How much protein is optimal for a CRON practioner is a topic that is still a moderately hot topic within the community. Unlike AGEs, the answer for how much protein is optimal is not agreed upon and the evidence is not black and white. When I started CR, I was shooting for zone (30P-30F-40C) levels because my initial (but brief investigations) indicated this was a good ratio for CR. Recently I have felt the need to address the topic of protein further, go into the sub-arguments, and reanalyze my initial choice so I can feel confident I am on the right path (at least for me).
First we have broad sweeping total protein intake for CR debate, and then there are two major sub-arguments within the protein debate: IGF-1, Methionine. I’m going to present the for and against arguments and research, then I will come to my own conclusions on how seriously I want to approach each topic. As usual, my final decision will not be set in stone.
Before I go into these debates, I want to discuss the minimum and recommended protein requirements. (Which also are not in total agreement amongst the nutrition communities).
How Much Protein Do Humans Need?
Current standards recommend people ingest ~0.8g/Kg/Day of protein to avoid protein deficiency. According to this, I need approximately 46 grams of protein per day.
Protein deficiency is possible, and is most often seen in children living in developing countries. This particular childhood protein deficiency, called Kwashiorkor, is characterized by swelling of the feet, enlarged liver, thinning hair, loss of teeth, distended abdomen, and dermatitis. These children also cannot produce antibodies after receiving a vaccination. In adults, protein deficiency can cause lowered immune function, muscle loss, fatigue and weakness, and fluid retention.
Proteins are used in the synthesis of proteins within the body, as an energy source, and as precursors to other compounds such as serotonin and adrenalin. Another reason protein is important is the maintenance of the nitrogen balance within the body.
Most of the nitrogen (in the form of ammonia: NH3) comes from protein consumption; any compounds in the body the contain nitrogen, are dependent on protein consumption. A positive nitrogen balance leads to a net synthesis of needed compounds in the body, while a negative nitrogen balance will cause a deficit in protein synthesis. Ideally, one wants the nitrogen balance to be in equilibrium. One problem with over consumption of protein is the negative effects of ammonia, which is an acidic byproduct of protein metabolism and is converted to urea. With high intake levels, protein can cause damage to the kidneys and liver as well as cause calcium loss due to the excessive urea the body must excrete.
The Conundrum
The main issue I find with these protein recommendations is their lack of specificity. I can easily find the recommended amount of protein, but not easily what is too much or too little. This is because so many factors can go into an individuals “ideal” protein intake. Needed protein intake depends on age, sex, pregnancy, activity (all do not agree more protein is needed with higher physical activity), possibly the rations of other macro nutrients.
One source showed kidney stress when 2g/Kg/day of protein was ingested. For me that would correlate to 114 grams of protein per day.
The National Academy of Sciences reported in 1980, that the minimum protein requirement was between 0.3-0.4 g/Kg/Day. For me that would correlate to 17-23 grams of protein per day.
From what I gather, the minimum protein recommendation seems easy to reach even in a CR diet. However, this is not the nature of my investigation. I want to know what is the ideal protein intake in relation to longevity! I will follow up this post with Part I: CR and Protein Intake Studies.
