Hype vs. Reality
As a continuation of our Hype vs Reality series on lifestyle interventions (and, more specifically, diets), we explore a big question in longevity: high vs low protein, which is better? Spoiler: there’s no clear answer, and science is still divided. Even the definitions of “low” and “high” protein vary by population and by how intake is measured.
Key evidence
The Verdict
In longevity-focused nutrition research, you can find studies to back almost any viewpoint. However, so far, the evidence suggests that a moderate protein intake in midlife may support long-term health. Later in life, however, higher protein intake, alongside strength training, becomes essential for keeping muscles and independence. Until we have stronger human studies, the safest path is “protein in balance,” matched to your age, activity, and health goals.
As a continuation of our Hype vs Reality series on lifestyle interventions (and, more specifically, diets), we explore a big question in longevity: high vs low protein, which is better? Spoiler: there’s no clear answer, and science is still divided. Even the definitions of “low” and “high” protein vary by population and by how intake is measured.
Key evidence
- A large study looked at how protein intake affects overall risk of death and found an interesting age-based pattern. For people under 65, eating less protein was linked to a lower risk of dying from any cause. But once people hit 65 and older, the pattern flipped: those who ate more protein actually lived longer and had better overall health outcomes (PMID: 24606898).
- One explanation lies in how protein affects growth signals in the body. When you eat protein, especially in larger amounts, it increases a hormone called IGF-1 (insulin-like growth factor 1). IGF-1 tells the body to grow and build, which can be helpful in some ways, but in middle age, too much of this “growth signal” has been linked to a higher risk of cancer and faster aging (PMID: 27130207).
- But it's not just about how much protein you eat per day. A recent 2024 study showed that this growth signal (IGF-1) only gets activated when a single meal has more than about 25g of protein (PMID: 38409323). That means spreading protein evenly through the day might avoid triggering the same strong growth response.
- In animal studies, reducing protein, especially certain types like leucine found in animal protein, has consistently shown benefits. Mice on low-protein or plant-based diets tend to live longer. These diets raise a hormone called FGF-21, which helps regulate metabolism and promotes a longer lifespan. (PMID: 35393401). But here’s the catch: lab animals don’t experience age-related muscle loss (sarcopenia) or bone thinning (osteoporosis) like humans do, so we must be cautious in applying these results.
- In humans, especially older adults, the risks of not getting enough protein are very real. Studies show that low protein intake in older adults is linked to lower muscle mass and sarcopenia, both of which increase the likelihood of falls and fractures (PMID: 35886571). This leads to frailty, loss of independence, and lower quality of life. Data modelling suggests that after age 50, the survival benefits of a higher-protein diet outweigh earlier-life downsides.
The Verdict
In longevity-focused nutrition research, you can find studies to back almost any viewpoint. However, so far, the evidence suggests that a moderate protein intake in midlife may support long-term health. Later in life, however, higher protein intake, alongside strength training, becomes essential for keeping muscles and independence. Until we have stronger human studies, the safest path is “protein in balance,” matched to your age, activity, and health goals.