“Protein is vital in the body for body systems and functions, such as the immune system and hormone function; proper digestion, transport and absorption of nutrients; and regulation of blood volume and movement. Protein promotes muscle tissue growth and repair after strenuous exercise,” explained Christine Steele, Ph.D., Director of Science, Innovation, and Education at Abbott Nutrition, in her presentation entitled “Protein Packing Products: The Nutritional Rationale.” In her update on protein nutritional attributes, she went on to explain that lean body mass (LBM) includes muscles, organs and bone; generally, everything except fat. LBM accounts for approximately 75% of normal body weight, and muscle is the largest component of LBM.
“Skeletal muscle functions in mobility, balance and physical strength; generates heat (energy); and pro- vides a protein and amino acid pool to support survival during periods of metabolic stress,” stated Steele. Complete proteins are those containing all of the essential amino acids in amounts that meet human requirements to prevent deficiency. An incomplete protein is too low in one or more of the essential amino acids. Complementary proteins are a combination of proteins that, when added together, result in a complete protein, i.e., beans and rice. Legumes can be generally low in methionine and high in lysine, while grains are the opposite—so they complement each other to form a complete protein source if consumed together.
Protein quality is measured by a number of methods. Examples include Biological Value (BV); Protein Digestibility (PD); Net Protein Utilization (NPU); Protein Efficiency Ratio (PER); and Protein Digestibility Corrected Amino Acid Score (PDCAAS), Steele said. The FAO/WHO assesses protein quality with PDCAAS, where complete proteins have scores of 1.00 and include milk, egg and soy proteins. Recommend- ed daily requirements for adults are based on grams dietary protein per kilogram body weight per day and based on intended population (lifespan/age, pregnancy, etc.). For example, the Institute of Medicine recommends 0.8g/kg body weight per day for adults 19-59 years, which is approximately 65g per day of protein for a 180lb (82kg) individual, or approximately 47g per day for a 130lb (59kg) person. (See chart “Protein Consumption Recommendations.”)
Protein requirements increase during pregnancy and lactation, as well as during trauma and metabolic stress. Many Americans consume adequate protein by this standard; however, adequate intake may not always be optimal for health or performance. Steele looked more closely at recent research into protein’s benefits in sports, weight management and during aging, said Steele.
- Sport—Protein needs in athletes may rise with in- creased physical activity and vary with type of activity. A recognized performance organization recommends endurance athletes consume 1.2-1.4g protein per kilogram body weight per day, and strength athletes to consume 1.2-1.7g per kilogram per day. However, increases in protein intake do not necessarily deliver enhanced performance alone, noted Steele.Studies continue to investigate types of proteins and times to consume protein for optimal results. For just one example, research by Churchward-Venne, TA, et al. published in a 2012 Nutrition & Metabolism, concluded that in order to maximize muscle strength and size, it was recommended that 20-25g of whey protein (or cow’s milk) be consumed immediately following exercise. The bio- chemical effects of exercise last for at least 24 hours and up to 48 hours after exercise, depending on the exercise type, intensity and duration; so, steady consumption of protein within this time may be optimal to maximize protein synthesis.
- Weight Management—High-protein meals are thought to help induce satiety by acting on brain regions involved in energy homeostasis. Additionally, higher protein diets may help muscle-sparing effects when dieting. Sustained periods of negative energy balance can de-crease body mass, as well as skeletal muscle mass, and consuming dietary protein at levels above recommended amounts may attenuate loss of muscle mass.
- Aging—Lean body mass typically declines with aging. Sarcopenia, a loss of mass and function, is prevalent in the aging population, and their protein needs may increase, said Steele. Age-related LBM loss can be driven, in part, by physical inactivity and poor nutrient intake. Aging, physical inactivity, bed rest, illness, injury and inflammation can all drive LBM loss. LBM loss can be debilitating, with loss of physical strength and increased susceptibility to illness.
Steele concluded her presentation by offering key take-away points. First, protein sources vary in amino acid composition and quality. Protein needs also change through lifespan and with exercise, catabolic stress and recovery. Thirdly, muscle mass is key to strength, physical activity and immunity. Lastly, protein is important for helping to maintain LBM and muscle health.
“Protein Packing Products: The Nutritional Rationale,” Christine Steele, Ph.D., Director of Science, Innovation, and Education at Abbott Nutrition
The summary above is an excerpt from the “2013 Protein Trends & Technologies Seminar Magazine.”