Efficacy of the Mediterranean diet on health outcomes in adults with cancer

Efficacy of the Mediterranean diet on health outcomes in adults with cancer

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

Efficacy of the Mediterranean diet on health outcomes in adults with cancer
Study: Mediterranean-style dietary interventions in adults with cancer: a systematic review of methodological approaches, feasibility and preliminary efficacy. Image credit: Marian Weyo/Shutterstock.com

Background

Today, almost 20 million people have been diagnosed with cancer, making it the leading cause of illness and death worldwide. Cancer treatment is also associated with numerous adverse effects that cause rapid aging, induce chronic metabolic aberrations, and reduce quality of life.

These side effects include early menopause, cognitive impairment, and cardiomyopathy, with persistent fatigue and weight loss. Such long-term ill effects can be mitigated by diet and exercise. Yet there is little evidence to support a proper dietary pattern for such problems occurring during or after cancer treatment.

About the Mediterranean diet

The MED diet has long been recognized as one of the healthiest eating patterns. Following this diet is associated with a reduced risk of many chronic diseases, including type 2 diabetes and cardiovascular disease.

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

Previous data showed that people on the MED diet had a 22% and 13% lower chance of dying from prostate cancer and breast cancer, respectively. This is very important because the hormonal treatment commonly used in these cancers adversely affects the metabolic profile 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 present study.

About the research

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

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

In most studies, the goal was to lose weight, but some focused on reducing fatigue, reducing levels of inflammatory mediators, improving diet, or maintaining a stable weight. Energy restrictions are applied at different levels for those who are overweight or obese. Others used strategies such as reduced portion sizes or eating more filling foods.

What changes are observed?

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

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

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

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

What are the conclusions?

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

The positive role of nutritionists in this type of intervention, with accompanying nutritional advice, cooking demonstrations and recipes tailored to individual clients, is evidenced by the significantly higher adherence observed in such studies.

Weight loss is particularly well supported by this energy-restricted diet, with overweight or obese individuals on hormone therapy or after treatment for prostate or breast cancer losing up to 4 kg. Currently, there is evidence for the benefit of the MED diet only for women who have completed breast cancer treatment.

Further studies are needed to confirm that the MED diet will help prevent and manage chronic diseases 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 should be explored.

Confounding factors that may have mediated the improvement in cardiometabolic status and quality of life include frequent interactions with health care providers and other dietary components such as green tea, which themselves have anti-inflammatory and antioxidant activity. Careful documentation of diet, adherence, and outcomes is needed to rule out the role of such factors in the prevention or management of 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.”

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