A recent study published in JAMA Network Open explores the impact of adherence to the Mediterranean diet (MedDiet) on the risk of developing obesity-related cancers (ORCs). Obesity is recognized as a major risk factor for several types of cancer, and dietary interventions such as the MedDiet have been studied for their potential to mitigate this risk.
How Does Obesity Affect Cancer Risk?
The global prevalence of obesity and overweight has risen significantly from 1975 to 2016, with an estimated 39% of the global population now classified as obese or overweight. Obesity is associated with an increased risk of cancer at various anatomical sites, including the kidney, liver, breast, endometrium, and esophagus, according to the International Agency for Research on Cancer (IARC).
Research has shown that excess body fat can contribute to cancer risk through multiple mechanisms, including insulin resistance, inflammation, and the secretion of adipokines, which promote cell growth. These factors play a crucial role in the relationship between obesity and cancer, but it remains unclear whether weight reduction or adherence to a specific diet like the MedDiet can effectively reduce this risk.
The Mediterranean Diet and Its Potential Benefits
The Mediterranean diet, rich in fruits, vegetables, whole grains, legumes, and healthy fats (primarily olive oil), has been shown to promote weight loss and reduce abdominal adiposity. Studies, such as the European Prospective Investigation into Cancer and Nutrition (EPIC)-Spain cohort, have demonstrated an inverse relationship between MedDiet adherence and obesity risk, particularly among individuals with excessive body weight. Additionally, previous research has suggested that MedDiet adherence improves survival rates following a breast cancer diagnosis and reduces overall cancer risk.
The EPIC study, which has contributed significantly to understanding the relationship between diet and cancer, found that a higher MedDiet score (indicating greater adherence) was linked to a 4% reduction in overall cancer risk for every two-point increase in the score. These findings were supported by a recent meta-analysis, which indicated that higher MedDiet adherence correlates with a reduced risk of cancer mortality and specific cancer incidences.
Despite these findings, it remains unclear whether adiposity mediates the MedDiet’s beneficial role in obesity-related cancers, prompting further investigation into the association between MedDiet adherence and ORC risk.
About the Study
This study utilized data from the EPIC cohort, which includes 521,324 individuals aged 35 to 70 from 23 centers across 10 countries. The research aimed to examine the relationship between MedDiet adherence and the risk of obesity-related cancers while also considering whether this relationship was mediated by body mass index (BMI) and waist-to-hip ratio (WHR).
Participants diagnosed with cancer at baseline, or those lacking follow-up data or dietary information, were excluded from the analysis. The study considered 14 food groups and nutrients to estimate daily intake and total energy consumption, using the Mediterranean diet score (MDS) and relative Mediterranean diet score (rMedDiet) to quantify adherence.
Over a 14.9-year follow-up period, the study identified new cancer cases and assessed the relationship between MedDiet adherence and ORC risk.
Study Findings
Out of the original 521,324 participants, 450,111 were eligible for the analysis. The cohort comprised 29.2% men and 70.8% women, with a mean age of 51.1 years. At baseline, the mean BMI was 25.3, and the mean WHR was 0.8.
Approximately 4.9% of participants who were cancer-free at baseline developed obesity-related cancers during the study period. This incidence was lower in individuals with high MedDiet adherence, with rates of 0.053, 0.049, and 0.043 per person-years in the low, medium, and high adherence groups, respectively.
Key Findings:
Higher MedDiet Adherence Reduces ORC Risk:
Greater adherence to the MedDiet was associated with a reduced risk of obesity-related cancers.
A moderate reduction in risk was observed for individuals with medium adherence to the MedDiet, with an inverse association noted for liver, colorectal, and kidney cancers.
Site-Specific Associations:
Higher adherence to the MedDiet was particularly beneficial for reducing the risk of hepatocellular (liver), colorectal, and kidney cancers.
Medium adherence was inversely associated with esophageal cancer, but no significant association was found for postmenopausal breast, endometrial, or ovarian cancers.
Lifestyle and Demographic Influences:
Individuals with the highest MedDiet scores were more likely to be younger, non-smokers, less physically active, and have higher energy intake. These factors might influence the observed associations between MedDiet adherence and ORC risk.
Mediation Analysis:
The mediation analysis indicated that the relationship between MedDiet adherence and reduced ORC risk was not significantly mediated by BMI or WHR, suggesting that the diet’s protective effects may extend beyond weight loss alone.
Conclusions
This study confirms that adherence to the Mediterranean diet is associated with a moderate reduction in the risk of obesity-related cancers, with medium adherence providing a modest reduction in cancer risk. Notably, the diet was found to be particularly effective in reducing the risk of liver, colorectal, and kidney cancers, and the benefits were not explained by changes in BMI or waist-to-hip ratio.
The study highlights the need for further research to elucidate the mechanisms by which the MedDiet reduces the risk of obesity-related cancers, particularly through its effects on inflammation, metabolism, and adiposity. Such research may help refine dietary recommendations for cancer prevention and contribute to the development of personalized, evidence-based dietary guidelines for individuals at high risk of obesity-related cancers.
Future Directions
Given the promising findings, additional studies are needed to further explore the role of the Mediterranean diet in cancer prevention. Future research should aim to better understand the diet’s mechanisms and investigate its long-term effects on cancer incidence and mortality, particularly in high-risk populations.
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