Getting enough daily servings of dairy in the diet—particularly those containing whey protein—may help fight oxidative stress associated with obesity and metabolic syndrome, according to researchers from University of Tennessee.
Their study, published in the August issue of The American Journal of Clinical Nutrition, found that dairy-rich diets eased oxidative stress and the burden of symptoms associated with metabolic syndrome in overweight and obese subjects.
The study confirms previous findings of a recent randomized crossover trial on overweight and obese adults showing that dairy-based shakes, but not soy-based shakes, significantly reduced oxidative stress biomarkers.
Oxidative stress is exacerbated by obesity because the increased oxidants acting on adipose tissue (fat tissue) can increase expression of harmful signaling molecules that may contribute to metabolic syndrome – a cluster of cardiovascular risk factors that includes increased blood pressure, elevated insulin levels, excess body fat around the waist and high cholesterol levels.
“An increase in dairy intake from suboptimal to adequate levels… significantly [reduces] both oxidative and inflammatory stress in metabolic syndrome,” the authors wrote.
The randomized controlled trial followed 40 overweight and obese adults already diagnosed with metabolic syndrome, with one group consuming a low-dairy diet (less than 0.5 dairy servings per day or less than 600 milligrams of calcium per day), and the other consuming an adequate-dairy diet (more than 3.5 dairy servings per day and at least 1,200 milligrams of calcium per day).
- The low-dairy group consumed a diet containing three daily servings of a combination of prepackaged nondairy foods including low-sodium luncheon meats, soy-based luncheon meat substitutes, fruit cups, granola bars and peanut butter crackers. Each serving contained less than 8 grams of protein and 50 milligrams of calcium. The subjects purchased all other foods in their diets and adjustments were made to ensure their choices didn’t alter the nutrient content of the overall diet.
- The adequate-dairy group consumed three servings of dairy every day, each providing 300 to 350 milligrams of calcium and 8 to 10 grams of dairy protein. Calcium from dairy totaled 1000 to 1050 milligrams per day while protein from dairy totaled 28 to 35 grams per day. As with the group above, subjects purchased the rest of their diet with adjustments made so not to mess up the diet’s overall nutrient composition. Two-thirds of the daily dairy servings ingested were milk and/or yogurt so that sufficient amounts of whey protein were consumed.
After 84 days, those in the adequate-dairy group had significantly reduced levels of the biomarkers of oxidative and inflammatory stress, as well as lowered blood pressure and improved insulin sensitivity.
The researchers wrote that believe that bioactive components in dairy, beyond its calcium content, contribute to its protective effect against inflammation and oxidative stress. Previous studies have shown that milk proteins, especially whey protein, have an insulin-stabilizing effect in healthy individuals. What’s more, regular consumption of low-fat dairy has shown to reduce the risk of type 2 diabetes, yet the way in which it does this is not yet well understood.
Stancliffe RA, Thorpe T, Zemel MB. Dairy attenuates oxidative and inflammatory stress in metabolic syndrome. Am J Clin Nutr 2011;94:422-30. doi: 10.3945/ajcn.111.013342