Almost everyone wants to lose weight and be healthy. However, it may be difficult when there are always new diets to choose from, new superfoods to try, or new approaches to eating. One diet that has consistently survived much public scrutiny is the Mediterranean diet.
This pattern of eating is inspired by the nutritional habits of the Mediterranean countries of Italy, Spain, Greece, and others. It encourages plenty of fruits, vegetables, whole grains, olive oil, and nuts; moderate amounts of seafood, poultry, and wine; and avoiding red meat and sweets. It does not recommend a specific caloric intake, but recommends regular physical activity and eating your meals with family. However, it is up for debate as to what the defining trait of the Mediterranean diet is, as the diet is as diverse as the people that practice it and the region it is found in.
What does the science really say here, though? Does the Mediterranean diet live up to the hype? In this article, we will go through its scientific origins as well as the modern research, and I will help you decide if the mediterranean diet is for you.
The State Of The Research
The Mediterranean diet has been studied extensively. Research has been performed on multiple populations and for many different health outcomes. Much of the research focuses on cardiovascular disease, diabetes, weight loss, dementia, and cancer. A preliminary search on Pubmed, a popular website indexing scientific research, reveals over 5,000 matches. An exhaustive review of all the evidence on the Mediterranean diet would test the limits of your time and attention, so we will only be taking a moderately deep dive into the research.
The Mediterranean diet was popularized by physiologist Ancel Keys, after his landmark Seven Countries Study. This study, which started in 1956 and went on for over 50 years, aimed to look at the relationship between cardiovascular disease and dietary and lifestyle factors that may influence it. While the results and interpretation of this study are still being debated, researchers did find that those in the Mediterranean countries had lower rates of heart disease (26). Naturally, everyone wanted to know what they were doing differently, and this sparked significant interest for further research.
The Lyon Diet Heart Study was a famous randomized interventional trial performed in 1994 on a group of about 600 people who just had their first heart attack. One group started a Mediterranean diet supplemented with linolenic acid from margarine, and the other group followed a more western diet. After a 27-month follow-up, the results showed those in the experimental group had only three cardiac-related deaths and five non-fatal heart attacks, while the control group had 16 deaths and 17 non-fatal heart attacks (17, 18).
Another much-publicized study was the PREDIMED study (taken from the spanish title Prevencion Con Dieta Mediterranea), which started in 2003 and was published in the New England Journal Of Medicine in 2013. This study took place in Spain and enrolled over 7,000 people. It aimed to study the development and progression of cardiovascular disease over a period of about five years.
One group was given olive oil to supplement their diet with every week, another group was given nuts, and a third group was advised to eat a lower-fat diet. The results showed that those in the experimental groups were less likely to have strokes than those on a low-fat diet control group (22).
However, there are significant methodological concerns regarding this study and the results are still debated today. Just recently, the original paper was retracted due to issues with how they decided to randomize their participants. The authors stated that although there was a problem with randomization, it only affected a small percentage of the participants, and the results are the same. Regardless of the interpretation of this paper by its endorsers and skeptics, it provided some evidence that there may be something to the Mediterranean diet.
Does It Help With Cardiovascular Disease?
The foundational research mentioned above made it clear the people of the Mediterranean were doing something helpful for their health. Since then, many more researchers sought to explore the relationship between this way of eating and cardiovascular disease.
In a robust and conservative study from 2013, researchers evaluted the current evidence on the diet and its role in cardiovascular disease prevention. They found 15 studies that looked at various cardiovascular outcomes in over 52,000 people. While those that followed a Mediterranean diet had small reductions in blood pressure and cholesterol compared to other diets, there were no changes in cardiovascular events like heart attacks or strokes (24).
In one review from 2016, researchers looked specifically at blood pressure. After statistically combining six studies, the researchers found that those that followed a Mediterranean diet were able to reduce their blood pressure by 1-2 points over the course of a year. The researchers noted that although there was a beneficial effect present, it was too small to show conclusively that the Mediterranean diet does reduce blood pressure (21).
