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Title

EFFECT OF STRAWBERRY ANTIOXIDANTS ON OXIDATIVE STRESS IN INSULIN RESISTANT INDIVIDUALS: A DOSE RESPONSE STUDY

Creator

Vijayakumar, Lakshmi Prabha

Date

2014, 2014-05

Description

Oxidative and inflammatory stress is associated with chronic disease development and progression. Recent studies suggest that consumption of...
Show moreOxidative and inflammatory stress is associated with chronic disease development and progression. Recent studies suggest that consumption of fruits and vegetables rich in antioxidant compounds attenuate oxidative stress and inflammation. Strawberries are abundant in polyphenolic compounds with antioxidant properties, which have attracted research attention for their possible health benefits. The aim of the project was to determine whether the antioxidant properties of strawberries formulated in a beverage would dose-dependently restore oxidative stress induced by a high fat/ high carbohydrate meal in insulin resistant individuals. Plasma was collected from insulin resistant individuals (n=25) every 30-60 min over 6 h after ingestion after a 650 kcal high fat/ high carbohydrate meal accompanied with a beverage containing 0, 10, 20 or 40 g freeze-dried strawberry powder. The antioxidant capacity of test beverages containing 10, 20 and 40 g strawberry powder were 9.31± 0.66, 19.10 ± 0.60 and 33.57 ± 1.75 μmol Trolox equivalents/mL based on the Oxygen Radical Absorbance Capacity (ORAC) assay. The ORAC value for the placebo (0 g) was below the detectable limits. Biologically relevant oxidative stress was determined using the ORAC assay to estimate antioxidant capacity of the plasma and oxidation of low density lipoprotein (ox-LDL) using an ELISA assay to determine the oxidative damage. Assessment of ox-LDL over 6 hr revealed a significant effect of time (p<0.0001), however no significant difference between the treatment dosages was evident (p>0.05). A marginal treatment by time interaction suggested possible time specific differences between treatments. The evaluation of antioxidant capacity of the plasma was split into assessment of the hydrophilic and lipophilic fractions. Hydrophilic ORAC results showed ix no significant differences between test beverages over 6 hr (p>0.05), including effects of time or treatment by time interactions (p>0.05). The lipophilic ORAC also did not reveal significant differences between treatments (p>0.05). Overall, it appears that beverages with different “doses” of antioxidant capacity did not result in dose-dependent changes in oxidative stress in insulin resistant individuals. There was a trend for protection of ox-LDL by the 20 g strawberry beverage revealed by differences among treatments at 240 min compared to the placebo/0 g strawberry beverage. The findings suggest that antioxidant food properties do not translate directly to plasma antioxidant capacity as measured by ORAC and alternative mechanisms are likely responsible for biological antioxidant effects of strawberry.
M.S. in Mechanical and Aerospace Engineering, May 2014
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