The Mediterranean Diet - Benefits Beyond Heart Health

By Felicity Curtain, Accredited Practising Dietitian

A Mediterranean eating pattern has long been heralded as the diet of all diets: seemingly unrestrictive, uncomplicated in rules and with strong credentials for heart health benefits. However, recent research suggests there may be more to the story than just heart health. The Mediterranean diet first sparked interest in the 1960s, when it was discovered that people in countries bordering the Mediterranean Sea experienced significantly lower rates of chronic disease than those in western countries. While most research in the past has focussed heart health benefits, studies have recently started connecting the diet to reduced risk of Type 2 diabetes, cancer, and cognitive conditions.

The Diet
Over twenty countries border the Mediterranean Sea, and while types and amounts of foods eaten vary between nations, all are characterised by similar principles. This includes plenty of fruit and vegetables, olive oil, legumes, nuts and whole grains; moderate consumption of fish, and low-moderate amounts of dairy foods and red meat. Very few processed foods are consumed, and red wine is consumed in moderation with meals (1). While studies do not explicitly outline the types of whole grains consumed, varieties common to the Mediterranean include barley, buckwheat, bulgur, faro, oats, polenta, rice, bread, couscous, and pasta. The past century has included white pasta, though traditionally bread was stone-ground sourdough, made from whole wheat and barley (2).

The Health Effects
If you believe the media coverage of the diet, the benefits of a Mediterranean appear boundless. In reality, high quality evidence exists to indicate the eating pattern is protective against cardiovascular disease (CVD) and Type 2 diabetes, and mounting evidence points to a positive association with cancer and neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease (3,4,5).

The most recent research indicates that for those already exhibiting CVD risk factors, following a Mediterranean diet can halve the risk of diabetes development and reduce the risk of mortality from cardiovascular events by 30 percent (6). Observational evidence and limited experimental trials demonstrate that those adhering to the diet exhibit improved blood lipid profiles, a reduction in blood pressure, and insulin resistance, all risk factors for CVD (7,8). In fact, the cardiovascular benefits of the Mediterranean diet have been compared to pharmacological interventions, such as statins, aspirin, physical activity, and even anti-hypertensive drugs (9). In healthy populations, observational evidence suggests a 10 percent decrease in the risk of mortality and/or incidence of CVD (10).

Interestingly, few studies of the Mediterranean diet are designed to induce weight loss, but many participants do lose weight, a risk factor for chronic disease itself. It has been suggested that that may be due to the high ratio of plant to animal foods, and limited refined and processed foods, making the diet high in fibre and filling, without providing excess energy.

In recent years, a small pool of trials has shown preliminary evidence that the Mediterranean diet may slow the onset and/or progression of age-related cognitive decline, and promote healthy cognitive ageing. One such study found that greater adherence to a Mediterranean diet corresponded with lower decline in cognitive function over a five-year period. In younger adults, there is growing interest in the effects of the diet on mood and affective disorders, based on population data showing low depression rates in Mediterranean countries. Limited high-level evidence exists on the subject, however a number of Australian randomised control trials are currently being carried out to determine the link between the diet and mood disorders (11).

Considerable research has sought to understand the mechanisms behind the Mediterranean diet’s apparent link to health, with no single food or nutrient appearing to contribute in isolation. While the mechanisms are not fully understood, there is a general consensus among experts that it is based on the combination of protective nutrients and foods. The high ratio of plant to animal foods may be a contributing factor, particularly as foods like olive oil, herbs and spices, fruit, vegetables, whole grains and legumes are rich in phytochemicals, with antioxidant, anti-inflammatory effects.

These factors are also thought to relate to the emerging link between a Mediterranean diet and positive cognitive health. The combination of foods and nutrients are thought to protect against cognitive decline through reductions in oxidative stress, inflammation, and lowering insulin resistance. The diet may also help to increase cerebral blood flow, a factor that is inversely affected by a typical Western diet (12,13).

However, it should not be forgotten that the good health of Mediterranean populations may also relate to lifestyle and cultural elements central to their traditions. Cooking, socialising, regular physical activity and rest are all important factors to consider in a balanced lifestyle.

Incorporating Mediterranean Eating Habits into Australian Diets
Interestingly the macronutrient distribution of the Mediterranean diet is not that dissimilar to the average Australian diet (Table 1). The Mediterranean diet is slightly lower in protein and carbohydrate and higher in fats, largely from the free consumption of olive oil, nuts, and seeds. The Mediterranean diet is significantly higher in fibre than the average Australian diet (33g/day compared to 22- 23g/day), a reflection of the higher intake of fibre rich foods including vegetables, legumes, whole grains and nuts.

