In my last two articles, I've first discussed how a recent study revealed the risk of a shorter lifespan from consuming too much protein, and specifically the anabolic and bodybuilder friendly amino acid L-Leucine. In the second article, I went on to cover that given this risk, what is the minimum protein level we can take in to optimize our muscle mass and fitness goals? For the next article in my series on protein, I'd now like to discuss my findings on the optimal protein intake for longevity - how much protein should we eat to live as long and healthy a life as possible?
As I've mentioned before, the daily recommendations for protein intake vary incredibly widely across the board, with some organizations and diet groups advocating extremely low levels of protein intake, and many experts and coaches in the health and fitness industry recommending very high intakes. All these conflicting guidelines can be very confusing, but given that our goal is to find what will result in the longest lifespan, and the evidence that too much protein can shorten lifespan, a low recommendation is what we should be expecting to find.
And that's exactly what it is. According to Dietary Reference Intakes of the National Academies Press, the daily requirement for protein in humans is only 0.8 grams per kilogram of bodyweight each day (0.8g/kg), or only 0.36 grams per pound of bodyweight daily - that's only 54g of protein per day for a 150lb individual! Clearly, getting enough protein to survive is no problem, but will that result in the longest possible life?
Studies examining the diets of long-lived populations such as in Okinawa, Japan and Bama, China have found people's average protein intakes there to be right at 1 gram per kilogram bodyweight each day (1g/kg, or slightly less than half a gram per pound bodyweight each day) , which is actually very close to the Academies Press figure. This means if our hypothetical 150 pound person lived in one of these longevity-friendly places and ate what the locals did, he or she would average 65 grams of protein a day. Again, that's a very easy number to hit!
And the type of protein you eat also has a big impact on how long you will live. An animal study comparing two groups eating the exact same level of calories and protein, with one group's protein coming from casein (animal protein) versus the other coming from soy (plant protein), showed that even at identical levels of calories and protein, the group getting its protein from plants lived an average of 15% longer and reached a higher maximum age - findings extremely consistent with the research referenced in the first article of this series. The take home point here is obvious: get all of your protein from plants!
So, depending on your goals, you should now have a good idea of how much protein to structure into your diet to maximize your muscle gains while maintaining a healthy life-span (1.6g/kg), or to go all out and strive for centenarian status (1g/kg)! Whatever your goals may be or what you decide to follow for yourself, I hope this series has helped you make informed decisions and removed some of the confusion surrounding everyone's favorite nutrient: protein.
“10 Protein and Amino Acids.” Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). Washington, DC: The National Academies Press, 2005
Iseki K et al, Estimated protein intake and blood pressure in a screened cohort in Okinawa, Japan. Hypertens Res. 2003 Apr;26(4):289-94
Iwasaki, Keisuke et al. The Influence of Dietary Protein Source on Longevity and Age-Related Disease Processes of Fischer Rats. Journal of Gerontology Volume 43, Issue 1 Pp. B5-B12 (1988)