The trial comes at a time when consumers are increasingly aware of the risk of skin cancer. They are also beginning to understand the benefits of nutrition for skin health.

For the randomized, double-blind study at Center Hospital University in Besançon, France, researchers induced UV skin burn on the inner-forearms of 50 healthy subjects once a week over a four-week period.

The participants took a supplement containing either GliSODin or a placebo each day, starting just two or three days prior to the first irradiation.

For the supplement group there was a significant increase in the minimum exposure to UV rays necessary to produce skin burn. Even fair-skinned subjects (phototypes II) required eight times more exposure to produce burns than the placebo group, said the researchers, led by leading French dermatologist Professor Philippe Humbert.

Once burning had occurred, the redness was seen to decrease more quickly in the GliSODin group and the number of capillaries assessed by videocapillaroscopy increased, indicating a reduction in inflammation.

“This study confirms the efficacy of GliSODin in the prevention of the consequences of oxidative stress resulting from exposure to the sun. This efficacy is of particular interest for phototypes II that represent a major part of the consultations in dermatology,” said the researchers.

Other supplements marketed for skin protection include Cyanotech's BioAstin natural astaxanthin as well as vitamin E, the most common antioxidant in sun care formulations.

However a 2000 study in the American Journal of Clinical Nutrition found that although oral vitamin E supplementation made a small difference to the sunburn received by 22-fair skinned men and women over a 12-week period, the results were not significant enough for them to advocate replacing topical barriers with supplements.

SOD has a different mode of action to vitamins. Dubbed ‘the enzyme of life' when first discovered in 1968, it is the first antioxidant mobilized by the cell for defence. It is thought to be more powerful than antioxidant vitamins as it activates the body's productions of its own antioxidants, including catalase and glutathione peroxidase.

Isocell published four studies on its product last year, president Francois Vix told NutraIngredients.com, adding to the scientific credibility of this still relatively new supplement, and its mechanism.

The supplement has also been difficult to bring to market in oral form as the small SOD molecule is easily destroyed in the digestive system.

Isocell Nutra, a research firm concentrating on free radicals, has developed a way of protecting the molecule, which it extracts from a special melon breed that contains seven times the antioxidants of a regular melon.

The company combines the SOD with a wheat protein that protects the enzyme and also binds it to the intestine wall, the site of most of the body's immune cells.

The final ingredient, produced in France by a partner company, first reached the Japanese market three years ago and is seeing rapid growth in demand. Sales to the end of June have already reached the total volume for 2004, said Vix.

It has been available in France for a year, and was recently introduced in Belgium. Further European markets are expected to follow shortly, driving up current production of between 10-15 tons per yer.

Other French companies, Bionov and Ninapharm, are also marketing SOD dietary supplements. Both are derived from watermelon, said to be the richest plant source of the enzyme.