Are You Eating Enough Protein? Probably Not.
Why Protein Matters Now More Than Ever
Protein has become a hotly contested topic in both Canada and the United States. Grocery store shelves are filled with protein bars, shakes, and fortified foods. At the same time, opinion pieces often warn that the “protein craze” is unnecessary or even harmful. Scientists, journalists, and health influencers all seem to have strong views.
But behind the headlines is a crucial truth: protein is not a passing fad. It is a macronutrient essential for survival, and even more importantly, for thriving across the lifespan. At LifespanMD, we carefully evaluate peer-reviewed research to guide our practice. Our general recommendation for clients is 1.4 to 2.2 grams of protein per kilogram of ideal body weight per day, which is significantly higher than guidelines in both Canada and the United States.
This target is not arbitrary. It reflects a growing body of evidence showing that higher protein intake is essential for preserving muscle, maintaining metabolic health, preventing frailty, and ultimately extending both lifespan and healthspan.
The Canadian and U.S. RDA: Origins and Limitations
Current Recommendations
Canada: Health Canada sets the Recommended Dietary Allowance (RDA) for protein at 0.8 g/kg/day for adults, the same as the Dietary Reference Intake (DRI) used in the United States .
United States: The RDA is also 0.8 g/kg/day, unchanged since 1989 .
These values are widely cited, but their original purpose is often misunderstood. They were designed to prevent deficiency, not to optimize health.
How the RDA Was Established
Protein requirements were determined through nitrogen balance studies conducted in the early and mid-20th century. Researchers measured nitrogen intake from dietary protein and nitrogen excretion in urine. If the two matched, the subject was said to be in balance, meaning their intake was adequate to prevent breakdown of body tissues.
However, several important limitations exist:
Incomplete measurements: Nitrogen lost through sweat, skin, and stool was rarely measured, which underestimates requirements.
Population bias: Most studies were done in healthy young men weighing about 68 kg (150 lbs), often university students. Women, older adults, ethnic minorities, children, and people with chronic diseases were not represented.
Protein quality assumptions: The RDA assumes consumption of high-quality animal proteins with excellent amino acid profiles. Plant proteins, which are less digestible and less anabolic, were not considered.
As a result, the RDA reflects the minimum needed to prevent deficiency in a narrow group, not the intake required for the diverse, aging, and active populations of Canada and the United States today.
Why “Adequate” Is Not the Same as “Optimal”
Meeting the RDA may be enough to avoid malnutrition, but it is far from enough to achieve optimal health. At LifespanMD, we emphasize optimization, not adequacy.
Skeletal Muscle: A Longevity Organ
Skeletal muscle is more than a system for movement. It is an essential metabolic organ that influences nearly every domain of health. Muscle accounts for the majority of glucose uptake after meals, making it central to blood sugar regulation. It is also a reservoir for amino acids needed in times of stress, illness, or injury.
Declining muscle mass, or sarcopenia, is associated with frailty, loss of independence, falls, fractures, and increased mortality.
Canada: By age 65, about 14 percent of Canadians have clinically significant sarcopenia. This increases sharply after age 75.
United States: Estimates suggest that up to 20 percent of adults over 70 are sarcopenic, with rates even higher in those living in long-term care facilities.
Protein intake is the key modifiable factor. Randomized controlled trials consistently show that intakes above 1.2 g/kg/day preserve muscle mass and function, with 1.6 to 2.2 g/kg/day maximizing muscle protein synthesis when paired with resistance training .
Anabolic Resistance and Aging
As people age, the muscle’s ability to respond to protein intake diminishes. This phenomenon is called anabolic resistance. Older adults require higher protein doses per meal (25 to 40 g) to trigger muscle protein synthesis compared with younger adults who respond to 15 to 20 g. This makes higher daily protein intake essential in midlife and beyond.
Metabolic Health and Glucose Control
Both Canada and the United States face alarming rates of diabetes and prediabetes.
Canada: About 11 million Canadians live with diabetes or prediabetes.
United States: More than 37 million Americans have diabetes, and 96 million have prediabetes according to CDC estimates.
Skeletal muscle is the primary site for glucose disposal. Without sufficient lean mass, insulin resistance develops more easily. Adequate protein intake, combined with exercise, improves insulin sensitivity, lowers hemoglobin A1c, and reduces risk of type 2 diabetes.
Weight Management and Body Composition
Nearly 30 percent of Canadians and more than 40 percent of Americans are obese. In both countries, over 60 percent of adults are overweight or obese. Weight loss often results in loss of both fat and lean mass. Preserving muscle during weight reduction is essential for metabolic health and long-term weight maintenance.
Higher protein intake supports weight management in several ways:
Satiety: Protein increases fullness more than carbohydrates or fat, leading to lower spontaneous caloric intake.
Thermogenesis: The thermic effect of protein is 20 to 30 percent, meaning a greater proportion of its calories are burned during digestion and metabolism.
