Leading Scientists From Ten Countries Urge Glycemic Index and Glycemic Load Food Labeling
Past research has shown that the effect on blood glucose levels of different foods with the same carbohydrate content can vary by as much as five-fold. This has led to foods being assigned a glycemic index (GI). According to a group of leading nutrition scientists from ten countries GI should be included in national dietary guidelines and on food labels.
The glycemic index (GI) is a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers--the higher the number, the greater the blood sugar response.
Glycemic Index and Glycemic Load
High-glycemic index foods, like white bread, white rice and potatoes, tend to spur a quick surge in blood sugar, while low-glycemic index foods, such as lentils, nuts, and barley create a more gradual increase in blood sugar.
A list of carbohydrates with their glycemic values in the chart at the bottom of the page. A GI is 70 or more is high, a GI of 56 to 69 inclusive is medium, and a GI of 55 or less is low.
The glycemic load (GL) is a relatively new way to assess the impact of carbohydrate consumption that takes the glycemic index into account, but gives a fuller picture than does glycemic index alone. A GI value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn't tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food's effect on blood sugar. That is where glycemic load comes in. The carbohydrate in watermelon, for example, has a high GI. But there isn't a lot of it, so watermelon's glycemic load is relatively low. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.
Foods that have a low GL almost always have a low GI. Foods with an intermediate or high GL range from very low to very high GI.
High blood glucose levels and excessive insulin secretion are thought to contribute to the loss of the insulin-secreting function of the pancreatic beta-cells that leads to irreversible diabetes and another diseases.
Scientists Urge Labeling
Following a two-day conference in Stresa, Italy -- the International Scientific Consensus Summit on Glycemic Index, Glycemic Load and Glycemic Response -- the committee concluded that carbohydrates in different foods affect post-meal blood sugar differently, with important health implications.
The resulting consensus statement says that based on a large body of scientific evidence, low GI foods are helpful to reduce the risk of type 2 diabetes and heart disease, can help control blood glucose for people with diabetes, and may also help with weight management.
"The GI complements other ways of characterizing carbohydrate-foods, such as fiber and whole grain content," the statement reads.
The scientists said that the rapid rise in diabetes and obesity means that there is a need to better communicate on GI and GL (glycemic load).
"This should be supported by inclusion of GI/GL in dietary guidelines and in food composition tables," they said in the statement.
"In addition package labels and low GI/GL symbols on healthy foods should be considered.
"More comprehensive high-quality food composition tables need to be developed for GI/GL at the national level."
Chairman of the Department of Nutrition at the Harvard School of Public Health and one of the participating scientists, Walter Willett, said: "Given essentially conclusive evidence that high GI/GL diets contribute to risk of type 2 diabetes and cardiovascular disease, reduction in GI and GL should be a public health priority."
After a high-glycemic load meal, blood glucose levels rise more rapidly and insulin demand is greater than after a low-glycemic load meal. High blood glucose levels and excessive insulin secretion are thought to contribute to the loss of the insulin-secreting function of the pancreatic beta-cells that leads to irreversible diabetes. High dietary glycemic loads have been associated with an increased risk of developing type 2 diabetes mellitus (DM) in several large prospective studies.
In the Nurses' Health Study (NHS), women with the highest dietary glycemic loads were 37% more likely to develop type 2 DM over a 6-year period than women with the lowest dietary glycemic loads.
Additionally, women with high-glycemic load diets that were low in cereal fiber were more than twice as likely to develop type 2 DM than women with low-glycemic load diets that were high in cereal fiber. The results of the Health Professionals Follow-up Study (HPFS), which followed male health professionals over six years were similar. In the NHS II study, a prospective study of younger and middle-aged women, those who consumed foods with the highest glycemic index values and the least cereal fiber were also at significantly higher risk of developing type 2 DM over the next eight years.
The foods that were most consistently associated with increased risk of type 2 DM in the NHS and HPFS cohorts were potatoes (cooked or French-fried), white rice, white bread, and carbonated beverages.The Black Women's Health study, a prospective study in a cohort of 59,000 U.S. black women, found that women who consumed foods with the highest glycemic index values had a 23% greater risk of developing type 2 DM over eight years of follow-up compared to those who consumed foods with the lowest glycemic index values.
In the American Cancer Society Cancer Prevention Study II, which followed 124,907 men and women for nine years, high glycemic load was associated with a 15% increased risk of type 2 DM. Further, in a cohort of over 64,000 Chinese women participating in the Shanghai Women's Health Study, high glycemic load was associated with a 34% increase in risk of type 2 DM; this positive association was much stronger among overweight women.
A U.S. ecological study of national data from 1909 to 1997 found that increased consumption of refined carbohydrates in the form of corn syrup, coupled with declining intake of dietary fiber, has paralleled the increase in prevalence of type 2 DM. Today, high-fructose corn syrup (HFCS) is used as a sweetener and preservative in many commercial products sold in the United States, including soft drinks and other processed foods. To make HFCS, the fructose content of corn syrup (100% glucose) has been artificially increased; common formulations of HFCS now include 42%, 55%, or 90% fructose. When consumed in large quantities on a long-term basis, HFCS is unhealthful and may contribute to other chronic diseases besides type 2 DM, including obesity and cardiovascular disease.
