Can a Mediterranean diet help keep heart disease, dementia, and cancer at bay?

For some time researchers have suggested that a Mediterranean diet — high in fresh fruit and vegetables, beans, nuts, whole grains, and fish — may help lower heart disease risk and increase life expectancy. An increasing amount of scientific evidence now backs up this notion. Recent studies have linked reduced rates of cardiovascular disease, dementia, and cancers with Mediterranean diets. Medical News Today looked at the evidence and spoke to experts about the science behind the benefits of this diet.

Over the years, many diets have been proposed for keeping healthy or reducing the risk of specific diseases, but few of them have stood up to rigorous scientific scrutiny.

One exception, however, appears to be the Mediterranean diet.

Increasingly, studies are showing that there are significant health benefits for people who follow this eating plan. Not only has research shown that it reduces cardiovascular disease, but it may also benefit cognition, decrease diabetes risk, reduce the risk of some cancers, and alleviate symptoms of multiple sclerosis.

The Mediterranean diet is an umbrella term referring to diets based on the historic eating habits of people who live around the Mediterranean Sea.

According to the American Heart Association, which recommends this type of diet for cardiovascular health, its key features are:

The Harvard School of Public Health adds to these recommendations, emphasizing the importance of healthy fats — olive oil, avocados, nuts, and oily fish.

It advises that people should eat red meat only occasionally, but get their protein from fish or seafood at least twice a week and eat small quantities of poultry, eggs, and dairy most days.

Although water should be a person's main drink, people may also drink one or two small glasses of red wine each day, as per the traditional Mediterranean diet.

Researchers add, however, that a healthy diet should also be paired up with some form of enjoyable physical activity every day.

Dr. Scott Kaiser, a geriatrician, and director of Geriatric Cognitive Health for the Pacific Neuroscience Institute at Providence Saint John's Health Center in Santa Monica, CA, noted:

"Research supports the benefits of adopting healthy lifestyle habits and indicates the critical importance this can play in shaping our future individual and collective health. […] Start with including lots of fresh vegetables — especially green leafy vegetables — and then enjoy fresh fruits— like berries — and other antioxidant-rich foods, along with fish, olive oil, and other foods rich in brain-healthy omega-3s."

Mediterranean diets have long been associated with benefits to cardiovascular health. In the mid-20th century, the Seven Countries study showed that dietary patterns in the Mediterranean and in Japan in the 1960s were associated with low rates of coronary heart disease and all-cause mortality.

Since then, research has shown that this type of diet not only benefits cardiovascular health, but it also reduces the risk of many other health conditions.

And recently, evidence has been increasing for the wide-ranging health benefits of following a Mediterranean diet. But what makes Mediterranean diets so healthy, exactly?

"The Mediterranean diet is characterized by high fruit and vegetables, high fiber, high levels of ‘good fats,’ moderate intakes of fish and meat, low amounts of high processed foods and sugary treat foods," noted Dr. Eamon Laird, a visiting research fellow at Trinity College, Dublin, in Ireland.

"These food components give high amounts of fiber, good fats, antioxidants, polyphenols, vitamins and minerals — choline, vitamin C, potassium, B-vitamins, vitamin D from fish, etc. — [and] proteins which give health benefits throughout a large number of organ and tissue systems," he explained.

Lots of research has investigated the effect of a Mediterranean diet on the risk for cardiovascular disease (CVD).

A meta-analysis of several studies published in March 2023, with a pooled sample of more than 700,000 female participants, has found that, by adhering closely to a Mediterranean diet, women reduced their risk of CVD by 24%, and their risk of death from any cause by 23%.

According to Dr. Laird, "[w]omen are also much more likely to stick with the diet compared to men, which could explain why we see more of the health benefits in women."

The meta-analysis seems to confirm the findings of previous research. For example, in 2015, another meta-analysis had found that the Mediterranean diet could be a major factor in preventing CVD.

And it was the complete diet, rather than any particular aspect, that seemed to have this effect, as Dr. Joanna Hodges, an assistant teaching professor of nutritional sciences at Pennsylvania State University, told MNT.

