Protein seems to be everywhere these days. Walk into any grocery store, and you’ll see shelves lined with protein shakes, powders, and snack bars. Social media is filled with fitness influencers promoting high-protein diets, and many doctors and health podcasters recommend bumping up your daily intake. The message is clear: if you want to live longer, get stronger, and stay healthier, you should eat more protein.
But at the same time, some of the world’s leading nutrition scientists are warning us that this trend could be a mistake. According to their research, eating too much protein may actually shorten our lives or raise our risk of serious diseases like cancer.
So, who should we believe? Are we wrong about the perfect protein intake? And if so, what’s the right number to aim for?
In this article, we’ll dig into the science behind protein recommendations. We’ll look at the arguments from researchers like Dr. Valter Longo, who urges caution, and compare them with evidence in favor of higher intake. We’ll also tackle common concerns like muscle mass, weight management, kidney health, and cancer risk. Finally, I’ll share where I’ve personally landed on the right protein target for myself and my patients.
Table of Contents
- Valter Longo’s Position
- Considerations in Favor of a Higher Target
- Responding to Longo
- Practical Conclusions
- References
Valter Longo’s Position
To understand the debate, we need to start with Dr. Valter Longo — one of the most respected voices arguing against the high-protein movement. Dr. Longo isn’t just a commentator; he’s a leading researcher in the biology of aging and longevity. His studies have significantly shaped our understanding of how diet affects health and lifespan.
One of his landmark studies followed over 6,000 adults aged 50 and older for 18 years [1]. The findings were startling: in people aged 50–65, those who consumed a high-protein diet had a 74% higher risk of dying from any cause and were more than 4 times as likely to die of cancer compared with those eating less protein [1].
Why would more protein be dangerous? According to Dr. Longo, the issue lies in how protein interacts with our body’s cellular pathways. Protein stimulates growth signals in the body, particularly through a mechanism called mTOR (mechanistic target of rapamycin). Think of mTOR as a sensor inside our cells: when resources like amino acids are abundant, it tells cells to grow and divide. That’s great for building muscle, but it can also accelerate the growth of cancer cells if mutations are present [1].
This is why Longo often compares protein’s effect to a fire. Cancer is like a spark that can turn into a blaze, and protein acts as the fuel that makes it spread faster.
Interestingly, the study found that not all protein is equal. The increased mortality risk was tied mainly to animal protein, particularly from meat and dairy. Plant proteins, on the other hand, didn’t show the same negative effects [1].
Another critical factor is age. The dangers of high protein appeared significant up to about age 65. After that, the pattern flipped. For older adults, lower protein intake was actually linked with higher mortality. The reason? Older adults are at greater risk of losing muscle mass, and too little protein can make this problem worse [1].
For adults under 65, Dr. Longo recommends between 0.31 and 0.36 grams of protein per pound of body weight per day (roughly 0.68–0.79 g/kg/day) [2]. That’s very close to the current RDA of 0.8 g/kg/day [2].
So, according to Longo, a moderate-to-low protein intake seems optimal for longevity — at least until later in life.
Considerations in Favor of a Higher Target
While Longo’s research is compelling, protein intake isn’t just about cancer risk. Other health concerns push us toward aiming higher — especially muscle mass, weight management, and metabolic health.
Muscle Mass and Aging
Muscle health is one of the biggest concerns as we get older. Starting as early as our 30s, we begin to lose muscle mass, and the decline accelerates with age. By the time we’re 80, many people have lost as much as 50% of their muscle mass [3]. This isn’t just a cosmetic issue. It has serious health consequences.
Loss of muscle mass leads to sarcopenia — a condition linked with reduced mobility, increased risk of falls, diminished quality of life, and longer hospital stays [4]. Preventing sarcopenia is one of the keys to healthy aging.
The question is: does the RDA of 0.8 g/kg/day provide enough protein to fight sarcopenia? The evidence suggests not. Expert groups like the International PROT-AGE Study Group and the European Society for Clinical Nutrition and Metabolism (ESPEN) recommend at least 1.0–1.2 g/kg/day for healthy adults over 65 [2]. Observational data supports this: older adults eating about 1.1 g/kg/day lost 40% less lean body mass over 3 years compared to those consuming 0.8 g/kg/day [2].
Protein and Resistance Training
Another area where protein shines is muscle building during resistance training. A massive meta-analysis published in 2017 found that increasing protein intake boosted muscle gains from training, but only up to a point. The benefits plateaued at about 1.62 g/kg/day [5].
A more recent review added nuance: it found a sharp improvement up to about 1.3 g/kg/day, after which gains continued but much more modestly [6].
This suggests that while you don’t necessarily need to push protein intake to the extreme, aiming above the RDA — and closer to 1.2–1.3 g/kg/day — gives you most of the benefits.
Protein and Weight Management
Obesity is another critical health issue tied to protein. According to the WHO, being overweight contributed to about 3.7 million deaths in 2021 from conditions like heart disease, diabetes, and cancer [7].
