A combination of garlic supplements and vitamin C reduced blood pressure back to normal levels in people with mildly elevated levels, says a pilot study.

"Combinations of garlic and vitamin C are an effective alternative in the control of marginally high blood pressure," wrote authors Adam Mousa and Shaker Mousa in the journal Nutrition Research (Elsevier).

"Garlic ingredients or garlic extract alone increased endothelial cell NO production, an effect that was shown to be enhanced by the combination with antioxidant vitamins," they said.

The study adds to a large body of science indicating cardiovascular benefits for garlic, with consumer awareness of potential health benefits already high. This has benefited the supplements industry, particularly since consumers seek the benefits of garlic without the odours that accompany the fresh bulb.

Garlic supplements are worth more than $100m (€79.5m) in the US and are also one of the biggest sellers in the UK market. According to a 1998 survey by Hartman and New Hope, garlic supplements are used twice as much as other herbal supplements.

Mousa and Mousa recruited six subjects with marginally elevated blood pressure (140/90 mmHg) and assigned them to take placebo for 10 days; followed by one-week washout, then vitamin C (2000 mg) for 10 days, a further week of wash-out period, then garlic tablets (650 mg of bulb powder) for 10 days. Finally, after the last washout, garlic and vitamin C were given together for 10 days.