Substitution of animal-based with plant-based foods on cardiometabolic health and all-cause mortality

There is growing evidence that substituting animal-based with plant-based foods is associated with a lower risk of cardiovascular diseases (CVD), type 2 diabetes (T2D), and all-cause mortality. The aim of this review was to summarize and evaluate the evidence for the substitution of any animal-based foods with plant-based foods on cardiometabolic health and all-cause mortality in a systematic review and meta-analysis.

The researchers systematically searched MEDLINE, Embase, and Web of Science to March 2023 for prospective studies investigating the substitution of animal-based with plant-based foods on CVD, T2D, and all-cause mortality. They calculated summary hazard ratios (SHRs) and 95% confidence intervals (95% CI) using random-effects meta-analyses. We assessed the certainty of evidence (CoE) using the GRADE approach.

In total, 37 publications based on 24 cohorts were included. The results are impressive:

• There was moderate CoE for a lower risk of CVD when substituting processed meat with nuts [SHR (95% CI): 0.73 (0.59, 0.91), n = 8 cohorts], legumes [0.77 (0.68, 0.87), n = 8], and whole grains [0.64 (0.54, 0.75), n = 7], as well as eggs with nuts [0.83 (0.78, 0.89), n = 8] and butter with olive oil [0.96 (0.95, 0.98), n = 3].
• There was moderate CoE for an inverse association with T2D incidence when substituting red meat with whole grains/cereals [0.90 (0.84, 0.96), n = 6] and red meat or processed meat with nuts [0.92 (0.90, 0.94), n = 6 or 0.78 (0.69, 0.88), n = 6], as well as for replacing poultry with whole grains [0.87 (0.83, 0.90), n = 2] and eggs with nuts or whole grains [0.82 (0.79, 0.86), n = 2 or 0.79 (0.76, 0.83), n = 2].
• Replacing red meat for nuts [0.93 (0.91, 0.95), n = 9] and whole grains [0.96 (0.95, 0.98), n = 3], processed meat with nuts [0.79 (0.71, 0.88), n = 9] and legumes [0.91 (0.85, 0.98), n = 9], dairy with nuts [0.94 (0.91, 0.97), n = 3], and eggs with nuts [0.85 (0.82, 0.89), n = 8] and legumes [0.90 (0.89, 0.91), n = 7] was associated with a reduced risk of all-cause mortality.

The authors concluded that their findings indicate that a shift from animal-based (e.g., red and processed meat, eggs, dairy, poultry, butter) to plant-based (e.g., nuts, legumes, whole grains, olive oil) foods is beneficially associated with cardiometabolic health and all-cause mortality.

I am not a vegetarian or vegan but have been interested in vegetarian diets for some time.

• In a 1997 review, I concluded that eating less meat is good advice; however, strict forms of vegetarianism are not entirely free of risks.
• And in 1986, we showed that, in vegetarians, blood and plasma viscosities were lower than in meat eaters. Stricter avoidance of animal products was associated with even lower values for these indices. These observations are in agreement with the fact that other low-cardiovascular-risk groups show better than average blood fluidity. They are consistent with the hypothesis that in vitro measurements of blood rheology may provide signs of early atherosclerotic changes in vivo.

The mechanisms by which a vegetarian diet bring about the health benefits are still not entirely clear and require more research. Likewise, we need more evidence on the question wether it is necessary to avoid all animal-based foods to generate the benefits. My reading of the evidence is that a reduction of such foods might suffice. Yet, the optimal balance is unclear as yet.