Considered one of the world’s healthiest dietary patterns, the Mediterranean diet is linked to a host of positive health benefits. The theme of the diet is one abundant in fruits, vegetables, wholegrains, legumes and olive oil and where fish and poultry feature more often than red meat. From less chronic disease right through to a longer life, in this podcast I’ll dig deeper into the health merits of adopting some of the key themes of the Mediterranean diet for your own individual way of eating.
The Mediterranean diet has long been considered a yardstick for a model of a healthy diet and is a favourite dietary pattern for researchers to study the world over. It is also recognised by the World Health Organization as a healthy and sustainable dietary pattern.
The Mediterranean diet is based on the traditional foods that people used to eat in countries like Italy and Greece back in the 1960s. It was at this time that interest in the Mediterranean diet began to grow, arising from the observation that people in this part of the world had lower rates of heart disease than in the United States or Northern Europe.
Although the term Mediterranean diet is used extensively, it is more a dietary pattern or dietary theme than a single fixed diet as the types of foods featured in it can vary based on geography.
The main components of the Mediterranean diet include:
Daily consumption of vegetables, fruits, wholegrains and healthy fats such as olive oil and nutsWeekly consumption of fish, poultry, beans and eggsModerate portions of dairy productsAnd amount of red meat.Other important elements of the Mediterranean diet are sharing meals with family and friends, and of course: enjoying a glass of red wine and being physically active.
With so much research into the Mediterranean diet, for this podcast, I’m going to profile a recent review bringing in all the research in the field together in one place. To collate the research, Italian researchers undertook an umbrella review of the evidence. An umbrella review allows the findings of reviews relevant to the question at hand to be compared. For the Mediterranean diet, there is already an abundance of meta-analyses of observational studies and randomised clinical trials so this review looked at them as a whole. And I’ll link to the review in the show notes https://www.nature.com/articles/ejcn201758
The review brought together 13 meta-analyses of observational studies and 16 meta-analyses of randomised-controlled trials. Studies investigated the association between adherence to a Mediterranean-style diet and 37 different health outcomes. All up, over 12 million people were part of the collective studies.
Let’s cut straight to the key findings. Convincing or highly suggestive evidence was seen for a positive role of the Mediterranean diet on longevity, cardiovascular diseases, coronary heart disease, heart attack, overall cancer incidence, neurodegenerative diseases, Alzheimer’s disease, dementia and diabetes. That is quite a list indeed. A positive benefit of the diet on body weight, blood pressure and total cholesterol was seen, but was considered weak.
For most specific types of cancers, apart from breast cancer, the evidence was only weakly suggestive of a benefit. This finding to do with cancer has since been repeated with an updated review looking at cancer and the Mediterranean diet published in just the last few weeks which I’ll link to in the show notes https://pubmed.ncbi.nlm.nih.gov/32770356 And in this review, they found that greater adherence to a Mediterranean diet was linked to a lower risk of dying from cancer, but again a lot of the research was ranked in the lower tier of quality.
The umbrella review is not without its limitations. Several of the health outcomes looked at only had a few studies to inform them, making definitive conclusions difficult. Many of the research studies were observational studies which cannot prove a direct benefit, only an association. The quality of the research was mixed and the researchers did find an indication of potential bias in the research field. But while the evidence may not be at the highest level for all health outcomes, the trend is glaringly obvious with the health ledger tipped hugely in the direction of the Mediterranean diet.
Bone health
But since this review came out, other studies have been published opening up new areas that show a favourable link to following a Mediterranean-style diet. And one of these finds reduced bone loss in as little as a year after switching to the diet.
In the latest research involving more than 1,100 participants aged between 65 and 79 years from 5 European countries, each person was randomised into one of two groups. One group followed a Mediterranean-style diet for 1 year while the other control group followed ‘healthy eating’ guidelines from their country of origin. And I’ll link to this study in the show notes https://ajcn.nutrition.org/article/S0002-9165(22)02953-7/fulltext
Bone density was measured at the start of the study and after 12 months. No discernible difference in overall bone density was seen between the two diet groups, but one place where there were differences though was at the femoral neck. This bone area connects the shaft of the thigh bone to its rounded head, which fits into the hip joint
The femoral neck is a particularly delicate area and is a common cause of hip fractures. Hip fractures are a major health worry and are common in elderly people with osteoporosis. For the 10 percent of people who had osteoporosis at the start of the study, these people showed a slower rate of bone loss in the femoral neck which is noteworthy.
