Of the three macronutrients — protein, carbohydrates and fat — protein has a pretty stellar reputation. Hey, proteins aren't called the "building blocks of life" for nothing. But eating too much protein can cause symptoms for some.
Luckily, being deficient in protein is almost unheard of in the U.S., according to the Physicians Committee for Responsible Medicine. That's good, because you need it in your diet to make and repair your cells, per the U.S. National Library of Medicine (NLM).
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David Buchin, MD, director of bariatric surgery at Huntington Hospital and founder of Long Island Obesity Surgery, says most adults need just 40 to 50 grams per day.
The daily protein intake for toddlers and kids varies based on age, per the Cleveland Clinic. For instance, how much protein a 1-, 2- or 3-year-old needs is different than how much protein a 4-year-old needs (more on that in a moment).
But when it comes to protein, it's possible to have too much of a good thing. Overloading on the nutrient can potentially lead to some unpleasant side effects.
So, are you eating too much protein? Well, it's possible: According to a 2015-2016 survey from the USDA, people assigned male at birth (AMAB) eat an average of 97 grams per day, while those assigned female at birth (AFAB) get 69 grams.
Here's what happens if you eat too much protein, including seven common signs of too much protein in your diet.
How Much Protein Should You Eat Per Day?
According to the Food and Nutrition Board, Institute of Medicine, National Academy of Sciences, here's how many grams of protein children and adults should eat every day:
- 0 to 6 months: 9.1 g
- 6 to 12 months: 11 g
- 1 to 3 years: 13 g
- 4 to 8 years: 19 g
- 9 to 13 years: 34 g
- People AFAB ages 14 to 18 years: 46 g
- People AMAB ages 14 to 18 years: 52 g
- People AFAB ages 19 and older: 46 g
- People AMAB ages 19 and older: 56 g
- People who are pregnant or lactating: 71 g
1. You’re Dehydrated
Dehydration is one side effect that can occur when protein consumption is in excess of your body's needs.
Indeed, even if your water intake hasn't changed at all, you could feel dehydrated as a result of eating a diet rich in meat, eggs, Greek yogurt and other high-protein foods, says Alicia Galvin, RD, LD, resident dietitian for Sovereign Laboratories.
The most likely reason is that a high-protein diet could lead to elevated nitrogen levels, per the Mayo Clinic.
"One of the components of protein is nitrogen," Galvin says. "And if you're eating too much protein, the body will try to flush out that extra nitrogen, which will lead to flushing out water and increasing urination."
That can lead to dehydration, Dr. Buchin says, whose bariatric patients mostly follow a high-protein diet. "You become dehydrated because you're losing a lot of water when you urinate all that nitrogen out," he says.
To avoid the symptoms of eating too much protein, stick to the daily recommended amounts and make sure no more than 35 percent of your daily calories come from protein, per the NLM.
2. You’ve Got a Headache and You Feel Weak
Headaches and general fatigue are two other potential side effects that can set in if you're dehydrated from eating too much protein, Galvin says.
These symptoms from too much protein also can come about as a result of the body being in ketosis, Dr. Buchin says. "When you're on a mostly protein diet, you are ketonic," he says.
Ketosis is a metabolic state that happens when the body relies on fat for fuel rather than sugar from carbohydrates, according to UChicago Medicine. It's the goal behind the keto diet.
"You feel weak because you don't have a lot of sugar in your body," Dr. Buchin says. "You feel really tired because there really is no sugar left. You've burned all of your sugar stores."
3. Your Breath Stinks
On your high-protein shopping list: chicken, almonds, eggs — and breath mints? It may be a good idea, because many people report dealing with nasty breath as a result of a high-protein diet.
The scent is pretty unmistakeable, too: "It smells like rotten fruit," Dr. Buchin says.
That's likely because a body in ketosis can produce acetone, the same ingredient found in nail polish remover. The presence of the ketone acetone in the breath can even be an indicator that a person is in ketosis, per a small April 2015 study in Nutrition Journal.
Galvin says that two amino acids found in protein may also be to blame.
"It could be because two of the amino acids that are used in the mouth and by the bacteria to make the bad breath are these sulfur-containing amino acids: cysteine and methionine," Galvin says. "So when people consume protein, they have certain types of bacteria that are going to convert amino acids into those sulfur compounds, and that can lead to bad breath."
