Study discovers secret of the Mediterranean diet

“The combination of olive oil and leafy salad or vegetables is what gives the Mediterranean diet its healthy edge,” BBC News reports.

The Mediterranean diet – a diet rich in vegetables, fruits, beans, whole grains, olive oil and fish – has long been associated with improved heart health. Though why this is the case is not fully understood.

A new study, on mice, examined a type of chemical called nitro fatty acids.

The researchers state that nitro fatty acids could be produced from foods consumed as part of the Mediterranean diet, as chemicals in olive oil and fish could combine with chemicals in vegetables.

In this study, nitro fatty acids were found to inhibit (block the action of) an enzyme called soluble epoxide hydrolase, and this in turn lowered blood pressure. They went on to show that the enzyme was also inhibited when mice were fed components of the Mediterranean diet.

High blood pressure is a major risk factor for cardiovascular diseases such as heart attacks. So the actions of nitro fatty acids may explain why the Mediterranean diet is associated with improved health.

Future research will be required to determine whether the same processes occur in humans and whether it is possible to harness the benefits of nitro fatty acids in some form of medication.

Where did the story come from?

The study was carried out by researchers from King’s College London, the University of California and the University of Pittsburgh School of Medicine. It was funded by the British Heart Foundation (BHF), King’s BHF Centre of Research Excellence, the UK Medical Research Council, Fondation Leducq, the European Research Council, the Department of Health, and the US National Institutes of Health (NIH) and National Institute on Environmental Health Sciences.

One of the authors reported a financial interest in Complexa Inc, a pharmaceutical company with a stated interest in developing new drugs.

The study was published in the peer-reviewed journal PNAS.

The research was well-covered by the UK media.

What kind of research was this?

This was a mouse study. It aimed to determine the impact of a group of chemicals called “nitro fatty acids” on the activity of an enzyme called soluble epoxide hydrolase and the knock on effects on blood pressure.

Inhibition of soluble epoxide hydrolase is thought to lower blood pressure.

The researchers state that nitro fatty acids could be produced from foods consumed as part of the Mediterranean diet, as chemicals in olive oil and fish could combine with chemicals in vegetables to produce nitro fatty acids.

Previous research has suggested that nitro fatty acids lower blood pressure, and can inhibit soluble epoxide hydrolase by binding to it.

This study aimed to determine whether nitro fatty acids lower blood pressure in mice by inhibiting soluble epoxide hydrolase.

Animal research is needed to address this sort of question. However, it remains to be seen whether the same processes occur in humans.

What did the research involve?

The researchers performed a series of experiments on mice to determine whether nitro fatty acids lower blood pressure in mice by inhibiting soluble epoxide hydrolase.

To do this, the researchers made genetically modified mice carrying a version of the enzyme without the binding site for nitro fatty acids and then performed a series of experiments comparing normal and genetically modified mice.

What were the basic results?

The researchers found that the enzyme from the genetically modified mice could not be bound or inhibited by a lipid nitro fatty acid.

The mice were given a hormone to make them have high blood pressure. Giving the mice a lipid nitro fatty acid reduced the blood pressure of normal mice but not the genetically modified mice.

After giving the mice the hormone to make them have high blood pressure, the size of their hearts increased. Giving the mice a lipid nitro fatty acid reduced the size of the heart of normal mice but not the genetically modified mice.

The researchers also fed the mice conjugated linoleic acid and sodium nitrate, which they say mimics aspects of the Mediterranean diet. They found that the enzyme was inhibited in normal mice but not the genetically modified mice.  

How did the researchers interpret the results?

The researchers concluded that their “observations reveal that nitro fatty acids mediate antihypertensive signalling actions by inhibiting soluble epoxide hydrolase”. Or in laypersons’ terms, blocking the actions of the soluble epoxide hydrolase enzyme triggers a series of reactions leading to a fall in blood pressure. And that this suggests “a mechanism accounting for protection from hypertension afforded by the Mediterranean diet.” 

Conclusion

By comparing normal and genetically modified mice this study has found that a type of chemical called lipid nitro fatty acids inhibits an enzyme called soluble epoxide hydrolase. This in turn lowers blood pressure.

The research also found that the enzyme was inhibited when normal mice were fed components of the Mediterranean diet. The researchers state that nitro fatty acids could be produced from foods consumed as part of the Mediterranean diet, as chemicals in olive oil and fish could combine with chemicals in vegetables to produce nitro fatty acids.

This interesting research suggests a mechanism for the benefits of the Mediterranean diet.

It is also possible that both nitro fatty acids and the Mediterranean diet could affect different processes as well. 

Future research will be required to determine whether the same processes occur in humans.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

Links To The Headlines

Olive oil and salad combined ‘explain’ Med diet success. BBC News, May 20 2014

The salad that could lower your blood pressure: Tossing lettuce in olive oil with a sprinkling of nuts and avocado boosts heart health. Daily Mail, May 20 2014

Olive oil on salad may save your life. The Daily Telegraph, May 20 2014

Why a Mediterranean diet is good for your health. Daily Express, May 20 2014

Links To Science

Charles RL, Rudyk O, Prysyazhna O, et al. Protection from hypertension in mice by the Mediterranean diet is mediated by nitro fatty acid inhibition of soluble epoxide hydrolase. PNAS. Published online May 19 2014