We've Got a Protein Problem

Experts can't agree on whether we need more or less of it. Here's why.

Protein is popular—to put it lightly. It’s also one of the most debated topics in nutrition and longevity.

Ask one expert and you’ll hear that most of us are eating too little, setting ourselves up for muscle loss, frailty, and declining health as we age.

Ask another (or read most of the recent headlines from mainstream news articles) and you’ll hear warnings that our obsession with protein—especially from animal sources—could fuel inflammation and accelerate aging and chronic disease. These people tend to claim that advice to “eat more protein” rests on shaky scientific ground.

Simply put, the current “experts” in aging and longevity can’t agree on whether people need to be eating as much protein as possible or restricting it. However, it’s not because we lack sufficient science or evidence to inform our recommendations. Rather, it’s that the experts are looking at the problem from two different angles concerning aging:

1. Optimization of healthspan and performance for the sake of longevity. We want to be as strong and fit as possible for as long as possible.

2. Optimization of lifespan and cellular mechanisms of aging. We want to counteract the biological processes associated with aging, in the hopes that tamping them down will help us live as long as possible.

If you read up on the topic enough, you’d think that it’s a tradeoff—either maximize muscle performance and healthspan with a high-protein diet and compromise lifespan in the process, or restrict protein intake and sacrifice potential muscle gains in the hope of living a longer life.

I don’t think it has to be this way.

Dueling Perspectives on Protein Intake

What sparked me to write this post—and a perfect example of why the narrative in this area keeps changing—was separate articles from two of the biggest names in health and science communication, Dr. Peter Attia and Dr. Eric Topol, each of whom published respective pieces on protein that seemed to come to two different conclusions.

Attia (here’s his recently published article/deep dive on protein intake) argues that the Recommended Dietary Allowance (RDA) of 0.8 g/kg per day is not an optimal target but simply the minimum needed to prevent deficiency. He points out that this figure was derived decades ago from nitrogen balance studies in small, unrepresentative populations and is often misinterpreted as a recommendation rather than a floor. Attia emphasizes that muscle is a critical metabolic organ, and maintaining it is essential for longevity, glucose regulation, and protection against age-related decline. He highlights that as people age, they experience anabolic resistance—meaning their muscles become less responsive to protein—and therefore require even higher intakes to preserve lean mass.

His overall summary is clear: for most people, especially those who are older or physically active, optimal intake is in the range of 1.6–2.2 g/kg per day (roughly 1 g per pound of body weight). I’d call him a “protein maximizer.” If the goal is not just survival but thriving and extending healthspan, most people should aim for significantly more protein than the RDA suggests. That’s how to be a kick-ass 70, 80, or 90 year old (to use one of Attia’s common frameworks).

Topol, a cardiologist and researcher, approaches protein from another angle. In his recent Substack post titled “Our Obsession with Protein Intake”, he acknowledges that older adults may benefit from somewhat higher intakes—perhaps 1.2 g/kg per day—to counteract sarcopenia.

But he also highlights the cracks in the evidence base: mainly the lack of long-term randomized trials and a few statistical concerns regarding one of the most-cited meta-analyses in this area, which shows a plateau in lean muscle gains during resistance training with a protein intake of around 1.6 g/kg per day. This analysis is often used as a benchmark for protein recommendations and to argue that eating any more than this amount won’t lead to further muscle gains, which (if we take this alternative analysis at face value) doesn’t seem to be the case. I’ve referenced this study dozens of times…it appears I should stop.

Most importantly, Topol points to data linking high protein consumption, especially from animal-derived amino acids like leucine and lysine, to accelerated atherosclerosis and inflammatory signaling. For him, declaring a universal “optimal” intake is premature and may even carry hidden risks.

I (and others) have a few problems with using this study to infer that a high-protein diet is harmful for cardiovascular health, and I’ve written about those issues and the study in a previous Substack post.

Physiology Friday #206: Is Too Much Protein Damaging to Your Arteries?

Attia and Topol’s perspectives reveal the core of the problem—we don’t actually know how much protein humans should eat for health and longevity. Attia wants us to eat more to protect muscle, hedging against sarcopenia and its related risks. Topol cautions us not to overshoot and damage our arteries in the process, advocating for a moderate protein intake primarily from plant-based sources (he claims to thrive on a Mediterranean-like, mostly plant-based diet). The tension between a muscle- and function-focused view of aging and one focused on cardiovascular health and “longevity pathways” leads to diverging recommendations.

