Protein is one of the three macronutrients, along with fat and carbohydrate. These are essential for the optimal functioning of the body. However, too much protein — especially with no fat or carbs — can be harmful. This is something to be aware of considering the prevalence of many high-protein diets.

Protein poisoning is when the body takes in too much protein with not enough fat and carbohydrate for a long period of time. Other names for this are “rabbit starvation” or “mal de caribou.” These terms came about to describe only consuming very lean proteins, such as rabbit, without consuming other nutrients. So, although you may be getting enough calories from protein, your body experiences malnourishment from lack of other nutrients, like fat and carbs.

The liver and kidneys play key roles in the metabolism of proteins. When excessive amounts are consumed, it can put the body at risk for increased levels of ammonia, urea, and amino acids in the blood. Although very rare, protein poisoning can be fatal because of these increased levels.

Symptoms of protein poisoning include:

To function properly, your body needs:

  • protein
  • carbohydrates
  • fats
  • vitamins
  • minerals

If there’s too little or too much of any of these, functioning will decline. Even if you’re getting adequate calories from one macronutrient, ensuring there’s balance is important for optimal health.

Excessive protein is defined as greater than 35 percent of total calories you eat, or more than 175 grams of protein for a 2,000-calorie diet. The acceptable macronutrient distribution range (AMDR) is defined as the range that’s associated with reducing the risk for chronic disease while fulfilling the body’s needs of nutrients. The current AMDR according to the Institute of Medicine recommends the following:

  • Protein intake: 10 to 35 percent of total calories
  • Carbohydrate intake: 45 to 65 percent of total calories
  • Fat intake: 20 to 35 percent of total calories

Excessive consumption of macronutrients outside the ADMR may lead to increased risk for chronic disease and insufficient intakes of essential nutrients.

There are exceptions to the AMDR for carbohydrate and fat macronutrients, but not for protein. Diet exceptions include the ketogenic diet, where fat makes up the majority of the diet, or in plant-based diets, where carbohydrates may make up more than 65 percent of the diet. Either of these diets can result in health benefits.

Protein intake exceeding the AMDR or 35 percent of calories doesn’t show these same benefits, and can lead to protein poisoning.

The recommended daily allowance (RDA) for protein is 0.8 grams per kilogram (0.36 grams per pound) of bodyweight. This is the amount necessary to meet the basic needs of the body.

However, recommendations for protein needs will vary depending on your:

  • height
  • weight
  • activity level
  • health status

Protein needs typically range from 1.2 to 2.0 grams per kilogram of bodyweight.

Treating protein poisoning is fairly simple. It involves simply consuming more fats and carbohydrates, and decreasing intake of protein. Finding a healthy balance of the macronutrients as discussed above is recommended.

Decreasing protein intake to no more than 2.0 grams per kilogram of bodyweight — while also including a moderate amount of healthy fats and carbohydrates in the diet — can treat protein poisoning, increase fiber intake, and promote overall well-being. Balance is key.

Most high-protein diets, including Atkins, keto, and paleo, encourage higher fat intake and some carb intake, so protein poisoning is unlikely.

Eliminating fats and carbs altogether isn’t recommended. It’s important to find a diet that works for you and your lifestyle and ensure there are no nutrient gaps that need to be filled.

When kidney functioning is insufficient and the body isn’t able to metabolize protein, a toxicity can occur. This is different than protein poisoning.

Protein poisoning is due to excessive protein intake without carbs and fat balancing out nutrients. Protein toxicity is the buildup of protein metabolic wastes due to under-functioning kidneys.

Protein toxicity is common in people with kidney disease who consume more protein than their body can handle.

Overall, protein poisoning is rare. However, due to the many diets promoting high protein, it’s something to be aware of.

If you have specific questions about how much of each macronutrient you need to support your current activity level and health needs, speak with a registered dietitian. Your needs will vary based on a number of factors.

Although protein is necessary for optimal functioning, there is such a thing as having too much of a good thing, particularly if other macronutrients are missing.