Media attention to protein has increased and resulted in significant scrutiny. Many individuals are unsure of how much protein to consume and whether higher intakes, like those recommended for exercise, are safe for cardiovascular health. This uncertainty is understandable because protein is often portrayed inconsistently across media coverage.

Science itself is not flip-flopping; it is evolving with the addition of incremental detail to a growing body of evidence.

What Protein Is and Why It Is Needed

Protein contains nitrogen, making it essential for tissue structure and function. It is crucial for providing the nine essential amino acids to support muscle protein synthesis, immune function, and overall physiology, while promoting protein remodeling and the net acquisition of new tissue when paired with exercise.

From a cardiovascular perspective, adequate protein intake supports preservation of lean body mass, exercise adaptations, and functional capacity, all of which are independently associated with cardiometabolic risk, physical resilience, and long-term cardiovascular outcomes.

Protein and Exercise Adaptation

Many people are aware that protein plays a role in muscle growth through its contribution to the hypertrophy of myofibrillar proteins, which is essential for strength and movement. However, exercise adaptations extend beyond muscle size. Protein also supports endurance adaptations that enhance cardiovascular fitness, including mitochondrial biogenesis and angiogenesis, and amino acids oxidized during endurance exercise must be replaced through the diet.

Protein turnover is a continuous process of breakdown, which predominates during fasting, and synthesis, which increases following protein intake (Figure 1). Exercise enhances the tissue response to dietary protein, driving greater net protein synthesis and musculoskeletal and cardiovascular adaptations.

Figure 1: Protein Turnover Schematic Illustrating Breakdown, Synthesis, and the Free Amino Acid Pool

Reproduced from Williamson E. Protein Requirements and Amino Acid Metabolism Following Endurance Exercise. PhD thesis, University of Toronto, 2022.

Current Protein Recommendations

Protein intakes near 0.8 g/kg/day reflect long-standing deficiency-prevention estimates and are generally adequate; however, higher intakes (≥1.2 g/kg/day) may better support functional outcomes such as muscle mass and strength, particularly in athletes and adults >60 years of age at risk for sarcopenia,¹ which is increasingly recognized as a contributor to cardiometabolic risk.

For individuals training regularly, the American College Sports Medicine and International Society of Sports Nutrition recommend 1.2-2.0 g/kg/day. Meta-analyses and randomized controlled trials (RCTs) show resistance training adaptations are optimized at approximately 1.6 g/kg, or 20% of energy intake in typical training conditions,² whereas endurance athletes may require approximately 1.8 g/kg, which corresponds to about 15% of energy intake with their higher energy requirements.³

Higher Protein Intake and Heart Health

As higher protein intake recommendations become more common, particularly in the context of exercise, concerns have emerged about their potential connection with cardiovascular risk; however, the key consideration is protein source. Findings from large meta-analyses suggest that protein intake itself is not associated with increased cardiovascular risk when it comes from appropriate sources.⁴

Confusion stems from typical Western dietary patterns, where higher protein intake often comes from red and processed meats. Higher consumption of animal protein, particularly from these sources, has been associated with increased cardiovascular disease risk in observational studies.⁴ These patterns are also associated with lower diet quality, including lower fiber and higher saturated fat consumption.⁵ In this context, cardiovascular risk reflects the broader dietary pattern rather than protein as a nutrient.

This becomes especially important with restrictive diet trends such as carnivore or poorly constructed ketogenic diets. In these approaches, higher protein intake is often coupled with high intakes of red and processed meats, excess saturated fat, low fiber, and reduced micronutrients. These dietary characteristics, rather than protein itself, are what plausibly increase cardiovascular risk.

In contrast, observational evidence suggests protein sources such as poultry, seafood, low-fat dairy, legumes, and soy are not associated with increased cardiovascular risk.⁴ This is further supported by RCTs in healthy adults, where intakes as high as 25-30% of total energy from these sources have neutral to modestly beneficial effects on blood pressure, lipid profiles, glycemic control, and waist circumference.⁶

Taken together, higher protein diets do not need to be feared when protein source and overall diet quality are prioritized.

Common Safety Concerns Relevant to Cardiovascular Patients

Concerns about protein safety in cardiovascular practice often extend to bone, kidney, and cancer outcomes, and can influence clinician willingness to recommend higher protein intakes for patients engaging in exercise-based cardiovascular prevention or rehabilitation.

Concerns about bone health stem from increased urinary calcium excretion with higher protein intake. However, controlled studies show this increase reflects enhanced intestinal calcium absorption rather than bone loss. With adequate calcium and vitamin D, protein intake is neutral or protective for bone health.⁷

Kidney concerns arise from studies in advanced chronic kidney disease, where higher protein intakes contribute to disease progression. However, in adults with normal kidney function, trials testing higher protein intakes (up to ~3.3 g/kg/day for up to 2 years) have not shown evidence of kidney harm.⁸

Protein and cancer risk are hypothesized through stimulation of growth factors. However, human evidence does not support an association between protein intake and cancer mortality.⁹

Overall, when interpreted in appropriate clinical context, these unfounded safety concerns may lead to unnecessary restriction of protein intake, potentially limiting cardiovascular adaptations to exercise.

