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Evidence Summary

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The Mediterranean diet lowers risk of developing cancer, particularly colorectal cancer.

Bloomfield HE, Koeller E, Greer N, et al. Effects on health outcomes of a Mediterranean diet with no restriction on fat intake: A systematic review and meta-analysis Ann Intern Med. 2016; 165: 491-500.

Review question

Do adults who follow the Mediterranean diet have better health outcomes, including lower risk of death, lower risk of being diagnosed with a chronic disease, or lower risk of disease progression in those with diabetes, cardiovascular disease, cancer, hypertension, cognitive impairment, arthritis, or kidney disease.

Background

The Mediterranean diet is a mostly plant-based diet with a high ratio of monounsaturated fats (healthy fats). Previous studies that included people who followed a Mediterranean diet showed a potential for a lower risk of death during the study period, and other positive health outcomes.

How the review was done

  • This is a review of 44 medium quality studies including over 2 million participants, published between 2001 and 2015. Only 2 included studies were randomized controlled trials.
  • 26 studies included both men and women, 14 studies included women only and 4 studies included men only. The average age of participants was 56.5 years, ranging from 36-83 years. 20 studies were conducted in the USA/Canada, 20 in Europe, and 4 in Asia/Australia.
  • All studies compared participants who followed a Mediterranean diet to those who did not. For this review, the Mediterranean diet was anything that included at least two of the following: high healthy fat ratio (ex. Use of olive oil), lots of fruits and vegetables, lots of legumes, lots of grains and cereals, moderate red wine, moderate dairy intake, small amounts of meat or meat products, and high amounts of fish.
  • The researchers included information on risk of death, risk of being diagnosed with a disease, and risk of disease progression in those with diabetes, cardiovascular disease, cancer, hypertension, cognitive impairment, arthritis or kidney disease.

 

What the researchers found

Based on the included studies, the Mediterranean diet had no impact on risk of death, risk of developing breast cancer or cognitive functioning. The Mediterranean diet does lower risk of all cancers, and colorectal cancer. There was not enough information to draw conclusions about other health outcomes.

Conclusion

The Mediterranean diet may lower risk of all cancers, particularly colorectal cancer but does not decrease one’s risk of death. More high-quality research is needed to understand the effect of the Mediterranean diet on other health outcomes.

 




Glossary

Cognitive function
Mental processes, including thinking, learning and remembering.
Cognitive impairment
Trouble remembering, learning new things, concentrating, or making decisions that affect everyday life.
Randomized controlled trials
Studies where people are assigned to one of the treatments purely by chance.
Vascular
The body's network of blood vessels. It includes the arteries, veins, and capillaries that carry blood to and from the heart.

Related Web Resources

  • Colorectal cancer test recommendations

    Health Link B.C.
    Colorectal testing every 1-2 years is recommended for people between ages 50 and 74. Your doctor may recommend screening before age 50 and more often if you have an increased risk of this type of cancer (eg. family history of colon cancer, polyps or Crohn's disease).
  • Breast cancer Screening video

    Canadian Task Force on Preventive Health Care
    Women ages 50-74 should have a mammogram every 2 to 3 years, if they are not at high risk of breast cancer. Discuss with your doctor whether you should have a mammogram if you are over age 75.
  • Dance therapy for people with cancer

    Evidently Cochrane
    Dance therapy does not appear to have a large benefit on improving physical or psychological symptoms of people with cancer, such as depression, fatigue or body image. However, you should dance if it helps you feel better.
DISCLAIMER These summaries are provided for informational purposes only. They are not a substitute for advice from your own health care professional. The summaries may be reproduced for not-for-profit educational purposes only. Any other uses must be approved by the McMaster Optimal Aging Portal (info@mcmasteroptimalaging.org).

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