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Protein is one of the building blocks of any healthy diet - it’s what our organs, muscles, hair, and skin are made out of. Protein is necessary to form blood cells, and is an essential part of the immune response and cellular repair. Consumed proteins are digested into amino acids, which become the building blocks of these structural and functional compounds. Amino acids can be classified as either ‘essential’, meaning that we must obtain them from diet or ‘nonessential’, meaning that they can be synthesized from other amino acids.
While it is recognized that well-planned vegetarian diets are consistent with good health, it is important to be aware of inadequacies if nutrient-dense choices are not made. According to NHANES data, vegetarians had a higher prevalence of inadequacy for protein, amongst other nutrients, than did nonvegetarians
Additionally, as protein is used less efficiently with aging, older vegetarian and vegan adults may require increased protein intake.
Nutritional adequacy of plant-based diets for weight management: observations from the NHANES
Farmer B. , Am J Clin Nutr, 2014
According to the International Society of Sports Nutrition (ISSN), the endurance athlete requires 1.0 g/kg to 1.6 g/kg of protein per day. For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, ISSN recommends an overall daily protein intake in the range of 1.4-2.0 g protein/kg body weight/day (g/kd/d). There is novel evidence that suggests that higher protein intakes (>3.0/g/kg/d) may have positive effects on body composition such as promoting loss of fat mass in resistance-trained individuals. Additionally, ISSN’s stand is that athletes consume protein from whey and casein sources due to superior digestibility and increased muscle protein accretion.
The European Food Safety Authority (EFSA) concluded that a cause and effect relationship has been established between the dietary intake of protein and the growth or maintenance of muscle mass. The Panel considers that in order to bear the claim a food should be at least a source of protein as per Annex to Regulation (EC) No 1924/2006.
International Society of Sports Nutrition position stand: protein and exercise
Campbell B, Kreider RB, Ziegenfuss T, et al., Journal of the International Society of Sports Nutrition, 2007
It is touted that dietary protein may increase energy expenditure by eliciting a greater postprandial thermic effect of food (TEF) than carbohydrates or fats. Dietary protein requires 20-30% of its usable energy to be expended for metabolism and/or storage, whereas carbohydrates require 5-10% and dietary fats require 0-3%. Additionally, higher-protein diets have been found to prevent a decline in resting energy expenditure (REE).
The effect of higher-protein diets on body weight management are thought to be partly due to modulations in energy metabolism, appetite, and energy intake.
The role of protein in weight loss and maintenance
Leidy H, Clifton P, Astrup A et al., Am J Clin Nutr, 2015