People who take omega-3 fish oil supplements may have a reduced risk of developing skin cancer, a new study indicates.

Omega 3 fatty acids are most commonly found in oily fish, such as salmon, mackerel and herring. Supplements are also available over the counter in pharmacies.

Studies suggest that omega-3 fatty acids may help prevent a number of conditions, including heart disease, high blood pressure and Alzheimer's.

Now scientists at the University of Manchester have found that regularly taking omega-3 supplements boosts the skin's immunity to sunlight. It does this by reducing suppression of the immune system that can be caused by sunlight. Known as immunosuppression, this can affect the body's ability to fight cancer of the skin.

"There has been research in this area carried out on mice in the past, but this is the first time that there has been a clinical trial directly in people. It has taken a number of years to get to this stage and the findings are very exciting," explained lead scientist, Prof Lesley Rhodes.

Participants in the study were divided into two groups. The first group took a 4g supplement of omega-3 every day, before being exposed to the equivalent of eight, 15 or 30 minutes of summer midday sun using a special light machine.

The other group took a placebo before being exposed to the light.

The study found that immunosuppression was 50% lower in those who took the omega-3 supplements and who were exposed to the sun for eight or 15 minutes compared to those who took the placebo.

There was little difference between the two groups when exposed to 30 minutes of light.

"This study adds to the evidence that omega-3 is a potential nutrient to protect against skin cancer. Although the changes we found when someone took the oil were small, they suggest that a continuous low level of chemoprevention from taking omega-3 could reduce the risk of skin cancer over an individual's lifetime," Prof Rhodes said.

She pointed out that the findings are particularly important because many people do not apply sunscreen adequately and only wear it when on holidays.

However, Prof Rhodes emphasised that omega-3 supplements are not a replacement for sunscreen and other protective measures, such as wearing a sunhat.

Details of these findings are published in The American Journal of Clinical Nutrition.