It’s one of the reasons most people are probably a bit confused about protein recommendations. The uncomfortable truth is that we don’t know where the sweet spot lies—or if it even exists universally. Protein needs are likely dynamic, shifting with age, activity, medication use, and genetic background. What protects one person’s muscle might, in another, accelerate processes related to cardiovascular disease. Exercise appears to play a major role here, specifically by how it impacts something called insulin-like growth factor 1 or IGF-1.

Protein and IGF-1: Exercise Changes the Story

Critics of high-protein diets argue that by raising IGF-1, especially from animal sources, protein may accelerate cancer risk and shorten lifespan. Some observational studies have shown higher mortality and cancer incidence in middle-aged adults consuming high-protein diets, but these associations typically disappear when accounting for lifestyle factors like obesity, smoking, and inactivity. The reality appears more nuanced: IGF-1 is a double-edged sword. While excessive levels may promote precancerous cell survival, overly low levels—like those seen in extreme calorie restriction—are tied to brain atrophy and higher mortality. The relationship looks U-shaped, with both extremes carrying risk.

https://pubmed.ncbi.nlm.nih.gov/35048526/

The missing piece is exercise, which fundamentally changes how IGF-1 behaves. Physical activity lowers circulating IGF-1 while redirecting it to muscle and brain, where it supports repair, growth, and neurogenesis while reducing its availability to cancerous pathways. Athletes, who eat more protein and maintain higher IGF-1 levels, consistently live longer than the general population—by two to eight years—with lower rates of cancer and cardiovascular disease.

This suggests that in the context of regular exercise, protein and IGF-1 are channeled toward healthspan rather than disease. In other words, protein isn’t inherently harmful; how it interacts with lifestyle—especially activity level—determines whether it functions as fuel for longevity or risk for disease.

Protein as a Moving Target

This leaves us with an opportunity to see protein intake for what it really is: contextual. How much you need depends on who you are, where you are in life, and what you’re optimizing for. And that’s why the experts will never fully agree.

If your lens is muscle (the Peter Attia approach), the answer is straightforward: more protein is almost always better. Preserving lean mass is one of the most powerful tools we have against frailty, falls, insulin resistance, and the downstream spiral of chronic disease. In this view, eating toward the higher end of the spectrum makes sense—especially if you’re aging or training hard.

But longevity isn’t just about muscle. It’s about metabolism, vascular health, immunity, and inflammation. Here, the picture becomes more nuanced (as highlighted by Eric Topol). Excessive intake, particularly from certain sources, may have trade-offs (emphasis on may) we don’t fully understand. And that’s where cautionary voices like Topol’s carry weight. I don’t think he means to scare us away from protein, but only wishes to remind us that biology is rarely one-dimensional and that any voices erring on the side of “extreme” should be viewed with caution.

That being said, I don’t buy the “anti-protein for longevity” narrative and tend to side more with Dr. Peter Attia in the idea that hedging against a higher protein intake is likely long-term beneficial.

The evidence that high protein causes harm in humans just isn’t there. We have animal studies, mechanistic signals, and correlations—but not the kind of long-term randomized trials that would justify telling people to dial protein down in the name of living longer.

On the flip side, we do have robust data linking low muscle mass to higher morbidity and mortality. If we’re going to hedge bets, muscle still wins. Not to mention, out of the three macronutrients, protein seems to be the one that, when consumed as a large(r) quantity of one’s total calories, appears to help with weight loss, body composition, and satiety. Eating more protein means eating fewer carbs and less fat—that’s a health-enhancing change for some people.

As for me, I probably tend to eat somewhere around 1 gram of protein per pound of body weight per day. At a weight of 145-150 pounds, it’s not that hard of a target to hit, especially given my daily caloric intake. The thing is, I don’t stress about it—some days I fall short of this amount, and some days I might surpass it. I think that’s how all of us should approach eating (at least protein)—with a semi-analytical attitude that recognizes biology doesn’t really know numbers, but rather, physiological needs.

So maybe the answer to “How much protein should I eat?” isn’t a specific number. Maybe it’s about respecting the trade-offs, recognizing the gaps, and adapting intake to context. One unifying perspective is that no matter one’s stance, protein matters. But how much matters most depends on the story of the body it’s fueling.

Thanks for reading

~Brady~