Editorial NexoScience
Eating more beans, lentils and chickpeas does not appear to help anyone in the United States or Europe live longer. That is not a contrarian reading of the evidence, it is what the subgroup numbers say inside one of the largest reviews ever assembled on legumes and death, published in the journal Advances in Nutrition by an international research team. The authors searched PubMed/Medline, Embase, Scopus and Web of Science from inception to September 2022, and pooled 32 prospective cohorts drawn from 31 publications, covering 1,141,793 participants and 93,373 deaths from all causes.
The headline result is real, but it is modest. Comparing people with the highest legume intake against those with the lowest, the risk of dying from any cause was 6% lower (HR 0.94; 95% CI 0.91 to 0.98, across 27 cohorts). The dose response analysis landed on the same figure: each additional 50 grams of legumes per day, roughly half a standard tin of cooked beans, was associated with a 6% lower risk of all-cause mortality (HR 0.94; 95% CI 0.89 to 0.99). Stroke mortality also came out lower, by 9% (HR 0.91; 95% CI 0.84 to 0.99). Those are the two findings that survived the full analysis, and neither is dramatic.
The protection vanishes the moment the research crosses into the West. When the authors split the cohorts by geography, the pattern broke apart. In the five cohorts conducted in the United States, the association was exactly nothing (HR 1.00; 95% CI 0.96 to 1.05). In the eleven European cohorts, it was nothing again, and pointing the wrong way (HR 1.01; 95% CI 0.95 to 1.07). The benefit lived entirely in the nine cohorts from Asia and Australia (HR 0.90; 95% CI 0.85 to 0.95) and in the two international ones (HR 0.78; 95% CI 0.69 to 0.87). Geographical location was flagged as one of the main sources of heterogeneity between studies.
The authors’ own explanation points at everything else on the plate. Most of the included studies never recorded how the legumes were prepared or what they were served with, and the researchers raise that omission directly in their limitations. Beans in Europe and the United States, they note, are frequently eaten alongside bacon, sausages and eggs, a very different proposition from a dish of mung dal with vegetables and brown rice. They stop short of claiming this explains the geographic split, writing only that whether it does requires further study. It remains a hypothesis, not a result.
Cause-specific mortality tells an even flatter story. There was no significant association with cardiovascular mortality (HR 0.99; 95% CI 0.91 to 1.09, in 11 cohorts), none with coronary heart disease mortality (HR 0.93; 95% CI 0.78 to 1.09, in 5 cohorts) and none with cancer mortality (HR 0.85; 95% CI 0.72 to 1.01, in 5 cohorts). The stroke result also proved fragile: removing either of two individual cohorts from the pool wiped out its statistical significance. In the opposite direction, dropping one Dutch cohort turned the cancer finding significant. Results that flip on the removal of a single study are results to hold loosely.
None of this establishes that legumes extend anything. Every study included was observational, which means the analysis captures a correlation between what people reported eating and when they died, not proof that the food caused the difference. People who eat more legumes tend to differ from those who eat fewer in dozens of ways that no statistical adjustment fully removes. Most cohorts measured diet only once, at baseline, using food frequency questionnaires. Using the GRADE system, the authors rated the certainty of the evidence as moderate for all-cause and stroke mortality, and low for cardiovascular, coronary and cancer mortality. Not one association reached high certainty.
The recommendation survives, but with an asterisk. The authors conclude that their findings support current dietary advice to eat more legumes, and there is no case here for eating fewer of them. The honest reading is narrower than the usual slogan: legumes look like a good swap for refined starches and sugars, they may not outperform whole grains and nuts, and what surrounds them on the plate may matter as much as the legumes themselves.
Source: Zargarzadeh N, Mousavi SM, Santos HO, Aune D, Hasani-Ranjbar S, Larijani B, Esmaillzadeh A. “Legume Consumption and Risk of All-Cause and Cause-Specific Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Studies.” Advances in Nutrition, 2023;14(1):64-76. DOI: 10.1016/j.advnut.2022.10.009.