In one review of 28 different studies with over 190,000 people, the authors assessed the relationship between adherence to the Mediterranean diet and the risk of stroke. They found that those that followed the diet closely had a 32% lower risk of stroke (15).
In one 2015 review of multiple studies looking at the Mediterranean diet and cardiovascular disease, there was good evidence to suggest following the diet resulted in a 30-45% reduction in risk of heart disease, heart attacks, and strokes. The authors noted that this effect was most likely from olive oil, fruit, vegetable, and legume consumption (11). A 2016 review on six studies with over 10,000 people echoed these results and found that there was a protective effect against strokes and heart attacks when following the diet (16).
Given much positive research, there are a few caveats. The current research base is significantly different, the estimates of how much the diet actually helps vary, and there are significant issues with the quality of how the experiments were performed. As mentioned by the author of the last review, “while the completed trials suggest it is likely that the Mediterranean diet protects against certain types of vascular diseases, the evidence base falls short of that required to make definitive conclusions or firm recommendations” (16).
Adherence to the Mediterranean diet seems to be associated with a protective effect against cardiovascular disease and things like heart attacks and strokes, but we need more high-quality research to explore this relationship further.
Does it Help With Diabetes?
The effects of the Mediterranean diet have also been looked at for the managing and preventing of type two diabetes. One systematic review and meta-analysis was performed in 2015 that aimed to take a very broad look at the literature. The authors of this study aimed to include all previous meta-analyses and any studies that were not yet included in a meta-analysis until that time.
The results were clear; in all of the meta-analyses and trials they found, there were beneficial effects related to diabetes. Subjects that adhered to a Mediterranean diet were able to lower their A1C level, a critical value for diabetic patients that shows their average blood glucose, by .3 to .47%, which is a significant effect size (a normal A1C level is less than 5.7%, while 6.5% or above suggests the patient is diabetic) (8).
An additional study by the same authors looked at 18 prospective studies from all over the world that assessed a few different dietary approaches and the prevention of diabetes. Six studies showed that following the diet can reduce your risk of getting diabetes by about 20% (7).
Observational studies and some experimental evidence show the Mediterranean diet may help reduce your risk of developing diabetes and can help manage it if you already have it.
Does It Help With Weight Loss?
Many may try to utilize the Mediterranean diet as a means to lose weight. Does it work? How does it fare against other diets? In 2008, researchers looked at 21 studies of different types; some were intervention studies, some were just observational studies. In a broad summary, they found that the Mediterranean diet was shown to be associated with weight loss in 13 studies, but had no association in eight studies (3).
One 2011 review and analysis looked at 16 trials with over 3,400 participants. It compared the Mediterranean diet to multiple other diets, including: a low-fat diet, a high-carb diet, the recommended American Diabetes Association diet, or general healthy eating tips. The researchers found that each trial lasted somewhere between four weeks to 24 months. In general, the Mediterranean diet was associated with greater weight loss than other diets, but the effect was more pronounced when it was coupled with exercise and reducing calories (6).
One systematic review from 2016 focused on five studies that compared the Mediterranean diet to a low-fat diet, a low-carb diet, and the American Diabetes Association’s prescribed diet for long term weight loss. The participants in the study were either overweight or obese, and some had cardiovascular risk factors. They reported that on average, the Mediterranean diet groups lost 8-22 pounds over a course of 12 or more months. When compared to other diets, the Mediterranean diet was more effective than a low-fat diet, but about the same as the ADA diet and low-carb diet (19).
In general, the types of studies we would need to say one diet is definitely better than another are difficult to perform and aren’t performed often (13). Because of this, any claims that a particular diet is the best, the Mediterranean diet included, are generally exaggerated.
The Mediterranean diet may help you lose weight, but the science comparing it to other diets is generally mixed.
Does It Help With Cognitive Function And The Prevention Of Dementia?
Because of the suffering associated with Alzheimer's disease, the most common type of dementia, there has been great interest in determining modifiable risk factors to prevent it. Diet has been proposed as one of these modifiable risk factors, and there is no shortage of research on the Mediterranean diet.
