New study links legume consumption to lower risk of colorectal cancer

By Hugo Francisco de SouzaFeb 8 2024Reviewed by Danielle Ellis, B.Sc.

In a recent study published in the European Journal of Clinical Nutrition, researchers collated and analyzed 12 studies comprising more than 17 years’ worth of case-control experiments aimed at elucidating site-specific cancer outcomes of legume consumption.

Their multiple logistic regression models revealed that, while the odds ratios of legume consumption are below unity for most investigated cancers (suggesting a protective effect), legumes were shown to cause a statistically significant decrease in colorectal cancer.

Increasing legume consumption by just one portion per week was sufficient to decrease colorectal cancer risk by 13%. This study adds to a growing body of research highlighting the clinical benefits of healthy diets.

Background

‘Cancer’ is an umbrella term for a cohort of non-transmittable diseases characterized by the uncontrolled growth and division of abnormal cells resulting in a malignant tumor. While combinations of genetics, environmental pollutants, lifestyles, and even some pathogen-transmitted diseases have been implicated in triggering cancers (‘carcinogens’), researchers have attributed the alarming recent global increase in cancer prevalence and mortality to medically associated increases in human life expectancy, especially in rich and developed countries.

Lifestyle and health behaviors have been observed to have a profound impact on cancer risk. The most updated World Cancer Research Fund International (WCRF) report emphasizes the positive benefits of healthy diets as an anti-cancer intervention and recommends the consumption of whole grains, fruits, vegetables, and beans, summing up to a quota of 30 g of dietary fiber per day. Legumes, plants belonging to the family Fabaceae, and, by extension, their seeds (pulses) fit this recommendation perfectly.

Many cultures around the world have traditionally consumed legumes and pulses due to their providing a rich source of proteins, carbohydrates, dietary fibers, and fatty acids. Recent research has further discovered the presence of several legume-derived non-nutrient metabolites with interactive bioactive properties. Unfortunately, the potential anti-cancer benefits of these foods remain scientifically unconfirmed, with the limited research in the field producing inconclusive results.

About the study

The present study derives from a series (n = 12) of case-control experiments collectively aimed at elucidating legume-cancer associations across multiple cancer sites, including the oral cavity, larynx, esophagus, stomach, breast, colorectum, endometrium, prostate, ovary, and kidney.

These studies were carried out between 1991 and 2009 in centers spread across ten provinces in Italy and Switzerland. The original studies were designed with shared methodology and outcomes metrics, thereby facilitating their comparisons and analyses in the current work.

Constituent studies enrolled incident, clinically (histologically) confirmed cancer patients with any of the aforementioned cancers, diagnosed within a year of volunteering (via interview) their participation (cases). Respective controls were derived from patients admitted to hospitals with acute and nonneoplastic conditions unrelated to cancers. Since the original studies aimed to investigate the associations between smoking, alcohol consumption, dietary habits, and cancers, controls were known to not indulge in smoking, drinking, or long-term diet modifications.

Data collated included sociodemographic information, anthropometrics, smoking habits, physical and medical histories, beverages (including alcohol) consumed, and cancer familiarity. Food habits, in particular, were assessed using a food frequency questionnaire (FFQ), which included queries on legume consumption (frequency and portion size). Statistical analyses included multiple logistic regression models used to generate Odds Ratios (ORs). ORs were computed for varying portion sizes and were adjusted for covariates, including sex, age group, education, smoking, alcohol consumption, body mass index (BMI), chronic disease status, and physical activity levels.

“To evaluate whether a sex-difference in the association between legume consumption and cancer risk exists, we tested the “sex-by-legume consumption” interaction in the regression models using the likelihood ratio test (LRT) between the model with and the model without the interaction term.”

Study findings and conclusions

The total sample size of all included studies was 10,482 cancer cases and an equivalent number of controls. Analyses revealed that 30-40% of included participants (cases + controls) consumed at least one legume portion per week. With endometrium cancer being the only exception, controls were found to consume more legumes than their corresponding cases.

Legume consumption was associated with below unity ORs across cancer types. Notably, while these findings highlight the general protective effect of legumes against cancer, colorectal cancer was the only cancer with a statistically significant OR. One portion of legumes per week resulted in an OR of 0.74 – individuals consuming at least one legume portion per week were 26% less likely to develop colorectal cancer in the future. Consuming two portions per week improved this probability to 35%, with each additional portion over two further decreasing colorectal cancer risk by 15%.

Adjusting for covariates (including sex) did not significantly alter these results. These findings highlight the importance of dietary choices in preventing chronic and potentially lethal diseases like cancers and validate the inclusion of legumes as an effective intervention against colorectal cancer risk in both men and women, irrespective of age.