The researchers say they have found that children who eat a normal Mediterranean diet are 30% less likely to develop hay fever.

They also found that a Mediterranean diet where very large quantities of fruit were consumed meant children were over 60% less likely to develop hay fever.

According to Paul Cullinan from the Royal Brompton Hospital and National Heart and Lung Institute, London, one of the authors of the study, although allergic hypersensitivity is fairly common among children living in rural Crete wheeze and rhinitis are rare.

The researchers were intrigued by this discrepancy and suspected it could be linked to the high consumption of fresh fruit and vegetables typical of the traditional Mediterranean diet.

Previous studies have indicated that a Mediterranean diet reduces the risk of developing diabetes type 2, hypertension (high blood pressure), heart disease and several cancers, but this particular study examined it's effect on children.

The researchers involved 690 schoolchildren living in Crete, Greece aged between 7 and 18 years whose parents were asked to complete a survey regarding their children's eating habits and allergies.

Virtually all the children in the study ate fresh tomatoes and several types of fruit at least weekly, while over half of them consumed them daily and most of the children ate nuts regularly.

The children all underwent skin prick tests with 10 common aeroallergens and it was evident that although 30% of children had allergies, which is the norm, whereas half should have exhibited symptoms such as asthma, runny nose and itchy eyes, very few did.

The researchers concluded that a traditional Mediterranean diet where fruits, vegetables and nuts are consumed regularly has a beneficial effect and may lower allergic symptoms in children.

The researchers say such effects are similar to those found using one-drug therapy with common blood pressure-lowering medications such as beta-blockers and ACE inhibitors.

Of the five studies on green or black tea none were associated with any significant reduction in blood pressure.

According to the researchers when these figures are applied to the population as a whole, they estimate that the blood pressure-lowering effect associated with cocoa would be expected to reduce the risk of stroke by about 20%, coronary heart disease by 10%, and death from all causes by 8%.

However, they do caution against their findings being used as an excuse to over-indulge in chocolate and say a reasonable approach would be to substitute a slice of cheesecake for a polyphenol-rich piece of dark chocolate and any dietary advice should take into account the high sugar, fat and calories existing in most cocoa products.

Researcher Dr. Dirk Taubert, says a rational approach might be to include cocoa products as part of a dietary guide to lowering a hypertension risk.

The research is published in the Archives of Internal Medicine, a publication of the American Medical Association.