You’re probably familiar with high-protein diets, which have seen a recent resurgence since diets like Atkins and the Zone gained popularity in the 1990s. Diets such as the Caveman or Paleo diet can vary in terms of macronutrient ratios, but are typically high in protein.

While the standard ketogenic (or “keto”) diet emphasizes fat, it can also be high in protein. Even mostly or entirely plant-based diets can be high in protein.

Protein is an essential part of a healthy diet. It helps to build and repair muscle, organs, and bones. High-protein diets have also been shown to be helpful with reducing fat, losing weight, increasing satiety, or a feeling of fullness, and retaining muscle.

However, high-protein diets have also been associated with several risks that are important to be aware of and understand. Nutritional experts don’t advocate consumption to exceed the recommended daily amount.

When calculating how much total protein you currently eat or should eat, factor in protein from your diet (e.g., food and drink sources). You should also factor in supplements, if the supplements you use contain substantial amounts of protein, such as protein powder.

Continue reading to learn more about a high-protein diet.

Consuming high amounts of any nutrient for a long period of time typically comes with risks, as can be the case with protein. Overconsumption may lead to an increased risk of certain health complications, according to research.

There are potential benefits to a high-protein diet for otherwise healthy people. However, it’s important to understand the health concerns related to excess protein in the body, especially if you follow an excessively high-protein diet for an extended period.

Weight gain

High-protein diets may tout weight loss, but this type of weight loss may only be short-term.

Excess protein consumed is usually stored as fat, while the surplus of amino acids is excreted. This can lead to weight gain over time, especially if you consume too many calories while trying to increase your protein intake.

A 2016 study found that weight gain was significantly associated with diets where protein replaced carbohydrates, but not when it replaced fat.

Bad breath

Eating large amounts of protein can lead to bad breath, especially if you restrict your carbohydrate intake.

In an older registry, 40 percent of participants reported bad breath. This could be in part because your body goes into a metabolic state called ketosis, which produces chemicals that give off an unpleasant fruity smell.

Brushing and flossing won’t get rid of the smell. You can double your water intake, brush your teeth more often, and chew gum to counter some of this effect.

Constipation

In the same study, 44 percent of participants reported constipation. High-protein diets that restrict carbohydrates are typically low in fiber.

Increasing your water and fiber intake can help prevent constipation. Tracking your bowel movements may be helpful.

Diarrhea

Eating too much dairy or processed food, coupled with a lack of fiber, can cause diarrhea. This is especially true if you’re lactose-intolerant or consume protein sources such as fried meat, fish, and poultry. Eat heart-healthy proteins instead.

To avoid diarrhea, drink plenty of water, avoid caffeinated beverages, limit fried foods and excess fat consumption, and increase your fiber intake.

Dehydration

Your body flushes out excess nitrogen with fluids and water. This can leave you dehydrated even though you may not feel more thirsty than usual.

A small 2002 study involving athletes found that as protein intake increased, hydration levels decreased. However, a 2006 study concluded that consuming more protein had a minimal impact on hydration.

This risk or effect can be minimized by increasing your water intake, especially if you’re an active person. Regardless of protein consumption, it’s always important to drink plenty of water throughout the day.

Kidney damage

While no major studies link high protein intake to kidney damage in healthy individuals, excess protein can cause damage in people with preexisting kidney disease.

This is because of the excess nitrogen found in the amino acids that make up proteins. Damaged kidneys have to work harder to get rid of the extra nitrogen and waste products of protein metabolism.

Separately a 2012 study looked at the effects of low-carbohydrate, high-protein versus low-fat diets on the kidneys.

The study found that in healthy obese adults, a low-carbohydrate, high-protein weight-loss diet over two years was not associated with noticeably harmful effects on renal filtration, albuminuria, or fluid and electrolyte balance compared with a low-fat diet.

Increased cancer risk

Studies have shown that certain high-protein diets that are particularly high in red meat-based protein are linked to an increased risk of various health issues, including cancer. Eating more red and/or processed meat is associated with colorectal, breast, and prostate cancer.

Conversely, eating protein from other sources has been associated with a decreased risk of cancer. Scientists believe this could be due, in part, to hormones, carcinogenic compounds, and fats found in meat.

Heart disease

Eating lots of red meat and full-fat dairy foods as part of a high-protein diet may lead to heart disease. This could be related to higher intakes of saturated fat and cholesterol.

According to a 2010 study, eating large amounts of red meat and high-fat dairy was shown to increase the risk of coronary heart disease in women. Eating poultry, fish, and nuts lowered the risk.

A 2018 study also showed that long-term consumption of red meat can increase trimethylamine N-oxide (TMAO), a gut-generated chemical that is linked to heart disease. Findings also showed that reducing or eliminating dietary red meat reversed the effects.

Calcium loss

Diets that are high in protein and meat may cause calcium loss. This is sometimes associated with osteoporosis and poor bone health.

A 2013 review of studies found an association between high levels of protein consumption and poor bone health. However, another 2013 review found that the effect of protein on bone health is inconclusive. Further research is needed to expand and conclude upon these findings.

The ideal amount of daily protein that you should consume varies depending on a number of factors, including age, gender, activity, health, total diet and other variables.

However, in most cases, the recommended daily amount of protein for adults can be calculated based on your body weight.

For most adults with minimal physical activity, experts recommend consuming a minimum daily average of 0.8 grams of protein per kilogram (kg) of body weight.

If you exercise primarily with weights or body weight for more than one hour most days of the week, you may do well eating up to 1.2 to 1.7 grams per kg of body weight each day.

However, some people, including elite athletes, may be able to eat as much as 3.5 g per kg of body weight without any side effects.

In general, experts also believe that most healthy adults can tolerate eating 2 g of protein per kg of body weight per day over the long term.

While others believe that otherwise healthy adults can safely consume even higher levels of protein regardless of activity level, this hasn’t been extensively studied over the long term.

When you’re choosing high-protein foods, be sure to select healthier options. This can help lower your risk for some of the negative effects of a high-protein diet. Healthy sources of protein include:

  • grass-fed lean meats and pasture-raised poultry
  • wild fish
  • eggs from pastured hens
  • grass-fed and organic dairy
  • legumes
  • nuts
  • whole grains

Try to avoid high-fat meats and dairy products as well as fried or processed protein sources. Eat heart-healthy proteins instead.

It’s important that you take the risks into consideration before starting a high-protein diet to determine whether or not it’s suitable for you. Always speak to your doctor before beginning any new diet, especially if you have any health conditions.

Your doctor and dietitian can help you weigh the pros and cons of a high-protein diet based on your individual needs.

Overall, it’s important that you eat a healthy, balanced diet and engage in an active lifestyle. Align your plan for achieving your goals, whether it’s weight loss or muscle gain, in a way that’s most beneficial to your health and that you can sustain long term.