Impaired glucose tolerance and insulin resistance are known to be risk factors for cardiovascular disease and type 2 DM. In addition to increased blood glucose and insulin concentrations, high dietary glycemic loads are associated with increased serum triglyceride concentrations and decreased HDL cholesterol concentrations; both are risk factors for cardiovascular disease.
High dietary glycemic loads have also been associated with increased serum levels of C-reactive protein (CRP), a marker of systemic inflammation that is also a sensitive predictor of cardiovascular disease risk. In the NHS cohort, women with the highest dietary glycemic loads had a risk of developing coronary heart disease (CHD) over the next ten years that was almost twice as high as those with the lowest dietary glycemic loads.
The relationship between dietary glycemic load and CHD risk was more pronounced in overweight women, suggesting that people who are insulin resistant may be most susceptible to the adverse cardiovascular effects of high dietary glycemic loads. A similar finding was reported in a cohort of middle-aged Dutch women followed for nine years. Yet, studies to date have reported mixed results, and there is little evidence to indicate low glycemic index diets decrease the risk for CHD.
Evidence that high overall dietary glycemic index or high dietary glycemic loads are related to cancer risk is inconsistent. Prospective cohort studies in the U.S., Denmark, France, and Australia have found no association between overall dietary glycemic index or dietary glycemic load and breast cancer risk.
In contrast, a prospective cohort study in Italy reported a positive association between breast cancer risk and high-glycemic index diets as well as high dietary glycemic loads. A prospective study in Canada found that postmenopausal but not premenopausal women with high overall dietary glycemic index values were at increased risk of breast cancer, particularly those who reported no vigorous physical activity, while a prospective study in the U.S. found that premenopausal but not postmenopausal women with high overall dietary glycemic index values and low levels of physical activity were at increased risk of breast cancer.
In a French study of postmenopausal women, both glycemic index and glycemic load were positively associated with risk of breast cancer but only in a subgroup of women who had the highest waist circumference (median of 84 cm [33 inches]). Higher dietary glycemic loads were associated with moderately increased risk of colorectal cancer in a prospective study of U.S. men, but no clear associations between dietary glycemic load and colorectal cancer risk were observed in a prospective studies of U.S. men, U.S. women, Swedish women, and Dutch men and women. However, one prospective cohort study of U.S. women found that higher dietary glycemic loads were associated with increased risk of colorectal cancer.
One meta-analysis of case-control and cohort studies suggested that glycemic index and glycemic load were positively associated with colorectal cancer, but a more recently published meta-analysis did not find glycemic index or load to be significantly associated with colorectal cancer. Two separate meta-analyses reported that high dietary glycemic loads were associated with increased risk of endometrial cancer. Although there is some evidence that hyperinsulinemia (elevated serum insulin levels) may promote the growth of some types of cancer, more research is needed to determine the effects of dietary glycemic load and/or glycemic index on cancer risk.
Lowering Dietary Glycemic Load
Some strategies for lowering dietary glycemic load include:
- Increasing the consumption of nuts, legumes, fruits, and nonstarchy vegetables
- Decreasing the consumption of starchy high-glycemic index foods like potatoes, white rice, and white bread
- Decreasing the consumption of sugary foods like cookies, cakes, candy, and soft-drinks
Both GI and GL are listed below. The GI is of foods based on the glucose indexâ€“where glucose is set to equal 100. The other is the glycemic load, which is the glycemic index divided by 100 multiplied by its available carbohydrate content (i.e. carbohydrates minus fiber) in grams. (The "Serve size (g)" column is the serving size in grams for calculating the glycemic load; for simplicity of presentation an intermediate column that shows the available carbohydrates in the stated serving sizes has been left out.) Take, watermelon as an example of calculating glycemic load. Its glycemic index is pretty high, about 72. According to the calculations by the people at the University of Sydney's Human Nutrition Unit, in a serving of 120 grams it has 6 grams of available carbohydrate per serving, so its glycemic load is pretty low, 72/100*6=4.32, rounded to 4.
Glycemic Index and Glycemic Load Values for Selected Foods
(Relative to Glucose)
Carbohydrate per serving (g)
Glycemic Load per serving
Puffed rice cakes
Russet potato (baked)
1 large slice
Table sugar (sucrose)
White rice (boiled)
Brown rice (boiled)
Spaghetti, white; boiled 10-15 min
Spaghetti, white; boiled 5 min
Spaghetti, whole wheat; boiled
Rye, pumpernickel bread
1 large slice
8 fl oz
Lentils, dried; boiled
Kidney beans, dried; boiled
Pearled barley; boiled
Karen Foster is a holistic nutritionist, avid blogger, with five kids and an active lifestyle that keeps her in pursuit of the healthiest path towards a life of balance.