A systematic review and meta-analysis published by Canadian researchers highlights the important role plant protein, and in particular soy protein, can have in reducing risk of cardiovascular disease (CVD).1 It also indirectly highlights the comprehensive dietary approach required to markedly reduced CVD risk.
The meta-analysis, which included 112 clinical trials, found that replacing animal protein with plant protein decreased LDL-cholesterol by a statistically significant 0.16 mmol/L, which worked out to be about a 4% reduction. The median protein substitution was ~30 g/d. The trials ranged in duration from 3 weeks to 4 years, with a median follow up of 6 weeks. Importantly, of the 112 trials included in the analysis, 94 used soy protein as the sole plant protein and 74 used dairy as the sole animal protein intervention.
The median intervention of 30 g protein substitution reflects the substitution of 1 to 2 servings of meat for plant protein replacements (meat analogues) or about three 250-mL cups of dairy milk for soymilk. This type of change would mean a shift to diets comprised of >50% plant protein. Currently, about two-thirds of the protein in the U.S. diet comes from animal sources. However, in the early 1900s, Americans obtained about half their protein from animal sources and half from plants.2 So consuming a diet comprised of 50% plant protein isn’t really that foreign of a concept.
In theory, the 4% reduction in LDL-cholesterol in response to replacing animal protein with plant protein could over time reduce risk of developing CVD by 4 to 8 percent. At the population level, that reduction in risk represents a significant public health benefit. On the other hand, some individuals may scoff at making dietary changes for as little as a 4% benefit. However, shifting from an animal-based diet to a more plant-based one will likely also lower risk for other chronic diseases, such as diabetes and certain forms of cancer. Furthermore, when the additional plant protein comes from whole soyfoods, CVD risk will be reduced not just because of the hypocholesterolemic effect of soy protein but because of the favorable change in the fatty acid content of the diet.3,4 The isoflavones naturally present in soybeans may also produce coronary benefits.5,6
There is no doubt that dramatically reducing risk of chronic disease requires making comprehensive dietary changes. On the other hand, making relatively simply changes, such as replacing cow’s milk with soymilk, can still result in significant benefit.
- Li SS, Blanco Mejia S, Lytvyn L, et al. Effect of plant protein on blood lipids: A systematic review and meta-analysis of randomized controlled trials. Journal of the American Heart Association. 2017;6.
- Smit E, Nieto FJ, Crespo CJ, Mitchell P. Estimates of animal and plant protein intake in US adults: results from the Third National Health and Nutrition Examination Survey, 1988-1991. J Am Diet Assoc. 1999;99:813-20.
- Li Y, Hruby A, Bernstein AM, et al. Saturated fats compared with unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease: A prospective cohort study. J Am Coll Cardiol. 2015;66:1538-48.
- Jenkins DJ, Mirrahimi A, Srichaikul K, et al. Soy protein reduces serum cholesterol by both intrinsic and food displacement mechanisms. J Nutr. 2010;140:2302S-11S.
- Pase MP, Grima NA, Sarris J. The effects of dietary and nutrient interventions on arterial stiffness: a systematic review. Am J Clin Nutr. 2011;93:446-54.
- Li SH, Liu XX, Bai YY, et al. Effect of oral isoflavone supplementation on vascular endothelial function in postmenopausal women: a meta-analysis of randomized placebo-controlled trials. Am J Clin Nutr. 2010;91:480-6.