Nutrition Guidelines

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Glycemic Load and Risk of Heart Disease

Written by Don Hall, DrPH, CHES
Feb. 10, 2002

High Glycemic Index Foods

White bread, rolls, biscuits

Pastry, cookies, cake

Sugar, sweets

Soda pop, punch, sugary drinks

Potatoes

Sweetened breakfast cereals

White rice, refined grains

Low Glycemic Index Foods

Whole wheat bread

Whole grain cereals, e.g. oatmeal

Fresh fruits

Vegetables

Legumes, lentils, garbanzos, beans

Soybeans and soy products

Protein rich foods

Nuts, seeds, avocado

Healthy fats

In summary, our findings suggest that a high intake of rapidly digested carbohydrate increase the risk of coronary heart disease, independent of conventional risk factors.

The relationship between diet and heart disease has generally centered around dietary cholesterol and saturated fat. A new report from the Nurse's Health Study also shows the importance of carbohydrate and especially glycemic index on heart health.

Glycemic index is a measure of how fast the carbohydrate is absorbed into the blood as glucose. The standard food used as a reference to evaluate all others is the rate at which white bread or pure glucose is absorbed. Both are rapidly absorbed and are given a glycemic index of 100. Foods absorbed rapidly, such as white bread or glucose, are high glycemic index foods. They increase blood sugar and insulin levels which if high contributes to high blood triglycerides, low HDL cholesterol levels, and risk of diabetes and heart disease.

Glycemic load is computed by multiplying the carbohydrate content of each food by its glycemic index. By adding the glycemic load of each food eaten in a day, you arrive at the glycemic load for the day. The glycemic load of 75,251 women were calculated and then compared to the rate of heart disease over a 10 year period.

Here is what they found. Women with a high glycemic load (top 20% of women, compared to women with a low glycemic load (bottom 20% of women) had twice as much heart disease (relative risk of 1.98) even after adjusting for BMI, smoking status, high blood pressure, physical activity, dietary fat, cholesterol intake, and other known risk factors. This is a significant increase in risk, as much or more than the affect of saturated fat in the diet or even smoking.

When researchers looked just at carbohydrate intake, there was no significant relationship to heart disease. Neither was there a relationship between simple sugar or starch intake when included in the statistical evaluation which included glycemic load. The increased risk seems to be linked to the rate at which the carbohydrate is absorbed. Thus, rather than talking about starch or simple sugars (as found in fresh fruits), it is more useful to evaluate the affect of carbohydrate on health in terms of glycemic load.

A high glycemic load diet contributes to high blood sugar, insulin resistance, and metabolic disorders that have long been recognized as important risk factors for coronary heart disease. It is also important to note that this increased risk was found only in people with a BMI greater than 23. Lean persons didn't seem to be affected. Insulin resistance occurs primarily in overweight persons.

In conclusion, the researchers state, "We found a significant positive association between dietary glycemic load and risk of coronary heart disease that was independent of known coronary risk factors, including other measured dietary variables."

How do we apply this information? To improve heart health it is now known that you need to watch the kind of carbohydrates eaten as well as fat intake. For best health:

Limit foods with a high glycemic index, eat them less often, and in smaller amounts (see list on left). This is especially important for overweight persons.

Keep in mind that it isn't just the glycemic index of the food but the glycemic load (glycemic index X carbohydrate gm).

Choose more low glycemic index foods. Make these foods your primary food choices.

Following these new dietary guidelines may cut your risk of a heart problem in half. Choosing healthy carbohydrates can make a significant contribution to heart health.

Reference

Simin Liu, Walter C Willett, et al, "A prospective study of dietary glycemic load, carbohydrate intake, and risk of coronary heart disease in US women, American Journal of Clinical Nutrition 2000;71:1455-61.

Updated 2-10-2002 DRH

Making Healthy Choices articles are written by Don Hall, DrPH, CHES president of LifeLong Health with contributions from associated health professionals. Content is general health information from evidence based research. It's purpose is not to treat disease or take the place of advice by your doctor but to promote healthy lifestyles. Persons with health problems should contact their physician for specific guidance.