FRIDAY, Aug. 20 (HealthDay News) -- For people with the metabolic syndrome -- a cluster of risk factors such as obesity, high blood pressure, high levels of blood fats or triglycerides and high blood sugar -- adding a little fish oil to a diet low in saturated fats and high in complex carbohydrates might be just the ticket, a new study suggests.

"When you add omega-3 to a high carbohydrate, low-fat diet, you can prevent the long-term adverse effect that a high-carbohydrate diet induces on [blood fats]," said study author Dr. Jose Lopez-Miranda, a professor of medicine at the Reina Sofia University Hospital and the University of Cordoba, Spain.

The study is published in the September issue of the Journal of Nutrition.

Lopez-Miranda and his team looked at 117 people with metabolic syndrome, which raises the risk of heart disease and stroke. They assigned them to one of four diets for 12 weeks. The diets were: high fat/rich in saturated fats; high fat/rich in monounsaturated fats (such as fish and olive oil), low fat and high in complex carbohydrates (such as whole grains, fruits, vegetables), low fat and high in complex carbs but with the fish oil supplement included.

All four diets included about the same number of calories. The researchers tested blood before and after eating, looking for blood fat levels.

At the study's start, all participants had similar post-meal blood fat responses. But by the end of the three-month trial, those on the high-fat/monounsaturated fat-rich diet or the low-fat, high complex carbohydrate diet with fish oil had better responses.

For example, those on the low-fat/high-carb diet plus fish oil showed lower levels of triglyceride blood fats, compared to people eating a high-fat diet rich in saturated fats, the researchers found. And people eating the low-fat/high-carb regimen alone (without fish oil) had a rise in triglycerides and cholesterol, compared to when fish oil was added.

The researchers believe that adding polyunsaturated fat -- such as those found in fish oil -- can help undercut the effects of a long-term low-fat, high complex carbohydrate diet on triglyceride levels in those with metabolic syndrome. In the study, participants got 1.24 grams of fish oil a day (between one and two standard capsules).

"This is a good study," said Tracy L. Nelson, an associate professor of health and exercise science at Colorado State University School of Public Health in Fort Collins, who has researched omega-3 fatty acids.

"The interesting aspects are that they found the low-fat complex carbohydrate group, when supplemented with a 'realistic' amount of omega-3 fats [1.24 grams] did not increase trigylcerides as seen with the low-fat complex carbohydrate diet without the addition of omega-3s."

"This study is encouraging, because these individuals consumed their 'own' food given the parameters of the study, similar to what a metabolic syndrome patient would be told to do in the 'real world,' and by simply adding a very realistic amount of omega-3s, these individuals can change [after-meal] triglycerides without weight loss," Nelson added. "The fact that they found changes in a 'diseased' group adds to the impact of the paper."

More information

There's more on the metabolic syndrome at the American Heart Association.