Protein is an essential nutrient that plays a vital role in our bodies. It is necessary for growth, repair, and maintenance of tissues, as well as for the production of hormones, enzymes, and other important molecules. However, the amount of protein that a person needs can vary depending on their age and other factors. There are a number of considerations to make when thinking about a high protein diet.
In the longevity community, protein is also a concern because it switches on the mTOR and IGF-1 growth pathways in the body, and switches off the AMPK repair pathway. This could cause us to age faster as the body devotes more time and energy to grow than to repair the damage caused by aging 1.
mTOR, or the mechanistic target of rapamycin, is a protein kinase that plays a vital role in regulating cell growth, metabolism, and aging 2. It is part of a complex system of proteins that helps determine how much energy is invested in growth and how much is dedicated to maintenance over the long haul 2.
When we are young and well-fed, mTOR is in full throttle, with our cells dividing rapidly to take us from babyhood to adulthood 2. However, as adults, if we continue to eat around the clock, especially consuming large amounts of animal protein, we may pay a high price in the form of unchecked cellular growth and an increased risk of cancer 2. mTOR interacts with methionine to rid the body of damaged and older cells, making way for regeneration.
One clear differentiator between nearly all plant and animal protein sources is the levels of methionine. Methionine is an essential amino acid that plays a critical role in metabolism, cell functioning, and health maintenance in addition to protein synthesis 3. However, consuming too much methionine can have adverse effects on the body. The study mentioned in a previous post found that the associations between protein intake and mortality (for those under 65y/o) were only found when the proteins were derived from animal sources 1. Plant-based proteins appeared to be the healthier option. A study found that lifespan was over 40% longer in mice fed a low-methionine diet 2. This longevity may be due to improved stress resistance and metabolism as well as maintaining the ability for cells of the body to reproduce 4.
As a precursor of homocysteine (HCys), high levels of methionine intake have also been associated with acute increases in plasma HCys, a potential risk factor for cardiovascular, brain, and liver diseases 3.
So should we just avoid eating too much protein? The Recommended Dietary Allowance (RDA) for protein is a modest 0.8 grams of protein per kilogram of body weight, or 0.36 grams per pound 5. This is the minimum amount required to stave off malnutrition and preserve muscle mass and strength as we age 5.
However, some experts suggest that these recommendations are all wrong and that we should be consuming more protein, up to twice the standard recommendations 5. A high-protein diet is generally considered to contain at least 20% of calories from protein 6. For weight loss and overall health, a high-protein diet should provide about 0.6-0.75 grams of protein per pound of body weight, or 1.2-1.6 grams per kilogram, and 20-30% of your calories per day 7.
Research suggests that consuming protein above the RDA can have several benefits, including promoting healthy aging, regulating appetite, managing weight, supporting athletic performance goals, supporting muscle growth in older adults and exercisers, and increasing strength and lean body mass in older adults and exercisers 8.
Studies have not found adverse effects of high protein intake on healthy kidneys and suggest that around 1 gram of protein per pound of body weight is safe. This means that normally functioning kidneys can handle excess protein without any adverse effects 9.
In conclusion, the RDA for protein is a modest 0.8 grams of protein per kilogram of body weight. However, some experts suggest that we should be consuming more protein for optimal health. Research suggests that consuming protein above the RDA can have several benefits. It is important to choose healthy sources of protein and to consume an appropriate amount for your individual needs.
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