Intact carbohydrates – whole grains and starchy vegetables – are more healthful than refined carbohydrates like white rice and white flour products, since they remain rich in micronutrients and fiber. Carbohydrates’ influence on heart disease was recently investigated based on glycemic index. The glycemic index (GI) evaluates the blood glucose response per gram of carbohydrate in particular foods on a 1-100 scale. Glycemic load (GL) is a similar ranking, but is thought to be more meaningful because it takes into account the carbohydrate content of a certain portion size of each food rather than a fixed number of grams of carbohydrate. In general, most refined carbohydrate foods, devoid of fiber to slow down absorption of sugars, are higher in glycemic index than unrefined foods. For example: high GI foods include sugar, white bread, and sweetened breakfast cereals; low GI carbohydrate foods include many whole grains, fresh fruits, beans, and vegetables.1 White potatoes, although they are a whole plant food, are also high in GI and GL, and potato consumption of even one serving per day is associated with increased risk of type 2 diabetes.2
Foods with a high glycemic index (or glycemic load) produce dangerous spikes in blood glucose. Diets including large quantities of high GL foods increase the risk of diabetes, breast cancer, colorectal cancer, endometrial cancer, and overall chronic disease.3
The current study followed subjects in Italy for 8 years, divided them into four groups according to intake from high GI and high GL foods, and recorded incidence of coronary heart disease. In women, the groups with the greatest intake of high GI foods were at 68% greater risk of heart disease than those with the lowest intake. Analyzing by glycemic load revealed an even more pronounced effect - women with the highest intake of high GL foods were more than twice as likely to develop heart disease compared to women with the lowest intake - a 124% increase in risk.4
Curiously, in this study, a similar pattern was not seen in men. The researchers noted that triglyceride and HDL levels were more sensitive to GI and GL in women than in men, but they are not sure why. However, a recent and similar study performed in men did find an increased risk of heart attack in men with the highest GI and GL food intake. In any case, most high GL foods are calorie-rich and nutrient-poor, and do not have a place in a health-promoting diet.5
Eating according to nutrient density automatically keeps the glycemic load of your diet low - the low GL carbohydrate sources are also the most nutrient rich – vegetables, beans, and fresh fruits, followed by whole grains and starchy vegetables.
1. Foster-Powell K, Holt SHA, Brand-Miller JC. International table of glycemic index and glycemic load values: 2002. Am J Clin Nutr 2002;76:5-56.
2. Halton TL, Willett WC, Liu S, et al. Potato and French fry consumption and risk of type 2 diabetes in women. Am J Clin Nutr. 2006 Feb;83(2):284-90.
3. Barclay AW, Petocz P, McMillan-Price J, et al. Glycemic index, glycemic load, and chronic disease risk--a meta-analysis of observational studies. Am J Clin Nutr. 2008 Mar;87(3):627-37.
Gnagnarella P, Gandini S, La Vecchia C, Maisonneuve P. Glycemic index, glycemic load, and cancer risk: a meta-analysis. Am J Clin Nutr. 2008 Jun;87(6):1793-801.
4. Sieri S, Krogh V, Berrino F, et al. Dietary glycemic load and index and risk of coronary heart disease in a large italian cohort: the EPICOR study. Arch Intern Med. 2010 Apr 12;170(7):640-7.
5. Mursu J, Virtanen JK, Rissanen TH, et al. Glycemic index, glycemic load, and the risk of acute myocardial infarction in Finnish men: The Kuopio Ischaemic Heart Disease Risk Factor Study. Nutr Metab Cardiovasc Dis. 2009 Oct 14. [Epub ahead of print]