11 May 2018

Monash scientists join race to reveal diet’s secrets

Monash researchers are checking 
out ingredients of the Mediterranean 
diet.
by Anne Crawford

The Mediterranean diet is one of the most researched, published and consumed diets on the planet. It’s been associated with health benefits that include delaying Alzheimer’s disease, better heart health, helping to fight certain cancers and reducing our risk of developing type 2 diabetes. But no one is completely sure why.

Mounting epidemiological, clinical and experimental evidence have all pointed to the biological benefits of the diet but the chemical compounds responsible for them remain elusive. Monash scientists are investigating.


The largely vegetarian diet typically includes a high consumption of olive oil as a main source of dietary fat – a factor Monash University scientist Dr Tom Karagiannis is investigating to try to home in on the beneficial compound or compounds. "Some key studies show that when you eliminate olive oil from the diet you don't get as many good effects," he said.

“What we’re trying to do is take the Mediterranean diet and break it down into individual chemical compounds,” Dr Karagiannis said.

Dr Karagiannis, from the Department of Diabetes, has released a paper that critically reviews the available evidence, shifting through thousands of papers to distill those best documenting the biological effects of bioactive compounds extracted from olive trees. If the methodology in a paper was not sufficiently documented or considered inadequate, the compound was excluded.

The OliveNet™ database that came out of the study catalogues more than 656 compounds associated with Olea europaea, the common olive tree, including those derived from the fruit, leaf and in extra virgin olive oil. (Extra virgin olive oil is mechanically or cold pressed rather than produced using chemicals.)

“Studies have been very disparate, done by different teams in different parts of the world, identifying different compounds – they’ve never been collated together under one database,” Dr Karagiannis said.

“To our knowledge OliveNet™ is the only curated open-access database with a comprehensive collection of compounds associated with Olea europaea,” he said.

Only a handful of compounds derived from extra virgin olive oil have been characterised for their biological effects to date, he said. The database opens the way for researchers anywhere to conduct computer modelling to identify new compounds to either isolate or synthesise. It also allows them to monitor how much of the right compound exists in different types of olive oil, that is, do quality control.
 
The Mediterranean diet, which mimics the traditional way of eating in the region, is loaded with fresh fruit and vegetables, nuts, legumes, has moderate amounts of fish, poultry, eggs, dairy and whole grains, generous amounts of olive oil, a glass of wine with a meal but infrequent serves of red meat, processed grains, sweets and saturated fats.

It has been a way of life for centuries in countries such as Greece, Italy and Spain but became more broadly popularised post World War II after US physiologist Ancel Keys oversaw the Seven Countries Study into heart and vascular diseases in areas with different eating patterns and lifestyles. Keys found that people in the Greek island of Crete had a low incidence of cardiovascular disease, which he attributed to their consumption of olive oil.

Various studies since have highlighted the diet’s antioxidant and anti-inflammatory properties and have shown it may reduce the risk of developing conditions such as high blood pressure, type 2 diabetes and raised cholesterol – all risk factors for heart disease. It is also held to be good for gut bacteria, cancer risk and asthma, and a longer lifespan.

One of the most prominent was the PREDIMED study, conducted in Spain for almost five years and published in 2013. More than 7400 people at high risk of cardiovascular disease were put on either a Mediterranean Diet with added extra virgin olive oil or a Mediterranean Diet with added nuts, or became part of a low-fat control group. Those eating the diet with the olive oil fared best with the risk of combined heart attack, stroke and death from cardiovascular disease reduced by 30 per cent, with those on the added nuts diet not far behind with a 28 per cent reduced risk.

But the beneficial effects of the diet are yet to be conclusively proved.

“They’re ‘associations’ at this point,” Dr Karagiannis said. “That’s where we come in – we want to change that from associations to determining which compounds are actually effective and which aren’t,” he said.

“For us, because we’re hardcore scientists, it’s very interesting to see, and delineate, which compounds have beneficial effects, trying to understand which compounds are responsible for helping different diseases. Then we can use them for different purposes.”

The team used the database for example, to computer-model oleocanthal, a compound with similar anti-inflammatory properties to the drug ibuprofen. In a yet-to-be-published paper, it found 10 compounds that were better than oleocanthal, he said.  

“My great hope it that we can find a potent compound that can improve fasting glucose and insulin resistance, which is what diabetes is,” Dr Karagiannis said.

The team has already synthesised a promising new compound in the US, detailed in another study not yet published.

Dr Karagiannis, who heads the Epigenomic Medicine Laboratory in the Department of Diabetes, worked with Dr Elizabeth McCord from the team’s commercial partner in the US, McCord Research. McCord Research funds Dr Karagiannis’ work.

He said the study took three years and 10 people to write. Professor Emeritus Dimitrios Boskou at the School of Chemistry, Aristotle University in Greece, provided the chemical expertise. First author is PhD student Natalie Bonvino who did the study for her Masters degree.

And, it must be asked, does Dr Karagiannis follow the diet?

"It was just natural for me – my parents migrated here from Greece in the seventies – but I supplement it with all the usual modern Western stuff!"

Reference
Bonvino NP, Liang J, McCord ED, Zafiris E, Benetti N, Ray NB, Hung A, Boskou D, Karagiannis TC. OliveNet™: a comprehensive library of compounds from Olea europaea. Database (Oxford). 2018 Jan 1;2018. doi: 10.1093/database/bay016.

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