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Vegetarian and vegan diets have historically been thought to lack complete protein sources. According to NHANES data, vegetarians had a higher prevalence of protein inadequacy than non vegetarians (1). As nutrition knowledge has evolved, it has become more apparent that a well-balanced, calorie-adequate vegetarian diet can be a very healthy source of protein, fat and carbohydrates.
Eating a variety of plant based protein sources is key. There is no need to consciously combine different plant proteins at each meal as long as a variety of foods are eaten from day to day, the human body maintains a pool of amino acids which can be used to complement dietary protein (2).
Older individuals on a vegetarian or vegan diet may require higher protein intake as the need for protein increases with advanced agen (1).
Muscle fibers are made of blocks of protein and adequate protein intake is required to maintain healthy muscle mass.
Protein needs can vary based on physical activity. For example, The International Society of Sports Nutrition (ISSN) recommends that endurance athletes consume 1.0g/kg to 1.6g/kg of protein per day. In order to build and maintain muscle mass, ISSN recommends an overall daily protein intake in the range of 1.4-2.0g/kg/day. There is evidence that suggests protein intakes greater than 3.0g/kg/day may have positive effects of body competition 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 (1).
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 (1).
The effect of higher-protein diets on body weight management is thought to be partly due to modulations in energy metabolism, appetite, and energy intake.
Higher-protein diets that contain between 1.2-1.6g/kg/d protein provide improvements in appetite, body weight management, and cardiometabolic risk factors compared with lower-protein diets. In studies where participants increased protein consumption, they reported increased satiety, weight loss, fat mass loss, and the preservation of lean mass were also observed. 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) (1).
Research suggests that protein improves satiety through elevation of anorexigenic hormones, including glucagon-like peptide-1 (GLP-1), cholecystokinin (CCK) and peptide tyrosine-tyrosine (PYY). Release of GLP-1, CCK, and PYY is stimulated by proteins that also stimulate the vagus nerve, thus reducing food intake (2)