Sustainable diets often linked to moderately lower cancer risk

In brief, the results in the studies reviewed included:

• A non-statistically significant increase in cancer risk for each unit of dietary greenhouse gas emissions (in Spain).
• A statistically significant increased risk of cancer for higher dietary greenhouse gas emissions, with an 11% increase in risk in cancer incidence between the upper and lower quartiles (note that the main text says 16% but this appears to be an error, as both Table 1 and the original paper say 11%), as well as a 16% increase in cancer-specific mortality (nine European countries).
• Higher dietary land use (upper versus lower quartiles) was linked to 13% higher cancer risk and 21% higher cancer mortality (nine European countries).
• No statistically significant difference in cancer risk with higher consumption of fruit with either low or high pesticide residues (France).
• Dietary intake of foods highly correlated with the pesticides chlorpyriphos, imazalil, malathion, profenofos, and thiabendazole was positively linked to the risk of post-menopausal invasive breast cancer risk (France).
• Higher intake of organic food was linked to a lower total risk of cancer (those in the upper quartile of organic food intake had only 76% of the risk of those in the lowest quartile)(France).
• Participants who reported “sometimes” eating organic food had a 3% higher total risk of cancer compared to those who “never” did (UK).
• Higher scores on the Sustainable Diet Index were linked to lower total cancer risk (those in the upper quartile had only 56% of the risk of those in the lower quartile) (France).
• Higher dietary biodiversity, measured as the number of unique biological species in a person’s diet, was inversely correlated with cancer mortality, with a 7% decrease in risk per 10-unit increase in dietary biodiversity score.
• Greater adherence to the EAT-Lancet diet was linked to lower cancer mortality although the results were only statistically significant for men.

The authors conclude that although the evidence is conflicting, most studies show a modest inverse association between sustainable diets and cancer risk. However, they note that six of the nine studies assessed carry a serious risk of bias due to confounding factors (such as age, sex and education level), with the remaining three carrying a moderate risk of bias due to confounding factors. The paper’s supplementary information also assesses several other types of bias that could be present in some of the studies. The authors note that the differing variations of sustainable diets make studying the issue difficult, and that there is a need for more studies to be conducted outside of the European/Western context.

Abstract

Purpose of Review

This review aimed to investigate the association of sustainable diets in relation to cancer risk, cancer recurrence, and cancer-specific mortality in adults.

Recent Findings

More than 500 articles were initially identified. Nine articles were eligible for inclusion, presenting data from 8 prospective cohort studies, conducted in Europe and the USA. The sustainability indicators investigated were greenhouse gas emissions, food biodiversity, land use, exposure to pesticides or organic food consumption, and the EAT-Lancet diet. One study reported a sustainability index that combined multiple sustainability indicators. A modest inverse association between higher adherence to sustainable diets and cancer incidence or cancer mortality was observed in most studies.

Summary

While sustainable diets may decrease cancer risk or mortality, the reviewed studies were heterogeneous regarding sustainability indicators and cancer outcomes. A common definition of dietary sustainability would facilitate better generalization of future research findings. Also, studies among non-western populations are needed.

Reference

Karavasiloglou, N., Pannen, S.T., Jochem, C., Kuhn, T. and Rohrmann, S., 2022. Sustainable Diets and Cancer: a Systematic Review. Current Nutrition Reports, pp.1-11.

Read the full paper here. See also the TABLE explainer How are food systems, diets, and health connected?