Sarcopenia
Protein intake and physical activity are important stimuli for muscle protein synthesis. A number of expert groups have proposed an increase in dietary protein recommendations for older age groups to 1.0-1.2 g/kg body weight per day.
Key nutrient supplementation in older adults is of interest in the prevention of sarcopenia and frailty, since it is a simple, low-cost treatment approach without major side effects.
Sport dog nutrition
Protein is an essential component in any dog's diet.  Muscle, hair, skin, ligaments, cartilage, and chest and abdomen organs are structurally supported by protein. In comparison to the average dog, a performance or sporting dog requires a greater protein intake. This is a result of wear and tear on muscles and other organ tissues caused by strenuous activity. Protein is also a vital component in bodily functions such as transporting oxygen and energy to the muscles, regulating blood glucose levels, fighting infections, and repairing tissues. Many diets targeted for performance dogs contain 30% protein. However, dogs performing in different athletic activities can require varying amounts of protein and essential amino acids. For instance, studies have shown that sled dogs require a high protein, high fat diet, where 30 to 40% of energy comes from protein and 50% of energy comes from fat. Greyhounds were found to require a moderate protein (25% energy) and moderately high fat (30-50% energy) diet. At present there are conflicting opinions concerning whether protein from animal sources is of higher quality than protein from non animal sources. For instance, a study completed by Brown et al., concluded that "In a 16-week controlled experiment, a meat-free diet maintained haematological characteristics in sprint-racing sled dogs (Siberian huskies)". No deficiencies or side effects were noted in this study. However, in previous studies it was discovered that when feeding non animal protein diets to performance dogs, a larger prevalence of anemia was found in comparison to when dogs were fed diets containing animal protein. Poor iron bioavailability can lead to anemia. As stated by Chausow and Czarnecki-Maulden, it is generally accepted that animal sources of protein have more iron bioavailability than plant sources. Studies have been conducted to compare iron bioavailability when feeding animal and non animal sources of protein. However, research on dogs for this topic is are lacking. Studies completed by Chausow and Czarnecki-Maulden conclude that more research needs to be done on iron bioavailability of plant and animal protein sources. Regardless of the source, when feeding the sporting dog, protein is an essential component of the diet. Nutritional demands must be met in order to achieve high performance levels.