Reduce the glycemic index / load of foods you eat
Lower your risk of type 2 diabetes, weight gain, and coronary heart disease
Glycemic index (GI) refers to the relative rise in blood sugar after consuming a particular food. Glycemic load (GL) adjusts the GI value for serving size. The bigger the serving size, the higher the GL. In practice, the GL of a meal reflects the types of carbohydrates eaten and their digestibility, as well as insulin secretion. Your body rapidly digests, absorbs, and transforms foods (and meals) with high GI values. Standard American diets are commonly loaded with high GI foods, such as refined grain products (breads, cookies, cakes) and potatoes. Since 1970, the proportion of fats in American diets declined, while that of high GI carbs increased.
Laboratory studies suggest that high GI meals result in less satiety, which may promote overeating. Researchers in Boston conducted an experiment with 12 overweight or obese boys (average age 16 years) to determine if a high GI meal would lead to higher subsequent voluntary food intake. The boys were fed three prepared meals, each separated by 1-2 weeks, all with the same caloric content and with high, or medium, or low GI values. The high-GI meal produced the highest subsequent rise in blood glucose, while the low-GI meal produced the lowest. More importantly, voluntary food intake after the high-GI and medium-GI meals was 81 and 53 percent higher, respectively, than that after the low-GI meal. The product of the height and duration of blood glucose post-meal rise (called the area under the curve) predicted post-meal voluntary food intake. Thus, different types of calories can elicit different bodily responses, contrary to what the energy-balance model predicts.
For years, medical authorities advocated a low-fat diet to reduce risk of cardiovascular disease. But accumulating evidence cast doubt on this guidance. One study used data from 75,521 women aged 38-63 years in 1984 in the Nurses’ Health Study. Compared to participants in the lowest quintile of GL, those in the highest quintile has a significant 57 percent higher risk of developing coronary heart disease during 10 years of follow-up. After adjusting for a host of confounding factors, the risk increased to 98 percent. Potatoes and cold-breakfast cereals held the top two spots in GL contribution (8 and 4 percent, respectively) . Women with body-mass index values greater than 29 (high overweight) had 97 percent higher risk of coronary heart disease than women with body-mass index less than 23 (normal weight). Thus, diets rich in easily digestible and absorbed carbohydrates (including many low-fat diets) predict greater risk of coronary heart disease, regardless of conventional coronary heart disease factors.
Harvard researcher David Ludwig reviewed the literature on the physiological effects of high- and low-glycemic diets. Would evidence support the use of either high- or low-glycemic foods to prevent or otherwise manage type 2 diabetes, obesity, and cardiovascular disease? Ludwig found that ingestion of high-glycemic foods caused a sharp rise in blood glucose and insulin for two hours post-meal, followed by sharp declines in both glucose and insulin for the next two hours. Blood glucose and insulin further declined to levels lower that which existed just prior to eating. In contrast, low-glycemic foods caused less increase in both glucose and insulin over two hours and a much more modest decline for the subsequent two hours. Calorie for calorie, high-glycemic foods evoked higher insulin secretion that low-glycemic foods.
Single-day studies showed lower satiety, increased hunger or higher voluntary foods intake after eating a high-glycemic index meal compared to a low-glycemic index meal. Intervention studies showed that low- compared to high-glycemic foods led to better blood chemistry (lower blood triglyceride and LDL-cholesterol levels and lower ratio of total cholesterol to HDL-cholesterol) than high-glycemic foods. Chronic consumption of high-glycemic foods may increase risk of type 2 diabetes, obesity, and cardiovascular disease.
Consuming foods and meals with lower GI and GL may reduce risk of developing type 2 diabetes. Might the same be true for coronary heart disease? Two British researchers conducted a meta-analyses of longitudinal studies to find out. Based on 12 studies, researchers found a significant 44 percent higher risk of developing coronary heart disease over an average 11 years of follow-up for every 65 grams per day increase in GL. Every 10 unit increase in GI predicted a 24 percent increase in risk of coronary heart disease. For an increase of 10 units in the GI of foods consumed, each 98 gram (3.5 ounces) increase in carbohydrate intake predicted a 66 percent increase in coronary heart disease risk. The researchers concluded that the relationship between GL and GI and coronary heart disease is likely causal, not just coincidental. If you want to reduce your risk of coronary heart disease and other ills, increase your intake of low-glycemic load and index foods (non-starchy veggies, berries, beans, unsweetened dairy products) and reduce your intake of high-glycemic load and index foods (refined grain products such as most breads, cookies, cakes, as well as sugar-sweetened beverages).
A diet with foods with high GI predicts increased risk of cardiovascular disease in high-income countries. A new study extends this link to low- and middle-income countries. PURE Study investigators used data from 137,851 participants with a baseline age of about 50 years in 20 countries on five continents . Compared to participants in the lowest quintile of GI, participants in the highest quintile had significant 25 percent higher risk of a composite outcome (major cardiovascular event, or cardiovascular-related death, or stroke) during an average 9.5 years of follow-up. Cardiovascular-related death and stroke showed 25 and 14 percent increased risks, respectively. Participants with cardiovascular disease at baseline showed even higher risks of the composite outcome (51 percent) and stroke (71 percent). Your diet quality and health will improve if you reduce intake of high-GI foods with lots of while flour (cookies, cakes, white bread) and added sugar (sodas, candy, cookies).