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Background:
In vitro studies from our lab showed that strawberry extracts exert anti-inflammatory activities, which were associated with concentrations of polyphenols and catechins in the extracts. In addition, recent epidemiologic studies reported inverse relations between the consumption of strawberries and plasma levels of C reactive protein (CRP) and the risk for cardiovascular diseases. These data indicate that regular strawberry consumption in real life situations is also associated with reduced chronic inflammation and cardiovascular disease risk. For other polyphenol and catechin-rich dietary products, i.e. chocolate and green tea, human intervention trials indicated that these products have anti-inflammatory and anti-oxidant activities and improve endothelial and vascular function. Therefore it is hypothesized that regular consumption of strawberries can reduce endothelial dysfunction by reducing inflammation and oxidative stress. This is thought to be mediated by polyphenols and catechins present in strawberries.



Objective:
The aim of the proposed study is to evaluate the effect of daily consumption of 400 gram strawberries as smoothies during 2 weeks on markers of endothelial function, inflammation and oxidative stress.
Study design: The study will be a randomized, single blind, placebo-controlled intervention study.



Study population:
40 metabolic syndrome patients fasting blood glucose levels between 5.5 and 7,8 mmol/l will be selected, aged between 40 and 70 years, both females and males. 20 patients will be randomly assigned to the strawberry group and 20 to the placebo group. Randomization will be done gender specifically, ensuring an equal number of males and females in both study groups.



Intervention:
The intervention period will be 2 weeks, with 20 patients consuming 400 gram strawberries as 2 smoothies per day, and 20 patients consuming 2 iso-caloric (compared to the smoothies) placebo strawberry lemonades of 200 cl, based on a commercially available lemonade with artificial flavor compounds.



Main study parameters/endpoints:
Markers of endothelial function, inflammation and oxidative stress will be measured after an oral glucose tolerance test (OGTT). The effect of the intervention will be measured on day 16 of the study, to exclude acute effects of strawberry consumption. The estimated outcome is a 25% reduction in the OGTT-induced inflammatory gene transcription.



Nature and extent of the burden and risks associated with participation, benefit and group relatedness:
Participants have to be in a fasting state and visit the laboratory for the prescreening and twice to perform an OGTT. They will consume 2 strawberry or placebo drinks per day during 2 weeks. The evening preceding the OGTT they consume a standard meal. Allergic or hypersensitivity reactions for strawberries can occur, and these are reasons to withdraw from the study.

Daily conumption of a portion of 400 gram strawberries will reduce the glucose induced inflammatory response and oxidative stress in metabolic syndrome patients with impaired glucose tolerance (beginning type 2 diabetes).

OGTT and other measurements are done before start of the intervention on day 1 and repeated on the second day after last consumption of straweberries (day 16).

1. Intervention: 400 gram strawberries as smoothies, daily for 14 days;

2. Placebo: 400 gram strawberrie lemonade with equal carbohydrate and protein content as strawberries.