Protein and Healthy Aging
Research is emerging that challenges the current protein recommendations for adults over 40 years old. They have found that there is a 30-50% muscle decrease from age 40 to age 80 with a decline in muscle strength starting at age 50. So 40 years old may be the optimal time to make dietary changes regarding protein intakes to help prevent and delay sarcopenia which is a disease in which muscle mass, strength and performance are compromised causing more falls, loss of independence, and often increased hospitalizations.
Currently the recommended daily amount of protein for adults is 0.8 grams per kilogram of bodyweight (0.35 grams per pound). This represents the minimum protein intake needed to maintain nitrogen balance without factoring in activity levels. People that have low physical activity levels have lower nitrogen retention so if protein needs aren't met the body needs to break down muscle to keep nitrogen at the appropriate level in the blood, which causes loss of lean muscle mass and puts the person at higher risk for undesirable events such as falls. As people age their activity levels decrease, this could be part of the reason for increased sarcopenia rates with age.
The research on protein needs is quite limited because nitrogen studies must be done in controlled clinical environment so we only really have short term studies. One of the longer studies did find that 70-79 year olds with 1.1gm/kg of bodyweight lost 40% less lean body mass over three years than those with intakes of 0.8gm/kg of bodyweight. This supports the suspicion that protein intake needs are higher than previously thought.
New research suggest the minimum protein needs for 65+ is:
1.0-1.2gm/kg bodyweight for healthy individuals
1.2-1.5gm/kg bodyweight for those with acute or chronic illnesses
2.0gm/kg bodyweight for those with severe illnesses, injuries, and malnutrition
The Type of protein can matter in the overall picture of health as well as the amount. Animal based proteins have been found to have higher digestibility and bioavailability than plant-based proteins. Specifically milk, whey, egg, casein, and beef. The downside is animal based proteins have saturated fats that are related to increased cardiovascular disease risk, dyslipidemia, and some cancer forms.
Plant proteins are often incomplete so must be paired appropriately to gain all the essential amino acids needed in daily food intakes. The digestibility and bioavailability is lower due to higher fiber content and phytochemicals like phytates or tannins. Both fiber and phytochemicals have been associated with better health outcomes, so may be worth the lower bioavailability.
Many researchers and experts are recommending focus on eating more plant based proteins, but not necessarily cutting out all animal based proteins. There are benefits to both, but the majority of people could benefit from high plant protein intakes paired with low to moderate animal protein.
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