Fish oil is healthy, and it can help to reduce obesity. But sugar in the diet can reduce its effects.

A spoonful of cod-liver oil or a little pill in the morning, followed by a glass of juice and a slice of bread and cheese. A normal way to start the day – but a poor start if what you are looking for is the health-promoting effects of the fish oil, a recent research project at NIFES has found.


The results, which are based on animal experiments, also showed that sugar blocks the ability of fish oil to lower the level of cholesterol in the blood.


“When you have sugar in your diet, omega-3 fatty acids behave just like any other fatty acid. In fact, as far as their effects are concerned, you might just as well take a spoonful of butter as one of cod-liver oil,” says NIFES scientist Lise Madsen.


Protein a better combination

 Recent experiments have shown that mice that were fed sugar in combination with fish oil put on a lot of weight. This did not happen to mice that were given fish oil plus protein. The more protein in the diet, the greater was the effect of the fish oil.


“Previous studies on rats and mice have shown that fish oil, which contains healthy fatty acids such as omega-3, can slow the development of obesity. What we have now shown is that this effect is cancelled if the diet includes sugar,” says Madsen.


So far, the results suggest that it is the simultaneous consumption of sugar and fish oil that has the negative effects.


The scientists behind the study stress that omega 3 still have several positive effects on human health in addition to reducing obesity.


Previous research at NIFES has shown that sugar in combination with different types of fat lead to obesity.


High glycaemic index

In the most recent experiments, the scientists studied how various carbohydrates, including sugar, act in combination with fish oil.


“We saw that sugar led to obesity. And that the more protein there was in the diet, the better was the effect of fish oil,” says Madsen.


Carbohydrates raise the level of insulin, and the higher the glycaemic index of the carbohydrates involved, the higher will be the concentration of insulin in the bloodstream. Insulin plays a central part in storing energy in the body, mostly in the form of fat.


The experiments carried out by NIFES are part of a major research project on fish oil and the reduction of obesity, in which the Institute is collaborating with the Universities of Copenhagen and Bergen and BGI (formerly Beijing Genomics Institute).


Contact: Lise Madsen

Tel: +47 414 76 177  


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