High Glycemic Load Foods Increase Probabilty Of A Heart Attack

Diets with a high glycemic load increase the risk of a myocardial infarction (heart attack) by as much as 98% according to a study published in The American Journal of Clinical Nutrition in June 2000.

The study, conducted by researchers from the Department of Medicine at the Harvard Medical School in Boston, involved 75,521 women aged between 38 and 63 who were followed over a 10 year period. The researchers looked at the impact of glycemic load and carbohydrate intake on the risk of myocardial infarction.

Glycemic load is similar to the glycemic index in that both are a measure of how a certain food affects blood sugar levels with high values indicating a greater effect on blood sugar. The difference between the two is that the glycemic load takes into account the amount of carbohydrate present in the food item. For example two foods may have the same glycemic index however one might contain twice the proportion of carbohydrates than the other, this item would therefore have twice the glycemic load as the other item.

During the 10 year study period, 761 of the women suffered a myocardial infarction of which 208 were fatal and 553 were non-fatal. After adjusting the results for factors such as BMI, smoking, and alcohol intake, the researchers found that the women in the highest quintile for dietary glycemic load were at a 98% increased risk of suffering a myocardial infarction.

Total carbohydrate intake also showed a modest association with myocardial infarction. Those in the highest quintile for carbohydrate intake were 23% more likely to suffer a myocardial infarction than those in the lowest quintile.

The major findings of the study are presented in the graph below.

Graph of heart attack risk compared to glycemic load and carbohydrate intake

The researchers also found that the increased risks of myocardial infarction associated with a high glycemic load diet were greatest in women with a BMI greater than 23. In contrast, glycemic load showed little association with myocardial infarction in women with a BMI lower than 23. The researchers hypothesized that the negative effects of high glycemic load foods were stronger in overweight women because consumption of foods with a high GL leads to a large insulin response from the body in order to control the rapid increase in blood sugar levels. Overweight women often have some degree of underlying insulin resistance which means that blood sugar levels remain high for some time, a state known as hyperglycaemia. Chronic high blood sugar levels have been implicated in the development of heart disease.

The researchers concluded that: “our findings suggest that a high intake of rapidly digested and absorbed carbohydrate increases the risk of CHD independent of conventional coronary disease risk factors”.

Foods that have a high glycemic load include refined breakfast cereals, white bread, white rice, baked or mashed potatoes, potato chips, most fruit juices and soft drinks, pasta, and raisins. Whenever possible, these should be substituted for foods that provide a slower blood sugar release such as wholegrain bread and pasta, rye bread, muesli (no added sugar), brown rice, new potatoes, sweet potatoes, beans, dairy products (excluding icecream), and leafy vegetables.