Mediterranean-style diet and cancer

In 1948 5,209 men and women who lived in Framingham, Massachusetts were recruited to participate in a prospective study designed to help identify the risk factors for heart disease. This became known as the Framingham Heart Study, which continues to the present.

In addition to the original participants, an Offspring Cohort (children of the original participants) was established in 1971 that included an additional 5,124 people. As with the original study, the participants in the Offspring Cohort visited the lab for a detailed physical examination and lab tests every two years, while also supplying demographic and health history information. Starting in 1991, the participants also responded to dietary questionnaires every four years.

The research that comes out of the Framingham Heart Study and its additional cohorts isn't limited to heart disease, however. Recently a team of researchers at Boston University and Tufts University sought to identify any links between diet and cancer (Nutrients 2021, 13, 4064).

Using the dietary questionnaires, the authors utilized a variation of the Mediterranean Diet Score that included 13 food groups: whole grains, fruit, vegetables, dairy, wine, fish, poultry, olives/legumes/nuts, potatoes, egg, sweets, meat, and olive oil. Except for olive oil, scores were assigned on a scale of 0-10 representing a percentage of the recommended amount - so if a participant consumed 70% of the recommended amount of vegetables, they received a score of 7 for that food group. The total of the scores for all 13 groups was then standardized to a scale of 0-100 and each food was weighted according to its percentage of the individual's total caloric intake. The maximum possible score was then 100 (where the usual Mediterranean Diet Score ranges from 0-9).

As of 2013, 611 participants in the Offspring Cohort had been diagnosed with cancer (excluding non-melanoma skin cancer).

Interestingly, the highest modified Mediterranean Diet Score in this cohort was just 50.9. Thus the researchers grouped the participants into three increasing levels of adherence: Low (4.0 - 19.0), Moderate (19.1 - 25.0), and High (25.1 - 50.9).

After comparing the dietary scores of those who developed cancer (611) with those who did not (2966 after exclusions), the authors found that compared to those with Low scores, those with Moderate and High Mediterranean Diet scores were about 15% less likely to develop cancer - an amount the authors note is not statistically significant.

That said, when the researchers grouped the participants by sex (male vs. female) they found that for women, those with a Moderate score were 29% less likely to develop cancer than those with a Low score. A High score didn't provide much additional benefit, with a 26% reduction in risk. On the other hand, men in the Moderate and High score groups were just 5% and 9% less likely to develop cancer, respectively.

What this means for you

As always, a prospective study, even the Framingham Heart Study, "considered the crown jewel of epidemiology", can only show association and not causation. This is yet another small piece of evidence supporting a Mediterranean-style diet - not only for heart health, but also to help prevent cancer.

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