Two experiments on about 1,000 subjects came out of the PREDIMED study mentioned earlier, one in 2013 and one in 2015. Both of these trials assessed cognitive performance and found those that supplemented their diet with olive oil or nuts had slightly improved scores on cognitive tests. While these effects were found to be better statistically, the differences were small enough to cast doubt on their importance (20, 30).
Another similar trial was performed in 2016. In this one, there were no differences in cognitive tests between groups following a Mediterranean diet or a normal diet over a period of 18 months (14).
A number of longer-term studies have been undertaken that have looked at the relationship between adherence to a Mediterranean diet and the development of dementia and cognitive impairment. While this is by no means an exhaustive list, it shows that there is a relationship between the Mediterranean diet and cognitive diseases. In long-term cohort studies, the Mediterranean-style diet has been shown to be associated with:
- A reduced risk of developing Alzheimer’s disease over a period of four years for a group of 2,000 people in New York (27)
- A reduced risk of dementia over a period of four years for over 8,000 people in France (1)
- A reduced risk of progressing from mild cognitive impairment to Alzheimer’s disease over a period of four-and-a-half years for over 1,000 people in New York (28)
- A reduced risk of mild cognitive impairment and dementia for over 1,000 people from the United States (25)
In contrast, one study from Australia on over 1,500 people found that adherence to a Mediterranean diet was not found to be associated with a reduced risk of cognitive impairment (4). In another study from 2012, researchers analyzed the diets via questionnaires of over 1,000 people from Australia. They found that those that were diagnosed with Alzheimer’s disease or mild cognitive impairment were less likely to eat a Mediterranean diet compared to controls (9).
Observational studies show that the Mediterranean diet is associated with a lower risk of developing cognitive diseases.
Does It Help With Cancer?
The effects of the Mediterranean diet on cancer have also been assessed. Since diet seems to be a modifiable risk factor for many chronic diseases, cancer included, much attention has been placed on determining if adhering to a Mediterranean diet might have a protective effect against cancer. And in fact, for some types of cancers, it may actually reduce your risk for getting them.
A sweeping review of 83 studies with over 2,000,000 participants found that overall, people that adhered to a Mediterranean diet the closest had a reduced risk of dying from cancer, including colorectal, breast, gastric, liver, head and neck, gallbladder, and biliary tract cancer. However, for cancer survivors, following the Mediterranean diet did not change their risk of getting cancer again or eventually dying from cancer (29). The authors suggest the main effect is driven by fruits, vegetables, and whole-grain intake.
Other similar studies that have focused on individual cancers found similar reductions in risk for a specific type of breast cancer (2), adenomas, a precursor to colorectal cancer (10), and prostate cancer (12). In addition, one researcher found that consumption of olive oil was associated with a lower risk of cancer, particularly with breast and digestive system cancer (22).
There are many observational studies that show adhering to a Mediterranean diet is associated with a reduced risk of many types of cancers.
The Mediterranean diet is a diet of modest recommendations and does not require severe caloric restrictions, the elimination of certain food groups, or specific times or patterns of eating. There is probably no risk to adopting a Mediterranean diet, but you should consult a dietitian or your doctor, especially if you have any chronic diseases.
The Mediterranean diet is recommended for good reason, despite problems that are common with many of the studies, and problems with nutrition research in general. The current research base suggests that it is associated with modest protective effects against many chronic diseases, including cardiovascular disease, diabetes, dementia, and cancer, and it may help you lose weight.
However, these links come mainly from observational studies which cannot speak to a cause-and-effect relationship and generally fall short of making definitive claims. It is still generally unclear as to how much of an effect the Mediterranean diet can have on these chronic diseases, what food or combination of foods is responsible for the effects, or if there are other variables associated with the improvements that are seen.
However, according to one overarching literature review of other literature reviews, there is robust evidence that following the Mediterranean diet results in reduced overall mortality, and a reduced risk of cardiovascular disease, cancer, neurodegenerative disease, and diabetes (5).
The patterns of eating associated with this diet are in line with general healthy recommendations; plenty of fruits and vegetables, whole grains, seafood and lean poultry, and healthy fats from olive oil and nuts. The Mediterranean diet is a reasonable and healthy way of eating.