Grape seed extract could be a useful weight management supplement, suggests a small study, the first to test the effects of the extract on calorie intake in people.
The researchers from Maastricht University in the Netherlands found the supplement to reduce the calorie intake of people with above average energy requirements by four per cent over a 24 hour period.
A long-term trial is needed to find out whether this reduction could be sustained over a longer period and therefore stop weight gain.
In vitro experiments have previously shown that polyphenols, the antioxidants present in high quantities in grape seed extract, stimulate the breakdown of fat. Grape seed extract has also been shown to reduce food intake in rats.
In a randomised, double-blind, cross-over study, 51 normal to overweight men and women took grape seed supplements three times daily, 30-60 minutes before breakfast, lunch and dinner, for three days. Lunch and dinner was eaten in the university restaurant while standard breakfasts and snacks were provided for eating at home. All meals were comparable in energy density and macronutrient composition and the subjects were asked to eat until they would feel satiated.
The grape seed tablets contained 300 mg grape seed extract (polyphenolics) containing more than 90 per cent procyanidines.
After a washout period of three weeks, the subjects repeated the exercise with a placebo pill.
While the scientists saw no difference in 24 hour energy intake between the grape-seed extract and placebo groups overall, in the 23 subjects with a higher than average energy requirement (7.5 megajoules a day), energy intake was reduced by 4 per cent after grape-seed extract compared to placebo treatment.
Energy requirement was calculated by determining the most likely combination of energy intake and physical activity index at which body weight remains stable.
Meanwhile, there were no significant differences in macronutrient composition, attitude towards eating, satiety, mood or tolerance, reports Neeltje Vogels and colleagues in the April issue of the European Journal of Clinical Nutrition (58, 667-673).
"These findings suggest that grape seed could be effective in reducing 24 hour energy intake in normal to overweight dietary unrestrained subjects, and could, therefore, play a significant role in body-weight management," they write.
They also noted that weight control methods often produce short-term success, but substances that reduce energy intake without a strong reduction in satiety may be useful.
Grape seed is thought to delay absorption of the diet, which means that subjects do not feel hungry and therefore eat less food.
If a year-long trial found energy intake to remain 4 per cent lower throughout the period, this could result in a weight loss (or prevention of weight gain) of 3.7 kg, suggest the authors.