If you recall, in Part One, what differentiates the macronutrient protein from fat and carbohydrates is the Nitrogen atom that is found in the amino acid’s chemical structure.
I will spare you from the actual Nitrogen Balance Studies Calculations/Formulas. In these Nitrogen Balance Studies they had subjects consume protein containing foods, and calculated the amount of nitrogen in those foods, then, they looked at the amount of nitrogen loss/excreted in their urine, feces and sweat (Gropper & Smith, 2013, pg. 242). You want what one consumes to be as close to equal as what one excretes, thereby having “balance”.
Again, this seems simple enough. Unfortunately, these Nitrogen Balance Studies have been criticized, and are often said to be the bare minimum amount people should consume in order to avoid disease and maintain growth and development. Not to support ideal metabolic health.
This makes things less clear.
Let’s see what more recent research has to say about protein needs while considering MPS (muscle protein synthesis), which was mentioned in Part 2.
This section is specific to those greater than 65 years of age, and while it may not be relevant in our own life, chances are, you have a family member who falls into this category. Because of the amount of misinformation there is regarding protein and the aging population, I felt it necessary to create this brief section. Feel free to skip to the next section though.
The PROT-AGE study, published in the Journal of the American Medical Directors Association (JAMDA) in 2013 reevaluated the protein requirements for those older than 65 years of age. What they found was intakes of at least 1.0 – 1.2 g/kg of *BW/day was recommended to ensure maintenance, and even gain, of muscle mass. However, older adults with an acute or chronic disease and/or severe injury or illness may need as much as 1.2 to 2.0 g/kg of *BW/day, which unfortunately includes many in the aging population.
Another point that the authors of the PROT-AGE study mention is the importance of meal timing and amount of intake. As we discussed, leucine is responsible for stimulating MPS, and the authors recommend an intake of 25 to 30 g of protein per meal, providing 2.5 to 2.8 g of leucine, to be consumed three times a day. (Younger men appear to require less at each meal)
So, those in the older population would benefit from consuming around 75 to 90 grams of high quality protein per day, divided into 25 to 30 g at each meal as a way to preserve, and even, build muscle mass alongside resistance training.
Great, we know how much to eat if we are over 65 years of age, but what about those of us who are not, myself included, are these recommendations relevant?
Let’s establish a minimum amount of protein everyone, regardless of age, should begin with.
Instead of using Nitrogen Balance studies, as they did to determine the RDA, another method, the indicator amino acids oxidation (IAAO) technique, has been shown to overcome the flaws of the Nitrogen Balance studies. Using the IAAO technique, researchers found 1.2 g/kg of BW is a more appropriate protein intake, as a minimum, for young men, older men, and older women.
Similar to the PROT-AGE study, we see protein recommendations higher than the RDA. Specifically, starting with 1.2 g/kg (or .54 g/lb) to ensure adequate health and lean body mass maintenance.
The other end of the spectrum is reserved for those trying to maximize muscle mass. You would not only want to increase your protein intake, but also provide a reason for your body to increase its muscle mass, via a well formulated resistance training regimen.
Researchers, Brad Schoenfeld and Alan Aragon, published a review in the Journal of the International Society of Sports Nutrition in 2018, finding that in order to maximize “resistance training-induced gain in muscle mass and strength” an intake of 1.6 g/kg/day should be utilized. Ideally, this should be spread throughout 4 meals. In the same paper, they mentioned that intakes higher than 1.6 g/kg/day should not be considered a waste of protein, as an Upper Confidence interval of 2.2 g/kg/day was found in a subset of young bodybuilders. So some may see additional muscle hypertrophy benefits from consuming 2.2 g/kg/day (or 1 g/lb/day) of protein.
We have a minimum, and a possible maximum:
There is obviously more research we can look at, but I believe this is great starting place for the majority of people.
What if you do not want to calculate your protein intake?
That’s perfectly fine. I advise my clients to use their hand as a portion guide when determining their protein intake, rather than worrying about performing calculations, unless that is something you enjoy doing.
What if you do not want to calculate your protein intake?
That’s perfectly fine. I advise my clients to use their hand as a portion guide when determining their protein intake, rather than worrying about performing calculations, unless that is something you enjoy doing, like me!
I know I went over Animal vs. Plant sources in Part 2, but I believe lists are helpful. Here is a list of animal and plant sources of protein that you can start adding to your meals using your palm as a guide. This should not be considered an exhaustive list.
*When Relevant, and Possible – Buy Pastured, Grass-fed, Organic, Wild Caught and Sustainably Raised Sources, but purchase what is realistic for your financial situation without worry.
*Fermented Soy Products are Typically Best Digested and Tolerated.
**Beans and Lentils are Best Digested when Soaked and/or Sprouted.
What I naively thought would be a single article turned into a 3 – Part Series on Protein, and could have easily become even longer. Those of you who stuck around, thank you! I really hope you enjoyed it and were able to not only learn the important role protein plays in our health and wellbeing, but are taking away some practicals that you can apply in your own life.
Up next in the Macronutrient Series will be Fats/Lipids, so be on the lookout.
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Gropper, S.S. & Smith, J.K. (2013). Advanced Nutrition and Human Metabolism. Belmont, CA: Wadsworth.