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What happens when you eat too much protein, and how much is healthy

Gabby Landsverk,Samantha Cassetty   

What happens when you eat too much protein, and how much is healthy
LifeScience6 min read
  • It is possible to each too much protein — if more than 35% of your daily calories come from protein, you might experience side effects.
  • Eating too much protein can worsen kidney problems, and over time can cause symptoms like bad breath, indigestion and dehydration.
  • Certain sources of protein like meat, dairy, and processed foods can increase the risk of chronic illnesses like heart disease and cancer.

Protein is an essential nutrient for regulating cell function, building tissue, and helping your blood carry oxygen throughout the body. However, it's possible to eat too much protein which can overload your liver and kidneys and cause some other minor side effects like bad breath and appetite loss.

Not getting enough protein can lead to fatigue, brain fog, hunger, and slower recovery from illness and injury. It can also cause loss of muscle mass, particularly in the elderly.

On the other hand, it's possible to experience side effects from getting too much protein, particularly if you have kidney problems.

It's important to know which sources of protein are better than others for avoiding health risks. What's more, there are ways to gauge if you're getting the right amount of protein, how to tell if you're getting too much, and when to see a doctor.

How much protein do you need?

In general, a person should get at least 0.36 grams of protein per pound of body weight per day. However, protein needs will vary depending on factors including age, lifestyle, and gender:

For example, a moderately active adult woman who works out for 2-3 hours a week and weighs 130 pounds would need between 70 to 118 grams of protein a day for health.

Is eating too much protein bad for your health?

Eating too much protein isn't a problem for most people, but if you do consistently overdo it for long periods of time, it can eventually overload your digestive system, liver, and kidneys leading to problems like:

  • Dehydration
  • Fatigue
  • Headaches
  • Digestive distress
  • Seizures

How much protein is too much? If more than 35% of your daily calories are coming from protein, that's when it's time to reconsider your diet.

Research suggests that it's safe to eat as much as 1 gram of protein per pound of body weight per day in the long term. And certain people (including athletes) can safely consume up to 1.6 grams per pound per day. That's equal to up to 35% of daily calories from protein, or as much as 219 grams of protein per day on a 2,500 calorie diet.

For most people who are otherwise healthy, too much protein isn't likely to be an issue.

"Your body will use what it needs for structural maintenance and tissue turnover, and the rest can be burned for energy," registered dietitian and sports nutritionist Georgie Fear told Insider.

All protein is broken down into amino acids. If you eat more than you can use, your body can't store the extra, so it's processed and ultimately excreted in your urine, says Fear. Extra calories from protein, though, can be stored as fat if not used.

Most people consume well within the recommended range for protein intake, according to Allison Knott, a registered dietitian based in Brooklyn, New York.

"On average, most people aren't coming close to the upper end of the protein range of 35%," she told Insider.

More than that, however, can cause problems like dehydration, fatigue, headaches, digestive distress, and even seizures, from overloading the digestive system, liver, and kidneys.

In particular, people with kidney problems should avoid excess protein, since it can cause extra stress on the kidneys by forcing them to break down and filter out whatever your body can't use. Research has also linked excess protein intake to higher risk of kidney stones in people with a family history of renal disease or who get most of their protein from animal sources.

Signs that you're eating too much protein

Most people don't have to worry about serious health risks from eating too much protein, but you may experience minor side effects:

Bad breath: Excess protein can sometimes cause bad breath, due to bacteria breaking down the protein and emitting odors that can smell like cabbage or rotten eggs.

GI issues: Eating too many protein-rich foods may also mean you're missing out on other essential nutrients like fiber, since protein-rich animal products don't contain fiber. A low-fiber diet can cause digestive issues ranging from constipation, diarrhea, mild nausea, or fatigue after meals. It can also change your microbiome, the colony of beneficial bacteria and microorganisms that live in your gut.

Loss of appetite: Eating a lot of protein can also decrease appetite, says Fear, since it keeps you feeling full for longer. That can make it useful for weight-loss goals.

Weight gain: However, eating too much of anything can still lead to weight gain, so if you're consuming too many calories in the form of protein, those excess calories will be stored as fat and lead to weight gain.

When too much protein might be harmful

Eating too much protein can lead to harmful side effects if you have existing kidney problems, or a family history of renal disease or kidney stones.

Some symptoms can indicate possible kidney disease or failure, a serious and potentially dangerous health problem, according to the National Kidney Foundation.

See a doctor if you experience some combination of the following symptoms of kidney problems:

  • Fatigue
  • Frequent urination
  • Blood or foam present in your urine
  • Trouble sleeping
  • Dry, itchy skin
  • Poor appetite
  • Muscle cramps
  • Swollen legs or ankles

What's the best way to get daily protein?

"There are no 'bad' protein sources, but keep an eye on the saturated fat and calorie content of your protein sources to optimize heart health," Fear said.

Protein sources like fatty meats and some processed foods are associated with an increased risk of cancer, diabetes, and heart disease, according to the Harvard T.H. Chan School of Public Health.

In addition, be wary of protein supplements, including bars and shakes, as they can contain a lot of additives. Some brands have more than 20 grams of sugar per serving (as much as a scoop of ice cream) or contain artificial sweeteners that may be just as bad for your health in the long term.

If you do decide to supplement, find a brand you trust, read the label and ingredient list carefully, stick to the recommended serving size, and use in moderation.

There's no ideal time to eat protein, so long as you get enough, experts say, but spreading your intake out throughout the day can be helpful.

"Balancing protein in meals throughout the day has shown to be beneficial for muscle protein synthesis and maintenance of lean body mass," Knott said.

Insider's takeaway

Protein is an important nutrient for health and most people don't have to worry about getting too much. However, you should aim for healthier sources of protein such as lean meats and whole plant foods to avoid higher risk of chronic diseases. People with kidney issues should monitor protein intake carefully, since too much could cause serious health problems.