Daily Consumption of Strawberries for Eight Weeks Increases Serum Levels of IGF‐1 in Postmenopausal Women

Abstract

Ovarian hormone deficiency may lead to over production of pro‐inflammatory molecules with a concomitant rise in oxidative stress. This cascade of events negatively affect bone metabolism with a subsequent development of osteoporosis and increased risk of fractures. Epidemiological studies suggest that consumption of fruits and vegetables is associated with decreased incidence of chronic diseases including osteoporosis which is mainly attributed to the polyphenol content of these foods. Strawberries are widely consumed in the United States and have high polyphenolic content which confers to them strong antioxidant and anti‐inflammatory activities. Thus, the main objective of this eight‐week randomized, double‐blind, placebo‐controlled clinical trial was to investigate the extent to which daily consumption of strawberries would favorably alter blood biomarkers of bone metabolism in postmenopausal women. Forty‐seven postmenopausal women (age: 59 ± 6 years; body mass index: 31.5 ± 4.1 kg/m2) were randomly assigned into one of two groups: 1) 25 g of freeze‐dried strawberry powder (FDSP) (equivalent to 1½ cups of fresh strawberries), or 2) 25 g placebo powder. As anticipated, there were no significant differences in baseline characteristics between the two groups. At baseline, no changes were noted for body composition and bone mineral density in either of the groups, as expected. Serum levels of bone‐specific alkaline phosphatase, a marker of bone formation and tartrate‐resistant acid phosphatase‐5b, a specific marker of bone resorption, were not affected by FDSP after eight weeks in comparison with placebo. In contrast, a significant time‐by‐treatment interaction (P = 0.041) was observed for serum insulin‐like growth factor 1 (IGF‐1), known to strongly stimulate bone formation. IGF‐1 levels were increased in the FDSP group (56.7 ± 4.0 to 69.9 ± 11.3 ng/ml) while they were not changed in the placebo group (60.6 ± 3.7 to 60.9 ± 6.1 ng/ml). Our findings suggest that regular consumption of strawberries may be beneficial for bone health due to their ability to increase the synthesis of IGF‐1; however, further studies are warranted to examine the efficacy of long‐term incorporation of strawberries into the diet on bone health.Support or Funding InformationThis study was funded, in part, by the California Strawberry Commission.