The efficacy of the Mediterranean diet on health outcomes in adults with cancer

By Dr. Liji Thomas, MDMar 15 2024Reviewed by Danielle Ellis, B.Sc.

Cancer treatment is often associated with undue weight gain, mostly due to fat deposition. The Mediterranean diet (MED diet) may help support such patients during this period. A new study published in the European Journal of Clinical Nutrition explores the safety and benefits of this diet in adults with cancer, in addition to its feasibility in this population.

Background

Almost 20 million people today have received a cancer diagnosis, making it the leading cause of illness and death globally. The treatment of cancer is also associated with multiple adverse effects that cause rapid aging, trigger chronic metabolic aberrations, and reduce the quality of life.

These side effects include early menopause, cognitive impairment, and cardiomyopathy, with persistent fatigue and weight loss. Such long-term ill effects could be mitigated by nutrition and exercise. Yet, there is little evidence to support the right nutritional pattern for such issues arising during or after cancer treatment.

About the Mediterranean diet

The MED diet has been long recognized as among the healthiest eating patterns. Compliance with this diet has been associated with reduced risk of many chronic illnesses, including type 2 diabetes and cardiovascular harm.

This dietary pattern is characterized by a high consumption of fish, vegetables, legumes, nuts, fruits, and extra virgin olive oil, a moderate intake of dairy and red wine, with little added sugar, processed foods, and red meat. The antioxidant and anti-inflammatory profile of this diet have been thought to mediate its beneficial effects on cardiac and metabolic health.

Previous evidence indicates that those on a MED diet have 22% and 13% lower odds of dying from prostate and breast cancer, respectively. This is very significant since the hormone treatment typically used in these cancers adversely affects the metabolic and body composition profile, increasing the risk of cardiometabolic disease.

This group of patients has been shown to benefit from nutritional manipulation with exercise by reducing body fat and body weight. Yet, there is little systematic evidence to support the recommendation of a MED diet for adults with cancer. This prompted the current study.

About the study

A systematic review was undertaken, including 15 articles covering the MED diet intervention among this group of patients. Of these, ten included breast cancer patients, all women, and one mostly female breast cancer patients. The remaining included prostate cancer, acute myeloid leukemia, and lung cancer.

In five of the studies, patients were being actively treated, while five were post-treatment studies. Three included patients who either had been or were being treated, with one starting within five years from the diagnosis.

In most studies, the aim was to lose weight, but a few were aimed at lessening fatigue, reducing inflammatory mediator levels, enhancing the diet, or maintaining a stable weight. Energy restrictions at varying levels were applied for those who were obese or overweight. Others used strategies such as reduced portion size or consuming more satiating foods.

What changes were observed?

Most participants adhered closely to the MED diet compared to controls, at 64% to 96% completion rates. In six studies, the body weight of the MED diet participants decreased compared to that of the control group. In seven studies, the body mass index (BMI) decreased in the intervention group vs controls.

A similar favorable change was reported in the body fat mass, though three also reported loss of lean mass.

Multiple metabolic biomarkers and inflammatory markers were favorably affected, including decreased glucose markers, reduced cardiovascular markers including triglycerides and total cholesterol, increased high-density lipoprotein (HDL, ‘good cholesterol’), higher albumin levels, and reduced interleukin-8 (IL-8).

The intervention was also associated with a higher quality of life and reduction in fatigue, as well as better emotional, physical, and cognitive health.

What are the conclusions?

The studies included in this review had widely varying study designs and MED diet content, making it difficult to provide a definitive recommendation to achieve these favorable outcomes. However, the safety and feasibility, as well as acceptability, of the MED diet as a nutritional intervention is established.

The positive role of nutritionists in this type of intervention, with accompanying advice on nutritional value, cooking demos, and recipes tailored to individual clients, appears from the significantly higher adherence seen in such studies.

Body weight reduction is particularly well supported by this diet with energy restriction, with overweight or obese subjects on hormone therapy or post-treatment for prostate or breast cancer losing up to 4 kg. Currently, evidence of the benefit of the MED diet is available only for women who have completed breast cancer treatment.

Further studies need to be done to confirm that the MED diet will help prevent and manage chronic disease in this population of cancer survivors who are at high risk for such conditions. Approaches that protect or increase muscle mass but are compatible with this dietary pattern need to be explored.

Confounding factors that may have mediated the improvement in cardiometabolic status and quality of life include frequent interactions with healthcare providers and other dietary components like green tea that have anti-inflammatory and antioxidant activity themselves. Careful documentation of the diet, adherence, and outcomes is necessary to rule out the role of such factors in preventing or managing chronic disease in future studies.

“Future longer term RCTs should focus on reducing the risk of, or managing, cardiovascular or metabolic disease after cancer treatment to improve the potential clinical implications of the MED-diet.”