Plant protein intake linked to longevity

Individuals with high total protein intake appear to have a much lower risk of death, and those who consume plant proteins may benefit from a reduced risk of all-cause and cardiovascular mortality, suggest the results of a systematic review and meta-analysis.

“Replacement of foods high in animal protein with plant protein sources could be associated with longevity,” according to the researchers.

Prospective cohort studies reporting the risk estimates for all-cause, cardiovascular, and cancer mortality in adults aged ≥18 years were retrieved from the databases of PubMed, Scopus, and ISI Web of Science until December 2019.

The researchers generated random effects models to calculate pooled effect sizes and 95 percent confidence intervals (CIs) for the highest versus the lowest categories of protein intake and to incorporate variation between studies. They also assessed the dose-response relations between protein intake and mortality by performing linear and nonlinear dose-response analyses.

Thirty-two prospective cohort studies were identified for the systematic review, and 31 were eligible for the meta-analysis. Among 715,128 participants, a total of 113,039 deaths (16,429 from cardiovascular disease and 22,303 from cancer occurred during 3.5–32 years of follow-up. [BMJ 2020;370:m2412]

An association was found between total protein intake and a reduced risk of death from all causes (pooled effect size, 0.94, 95 percent CI, 0.89–0.99; I², 58.4 percent; p<0.001). Furthermore, plant protein intake significantly correlated with a lower risk of both all-cause (pooled effect size, 0.92, 95 percent CI, 0.87–0.97; I², 57.5 percent; p=0.003) and cardiovascular mortality (pooled hazard ratio, 0.88, 95 percent CI, 0.80–0.96; I², 63.7 percent; p=0.001), but not cancer mortality.

On the other hand, intake of total and animal protein did not significantly correlate with the risk of cardiovascular and cancer mortality.

On dose-response analysis, a significant inverse dose-response association was seen between plant protein intake and all-cause mortality (p=0.05 for nonlinearity). An additional 3-percent energy from plant proteins a day resulted in a 5-percent lower risk of all-cause mortality.

“Given that plant protein is part of total protein, the observed inverse association for intake of total protein seems to be related to its plant protein component,” the researchers said. “The mechanisms through which plant proteins could affect human health are not well known.”

Additionally, dietary plant proteins were associated with favourable changes in blood pressure, waist circumference, body weight, and body composition, which could help prevent several chronic diseases, including cardiovascular disease and type 2 diabetes. [Arch Intern Med 2006;166:79-87]

Studies also showed the association between animal protein intake and hypercholesterolaemia, independent of body weight, while plant protein intake correlated with low levels of plasma cholesterol. [J Food Sci 1975;40:18-23; J Nutr 2017;147:281-292]

Of note, caution is warranted when generalizing these findings as most studies included in the meta-analysis are from Western nations, and few studies have been reported from other countries, according to the researchers.

“Therefore, further studies are required. Additional studies should also focus on the mechanisms through which dietary protein affect mortality,” they added.