Increased Dietary Protein in Sedentary Vegans and Vegetarians and its Effect on Body Composition and Strength

Chronic diseases, such as diabetes, heart disease, and cancer are leading causes of death in the United States. Although they result from a host of personal and environmental factors, diet remains a critical way to reduce the risk. Plant-based diets in particular are associated with reduction in risk for chronic disease due to an intake that closely mirrors the Dietary Guidelines for fruit and vegetable consumption, fiber, and fat intake. Additionally, plant-based diets offer a sustainable alternative in relation to food production as they often require fewer natural resources overall.

While there are many benefits to following a plant-based diet, potential concerns arise as well. Certain micronutrients can be lacking and protein intake can be inadequate without careful consideration of dietary intake. Protein is especially important for its role in maintaining lean body mass, which allows individuals to function in activities of daily living. Plant-based sources of protein are often less digestible; therefore, those consuming vegetarian and vegan diets may benefit from increased protein intake for preservation and perhaps improved lean body mass as well as strength changes.

Recent research has shown that vegetarians had significantly less muscle mass compared to omnivores despite similar amounts of protein intake in grams per day. Other research has shown that vegetarians do not necessarily see an increase in muscle mass when exposed to resistance exercise, whereas those following an omnivorous diet or lacto-ovo-vegetarian diet do. However, other studies have found that vegetarians can achieve increases in lean body mass comparable to omnivores if 30g/meal of plant-based protein is ingested consistently.

It remains unclear what effect protein supplementation might have on strength and muscle mass among sedentary plant-based eaters. As such, the present study assessed sedentary vegetarian and vegan individuals as to whether increases in dietary plant-based protein could elicit changes in body composition, hand grip and lower body strength independent of exercise. After an 8-week intervention, no significant differences for lean body mass or strength were noted. Results are discussed in the context of trial integrity and supplement consumption issues.