Alongside carbohydrates and fats, protein is one of the body’s essential nutrients. In Canada and the U.S., the official minimum Recommended Dietary Allowance (RDA) is 0.8 grams per kilogram of body weight per day⁽¹⁾. 

For someone weighing 150 pounds, that works out to be about 55 grams of protein (about what is found in two chicken breasts).

But broader nutrition guidelines say protein can safely account for 10 to 35 percent of daily calories, which is several times higher than the minimum. That wide reccomendation gap has fueled years of debate, especially about whether eating more protein increases the risk of disease or promotes long-term health⁽²⁾.

The Central Question is Does Too Much Protein Help or Harm?

Protein is indispensable because it repairs muscle, builds cells, and helps regulate hormones. But some scientists worry that very high intakes, particularly from animal sources like red meat and dairy, may overstimulate the body’s growth signals. Over decades that extra 'push' could in theory, fuel conditions such as cancer or heart disease.

Much of this debate centers on IGF-1, a hormone that acts as a growth regulator.

Higher protein intake raises IGF-1, and both unusually high and unusually low levels have been linked in some studies to greater risks of chronic disease⁽³⁾. 

In other words, the relationship may follow a 'Goldilocks principle', which is balance appears safer than either extreme.

What Past Research Suggested

A widely cited 2014 study reported that middle-aged adults (ages 50–65) who ate a lot of protein were four times more likely to die of cancer than those who ate very little. Strikingly, the effect was seen with animal protein, but not with plant protein⁽⁴⁾.

Other studies pointed in the opposite direction, suggesting that plant protein lowers the risk of heart disease and early death, perhaps because it comes packaged with fiber and protective plant compounds (i.e., phytochemicals)⁽⁵⁾.

Still others found no clear harm from high protein diets, and in some cases, even modest benefits, including from animal sources⁽⁵⁾.

The result is a conflicting evidence base that has left many people unsure how much protein is truly safe.

The New Study

To clarify, researchers recently turned to NHANES III, a large U.S. survey that followed tens of thousands of people, tracking both diet and health outcomes⁽⁵⁾. 

They asked two central questions:

• Does eating more protein (especially animal protein) increase the risk of dying from cancer, heart disease, or any cause?
• Is there a meaningful link between protein intake, IGF-1 levels, and mortality?

Major Findings

• No evidence of harm. Higher protein intake, from either plants or animals, was not linked to increased risk of death from cancer, heart disease, or overall causes. 
• In a surprise twist, animal protein was associated with a slight reduction in cancer mortality.
• While protein intake did raise IGF-1 levels, those higher levels did not translate into greater mortality risk in this analysis.

These results stand in sharp contrast to the dramatic 2014 study, which the authors suggest may have exaggerated risk because of uneven study groups and less reliable dietary reporting methods.

Why the Confusion?

Nutrition science is notoriously difficult. Most studies rely on people recalling what they ate from memory. This method is about as reliable as reconstructing a grocery list from memory a week after going shopping.

Beyond that, not all protein comes in the same 'package.'

A serving of steak brings protein alongside saturated fat, but a serving of beans provides protein plus fiber and antioxidants. Those nutrients associated may explain much of the difference in health outcomes.

Age adds another layer of complexity.

While middle-aged adults may benefit from moderate intake, older adults often need more protein to preserve muscle and prevent frailty. The 'right' amount may therefore shift across the lifespan.

The Bottom Line

Protein itself does not appear to be the villain. In this large U.S. dataset, neither animal nor plant protein increased the risk of death, and plant protein was not consistently more protective⁽⁵⁾.

The broader lesson may be less about how much protein you eat, and more about the form it comes in. Protein is the passenger, but the nutritional 'vehicle', whether it’s steak, yogurt, beans, or lentils carries very different cargo that influences long-term health.

As people age, maintaining muscle becomes more difficult, partly because of anabolic resistance (muscle is less responsive to protein intake). This means older adults generally need more protein, especially if they are doing resistance exercise.

These higher levels help offset muscle loss, help strength, support recovery.

Also, distributing protein evenly across meals helps. This means not loading one big protein meal and having low protein in other meals. Older muscle responds better when there is enough protein per meal. Some guidelines suggest ~25-40 g protein per meal depending on size of person, and making sure there are enough key amino acids (especially leucine).

Practical Implications and Suggestions

Putting this together, here’s what seems to make sense if the goal is to maintain or build muscle as you age:

1. Target protein in the 1.2-1.6 g/kg/day range, especially if you are past 50, doing resistance/strength training, or recovering from stress/injury. If just maintaining and relatively sedentary, perhaps the lower end (1.0-1.2 g/kg) will suffice.
2. Distribute protein throughout the day, don’t have most in one meal and little in others. Try to include a moderate amount in each of 2-3 (or more) meals.
3. Include high-leucine or high-EAA protein sources like dairy, eggs, meat/fish/seafood, or plant proteins that are rich in EAA or especially leucine (soy, pea, mixtures, etc.), or fortified isolates.
4. Combine with resistance training / strength work. Protein is necessary but not sufficient: the stimulus of strength training helps make muscle more responsive.
5. If mostly plant-based, plan to eat a variety (legumes, grains, nuts, seeds), possibly plant protein isolates or fortifications; ensure sufficient total protein; compensate for lower digestibility or lower EAA in some sources.
6. Also consider individual factors such as health status (kidney, gut), calories (if you're in energy deficit, you may need more protein to preserve lean mass), overall dietary pattern

Your Muscles Don't Care About the Debate, They Just Need Fuel.

Getting enough high-quality protein is essential for maintaining strength, independence, and vitality as you age. While researchers argue over percentages and study designs, your body is making real-time decisions about whether to build muscle or break it down, and every meal is an opportunity.

The real challenge is getting the right amount, at the right times, from the right sources.

Whether you're recovering from an injury, working to maintain muscle mass, or training to stay strong, give your body what it needs to stay resilient, active, and strong for years to come.

All of our delicious proteins are formulated to deliver the leucine-rich nutrition your muscles need to thrive without any guesswork! 

References:
    1.    Medicine Io: Dietary reference intakes for energy, carbohydrate,fiber, fat, fatty acids, cholesterol, protein, and amino acids., in National Academies Press (ed). Washington, DC., 2005
    2.    Wolfe RR, Cifelli AM, Kostas G, et al: Optimizing Protein Intake in Adults: Interpretation and Application of the Recommended Dietary Allowance Compared with the Acceptable Macronutrient Distribution Range. Adv Nutr 8:266-275, 2017
    3.    Rahmani J, Montesanto A, Giovannucci E, et al: Association between IGF-1 levels ranges and all-cause mortality: A meta-analysis. Aging Cell 21:e13540, 2022
    4.    Levine ME, Suarez JA, Brandhorst S, et al: Low protein intake is associated with a major reduction in IGF-1, cancer, and overall mortality in the 65 and younger but not older population. Cell Metab 19:407-17, 2014
    5.    Papanikolaou Y, Phillips SM, Fulgoni VL: Animal and plant protein usual intakes are not adversely associated with all-cause, cardiovascular disease–, or cancer-related mortality risk: an NHANES III analysis. Applied Physiology, Nutrition, and Metabolism 50:1-8, 2025