Mediterranean Diet Offers Modest Protection Against Obesity-Related Cancers

Adhering to a Mediterranean diet may provide a small but significant reduction in the risk of developing obesity–related cancers, according to a major European study published yesterday in JAMA Network Open.

The research, which followed more than 450,000 participants across 10 European countries for nearly 15 years, found that people with high adherence to the Mediterranean diet had a 6% lower risk of developing cancers linked to obesity compared to those with low adherence.

“These findings indicate that higher adherence to the Mediterranean diet is associated with a modest reduction in the risk of obesity-related cancers, independent of adiposity measures,” wrote the researchers, led by Dr. Inmaculada Aguilera-Buenosvinos from the University of Navarra in Spain.

The study draws on data from the European Prospective Investigation Into Cancer and Nutrition (EPIC), which enrolled participants aged 35 to 70 years from 1992 to 2000 across 23 centers in Europe. Researchers tracked participants for a median of 14.9 years, during which about 5% developed one of the 13 types of cancer that have been convincingly linked to excess body weight.

These obesity-related cancers include postmenopausal breast cancer, colorectal cancer, endometrial cancer, pancreatic cancer, and liver cancer, among others. The prevalence of excess body weight has been rising globally, with approximately 39% of the world’s population now classified as overweight or obese despite extensive public health efforts.

The Mediterranean diet, characterized by high consumption of vegetables, fruits, legumes, nuts, whole grains, fish, and olive oil, has long been associated with various health benefits. In this study, adherence was measured using a 9-point scale that assessed consumption patterns across various food groups. Participants were categorized as having low (0-3 points), medium (4-6 points), or high (7-9 points) adherence.

While the overall risk reduction was modest, the researchers observed stronger protective associations for specific cancer types. High Mediterranean diet adherence was linked to a reduced risk of colorectal cancer (8% lower risk), hepatocellular cancer (48% lower risk), and kidney cancer (33% lower risk). Medium adherence to the diet was associated with a 34% lower risk of esophageal cancer.

Surprisingly, the study found that the relationship between the Mediterranean diet and cancer risk was not mediated by body mass index (BMI) or waist-to-hip ratio, suggesting that the diet’s potential protective effects operate through mechanisms beyond just weight control.

“Our mediation analysis did not show any significant result when considering high vs low adherence to the Mediterranean diet and the risk of obesity-related cancer mediated by BMI or waist-to-hip ratio,” the researchers noted.

The protective association was particularly pronounced among smokers. Current smokers with high adherence to the Mediterranean diet had a 14% lower risk of obesity-related cancers compared to smokers with low adherence, suggesting that the diet might partially offset some of the cancer risk from tobacco use.

Dr. Estefania Toledo Atucha, one of the study’s senior authors, emphasized that the research demonstrates the importance of dietary patterns rather than individual nutrients in cancer prevention.

“The potential benefits of the Mediterranean diet for cancer prevention may be from interactions and synergistic effects among its various components, collectively enhancing health benefits beyond those observed for individual foods alone,” the paper stated.

The study’s strengths include its large sample size, substantial number of cancer cases, and extended follow-up period. Unlike prior analyses, this study assessed various cancer subtypes and obesity-cancer associations across diverse populations with varying levels of Mediterranean diet adherence.

However, the researchers acknowledged limitations, including the assessment of diet only at baseline and the possibility that the Mediterranean lifestyle pattern may not be fully captured by the scoring system used.

While a 6% reduction in cancer risk might seem small at the individual level, it could translate to significant public health benefits across populations. The findings add to a growing body of evidence suggesting that even moderate adherence to healthy dietary patterns may contribute to cancer prevention.

As global obesity rates continue to rise, these results offer a relatively accessible dietary approach that could complement other cancer prevention strategies. The researchers call for further studies to better understand the mechanisms through which higher adherence to the Mediterranean diet might reduce cancer risk, independent of its effects on body weight.