Researchers at Aberdeen University have made a breakthrough in the fight against Alzheimer's by finding that the disease can be combated with omega-3 oils.

In the study, researchers found that individuals, whose diets are high in omega-3 oils - found in found fish, walnuts and a number of seeds - do better in mental tests than those without the oils in their diets.

The study also found a genetic link that explains why some fish oil studies have been inconclusive in the past.

Alzheimer's, a degenerative terminal disease for which there is currently no known cure, begins with short-term forgetfulness and leads to severe memory loss, personality changes and the inability to live an independent life.

"Ten years ago this would have been science fiction. What we are touching on here is how nutrients can interact with specific genes in the body," the Scotsman quoted Lawrence Whalley, professor of mental health at Aberdeen University, who led the research, as saying.

For the study, researchers involved 120 people over the age of 64 and asked them to sit for intelligence tests in Scottish schools in 1947.

The tests were given at the ages of 64, 66 and 68.

Researchers also took blood samples so that the partcipants' DNA and the presence of omega-3 fats in their blood could be analysed.

The results of the tests were separated based on whether the individuals possessed a crucial gene known as APOE e4.

According to experts, APOE e4 is linked to the likelihood of contracting Alzheimer's at an earlier age than is more usually the case.

Researchers found that in case of 68-year-old individuals without the APOE e4 gene, there was a clear link between better results and the presence of omega-3s.

People with more than 2.1 percent omega-3 in the membrane of their blood cells got the best scores of more than 50.

Meanwhile, no one with less than 2 percent of the fats in their blood cell membranes managed more than 40 in the tests.

However, in participants with the crucial APOE e4 gene present, the omega-3 oils made no difference to their test scores.

According to experts, APOE e4 is the key as to whether fish oils help stave off dementia in later life and that omega-3s make the difference for those without the gene.

In previous studies, tests trying to link fish oil and intelligence in the elderly that did not make allowance for the gene have produced mixed results.

"What emerges from this research is that if you don't have this gene, omega-3s can make a difference. The next big thing will be to identify what factors can influence how these genes can be switched on and off, and also what to do if you have the gene," Whalley said.