Protein serves as a crucial building block for the human body, playing a vital role in muscle building and repair. For those aiming to increase muscle mass or lose fat, boosting daily protein intake is essential. But is there a limit to how much protein one should consume? How much is considered excessive?
While there are guidelines, it is challenging to go overboard with protein consumption. Here’s what experts have to say.
Are High-Protein Diets Safe?
Consuming an excessive amount of protein to the point of negatively impacting health is highly unlikely. Research published in the American Journal of Clinical Nutrition indicates that the average American consumes less than half of the widely accepted “upper limit” of protein intake: 35% of daily calories.
Studies suggest that even active individuals exceeding this upper limit may not experience adverse effects. A study published in the Journal of Nutrition and Metabolism in 2016 involved 14 healthy, resistance-trained men who alternated between their regular diet and a “high-protein diet” (exceeding 3 grams per kilogram of body weight daily). To put this into perspective, a 154-pound individual would need to consume over 210 grams of protein per day on this high-protein diet, equivalent to nearly two pounds of chicken.
After monitoring the subjects for a year, researchers found no detrimental effects on blood lipids, liver function, or kidney function, which are typically where adverse reactions to excessive protein intake manifest.
Furthermore, research suggests that current protein recommendations may be insufficient for specific populations, including individuals over 65, pregnant or lactating women, and healthy children above 3 years of age. As the scientific community continues to debate the ideal protein intake, it is important to recognize emerging literature that supports the safety and effectiveness of high-protein diets for those with increased protein requirements.
3 Effects Associated With High-Protein Diets
While studies have explored potential risks of excessive protein intake, the Institute of Medicine’s Dietary Reference Intakes states that there is “insufficient data” to establish causal relationships between protein consumption and health complications, underscoring the need for controlled clinical trials.
1. Stomach Upset/Discomfort
Some individuals may experience gastrointestinal issues due to protein supplementation, potentially linked to lactose content in certain protein shakes containing whey protein concentrate. Opting for whey protein isolate or plant-based protein, which have lower lactose content or none at all, can help mitigate these problems.
Gastrointestinal issues can also arise from whole foods. “Consuming excessive animal-based protein without an adequate intake of complex carbohydrates, which are rich in fiber, may lead to mild constipation,” explains Quyen Vu, MS, RDN.
2. Kidney Issues
Some studies have suggested a connection between high-protein diets and kidney function. However, the likelihood of exercisers developing kidney problems or other metabolic disorders due to high protein consumption is considered “extremely rare,” according to Glenn Gaesser, PhD, FACSM, a professor of exercise physiology at Arizona State University.
3. Heart Issues
Research indicates that excessive protein intake may impact the cardiovascular system.
“Several cohort studies on the general population suggest a higher risk of premature mortality associated with diets high in protein, such as the traditional low-carb diet, which typically contains more protein than the standard American diet,” notes Gaesser.
However, he adds, “The issue may not lie solely in the higher protein intake, but rather in other aspects of the diet, such as high levels of animal fat and low fiber content.”
Can Excessive Protein Consumption Affect Weight Loss?
Indeed, protein contributes calories to the diet. When aiming to lose weight, creating a calorie deficit—where you burn more calories than you consume—is crucial. Consuming excessive protein that hinders or eliminates this calorie deficit can impede weight loss.
“Protein not utilized for the body’s regular growth and maintenance functions may be converted to energy if other sources are lacking and could potentially be stored as fat,” explains Mindy Haar, Ph.D., RDN, CDN, FAND, a registered dietitian nutritionist and assistant dean at New York Institute of Technology’s School of Health Professions. “Overconsumption of protein leading to surplus calorie intake can result in weight gain.”
However, protein remains a key component of most weight loss strategies. A meta-analysis of 24 studies revealed that calorie-restricted, high-protein diets yielded more favorable changes in overall body composition compared to standard-protein diets. This is likely attributed to protein’s satiating effect and its ability to preserve muscle mass.
How to Identify Excessive Protein Consumption
Your first indicator may be a stomachache or other minor gastrointestinal issues. Even individuals with strong digestive systems can exceed their body’s optimal protein processing capacity.
“The body can only effectively utilize a specific amount of protein per meal—approximately 30 grams,” notes Lisa Moskovitz, RD, CDN, CEO of New York Nutrition Group. “This equates to about four ounces of cooked chicken breast or fish, one cup of Greek yogurt, or two cups of black beans.”
It’s also essential to distribute protein intake throughout the day since the body does not store excess protein.
“In my practice, I often see athletes attempting to consume all their protein in one or two meals,” says Maddi Osburn, RDN, LD, a registered dietitian nutritionist in Wichita, Kansas. “If an athlete overindulges in protein during a couple of meals, they may not achieve the optimal muscle growth response, and the excess protein may either be excreted or stored as fat. Moreover, excessive protein intake could displace other vital nutrients—such as carbohydrates, fats, and fiber—that are equally important for optimal recovery and performance.”