Are Low-Protein Diets Better For Aging? What A New Study Actually Shows
How much protein is actually best for your health? It's the question everyone has been asking for the last few years, and the answer has pretty firmly leaned toward "more is better."
But a new review1 published in Cell Press Blue is challenging this thought. Researchers from the University of Wisconsin-Madison pulled together decades of research on dietary protein restriction (eating less protein than the standard recommendation) and laid out what they're calling the "hallmarks" of how a lower-protein diet may support healthy aging. Their conclusion? In animal studies, eating less protein (and, more specifically, restricting certain amino acids) showed up alongside better metabolic health, reduced cellular "aging" signals, and longer lifespans.
Before you panic, let's break down what this review actually found, why it's not quite time to ditch your protein goals, and what the current science actually supports for how much protein humans need for optimal health.
Protein & aging
Adequate protein intake is essential for maintaining muscle mass, strength2, and physical function as we age. And older adults often under-consume protein, which can contribute to muscle loss and and frailty.
However, animal studies (in which mice are fed very specific, controlled diets) have shown potential downsides of higher protein intake. The goal of this current review was to explore the biological pathways that may explain why protein restriction has been linked to longer lifespan and improved healthspan in a wide range of organisms.
Rather than looking at protein intake as a simple “more or less” question, the researchers focused on how the amount and composition of dietary protein may influence the aging process by analyzing 350 studies.
The authors organized their findings around several key “hallmarks” of aging:
- Metabolic health: Lower-protein diets in young rodents tend to improve blood sugar regulation, reduce fat accumulation, and increase energy expenditure—largely through a hormone called FGF21, which ramps up in response to reduced protein intake and helps regulate appetite, fat metabolism, and glucose control.
- Nutrient-sensing pathways: Amino acids act as signals that tell cells when to prioritize growth, maintenance, or repair. When certain amino acids are limited, pathways like mTOR and GCN2 shift activity, which may encourage processes like autophagy, the body’s cellular cleanup system.
- Cellular senescence: So-called "zombie cells" that stop dividing but linger and release inflammatory signals tend to build up with high-protein feeding in animal studies, while protein restriction appears to reduce this buildup in the liver and fat tissue.
- Mitochondrial function: Some (though not all) studies suggest lower-protein diets support healthier mitochondria, the energy-producing structures in your cells, while very high-protein diets have been linked to reduced mitochondrial efficiency in muscle tissue.
- Epigenetic changes: Amino acid availability appears to influence how genes are switched on or off over time, which may play a role in how organisms age.
- Healthy aging and frailty: Some studies find that higher protein protects against frailty and muscle loss in older age, while others, including protein restriction studies, find the opposite. The review authors note that exercise seems to help offset the muscle loss that can come with a lower-protein diet.
Interestingly, the researchers found that restricting certain amino acids may be more important than cutting protein overall. Methionine and the branched-chain amino acids (BCAAs)—leucine, isoleucine, and valine—were most consistently linked to these effects, with isoleucine restriction showing some of the strongest benefits for metabolic health and lifespan in animal studies.
But BCAAs also play a critical role in maintaining muscle. Leucine, for example, is one of the primary amino acids that stimulates muscle protein synthesis, which is why it's often emphasized for older adults and people who strength train.
Remember, these findings are mainly from animal research
The vast majority of the data behind these "hallmarks" comes from yeast, fruit flies, worms, and rodents, not people. The few human studies that exist are short-term (weeks, not years) and tend to look at metabolic markers like insulin sensitivity or triglycerides, not actual lifespan (you can't really run a decades-long human protein-restriction clinical trial).
Some large observational studies1 have linked higher protein intake to increased risk of diabetes, certain cancers, and cardiovascular events. An often-cited critique of these types of population studies is that they often can't fully isolate protein as a clean variable, as high-protein diets in Western populations frequently overlap with more processed and red meat, less fiber, and fewer plants overall (which is not ideal for metabolic health).
But other studies (including a well-known UK Biobank analysis) found that higher protein intake was associated with a lower risk of frailty in adults over 50. Since preserving muscle is one of the strongest predictors of healthy aging and independence, many experts continue to recommend meeting (or even modestly exceeding) current protein recommendations as we age.
How much protein do you actually need?
Now we're back to our original question. And the answer is, it depends. In a press release, the study authors emphasize how protein needs will vary from person to person. This is something that has always held true. Your protein needs depend on your age, activity level, and overall health goals. Sedentary adults need less protein than those who exercise regularly.
The Dietary Guidelines for Americans recommend people get between 0.55–0.73 grams per pound of body weight a day, whereas some experts recommend eating up to 1 gram or protein per pound of bodyweight. A healthcare provider can help you determine what your best range is.
Personally, I like to simplify things further. Instead, I like to focus on getting 30+ grams of protein at each meal (and familiarizing myself with what that actually looks like on my plate) and in an afternoon snack. Without thinking too hard about it, I easily get to 100+ grams a day. And remember, even "higher-protein" diets are still ones that are rich in fiber (think beans, lentils, fruits, veggies, and seeds) and healthy fats. It's about balance.
Strength training also matters
The takeaway
The best diet (and macronutrient composition) for healthy aging is still up for debate. This new review shows that there seem to be perks for lower-protein eating patterns in animals, however, people are different. We don't eat (or live) in lab-controlled environments. Human research continues to show that adequate protein is essential for preserving muscle, strength, and independence with age.
So for now, keep eating your quality protein sources (like poultry, fish, eggs, dairy, and meat) as part of an overall, balanced, whole foods diet. And prioritize physical activity in your daily, and weekly, routines.
