The study –published in the Journal of Nutrition – reports that diet rich in slowly digested carbohydrates, such as whole grains, legumes and other high-fibre foods, significantly reduces markers of inflammation associated with chronic disease. The research also suggests that such a diet increases levels of the hormone adiponectin, which helps to regulate the metabolism of fat and sugar.
The randomised controlled study, involving 80 healthy men and women – half of normal weight and half overweight or obese – found that among the overweight and obese study participants the low-glycemic-load diet reduced an important biomarker of inflammation called C-reactive protein by about 22%.
"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," said lead author Dr Marian Neuhouser, of the Public Health Sciences Division at the Fred Hutchinson Cancer Research Centre, USA.
"Lowering inflammatory factors is important for reducing a broad range of health risks,” she said.
“Showing that a low-glycemic-load diet can improve health is important for the millions ... who are overweight or obese."
In recent years there has been pressure from consumer groups and government organisations for food manufacturers to reformulate products with healthier ingredients.
As a result, there has been a growth in the number of products containing more slowly digested carbohydrates (low-glycemic-load) in place of flours and sugars that are digested faster.
In the study, participants completed two 28-day feeding periods in a random order – one featuring high-glycemic-load (high-GL) carbohydrates, and the other featuring low-glycemic-load (low-GL) carbohydrates. The diets were identical in carbohydrate content, calories and macronutrients, noted the research team.
"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," explained Neuhouser.
The team analysed blood taken from participants at the beginning and end of each feeding period, to look for changes in important biomarkers like; high-sensitivity C-reactive protein, serum amyloid A, Interleukin-6, leptin, and adiponectin.
The team found that among people with high-body fat mass the low-GL diet significantly reduced C-reactive protein and marginally increased adiponectin (by around 5%).
"The bottom line is that when it comes to reducing markers of chronic-disease risk, not all carbohydrates are created equal. Quality matters," said Neuhouser.
Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/jn.111.149807
“A Low-Glycemic Load Diet Reduces Serum C-Reactive Protein and Modestly Increases Adiponectin in Overweight and Obese Adults”
Authors: M.L. Neuhouser, Y. Schwarz, C. Wang, K. Breymeyer, G. Coronado et al