Effects of dietary strawberry powder on blood lipids and inflammatory markers in obese human subjects

Authors: Zunino, Susan; PARELMAN, MARDI - University Of California; Freytag, Tammy; Stephensen, Charles; Kelley, Darshan; Mackey, Bruce; Woodhouse, Leslie; BONNEL, ELLEN - University Of California

Submitted to: British Journal of Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2011
Publication Date: 11/9/2011
Citation: Zunino, S.J., Parelman, M., Freytag, T.L., Stephensen, C.B., Kelley, D.S., Mackey, B.E., Woodhouse, L.R., Bonnel, E. 2011. Effects of dietary strawberry powder on blood lipids and inflammatory markers in obese human subjects. British Journal of Nutrition. 1-10. DOI: 10.1017/S0007114511006027.

Interpretive Summary: Obesity is a strong risk factor for the development of a number of chronic diseases which include hypertension, cardiovascular disease, and type II diabetes mellitus and has now become a major health problem worldwide. Elevated serum cholesterol and lipids are commonly observed in obesity. Fat tissue is a major source of inflammatory molecules that can contribute to chronic inflammation in obese individuals. Strawberries are a fiber-rich food and contain high levels of antioxidant phytochemicals that display anti-inflammatory abilities. The overall goal of this was to feed four servings of strawberries per day, in the form of freeze-dried powder, to obese subjects to determine whether dietary strawberries beneficially altered lipid profiles and reduced blood markers of inflammation. Twenty healthy obese male and female volunteers between 20-50 years old were recruited for this study. Each volunteer received a prepared diet of 3 meals per day, 7 days a week for 7 wks. The background diet consisted of approximately 35% fat, 20% protein, 45% carbohydrate, and 14 g fiber which is a typical American diet, and was low in fruits and vegetables. The intervention with strawberries, in the form of strawberry powder, occurred at breakfast and dinner and was the equal to about 4 servings of fresh strawberries per day. In the first week of the study, volunteers received prepared meals without intervention. Blood was collected on day 1 of the study and at the end of the first week before the intervention to obtain baseline information. After the first week, subjects received either the strawberry or control intervention for 3 wks. For the remaining 3 wks, subjects crossed over to the opposite intervention. All subjects fasted 12 hrs before each blood draw. Blood was collected again at weeks 3, 4, 6, and 7 during the study. Measurements for each blood draw were made and included a complete blood cell count, a comprehensive blood chemistry panel, lipid profiles, and test for inflammatory molecules. A 3 wk dietary intervention with strawberry powder was able to significantly reduce blood concentrations of small HDL particles and cholesterol and increase the size of LDL particles in healthy obese volunteers. These changes in lipid subfractions represent a beneficial reduction in risk factors for cardiovascular disease, stroke, and type II diabetes in our obese volunteers, and these data strengthen the role for strawberries, and likely other fruits, as a dietary means to decrease obesity-related disease.

Technical Abstract: Obesity is a strong risk factor for the development of a number of chronic diseases which include hypertension, cardiovascular disease, and type II diabetes mellitus and has now become a major health problem worldwide. Elevated serum cholesterol and lipids are commonly observed in obesity. Adipose tissue is a major source of pro-inflammatory molecules that can contribute to chronic inflammation in obese individuals. Strawberries are a fiber-rich food and contain high levels of antioxidant phytochemicals that display anti-inflammatory abilities. The overall goal of this study was to feed four servings of strawberries per day, in the form of freeze-dried powder, to obese subjects to determine whether dietary strawberries beneficially altered lipid profiles and reduced blood markers of inflammation. The specific hypothesis was that dietary strawberries would reduce risk factors for CVD and other health problems known to be associated with morbidity and mortality of obese individuals. Twenty healthy male and female subjects between 20-50 yrs old with a body mass index between 30-40 kg/m2 were recruited for this study. The study was a 7 wk double-blind, randomized, cross-over trial. Each subject received a prepared diet of 3 meals per day, 7 days a week for 7 wks. The background diet consisted of approximately 35% fat, 20% protein, 45% carbohydrate, and 14 g fiber and was low in fruits and vegetables. Intervention with strawberries, in the form of strawberry powder, occurred at breakfast and dinner and was the equivalent of 4 servings per day. In the first week of the study, subjects received prepared meals without intervention. Blood was collected on day 1 of the study and at the end of the first week before the intervention to obtain baseline information. After the first week, subjects received either the strawberry or control intervention for 3 wks. For the remaining 3 wks, subjects crossed over to the opposite intervention. All subjects fasted 12 hrs before each blood draw. Blood was collected again at weeks 3, 4, 6, and 7 during the intervention periods. Measurements for each blood draw included a CBC with the differential leukocyte count, a comprehensive chemistry panel, lipid profile analyses and measurement of inflammatory mediators. A 3 wk dietary intervention with strawberry powder was able to significantly reduce plasma concentrations of small HDL particles and cholesterol and increase LDL particle size in healthy obese subjects (p < 0.05). The alterations in lipid subfraction that were observed represent a beneficial reduction in risk factors for CVD, stroke, and metabolic syndrome/diabetes in our obese volunteers, further strengthening the role for strawberries, as well as other fruits, as a dietary means to decrease obesity-related disease.