Protein Adequacy, Plant Protein Proportion, and Main Plant Protein Sources Consumed Across Vegan, Vegetarian, Pescovegetarian, and Semivegetarian Diets: A Systematic Review

Abstract

Background

There are several types of plant-based diets, with unknown differences across diets on total/plant protein intake and variety of plant protein sources consumed.

Objectives

This systematic review aimed to compare total protein intake, proportion of plant proteins, and main plant protein sources consumed across 4 primarily plant-based diets: vegan, vegetarian, pescovegetarian, and semivegetarian.

Methods

We included observational studies reporting on protein intake and/or protein sources in generally healthy adults that were published between 2002 and 2023. We determined the following: 1) % energy from total and plant protein; 2) the proportion of plant protein relative to total protein intake; and 3) main plant protein sources (median percentage contribution of each source to total plant protein intake; interquartile range) consumed across the 4 diets. The plant protein sources were broadly classified into the following United States Department of Agriculture food groups: grains; nuts and seeds; soy products; and beans, peas, and lentils.

Results

We included 13 studies reporting on protein intake/sources that were conducted in the United States, Europe, and South Korea. Of these, 7 reported on vegan, 11 on vegetarian, 7 on pescovegetarian, and 7 on semivegetarian diets with total protein intake ranging from 10% to 17.4%. Vegan diets had the highest plant protein proportion (range: 77%–98%) and semivegetarian diets the lowest (range: 37%–83%). Plant protein source contribution was the highest from grains (range: 60%–78%). Nuts and seeds were the most consumed in vegetarian diets (7.9%; 2.9%–10.3%) and least in semivegetarian diets (3.7%; 2%–14.8%). Soy products and beans, peas, and lentils were most consumed in vegan diets (17.3%; 16.3%–19.9, and 19.6%; 14.6%–21.3, respectively) and least in semivegetarian (3.7%; 1.3%–13.9%, and 8.5%; 5.2%–10.2%) diets.

Conclusions

Vegan diets has the highest plant protein proportion and a variety of plant protein sources, while semivegetarian diets has the lowest plant protein proportion and mainly relied on grains as a plant protein source.