A diet rich in slowly digested carbohydrates such as high-fiber whole grains & legumes and milk significantly reduces a marker of systemwide inflammation associated with chronic disease, according to a new study at Fred Hutchinson Cancer Research Center in Seattle.
The study also found that such a “low-glycemic-load” diet slightly increases a hormone known to regulate the metabolism of fat & sugar and reduce risk of several cancers and other disorders. These findings were published online Jan 11 by the Journal of Nutrition.
The controlled, randomized feeding study, which involved 80 healthy Seattle-area men and women – half of normal weight and half overweight or obese – found that among the overweight and obese study participants, a low-glycemic-load diet reduced a biomarker of inflammation called C-reactive protein by about 22%.
[Note: Cancer researchers at M D Anderson Center reported in 2005 that CRP may be produced by fat cells, adding to the understanding of how body fat participates in the inflammatory process. They suggested that aspirin and statin drugs could help to counteract the process, but the findings of this study may suggest a more natural strategy.]
“This finding is important and clinically useful, since C-reactive protein is associated with an increased risk for many cancers as well as cardiovascular disease,” says lead author Marian Neuhouser, PhD, RD, a member of the Hutchinson Center’s Cancer Prevention Program.
“Lowering inflammatory factors is important for reducing a broad range of health risks. Showing that a low-glycemic-load diet can improve health is important for the millions of Americans who are overweight or obese.”
Dr. Neuhouser and colleagues also found that, among the overweight and obese study participants, a low-glycemic-load diet modestly increased – by about 5% – blood levels of a protein hormone called adiponectin.
This hormone plays a key role in protecting against several cancers, including breast cancer, as well as metabolic disorders such as type-2 diabetes, nonalcoholic fatty liver disease and hardening of the arteries.
“Glycemic load” refers to how the intake of carbohydrates, adjusted for total grams of carbohydrate, affects blood-sugar levels. Lentils or pinto beans have a glycemic load that is approximately three times lower than instant mashed potatoes, for example, and therefore won’t cause blood-sugar levels to rise as quickly.
Study participants completed two 28-day feeding periods in random order:
• One featuring high-glycemic-load carbohydrates, which typically are low-fiber, highly processed carbs such as white sugar, fruit in canned syrup and white flour;
• And the other featuring low-glycemic-load carbohydrates, which are typically higher in fiber, such as whole-grain breads and cereals.
The diets were identical in carbohydrate content, calories and macronutrients. All food was provided by the Hutchinson Center’s Human Nutrition Laboratory, and study participants maintained weight and physical activity throughout.
“Because the two diets differed only by glycemic load, we can infer that the changes we observed in important biomarkers were due to diet alone,” Neuhouser said.
“The bottom line is that when it comes to reducing markers of chronic-disease risk, not all carbohydrates are created equal. Quality matters,” she said. “There are easy dietary changes people can make. Whenever possible, choose carbohydrates that are less likely to cause rapid spikes in blood glucose.”
These types of low-glycemic-load carbs include whole grains; legumes such as kidney beans, soy beans, pinto beans and lentils; milk; and fruits such as apples, oranges, grapefruit and pears.
Neuhouser also recommends avoiding high-glycemic-load carbohydrates that quickly raise blood glucose. These include highly processed foods that are full of white sugar and white flour, and sugar-sweetened beverages and breakfast cereals.
Sources: Based on Fred Hutchinson Cancer Research Center press release, Jan 11, 2012; article abstracts, Wikipedia.