The Case for "Too Much" Protein

Excessive protein intake is possible, but the risk is rarely due to protein itself. The more relevant concern is dietary displacement.

Very high protein intakes can crowd out carbohydrate and fat sources that provide fiber, essential fatty acids, and other nutrients for cardiovascular health. This risk may be amplified when higher protein intakes come from ultraprocessed foods with added protein rather than whole food sources, which may contribute surplus energy, added sugars, saturated fat, and overall lower diet quality, factors linked to poorer cardiovascular outcomes.

This concept underpins the acceptable macronutrient distribution range (AMDR) of 10-35% of total energy intake from protein. Individuals who fall within this range, alongside recommended carbohydrate and fat ranges, are able to meet micronutrient needs and demonstrate lower cardiovascular disease risk.¹⁰

Many adults already consume protein intakes that meet or exceed requirements, and typical intakes among physically active individuals often fall near exercise recommendations (i.e., ~15% of total energy intake and ~1.2 g/kg/day), suggesting that although there may be room for optimization toward the approximate 1.6-1.8 g/kg/day targets discussed earlier, diet quality should remain a significant focus.^2,3,9

Practical Takeaways for Clinicians and Patients

Protein needs vary based on age, activity level, health status, and dietary context. For most individuals, remaining within the AMDR while prioritizing higher-quality protein sources supports cardiovascular health.

Source matters as much as quantity, and additional protein should come from lean and nutrient-rich sources such as poultry, seafood, low-fat dairy, and plant proteins. Collaboration with a registered dietitian can help ensure protein adequacy without compromising carbohydrate intake, healthy fats, or micronutrient sufficiency.

Protein does not exist in a vacuum. Like all macronutrients, its cardiovascular impact depends on source, pattern, and context (Figure 2).

Figure 2: Same Protein, Different Sources

BP = blood pressure.

References

1. Weiler M, Hertzler SR, Dvoretskiy S. Is it time to reconsider the U.S. recommendations for dietary protein and amino acid intake?. Nutrients. 2023;15(4):838. Published 2023 Feb 6. doi:10.3390/nu15040838
2. Nunes EA, Colenso-Semple L, McKellar SR, et al. Systematic review and meta-analysis of protein intake to support muscle mass and function in healthy adults. J Cachexia Sarcopenia Muscle. 2022;13(2):795-810. doi:10.1002/jcsm.12922
3. Williamson E, Fung HJW, Adams C, West DWD, Moore DR. Protein requirements are increased in endurance-trained athletes but similar between females and males during postexercise recovery. Med Sci Sports Exerc. 2023;55(10):1866-1875. doi:10.1249/MSS.0000000000003219
4. Naghshi S, Sadeghi O, Willett WC, Esmaillzadeh A. Dietary intake of total, animal, and plant proteins and risk of all cause, cardiovascular, and cancer mortality: systematic review and dose-response meta-analysis of prospective cohort studies. BMJ. 2020;370:m2412. Published 2020 Jul 22. doi:10.1136/bmj.m2412
5. Bowman SA, Clemens JC. Saturated Fat and Food Intakes of Adults: What We Eat in America, NHANES 2017-2018. In: FSRG Dietary Data Briefs. Beltsville (MD): United States Department of Agriculture (USDA); May 2022.
6. Vogtschmidt YD, Raben A, Faber I, et al. Is protein the forgotten ingredient: effects of higher compared to lower protein diets on cardiometabolic risk factors. A systematic review and meta-analysis of randomised controlled trials. Atherosclerosis. 2021;328:124-135. doi:10.1016/j.atherosclerosis.2021.05.011
7. Zittermann A, Schmidt A, Haardt J, et al. Protein intake and bone health: an umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society. Osteoporos Int. 2023;34(8):1335-1353. doi:10.1007/s00198-023-06709-7
8. Remer T, Kalotai N, Amini AM, et al. Protein intake and risk of urolithiasis and kidney diseases: an umbrella review of systematic reviews for the evidence-based guideline of the German Nutrition Society. Eur J Nutr. 2023;62(5):1957-1975. doi:10.1007/s00394-023-03143-7
9. Papanikolaou Y, Phillips S, Fulgoni V 3rd. Animal and plant protein usual intakes are not adversely associated with all-cause, cardiovascular disease-, or cancer-related mortality risk: an NHANES III analysis. Appl Physiol Nutr Metab. 2025;50:1-8. doi:10.1139/apnm-2023-0594
10. Millen BE, Abrams S, Adams-Campbell L, et al. The 2015 Dietary Guidelines Advisory Committee scientific report: development and major conclusions. Adv Nutr. 2016;7(3):438-444. Published 2016 May 16. doi:10.3945/an.116.012120