4. You Feel Constipated
If you're eating a lot of protein, chances are you're cutting back in another area of your diet. Take a popular high-protein diet like Atkins, for instance. It calls for eating lots of protein and severely restricting carbs. Per the Mayo Clinic, that means you could be missing out on fiber, which can lead to constipation.
According to the Mayo Clinic, here's how much fiber adults should get every day:
- People AFAB: 21 to 25 g
- People AMAB: 30 to 38 g
Eating fiber-rich foods, such as whole grains and legumes, can help produce softer, more bulky stool, which helps prevent and relieve constipation.
Constipation can also happen when you add protein back into your diet — for example, vegetarians and vegans who begin eating meat again, Galvin says.
Dehydration is another common cause of high-protein diet poop problems like constipation. Your kidneys have to work harder to rid the body of waste products from protein digestion, and they rely on water to do their job efficiently, according to the American Kidney Fund. Combined with low fiber intake, this can cause a noticeable change in your bowel habits.
How Much Water Should You Drink Per Day?
Stay hydrated by using this equation to determine how much water you should drink every day:
- Body weight (in pounds) ÷ 2 = minimum ounces of water you should drink per day.
5. You Have Diarrhea
Constipation isn't the only bathroom issue you may deal with on a high-protein diet. Indeed, protein does make you poop in some situations: For instance, too much protein can cause diarrhea.
So, why does protein make you poop? Well, a high-protein diet alone isn't necessarily to blame. Rather, it's the type of protein you eat that can make you poop.
For instance, food sensitivities are a leading cause of diarrhea, and dairy products are among the more common culprits, according to the Mayo Clinic. Many people don't make enough of the digestive enzymes needed to digest the lactose in dairy, which leads to digestive distress, including that protein diarrhea.
A lot of whey protein can make you poop for the same reason: Many whey supplements contain lactose, which can cause diarrhea for some, according to the Mayo Clinic. The amount of lactose can vary from brand to brand, so check the label to determine if a particular product is right for you
Another reason protein might make you poop more is that many foods rich in the nutrient are also high in fat, which can contribute to diarrhea, per Harvard Health Publishing.
For example, if you eat a lot of red meats, bacon, cheese or other fatty or fried foods, too much of these proteins do cause diarrhea for some.
To avoid diarrhea from too much protein and fat, opt for leaner sources of the nutrient, such as:
- Legumes like beans and lentils
Does Protein Help You Poop?
While a high-protein diet does make you poop more or can give you diarrhea in certain contexts, eating a lot of protein to make yourself poop isn't the solution for issues like constipation.
Instead, incorporate fibrous foods into your diet to help normalize bowel movements and soften your stool, according to the Mayo Clinic.
6. You're Gaining Weight
Another possible effect of too much protein is weight gain. This may be the case if you're replacing nutrients like carbohydrates with protein, according to April 2015 research in Clinical Nutrition, which found that such high-protein diets were linked to higher risk for weight gain.
What's more, getting too much protein from sources like red meat, fried foods or full-fat dairy products may not support weight loss or maintenance, per the Mayo Clinic.
Accordingly, make sure the protein you eat is quality. The Mayo Clinic recommends:
- Soy products like tofu and tempeh
- Skinless poultry
- Low-fat dairy products like skim milk or low-fat yogurt
Eating too much protein can also mean you're taking in too many calories. And here's what happens to excess protein in the body: It's stored as fat, according to the Mayo Clinic.
7. You’re Dealing With Kidney Stones
For most people, the symptoms of too much protein listed above aren't a huge deal. But if you have kidney issues, eating too much protein could be something to worry about.
"The biggest thing is long-term kidney damage from having very high protein for an extended period of time," Galvin says.
There are a few reasons why. Eating too much animal protein — as in meat, eggs and seafood — could increase your body's levels of uric acid, which could then lead to the development of kidney stones, per Harvard Health Publishing. A high-protein diet also decreases the body's levels of urinary citrate, which is a chemical that keeps kidney stones from forming.
Plus, eating a lot of protein tells the body to excrete calcium, which may also lead to the formation of kidney stones, according to the National Kidney Foundation.
