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Protein is still (somehow) controversial.

Should we restrict protein in favor of longevity and reducing cancer risk, or should we maximize our intake in favor of building muscle mass and enhancing performance?

The answer lies somewhere in the middle. But one thing is for certain—the current recommendations don't accurately reflect the scientific evidence.

That's why I sat down with Dr. Peter Attia as a guest on his podcast to dispel myths about protein and set the record straight on what's optimal. You can find the entire episode here.

Peter and I make the case for a higher protein intake based on four fundamental tenets. We argue (with evidence) that the current RDA is too low for optimal muscle health, that higher protein intakes are not only better, but likely necessary to build and maintain muscle with age; that higher protein intakes are optimal for physically-active individuals; and that there are no health risks associated with higher protein intakes.

Peter and I are both willing to defend higher protein intakes until there are data to convince us otherwise. Currently, the benefits likely outweigh any potential risks.

I hope you enjoy this synthesis of our discussion—it should help you separate evidence from noise in the ongoing conversation about protein intake.

The RDA is too low for optimal muscle health

The current RDA (0.8 g/kg/day) describes the minimum to stave off deficiency, not the optimal intake for performance or aging. It's better to think about the RDA as a "minimal daily allowance" instead. "Recommended," unfortunately gets misread as "ideal"—and that's where many people go wrong.

The RDA underestimates protein needs because it was built on nitrogen-balance studies, which ask, "Is nitrogen in roughly equal to nitrogen out?" But the method has real flaws worth mentioning.^[1]

• Urine collection is often incomplete, undercounting nitrogen losses.
• We lose nitrogen through sweat, feces, skin, and breath—which aren't fully captured.
• Different foods have different nitrogen to protein ratios, adding noise to the system.
• Hitting "zero balance" says nothing about what's optimal for muscle recovery or function. Why shoot for the bare minimum when benefits can be gained with more?

Newer methods, such as stable-isotope techniques, are better at capturing what humans really need to avoid a negative protein balance.^[2] These lines of work consistently point higher—~1.2 to 1.6 g/kg/day (0.54–0.72 g/lb) or 50% higher than current recommendations—as a realistic floor for maintaining protein balance and supporting muscle-centric outcomes like strength and lean body mass (for more perspectives on how much protein we actually need, check out these clips with Dr. Brad Schoenfeld, Dr. Luc van Loon, and Dr. Stuart Phillips).

Avoiding a negative protein balance is imperative, especially for older adults.

We can store fat and carbs (as glycogen), but we don't store free amino acids. When intake drops, the body quickly turns to its major amino acid reservoir—skeletal muscle. Flirting with inadequate intake means you immediately start breaking down muscle tissue, which is especially costly with aging where losses carry functional consequences.

Higher intakes promote muscle health with aging

Real-world outcomes support higher protein intakes for older adults to combat age-related muscle loss and anabolic resistance. A 50% increase in protein intake above the RDA (to ~1.2 g/kg/day) is linked to less age-related muscle loss vs. those sticking to the RDA, and older women consuming ~1.2 g/kg/day are ~30% less likely to become frail with aging.^[3]

There is also the issue that aging (and often inactivity) brings anabolic resistance—older muscle is less sensitive to the same amino-acid signal that drives muscle protein synthesis (MPS). This means that older adults need more protein per-meal to stimulate the same amount of MPS as a young adult. Studies have quantified what this dose-response looks like—and they suggest the per meal dose may be twice as much.

• Young adults: ~0.24 g/kg per meal saturates MPS. For an 80-kg (176-lb) person, that's ~20 grams of protein per meal.
• Older adults: ~0.4 g/kg per meal is required to hit the same ceiling—~32 grams for that same 80-kg adult.

The daily pattern of protein also matters. Simply eating "some protein" isn't enough; hitting robust per-meal doses is key for older adults—and that dose appears to be 30–40 grams of protein minimum, ideally spread over 3–4 meals throughout the day.

Even though anabolic resistance is thought to be related to age, the role of inactivity has been highlighted as a major (perhaps the main) contributing factor. Only ~1 in 5 older adults perform regular resistance training. That's a problem because strength training eliminates much of the anabolic resistance—studies by Luc van Loon (who appeared on episode #93 of the FoundMyFitness podcast) show that performing resistance exercise prior to protein intake restores the MPS response so older adults can look metabolically like the young, at the same protein dose.

Higher protein intakes promote greater gains in muscle strength and mass

For people training (especially with resistance exercise), total daily protein matters—and benefits accrue as you move from "adequate" to "optimized." Even doubling the RDA continues to accrue benefits for these outcomes. But is there an upper limit?

