I’m anxious to see where all this protein mania leads us health wise. But I wouldn’t bet against diets we already know promote longevity, none of which are high in animal protein, or protein, period.
The more I read about it and the more it's studied, the more I think middle aged men need to increase their protein take if they're lifting weights and want to build/sustain muscle. Of course, it depends what your goals are. I don't want to look like a marathon runner and hope to maintain a lean physique while being strong and agile.
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What I've seen is that high protein intake in middle age is a good idea
if you use it, like consistent time in the gym, but that it can be detrimental if you're not active enough. That risk decreased and become beneficial over the age of 65 active or not.
Probably better articles than this one, but just a quick search.
TUESDAY, March 4, 2014 (HealthDay News) -- Millions of middle-aged Americans chow down each day on steaks, cheeseburgers and other protein-rich fare. Now two s
www.healthday.com
I don’t think there’s any data showing
high protein intake in middle age is beneficial. On the contrary, your link suggests harm from excess, and animal studies have shown limiting protein/specific amino acids promotes longevity. But it's a really interesting topic.
You're right, any excess calories, whether derived from carbohydrate, fat, or protein are harmful. So utilizing all your calories intuituitively makes sense. With protein, that generally means building muscle.
Muscle is great, don't get me wrong, but I don't think it's as simple as get yooge = get healthy. While there's nothing wrong with building muscle for functionality, athletic performance, or even vanity, the anabolism activated by protein also promotes diseases of aging, via central metabolic regulators called mTOR and IGF-1. Certain amino acids are particularly potent up regulators of these pathways, namely branched chain amino acids (body builders know these are key for muscle growth) and methionine. As it turns out, animal protein, including whey, contains far more of these AAs than that derived from plants. This probably (partially) explains why the correlation between protein intake and disease (usually cancer, but also diabetes and vascular disease) seems to be limited to animal sources.
This all gets muddled a bit with aging, as we lose muscle mass and IGF-1 production. Sarcopenia and frailty can limit our functionality and promote falls, which also pose risk for untimely demise. So over age 65 or so, staving off muscle loss becomes more important than preventing cancer, and protein intake should be liberalized. But even then, there's no clear benefit in taking more than 1.6 g/kg body weight protein daily. That's 2/3 of the commonly cited bro-science goal of 1 gram per
pound, or more. We don't have convincing evidence the body can effectively use that much, eg. that it promotes further muscle growth/maintenance. So I see no reason to expose oneself to the added health risks.
Peter Attia, a longevity guru with whom I generally agree, is at the forefront of bulking up to promote functional longevity, without concern for excess protein intake. He argues we'll invariably lose muscle mass with age, so we should start with as much reserve as possible. Again, this sounds good on the surface, but I think there is a ceiling to optimal muscle mass for healthy aging. While I can't pinpoint exactly what that amount is, I can safely say all the functional octa- and nonagenarians I've encountered are rail thin, and extremely active. They weren't ever fixated on protein intake, or muscle bulk (athletes live longer than general population, but not body builders). Moreover, the long-lived "blue zones" all consume diets with low protein content, typically less than 10-15% daily calories. That's like 50-75 grams of protein daily, for a 2000 kCal diet.
Attia summarily dismisses the entirety of nutrition research, including both animal and human studies on protein intake, in favor of frequent, intense exercise, powered by venison jerky. I'm all for frequent exercise (as long as you don't injure yourself

), but I don't think the usually scholarly Attia is following the science here. There are certainly limitations to our knowledge base, and nutrition + longevity research is plagued by conflicting data. Still, there are enough data dots to connect, in lab and population studies, along with biologic plausibility behind harm from too much protein.
TL;DR Like everything else in the body, there is an optimal amount of protein intake, and by extension, muscle. Too little, and too much can be harmful. While bulking up may make you seem "fit" as a middle ager, there's reason to believe all that extra protein and bulk aren't doing you any favors in the long run. Pop nutrition's current obsession with protein has gone way overboard, imo, but it will take decades to realize the harm.