which controls release of fats stored in fat cells. People with reduced activity of this enzyme have lower levels of glucose, insulin and fats in the blood. Thus, it is thought that the decreased activity of this enzyme probably accounts for some of the benefits of diets designed to lower insulin secretion.

The low-insulin response diet also reduced the presence of another gene, one which is known to be a strong predictor of development of type 2 diabetes. In contrast, the high-insulin response diet increased the activity of other genes related to stress and inflammation - processes related to adverse effects of obesity, including type 2 diabetes and cardiovascular disease.

The general application of these findings for each of us is simple. We should eat more fruits, vegetables and legumes (dry peas, beans and peanuts), choose whole-grains or products that are minimally processed, such as pasta and old-fashioned oatmeal and cereals, and limit intake of products high in concentrated sugar. These recommendations have the benefit of replacing high calories with high nutrient (vitamin, mineral and fiber) content foods.

Last Modified: 9/5/2007
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