Glycemic index database reveals health impact of common carbs

05 Aug 2024 --- US-based researchers developed a national database of foods’ glycemic index (GI) and glycemic load (GL) to offer consumers insights into the quality of carbohydrates consumed in the US and improve dietary awareness. According to the team, the database facilitates large-scale and high-quality surveillance or cohort studies of diet and health outcomes in the US.

The researchers underscore that carbohydrate intake quality, measured by the GI, has not been evaluated in the US over the past two decades. Foods with a high GI content, such as white flour and sugary cereals, cause a “sugar rush” that can negatively impact metabolic health. GL also considers the quantity of carbohydrates consumed. 

“Large-scale studies have shown that both high GI and GL diets are associated with an increased risk of type 2 diabetes, cardiovascular disease and some cancers,” says Karen Della Corte, nutrition and dietetics professor at Brigham Young University, US, and the study’s lead author. 

“High-GI foods also lead to quicker hunger and increased caloric intake and contribute to weight gain.”

AI model 
For the study published in The American Journal of Clinical Nutrition, the researchers used an AI-enabled model to analyze foods based on their GI and GL. They used a sample list of foods US citizens eat daily from the National Health and Nutrition and Examination Survey (NHANES). The AI matched the foods from this survey, based on their food descriptions and correlated GI and GL values to create the database. 

“Using open AI for the [creation] of the GI database was a novel application of ours and marks an advancement in nutritional research methodology,” explains Della Corte. “Looking forward, many new and important questions can now be investigated using this database relating to the role GI and GL play for chronic disease risk in the US.”

The database allowed the researchers to analyze the carbohydrate intake from collected data on 7,975 unique food codes. Using NHANES data, they also examined nationally representative distributions of GI and GL from 1999 to 2018.

Low-GI foods include whole grains, beans, lentils, chickpeas, brown or wild rice, quinoa, non-starchy vegetables, fruits and nuts.GI and GL changes 
The mean dietary GI was 55.7, and the energy-adjusted dietary GL was 133 across the 49,205 NHANES participants over the survey’s 20-year run time. From 1999 to 2018, dietary GI and GL decreased by 4.6% and 13.8%, respectively. 

At the same time, the researchers caution that “the proportion of energy intake from low-quality carbohydrates was still high at 42%.” 

Moreover, the researchers found dietary patterns within GI and GL based on sex, race, ethnicity, education and income levels. Dietary GL was higher among women, people with a lower education and people living under the poverty level. Moreover, Black adults had a higher GI/GL rate than White adults. 

“We hope that future studies derived from this database will add to the body of evidence needed to advocate for the incorporation of GI into public health guidelines and dietary recommendations.”

“GI-friendly zone” 
The study lists the top 20 carbohydrate sources consumed from 1999 to 2018 and their GI values. These foods account for 45% of the total carbohydrate intake. The food products that make the most considerable GL contributions to the US diet include soft drinks, white bread, rice and fruit juice.

Among these top 20 foods, products with a low GI score (under 55) include milk, tortillas and sweetened tea. Examples of foods with a medium GI score (55–70) include corn chips and snacks, pizza and bananas, while foods with a high GI score (over 70) include white bread, beer, French fries and rice. 

Della Corte underscores the potential impact of understanding which foods have a low GI to make more informed food choices. She suggests consumers turn their pantry into a “GI-friendly zone,” focusing on whole grains, beans, lentils, chickpeas, brown or wild rice, quinoa, barley, steel-cut or rolled oats, non-starchy vegetables, fruits and nuts. 

Last year, researchers found that kombucha reduced the GI and insulin index when consumed with a high-GI meal. Meanwhile, scientists in the Philippines formulated rice with a low GI score of 44 after discovering the genes responsible for the low and ultra-low GI in rice. 

“One key takeaway from this study is the importance of prioritizing low-glycemic carbohydrates in the diet. This means focusing on whole, minimally processed foods that release glucose slowly into the bloodstream and prevent spikes in blood sugar levels,” explains Della Corte. 

“Making swaps from refined grains to whole grains can help improve the healthfulness of the diet and lower the overall dietary GI,” she concludes.

By Jolanda van Hal