"[The study] concludes that no specific component of the Mediterranean diet has been shown to be as beneficial as the whole diet [in CVD prevention]," she told us.

There is also increasing evidence that the diet may enhance cognitive function. A study published in March 2023 that used UK Biobank data has just reported that individuals with a higher adherence to a Mediterranean diet had up to 23% lower risk for dementia compared with those who had lower adherence to a Mediterranean diet.

The study, which used data from more than 60,000 people, concluded that the Mediterranean diet lowered dementia risk even in those with a genetic predisposition for dementia.

The authors conclude that adopting a diet high in healthy, plant-based foods may be a strategy for reducing dementia risk.

Another study, also published in March 2023, which looked at postmortem Alzheimer's pathology, found that those who had followed a Mediterranean or MIND diet, particularly one rich in leafy greens, had a much lower beta-amyloid load.

Beta-amyloid is thought to be responsible for many of the symptoms of Alzheimer's disease.

The diet may also be beneficial for people with multiple sclerosis (MS). A preliminary study to be presented at the American Academy of Neurology's 75th Annual Meeting in April 2023, found that people with MS who followed a Mediterranean diet had a 20% lower risk of cognitive impairment than those who followed it the least.

The diet has been found to both reduce the risk of some cancers and improve the efficacy of some cancer treatments.

A 2019 review found that high adherence to the Mediterranean diet was associated with a lower rate of several cancers, including breast, colorectal, and prostate cancers.

This study concluded that the antioxidant and anti-inflammatory properties of components of the diet "prevent and counteract DNA damages and slow down the development of various forms of cancer."

For prostate cancer, recent research has shown that eating a diet high in colorful fruits and vegetables both reduces the risk of developing prostate cancer and speeds recovery in those who undergo radiation therapy for the disease.

The studies, from South Australia, found that diets high in lycopene and selenium reduced the risk.

Tomatoes, melons, papayas, grapes, peaches, watermelons, and cranberries are rich in lycopene, and white meat, fish, shellfish, eggs, and nuts contain high concentrations of selenium. All of these are recommended in the Mediterranean diet.

And it is not only prostate cancer patients whose treatment may be more effective on a Mediterranean diet.

A recent study presented at UEG Week 2022 found that the diet was significantly associated with an improved response to immunotherapy drugs in people with advanced melanoma.

Although the exact mechanism by which the Mediterranean diet benefits health is unclear, there is increasing evidence that the diet can have five main effects:

Dr. Laird explained to MNT how some components of the diet benefit health:

"Omega-3 fatty acids, phytosterols, resveratrol, vitamins, and polyphenols may contribute to lower levels of inflammation (CRP, inflammatory cytokines), and may improve endothelial function. By reducing levels of inflammation, improving blood flow, improving insulin sensitivity, and improving lipid metabolism, by default you are also reducing some of the major risk factors for CVD, cognitive decline, cancers, and diabetes."

Studies have found that it is best to take in these nutrients in their natural form as part of a healthy diet, such as the Mediterranean diet.

Although they can be obtained through supplements, there may be side effects to taking excessive amounts.

The Mediterranean diet is just one of many diets that have health benefits. Others include the MIND, Nordic, and DASH diets.

"The common thread throughout all the [healthy] diets is a heavy influence of plant foods, which we see […] has numerous benefits in increasing dietary fiber, antioxidants, phytonutrients, vitamins, and minerals," said Kate Cohen, a registered dietitian at the Ellison Clinic at Saint John's, part of the Ellison Institute for Transformative Medicine and Providence Saint John's Health Center in Santa Monica, CA.

So, key to any healthy diet is incorporating plenty of vegetables, whole grains, and healthy fats. Most importantly, any dietary changes made should be long-term and sustainable to give health benefits.

"Long term it [the Mediterranean diet] may be difficult to follow in its true form, particularly to those accustomed to processed food diets. A good approach would be to slowly integrate components into your current diet and to build slowly — again variety is the spice of life and we should have a varied and diverse diet and not rely solely on one dietary pattern to meet all our needs and requirements and tastes — food is to be enjoyed too!"

– Dr. Eamon Laird