What the training literature shows:

• A widely cited meta-analysis by Dr. Stuart Phillips (who appeared on episode #76 of the FoundMyFitness podcast) in resistance-trained adults found that increasing intake from ~1.2 to ~1.6 g/kg/day improved outcomes—lean mass increased ~27% more and strength went up ~10% versus lower intakes.^[4]
• There's a diminishing-returns threshold around ~1.6 g/kg/day for most. Beyond that, gains flatten—they're not zero, but are likely smaller and context-dependent.
• Going even higher—to ~2.0–2.2 g/kg/day or 1 g/lb—can make sense. For example, gaining muscle and losing fat simultaneously (referred to as body recomposition) often requires a caloric deficit but an amino acid surplus, which can be achieved by prioritizing protein. Athletes may also benefit from higher intakes due to their elevated requirements for protein.

In our discussion, Dr. Attia provided some much-needed "diet realism" to make his case for recommending a much higher dose to his patients and clients. People don't live in labs. Aiming for ~2 g/kg/day helps ensure that on "off" days you still land at or above ~1.6 g/kg, because the downside of undershooting protein is worse than the marginal downside of overshooting. In short: aim high to avoid low days.

There are no health risks from higher protein intakes

Detractors of higher-protein diets commonly cite two main downsides for overall health and longevity: kidney function and accelerated aging and cancer risk.

Let's address kidney health first.

In people without preexisting kidney disease, higher-protein diets do not damage kidneys. Increases in filtration and nitrogenous waste markers reflect a normal adaptation to processing more protein, not dysfunction. Even extreme intakes in trained populations—~3.2–4.5 g/kg/day for up to one year—show no adverse changes in standard kidney or liver markers among athletes.^[5]

If someone has chronic kidney disease, that's a different clinical context—following medical guidance is prudent; however, emerging studies suggest that a higher protein intake is associated with reduced mortality risk in people with chronic kidney disease, which challenges traditional protein restriction guidelines.^[6]

Now, what to make of the controversy surrounding protein and aging, mTOR, IGF-1, and cancer?

There's a narrative that high protein means more IGF-1/mTOR and thus, faster aging and cancer. That idea draws from animal protein restriction studies (which tend to show lifespan benefits in protected lab settings) and observational links to mortality in humans. There's also a 2024 mechanistic study that raised a hypothesis that high-protein meals (with leucine—the key amino acid that triggers muscle protein synthesis via mTOR) may activate mTOR in immune cells, potentially accelerating atherosclerosis.^[7]

But in humans, the apparent risk clusters with unhealthy lifestyle factors like obesity, smoking, heavy drinking, and inactivity. Among healthy, active people, these associations attenuate or disappear, and the plausible mechanisms are unlikely to translate.

The reality is that real-world outcomes likely hinge on what you do with those amino acids. Inactivity changes the equation.

Exercise fundamentally alters how IGF-1 behaves in the body. It reduces circulating IGF-1 levels, redirecting them to muscle—where it supports repair and growth—and the brain—where it supports neurogenesis, rather than letting it linger in circulation to activate immune-cell mTOR. Exercise also binds IGF-1 to protective proteins and reduces its availability to precancerous cells.

It's a simple "supply-demand" issue. Athletes and active individuals eat more protein and have higher demand (greater muscle protein turnover). In that context, protein is directed to repair and adaptation, not sitting idle to drive unwanted signaling elsewhere. For the sedentary person eating a high-protein diet, the same intake isn't leveraged the same way—another reason why movement quality and quantity are as important as grams.

If chronically high protein plus high training-induced mTOR were broadly harmful, we'd expect shorter lifespans in lifelong athletes who both eat more protein and train hard. Instead, elite athletes typically live longer (e.g., Olympians by ~5 years; endurance pros and major-league athletes by ~4–8 years), with lower cancer and cardiovascular mortality. Selection effects exist, but as a population stress test, it undercuts the notion that protein-driven mTOR is inevitably harmful to longevity.

Conclusion

After interviewing numerous experts on protein (including those who advocate lower-protein approaches to favor longevity, such as Dr. Valter Longo), it's clear to me that one should skew toward a higher-protein approach if their goal is healthy aging. Does this mean eat as much protein as possible? No. One needs to make room in their diet for healthy fats and fiber- and antioxidant-rich fruits and vegetables, after all.

One thing not covered in my talk with Peter was the debate about animal versus plant protein. Here again, I'll lean on the evidence, which shows that in the context of an otherwise healthy lifestyle, consuming unprocessed meat (and even the occasional red meat) isn't associated with a greater risk of death or chronic disease compared to non-meat-containing diets. But that's a topic for another day.

Peter and I were both confused about why the "anti-protein" narrative exists, and why it won't go away. But him being a clinician who deals with real people every day, and me being someone who is constantly diving into the research and speaking with experts on this topic, we both agree that any argument to "eat less protein" stands on unstable grounds.

This might seem a complicated issue—but it doesn't have to be. If you focus on eating multiple protein-containing meals each day and are thoughtful about your sources, it's likely you'll meet daily protein needs and thrive, whether your goal is gaining more muscle or just staying strong into your later years.