How Much Protein Is Too Much?
Now you know what happens if you get too much protein. But unfortunately, there isn't a straightforward answer to how much protein you should eat per day, because it depends on a person's age, body weight and lifestyle.
"Generally, the rule of thumb is 0.8 grams of protein per kilogram of body weight," Galvin says. "With that, you'll be hitting most of your needs."
Keep in mind that 1 kilogram equals 2.2 pounds. So, for example, a 140-pound person should eat about 51 grams of protein each day. But some people will need more.
"If you're very physically active, you're an athlete or you're working out on a regular basis, that'll increase to 1.2 to 1.7 grams of protein per kilogram," Galvin says. "Sometimes it's even higher, like if someone's a professional athlete. There's a range."
How high you can go safely is a different story, and there's no agreed-upon limit. "It's very dependent on the size of the patient, how much exercise that person is doing and how much muscle mass that person has," Dr. Buchin says.
A review from March 2016 in Food & Function concluded it's OK to eat 1 gram of protein per pound of body weight per day. In the example of the 140-pound person, then, that'd be 140 grams of protein in a day.
Harvard Health Publishing puts the limit at 2 grams per kilogram of body weight, which is 125 grams per day for that 140-pound person.
When you take your whole diet into account and consider what happens if you take too much protein, no more than 35 percent of your daily calories should come from protein, per the NLM.
But taking in more than that shouldn't become a habit. That's because a consequence of excess protein intake is that, over time, it can lead to digestive, kidney and blood health issues, according to the Food & Function review.
What's more, certain high-protein diets (like those high in red meat) can up your risk for cancer and heart disease, according to April 2012 research in JAMA Internal Medicine. It can also increase your odds of developing bone disorders like osteoporosis, as well as kidney and liver problems, per January 2013 research in International Scholarly Research Notices.
And what happens if a child has too much protein? Like adults, it is bad for children to get too much protein (particularly from supplements) because it can cause side effects like weight gain, digestive issues and kidney problems, according to the Cleveland Clinic.
Instead, focus on feeding your kid the correct recommended daily dose of natural protein sources like legumes, low-fat dairy, nuts and poultry.
The good news is that most of the symptoms covered above will clear up as soon as you reduce your protein and eat more carbohydrates. "Drink some Gatorade," Dr. Buchin says. "That will give you more energy and will make you feel a lot better and stop that ketosis process."
- U.S. Department of Agriculture (USDA): "What foods are in the Protein Foods Group?"
- Physicians Committee for Responsible Medicine: "Protein"
- USDA: "Protein Intake of Adults"
- UChicago Medicine: "Ketogenic diet: What are the risks?"
- Nutrition Journal: "Acetone as Biomarker for Ketosis Buildup Capability - A Study in Healthy Individuals Under Combined High Fat and Starvation Diets"
- Mayo Clinic: "Are High-Protein Diets Safe for Weight Loss?"
- Mayo Clinic: "Dietary Fiber: Essential for a Healthy Diet"
- Harvard Health Publishing: "5 Steps for Preventing Kidney Stones"
- National Kidney Foundation: Kidney Stone Diet Plan and Prevention
- Food & Function: "Dietary Protein Intake and Human Health"
- Harvard Health Publishing: "When It Comes to Protein, How Much is Too Much?"
- U.S. National Library of Medicine: "Protein in Diet"
- JAMA Internal Medicine: "Red Meat Consumption and Mortality"
- International Scholarly Research Notices: "Adverse Effects Associated with Protein Intake above the Recommended Dietary Allowance for Adults"
- American Kidney Fund: "Kidney diet and foods for chronic kidney disease (CKD)"
- Mayo Clinic: "Food intolerance or food allergy?"
- Mayo Clinic: "Whey protein"
- Harvard Health Publishing: "Is something in your diet causing diarrhea?"
- Clinical Nutrition: "High dietary protein intake is associated with an increased body weight and total death risk"
- Mayo Clinic: "Are you getting too much protein?"
- Cleveland Clinic: "Why Extra Protein for Your Child Is Unnecessary – and Possibly Dangerous"
- Food and Nutrition Board, Institute of Medicine, National Academy of Sciences: "Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes, Total Water and Macronutrients"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.