Lean mass preservation: In weight loss programs, higher protein diets reduce the proportion of lean tissue lost from ~25 percent to closer to 10 to 15 percent.
Addressing Concerns About High Protein Intake
Kidney Function
One of the most common concerns is kidney health. High protein intake increases urea production, which has led to speculation that it damages the kidneys. However, studies in humans consistently show that higher protein diets are safe for people with normal kidney function.
Poortmans & Dellalieux (2000): No adverse renal effects were found in athletes consuming up to 2.8 g/kg/day.
Antonio et al. (2016): Resistance-trained individuals consuming more than 3 g/kg/day for one year showed no negative effects on kidney or liver function.
Cochrane Review (Fouque et al., 2009): In patients with chronic kidney disease, protein restriction had little effect on mortality or disease progression.
Cancer Risk and Aging Pathways
Concerns about protein and cancer risk often focus on mTOR, a nutrient-sensing pathway involved in growth. While chronic overactivation of mTOR may be harmful, pulsatile activation through dietary protein is necessary for maintaining muscle and metabolic function.
Epidemiologic studies linking red meat to cancer risk are confounded by lifestyle factors such as smoking, alcohol intake, and low vegetable consumption. Importantly, no randomized controlled trial has shown that higher protein intake per se increases cancer risk. On the contrary, sarcopenia and low muscle mass predict poorer cancer outcomes, greater treatment complications, and lower survival rates.
Practical Recommendations
Protein intake should be tailored to the individual, taking into account age, health status, activity level, and goals. Some general guidelines include:
Younger adults: 1.4 to 1.8 g/kg/day for performance and lean mass.
Older adults (50+): 1.6 to 2.2 g/kg/day to overcome anabolic resistance and prevent sarcopenia.
Athletes and active clients: 1.8 to 2.2 g/kg/day to support recovery and adaptation.
Weight loss clients: At least 2.0 g/kg/day to preserve muscle during caloric restriction.
Plant-based diets: Emphasis on protein quality and amino acid balance. Soy, pea, and rice blends, as well as supplementation, may be needed to achieve equivalent results.
We also encourage distributing protein evenly across meals. Research shows that spreading intake into three or more meals, each containing 25 to 40 g of protein, stimulates muscle protein synthesis more effectively than skewed intake concentrated at dinner.
Evidence Highlights
Morton et al. (2018): Meta-analysis of 49 RCTs found ~1.6 g/kg/day maximizes muscle mass and strength gains with resistance training.
Devries & Phillips (2015) (Canadian researchers): Higher protein intakes improve muscle outcomes in older adults and are safe.
Srikanthan & Karlamangla (2014): Muscle mass is a stronger predictor of survival than BMI in older adults.
Leidy et al. (2015): Higher protein improves satiety, body composition, and metabolic outcomes.
Antonio et al. (2016): Long-term intake above 3 g/kg/day safe in resistance-trained adults.
Cermak et al. (2012): Protein supplementation enhances resistance training adaptations in both young and older adults.
Canadian Longitudinal Study on Aging: Low protein intake associated with frailty and mobility limitations.
Conclusion
The Canadian and U.S. RDAs for protein (0.8 g/kg/day) are designed to prevent deficiency. They are not intended as optimal targets for health. For individuals seeking to maximize healthspan and lifespan, the evidence strongly supports higher intakes.
At LifespanMD, we generally recommend 1.4 to 2.2 g/kg of ideal body weight per day, customized to the individual. This level of intake is consistently associated with better muscle retention, improved glucose regulation, lower risk of frailty, and superior body composition outcomes.
Protein is not a marketing trend. It is a cornerstone of preventive and longevity medicine. For Canadians and Americans alike, adequate is not enough—optimal is the goal.
References
Health Canada. Dietary Reference Intakes: Macronutrients. 2005.
Institute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. 2005.
Rand WM et al. Am J Clin Nutr. 2003;77(1):109-127.
Millward DJ. Br J Nutr. 2012;108(S2):S31-S49.
Srikanthan P, Karlamangla AS. Am J Med. 2014;127(6):547-553.
Newman AB et al. J Gerontol A Biol Sci Med Sci. 2006;61(1):72–77.
Morton RW et al. Br J Sports Med. 2018;52(6):376-384.
Cermak NM et al. Am J Clin Nutr. 2012;96(6):1454-1464.
Devries MC, Phillips SM. Appl Physiol Nutr Metab. 2015;40(6):582-588.
Phillips SM et al. J Am Coll Nutr. 2016;35(7):679-691.
Leidy HJ et al. Obesity. 2015;23(9):1729-1734.
Antonio J et al. J Int Soc Sports Nutr. 2016;13:3.
Fouque D et al. Cochrane Database Syst Rev. 2009;(3):CD001892.
Poortmans JR, Dellalieux O. Int J Sport Nutr Exerc Metab. 2000;10(1):28-38.
Fontana L et al. Nature. 2010;464(7288):337-342.
