Protein is an essential nutrient that your body can use every day, so you’re not likely to eat so much of it that you’ll experience significant negative effects. However, most Americans eat more protein than they need daily, according to the Physicians Committee for Responsible Medicine, and consistently taking in excess protein can harm your health over time.
What's an Overdose?
According to Rice University, a typical active adult needs about 0.4 to 0.6 gram of protein per pound of body weight per day. Your age, sex, weight and physical activity level also influence the amount of protein you need, so a college-aged man who lifts weights regularly can likely use dozens more grams of protein than a sedentary middle-aged woman. Thus, it can be hard to predict what “overdose” levels might be. According to one study published in 2013 in the “American Journal of Clinical Nutrition,” men who strength trained and then ate protein got the most benefit from eating about 20 grams total; their bodies were not able to effectively use more than that at a single meal. That means if you eat three or four times a day, your body is likely only able to use 20 grams of protein at each meal or snack -- and any more than that means you're overdosing.
Ways to Go Overboard
A T-bone steak is obviously high in protein, but so are many other foods that may not immediately leap to mind, including dairy products, tofu, soybeans, other beans and lentils, quinoa, eggs, nuts and seeds. If protein-rich foods are in most of your meals and snacks and you eat a lot of them, you may be getting more of the nutrient than you need. If you take protein powder regularly, experiencing gas, bloating and digestive discomfort can sometimes be symptoms of taking in too much of the nutrient, so if you notice those signs, consult your doctor.
Side Effects of Too Much Protein
How do you know if you’re getting too much protein? The signs are rarely obvious, so it can be hard to tell. Weight gain, for example, could be attributed to eating more protein -- and calories -- than your body can use, although that’s not always the case. Another potential side effect is nutrient deficiencies, which you could acquire over time if you’re focusing too heavily on protein in your diet in lieu of other macronutrients -- for example, fiber doesn't appear much in protein-rich foods, but it is prevalent in carbs. More severe side effects include elevated risks of osteoporosis, kidney stones, kidney disease, heart disease and cancer.
The Physicians Committee for Responsible Medicine advocates for moderating your protein intake, noting that long-term high-protein diets can be associated with increased disease risk. Harvard University researchers acknowledge that although eating a lot of protein may harm kidney function in individuals who already have kidney damage, it has never been shown to harm kidneys in healthy individuals. The International Society of Sports Nutrition suggests that for healthy people who exercise regularly, there is no harm in consuming up to 2 grams of protein per kilogram of body weight per day, which is about 136 grams for a 150-pound person.
- Physicians Committee for Responsible Medicine: The Protein Myth
- Institute of Medicine: Dietary Reference Intakes -- Macronutrients
- American Journal of Clinical Nutrition: Myofibrillar Muscle Protein Synthesis Rates Subsequent to a Meal in Response to Increasing Doses of Whey Protein at Rest and After Resistance Exercise
- Harvard University Gazette: Too Much Protein May Cause Reduced Kidney Function
- Journal of the International Society of Sports Nutrition: International Society of Sports Nutrition Position Stand -- Protein and Exercise
- Rice University: Protein Requirements for Athletes
- Men's Fitness: Whey Protein