Table 1. Average macronutrient contribution to energy and total fibre intake of Australians average intakes compared to estimated Mediterranean diet macronutrient distribution ranges and fibre intakes.

 

	Mediterranean Diet	Australian Average(14)
Protein	10-15%	16%
Carbohydrate	43%	45%
Fat	30-40%	31%
Fibre	33g/day	22g (F) 23g (M)

Comparing the diets from in terms of foods, a noteworthy distinction between the Mediterranean Diet Pyramid and the Australian Dietary Guidelines is the former does not detail serve sizes, instead emphasizing overall food quality according to dietary patterns.

Table 2. The Mediterranean Diet Pyramid compared to the Australian Dietary Guidelines

Food Group	Mediterranean Diet Pyramid	Australian Dietary Guidelines (men and women 19-50).
Vegetables	2 or more serves per meal (6+ per day)	5 serves per day
Fruit	1-2 serves per meal (3+ per day)	2 serves per day
Breads & Cereals	1-2 serves per meal (3+ per day)	6 serves per day
Dairy	2 serves per day	2 ½ - 3 serves per day
Meat & Alternatives	2 serves of red/white meat per week, 2 or more serves of fish/seafood, and legumes per week, 2-4 serves of eggs per week, 1 or fewer serves of processed meat per week.	2 ½ - 3 serves per day (inclusive of red meat, poultry, fish, legumes, nuts, seeds).
Oils	Olive oil in unspecified amounts daily	4 serves per day
Olives, nuts, and seeds	1-2 serves daily	-
Discretionary Foods	2 or fewer serves daily	0-3 serves per day

In reality we know that Australian diets do not reflect the guidelines, with an average of one third of total daily energy stemming from discretionary foods, and less than seven percent of the population meeting the recommendations for vegetable intake (14).

A simple way for Australian to adjust their diets and reap the benefits of the Mediterranean diet is to increase the amount of vegetables, nuts, whole grains and legumes eaten each day. This can be coupled with including small amounts of red meat a few times a week and increasing consumption of fish, using olive oil and as the main fat source, and using fresh herbs and spices to add flavour to meals in place of salt.

References
1. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92:1189-96
2. D'Alessandro A, De Pergola G. Mediterranean Diet Pyramid: A Proposal for Italian People. Nutrients. 2014;6(10):4302-4316.
3. Itsiopoulos C. The Mediterranean Diet. Melbourne: Pan Macmillan Australia; 2013.
4. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92:1189-96
5. Trichopolou A, et al. Definitions and potential health benefits of the Mediterranean diet: views from experts around the world. BMC Medicine. 2014; 12:1121-16.
6. Estruch R, et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet. N Engl J Med. 2013; DOI: 10.1056/NEJMoa1200303
7. Kastorini C, Milionis H, Esposito K, Giugliano D, Goudevenos J, Panagiotakos D. The Effect of Mediterranean Diet on Metabolic Syndrome and its Components. Journal of the American College of Cardiology. 2011;57(11):1299-1313.
8. Grosso G, Mistretta A, Frigiola A, Gruttadauria S, Biondi A, Basile F et al. Mediterranean Diet and Cardiovascular Risk Factors: A Systematic Review. Critical Reviews in Food Science and Nutrition. 2013;54(5):593-610.
9. Trichopolou A, et al. Definitions and potential health benefits of the Mediterranean diet: views from experts around the world. BMC Medicine. 2014; 12:1121-16.
10. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an updated systematic review and meta-analysis. Am J Clin Nutr. 2010;92:1189-96
11. Preedy V, Watson R. The Mediterranean diet. USA: Elsevier; 2015.
12. Knight A, Bryan J, Wilson C, Hodgson J, Murphy K. A randomised controlled intervention trial evaluating the efficacy of a Mediterranean dietary pattern on cognitive function and psychological wellbeing in healthy older adults: the MedLey study. BMC Geriatric. 2015;15:55
13. Keast R, Parkinson L. 2016. Available from: http://eds.a.ebscohost.com.ezproxy-b.deakin.edu.au/eds/pdfviewer/pdfviewer?sid=e44b952b-b40c-49f5-8c2d-2a746edcb669@sessionmgr4001&vid=5&hid=4103
14. Australian Bureau of Statistics. Australian Health Survey: Nutrition First Results. 2015. Available from: http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/4364.0.55.007~2011-12~Main%20Features~Cereals%20and%20cereal%20products~720