Dietary polyphenols, such as those from grape products, may exert beneficial effects on cardiovascular health, including anti-hypertensive effects. We investigated the effect of a specific grape seed extract (GSE) rich in low-molecular-weight polyphenolic compounds on ambulatory blood pressure (ABP) in untreated subjects with pre- and stage I hypertension. In addition, potential mechanisms that could underlie the hypothesised effect of GSE on blood pressure (BP), and platelet aggregation, were explored. The study was designed as a double-blind, placebo-controlled, randomised, parallel-group intervention study including seventy healthy subjects with systolic BP between 120 and 159 mmHg. A 1-week run-in period was followed by an 8-week intervention period, during which subjects consumed capsules containing either 300 mg/d of GSE or a placebo (microcrystalline cellulose). Before and after the intervention, daytime ABP readings, 24 h urine samples and fasting and non-fasting blood samples were taken. The mean baseline systolic BP was 135·8 (se 1·3) mmHg and diastolic BP was 81·5 (se 0·9) mmHg. BP values were modestly, but not significantly, affected by the polyphenol-rich GSE treatment v. placebo with an effect of − 3·0 mmHg for systolic BP (95 % CI − 6·5, 0·5) and − 1·4 mmHg for diastolic BP (95 % CI − 3·5, 0·6). Vasoactive markers including endothelin-1, NO metabolites and asymmetric dimethylarginine, plasma renin activity and platelet aggregation were not affected by the GSE intervention. Our findings show that consumption of polyphenol-rich GSE does not significantly lower ABP in untreated subjects with pre- and stage I hypertension.

The aim of the present investigation was to study the effect of a dietary intervention which combined nutrition information with increased availability of vegetables, fruits and wholegrain bread. The effect of the intervention was determined by changes in the intake of vegetables, fruits, wholegrain bread and estimated nutrients. Furthermore, the study investigated whether changes in relative contribution from different food sources of folate were related to changes in the concentration of plasma total homocysteine (p-tHcy). The 5-month intervention study included 376 male recruits from the Norwegian National Guard, Vaernes (intervention group) and 105 male recruits from the Norwegian National Guard, Heggelia (control group). The study resulted in an increase in the total consumption of vegetables, fruits, berries and juice (P < 0·001) and of wholegrain bread (P < 0·001). The participants in the intervention group showed a higher increase in the intake of dietary fibre (P < 0·001) and folate (P < 0·001) compared with the control group. The relative contribution of folate intake from fruits, vegetables and wholegrain bread was higher in the intervention group compared with the control group (P < 0·001 for all). The increased intake of folate from wholegrain bread was inversely associated with a reduced concentration of p-tHcy (P = 0·017). In summary, the dietary intervention resulted in an increased intake of vegetables, fruits and wholegrain bread and a subsequent increase in folate intake from these food components. Reduction in the concentration of p-tHcy was significantly related to an increased folate intake due to an increased consumption of wholegrain bread.

Many studies have shown that overall dietary patterns, dietary components consumed, or mode of food preparation are all possibly relevant in either reducing or increasing the risk of cancer in animals or man. Yet, dietary intervention studies, stemming from laboratory and epidemiological observational studies have often failed to demonstrate the anticipated protection against cancer. One possible explanation for the discrepancy between the results of various observational and experimental chemo-prevention studies is the lack of control for biological diversity of the participants of these studies. It is suggested that future epidemiological studies provide evidence stratified by status of major metabolic polymorphisms pertinent to the study subject, and that future intervention studies take these differences into account in the design and analysis phases.