If you want the full health benefits of omega-3, it’s best to get them from natural food sources like oily fish than in supplement form.

That’s the overriding conclusion out of a pair of studies published this week in the Proceedings of the National Academy of Sciences that showed that while omega-3 from dietary sources such as herring, mackerel and salmon can help lower blood pressure in mice, supplements showed no anti-hypertensive effects.

In fact, omega-3 in supplement form was actually found to diminish the beneficial health effects of the natural fatty acid acid docosahexaenoic acid (DHA) found in fish oil, said the team of researchers from the US and Germany who conducted both studies.

"The intake of non-natural omega-3 fatty acids can therefore also have counter-productive effects," said Michael Bauer from Jena University Hospital in Germany.

When mice were fed the DHA, the kind found in natural food sources, as expected it resulted in the expansion of blood vessels and consequently a drop in blood pressure.

By comparison, DHA ethyl ester, found in most fish oil pills, failed to do the same and even appeared to “antagonize” or compete with the positive effects of DHA from natural sources, scientists said.

The latest study builds on previous research published in the British Medical Journal last year that likewise found that food sources of omega-3 carry more health benefits than supplements.

In a meta-review of 38 studies that involved 80,000 participants across 15 countries, researchers from Cambridge University and Erasmus MC Rotterdam in the Netherlands found that those who ate at least two servings of oily fish a week – sardines, mackerel, herring and salmon – reduced their risk of stroke by up to six percent, while fish supplement intake failed to show any benefits in reducing stroke risk.