Even though the study only ran for one year, which is a short time to see changes in bone growth, to see some level of difference between the diet groups was impressive and certainly worthy of further study. Compounds found in extra virgin olive oil are thought to be responsible for the effect on bone. These compounds can increase the proliferation of bone-building cells and deposition of calcium ions in the extracellular matrix.
Gestational diabetes
And the news continues to be positive on the health merits of a Mediterranean diet with a recent clinical trial of this during pregnancy showing promise in reducing the risk of excess pregnancy weight gain and gestational diabetes.
Gestational diabetes or GDM, is a form of diabetes that occurs during pregnancy. Affecting between 5 and 10 percent of all pregnancies in Australia, GDM is high on the health concern radar. The high blood sugars from GDM can result in the developing baby growing too large, causing birth complications. Following delivery, the baby can also experience low blood glucose levels caused by being removed from the glucose-rich environment of the mother. The mother also suffers a much higher lifetime risk of developing type 2 diabetes.
Women who enter pregnancy who are already carrying too much weight or have risk factors for metabolic disease such as high blood pressure or elevated blood lipids are at greater risk of pregnancy complications such as gestational diabetes and pre-eclampsia. This puts both the mum and the bub at a heightened risk of diabetes and cardiovascular disease in the future.
A Mediterranean-style diet has shown favourable benefits in reducing the risk of type 2 diabetes and cardiovascular complications. But as yet, not as much is known how it may fare when followed during pregnancy in women who are at higher risk of metabolic disease.
A recent clinical trial tested how following a Mediterranean-style diet could help pregnant women who already are carrying significant risk factors for diabetes and heart disease. Called the ESTEEM study, it was a study involving over 1,200 women at five UK maternity units. And I’ll link to the study in the show notes https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1002857
Women from various ethnic inner-city backgrounds with metabolic risk factors such as obesity, high blood pressure or high blood triglycerides were randomised to either receive routine antenatal care or to receive ongoing individualised advice on following Mediterranean-style diet in addition to their antenatal care.
Women allocated to the Mediterranean-style diet gained on average 1.25 kg less weight than those who had routine care. This was a positive seeing as most of the women were carrying too much weight into their pregnancy to begin with.
The other key finding was a drop in the incidence of GDM by over a third in women following the Mediterranean diet. Other pregnancy complications such as high blood pressure, pre-eclampsia, stillbirth, small for gestational age foetus, or admission to a neonatal care unit were not different between the two groups of women. Women in the Mediterranean-style diet group did though report better overall quality of life than those in the control group.
Adding further support to the key study finding, when the results were combined with a similar type of trial done in Spain involving 874 pregnant women, there was a similar reduction in the risk of GDM by one-third.
So it seems that a Mediterranean-style diet could be an effective way for women who enter pregnancy with a high risk of GDM to mitigate this with an eating plan that has a host of health benefits both short- and long-term.
Summary
What particular aspect of the Mediterranean diet that could explain its many health benefits isn’t clear. And there may eventually be found to be certain foods in the diet that have greater health significance. For now, though, it seems it is the overall diet approach and the combination of foods that matter, rather than any individual ‘superfoods’ that make this such a healthy way to eat. It is also a clear case here of what it displaces from your diet. Because if you’re eating more in line with this type of dietary pattern, then you’ll be eating less ultra-processed foods.
Dietary trends come and go, but there is a good reason why the traditional Mediterranean-style dietary pattern consistently receives endorsement from health groups and research teams from around the world. There is no one best way to eat, but we certainly can take some cues from the messages it gives about what sort of choices to make for a 'healthy diet'.
So that’s it for today’s show. You can find the show notes either in the app you’re listening to this podcast on if it supports it, or else head over to my webpage www.thinkingnutrition.com.au and click on the podcast section to find this episode to read the show notes.
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I’m Tim Crowe and you’ve been listening to Thinking Nutrition.