Twelve weeks of 50 grams per day of the berries was also associated with significant reductions in small LDL particles, reported to be more likely to cause atherosclerosis, according to findings published in the Journal of Nutrition .
The new data, published by researchers from Oklahoma State University, Queen’s University of Belfast (Northern Ireland), and the University of Oklahoma Health Sciences Center, adds to the potential heart health benefits of strawberries and their extracts. In 2009, researchers from Oklahoma State University reported that eight weeks of supplementation with a freeze-dried strawberry powder was associated with a reduction of LDL-cholesterol levels of 11% in obese people (Nutrition Research, Vol. 30, pp. 462-469).
A study in overweight women a year earlier reported that freeze-dried strawberry powder may reduce total and LDL cholesterol levels by 5 and 6%, respectively (Nutrition Journal, 8:43).
Recently, Italian scientists reported in the Journal of Nutritional Biochemistry that one month of eating 500 grams per day of the Alba cultivar of strawberries resulted in significant reductions to total cholesterol of almost 9%, LDL cholesterol of about 14%, and triglycerides of almost 21.
Improvements were also recorded in antioxidant status of the 23 healthy volunteers, while levels were reduced of 8-hydroxy-2'-deoxyguanosine (8-OHdG), a marker for oxidative stress, wrote the researchers.
For the new study, Oklahoma State University’s Arpita Basu and her co-workers recruited 60 adults with excess fat around their belly (abdominal adiposity) and elevated lipids levels to participate in their randomized dose-response controlled trial. The participants were randomly assigned to receive either a low-dose strawberry beverage (25 grams per day), a high dose strawberry drink (50 grams per day), or control versions of each drink.
After 12 weeks of intervention, the results showed a dose-dependent effect on total and LDL cholesterol, and small LDL particle concentration, with the results only statistically significant in the high-dose group, compared to controls.
Indeed, total and LDL cholesterol decreased by 33 mg/dL and 28 mg/dL, respectively, said the researchers, while the small LDL particle concentration decreased by 301 nmol/L.
In addition, both doses of strawberries were found to decrease levels of malondialdehyde (MDA - a reactive carbonyl compound and a well-established marker of oxidative stress). The decrease was similar for both doses, added Dr Basu and her co-workers.
No effects were found on other biomarkers, including HDL cholesterol, adiposity, triglycerides, blood pressure, and blood glucose levels.
“To the best of our knowledge, this is the first report of a 12-wk randomized controlled trial showing the effects of a higher dose of strawberries in lowering conventional serum total and LDL cholesterol and NMR-derived small LDL particle concentrations when compared with a lower dose in obese adults,” wrote the researchers. "In general, strawberries exerted antioxidant effects by decreasing lipid peroxidation, although no effects were noted on adiposity, blood pressure, glycemic control, or inflammation.
"Thus, strawberries as a popular fruit in the U.S. diet deserve additional investigation concerning their effects on biomarkers of CVD risk in adults, including those with type 2 diabetes and related lipid and vascular abnormalities."
The study was partly funded by the California Strawberry Commission.
Source: Journal of Nutrition
Published online ahead of print, doi: 10.3945/jn.113.188169
“Freeze-Dried Strawberries Lower Serum Cholesterol and Lipid Peroxidation in Adults with Abdominal Adiposity and Elevated Serum Lipids”
Authors: A. Basu, N.M. Betts, A. Nguyen, E.D. Newman, D. Fu, T.J. Lyons