Protein can play a powerful role in weight management. Multiple studies have shown that high-protein diets outperform standard diets when calories are matched. A meta-analysis found high-protein diets led to greater fat loss and body weight reduction while preserving lean body mass [8].
Another study found that people on a high-protein diet lost nearly half the lean mass compared to those on a normal protein diet during a 12-week calorie-restricted program [9]. Plus, the high-protein group reported feeling fuller and enjoying meals more [9].
In practice, the high-protein diets studied ranged from 1.07 to 1.6 g/kg/day [8]. Even the low end of that range is well above the RDA.
Kidney Health: Reconsidering the Risk
For years, doctors warned that high-protein diets could damage the kidneys. This concern was especially strong for people with chronic kidney disease (CKD). Current guidelines often suggest limiting protein intake to 0.6–0.8 g/kg/day for moderate or severe CKD [10].
However, a recent large study turned this assumption on its head. Among older adults with mild to moderate CKD, higher protein intake was actually associated with significantly lower mortality. In fact, those consuming 1.6 g/kg/day had a 33% lower risk of death compared to those at 0.8 g/kg/day [10].
The takeaway: in many cases, the benefits of higher protein may outweigh the risks — even for some people with kidney issues.
Responding to Longo
The biggest question lingering is: what about cancer? Dr. Longo’s warnings are serious, and nobody wants to ignore a risk that could impact longevity.
The truth is, the evidence linking protein to cancer is mixed and nuanced.
A recent umbrella review concluded that higher protein intake didn’t appear linked to colorectal or breast cancer, and evidence for other cancers is currently insufficient [11].
When it comes to mortality, the picture becomes clearer. Several large studies have shown that the risk is tied to protein source rather than total protein. One cohort study found the highest protein consumers had a 12% higher mortality risk, but this was mainly due to animal protein, especially from meat and dairy [12].
Other research backs this up. A study reported that plant proteins reduced mortality risk by 36%, while animal proteins increased it by 52% [13]. Interestingly, fish protein was associated with a 21% reduction in mortality [13].
A meta-analysis of 32 cohort studies published in the BMJ reinforced these findings: total protein intake was linked to lower all-cause mortality, with plant protein being particularly beneficial. It also found no significant increase in cancer mortality linked to total protein [14].
This aligns with what we already know about red and processed meats, which are well-documented risk factors for heart disease and cancer [15]. Meanwhile, plant proteins and lean sources like fish consistently show health benefits.
So, the real issue doesn’t seem to be how much protein we eat — but where we get it from.
Practical Conclusions
Bringing everything together, what’s the right protein intake for most people?
Based on the evidence, aiming for 1.2–1.6 g/kg/day strikes the best balance. At this range, we support muscle health, aid in weight management, and still stay within levels shown to be safe. Since the benefits level off past about 1.3 g/kg/day, the upper end may not be necessary for everyone.
Personally, I’ve adjusted my intake from 1.6 g/kg/day down to 1.2 g/kg/day. To calculate this, I use an ideal body weight calculator [16]. For me, that works out to around 94 grams of protein per day.
I recommend prioritizing plant-based proteins (legumes, beans, nuts, and seeds) and incorporating lean meats and fatty fish. At the same time, I advise minimizing red and processed meats. For convenience, I sometimes use a high-quality pea protein powder, which is lower in methionine — an amino acid linked to cancer risk in Longo’s research.
While protein powders and bars aren’t necessary, they can help some people hit their daily target — especially those with busy lifestyles or higher needs.
Ultimately, the “perfect” protein intake isn’t one-size-fits-all. It depends on your age, activity level, and health status. A young athlete, for example, will need more than a sedentary middle-aged adult. But for most, 1.2 g/kg/day is a solid target that maximizes benefits without unnecessary risks.
References
1. https://pmc.ncbi.nlm.nih.gov/articles/PMC3988204/
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC5872778/
3. https://pmc.ncbi.nlm.nih.gov/articles/PMC5872778/
4. https://pmc.ncbi.nlm.nih.gov/articles/PMC6442923/
5. https://pmc.ncbi.nlm.nih.gov/articles/PMC5867436/
6. https://pmc.ncbi.nlm.nih.gov/articles/PMC7727026/
7. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight
8. https://pmc.ncbi.nlm.nih.gov/articles/PMC7539343/
9. https://pubmed.ncbi.nlm.nih.gov/17299116/
10. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2822055
11. https://pmc.ncbi.nlm.nih.gov/articles/PMC11329548/
12. https://pmc.ncbi.nlm.nih.gov/articles/PMC7250948/
13. https://www.nature.com/articles/s41598-023-30455-9
14. https://pmc.ncbi.nlm.nih.gov/articles/PMC7374797/
15. https://www.sciencedirect.com/science/article/pii/S026156142030251X
16. https://www.mdcalc.com/calc/68/ideal-body-weight-adjusted-body-weight
