You have high hopes that your new diet will help you lose fat or build muscle, or both. What you didn't wish for is the frequent urination during a high-protein diet. Unfortunately, increased protein does lead to increased urine output, and it's not always safe in the long term.
High-Protein Diet and Urine
Protein and is made up of long chains of amino acids, which your body must break down in order to reassemble them into the proteins that make up the body's tissues and also circulate in the blood and other fluids. The body uses digestive juices and enzymes to break down the protein into smaller and smaller pieces and finally into individual amino acids.
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From the intestine, the amino acids travel through the bloodstream to the liver, the "checkpoint" for amino acid distribution and further processing. Amino acids are composed of atoms, the most prevalent of which are carbon, hydrogen, oxygen, nitrogen and sulfur, according to Princeton University.
Further breakdown of nitrogen releases ammonia, which is toxic, so the liver converts it to urea. Urea is a molecule containing two nitrogens, and it is highly water-soluble, so it is an efficient method for the body to dispose of excess nitrogen.
When protein intake is normal, the demand for urea excretion isn't as high, which results in a normal urine output. However, increased protein consumption requires an increase in urea excretion — hence, more frequent urination during a high-protein diet.
Increased Risk of Dehydration
For most people, increased urea production and more frequent urination during a high-protein diet don't pose much of a problem, at least not in the short-term. In healthy adults, the most common problem is dehydration. Increased urine production requires increased fluid intake.
One common recommendation is about 64 ounces of fluids per day. However, Mayo Clinic says women need 92 ounces of fluids and men need 124 ounces of fluids each day. About 20 percent of this amount comes from food, but the rest should come from water and other unsweetened beverages.
However, if you have increased your protein intake, you will need more fluids than this; otherwise, you risk dehydration. Signs and symptoms of dehydration include:
- Excessive thirst
When you get to a point of dehydration, your urine may appear a dark brown color and urination may be less frequent. But this means that your body is not able to adequately excrete wastes, including urea. According to Michigan Medicine, both dehydration and a high-protein diet can increase your blood urea nitrogen levels.
Even in healthy people, dehydration — especially chronic or severe — can lead to kidney damage. For people with existing kidney disease, even mild dehydration is a risk factor for progression of the disease, according to a review published in Annals of Nutrition & Metabolism in June 2015. This is one of the reasons people with kidney disease should not eat a high-protein diet, unless you're on dialysis.
Read more: 7 Popular Protein Myths Totally Busted by Science
Potential Protein Problems
Another reason that people with kidney disease should avoid a high-protein diet is that kidneys that aren't functioning properly can't effectively get rid of excess urea. When urea builds up in the bloodstream, it results in loss of appetite and fatigue, according to the National Kidney Foundation. In addition to more frequent urination and dehydration, chronic high protein intakes, especially animal protein, may have other deleterious effects.
A research review and meta-analysis published in May 2014 in the journal PLOS One found that high-protein diets were associated with increased glomerular filtration rate, blood urea, urinary calcium excretion and blood concentrations of uric acid, all of which increase the risk of kidney disease. The researchers concluded that high-protein — especially animal protein — weight-reduction diets for people with obesity should be handled with caution, due to increased risk of kidney disease in that population.
A high-protein diet containing a lot of red meat, and charred, fried and processed meats, also increases the risk of breast, stomach, colorectal and stomach cancers, according to the Osher Center for Integrative Medicine at the University of California San Francisco. Research also has shown that high egg consumption may increase the risk for prostate, breast, ovarian, colon and bladder cancers.
Additionally, Harvard Health Publishing reports that a high animal protein intake can increase the risk of high cholesterol and cardiovascular disease.
Benefits of a High-Protein Diet
For healthy people, a well-planned diet that includes extra — but not excessive — protein can be safe and effective. Research shows that a diet higher in protein can aid weight loss by enhancing satiety and helping dieters reduce their calorie intake.
Protein digestion induces the release of hormones in the gastrointestinal tract that send satiety signals to the brain. Protein intake may also lower brain-reward mechanisms, according to a research review published in Advances in Nutrition in May 2015. When the central mesolimbic reward system is activated, it generates a pleasurable sensation and encourages the motivation for food consumption. When it is suppressed, hunger sensations decrease.
The dietary reference intake (DRI) of protein for the general population, established by the Food and Nutrition Board of the National Academies of Medicine, is 0.8 grams of protein per kilogram of body weight.
According to a summary published in the American Journal of Clinical Nutrition in June 2015, over 60 nutrition scientists and educators who convened at the Protein Summit 2.0 in Washington, D.C., in 2013 suggested that an intake of 1.2 to 1.6 grams of protein per kilogram of body weight per day is ideal for weight loss.
In a study published in Obesity Facts in June 2017, participants who ate a diet providing 1.34 grams of protein per kilogram of body weight daily lost significantly more weight than those who ate a standard protein diet based on the DRI.
People who exercise regularly and intensely, especially strength-trained athletes, need more protein than sedentary people or those who exercise infrequently or at a low intensity. Intense exercise breaks down muscle fibers, and the body needs extra protein to repair the damage and rebuild the muscles stronger and larger.
According to the International Society of Sports Nutrition Position Stand: Protein and Exercise, 1.4 to 2 grams per kilogram of body weight is a more appropriate daily protein intake for healthy, exercising individuals.
Healthy High-Protein Dieting
There is such a thing as too much of a good thing. Eating too much protein will crowd out other foods and nutrients you need for good health and increase your risks of the adverse effects associated with high protein intakes. According to Harvard Health Publishing, if you aren't an elite athlete or bodybuilder, there is no reason to eat more than 2 grams of protein per kilogram of body weight each day.
But more important than the amount you eat is what you eat. For good health, everyone should reduce their consumption of red meat and avoid charred, fried and processed meats. Lean poultry, fish, eggs in moderation and low-fat dairy are the best animal sources of protein. But a healthy diet should also include plant protein, such as beans, nuts and seeds.
When choosing animal proteins, UCSF recommends buying the best quality you can find, which will lower your exposure to environmental carcinogens, antibiotics and hormones. Meat, dairy and eggs from 100 percent grass-fed, pasture-raised animals are higher in heart-healthy omega-3 fatty acids and lower in cholesterol, which reduces the inflammatory effects of foods that can cause cancer and other diseases.
- LibreTexts: "5.4: Protein Digestion, Absorption and Metabolism"
- Princeton University: "Proteins"
- Mayo Clinic: "Water: How Much Should You Drink Every Day?"
- Mayo Clinic: "Dehydration"
- Michigan Medicine: "Blood Urea Nitrogen"
- Annals of Nutrition & Metabolism: "Mechanisms by Which Dehydration May Lead to Chronic Kidney Disease"
- National Kidney Foundation: "Low-Protein Recipes"
- PLOS One: Comparison of High vs. Normal/Low Protein Diets on Renal Function in Subjects Without Chronic Kidney Disease: A Systematic Review and Meta-Analysis
- Osher Center for Integrative Medicine at the University of California San Fransisco: "Animal Protein and Cancer Risk"
- Harvard Health Publishing: "When It Comes to Protein, How Much Is Too Much?"
- Advances in Nutrition: "Controversies Surrounding High-Protein Diet Intake: Satiating Effect and Kidney and Bone Health"
- National Academies of Medicine: "Summary Tables, Dietary Reference Intakes"
- American Journal of Clinical Nutrition: "Introduction to Protein Summit 2.0: Continued Exploration of the Impact of High-Quality Protein on Optimal Health"
- Obesity Facts: "Effect of a High-Protein Diet Versus Standard-Protein Diet on Weight Loss and Biomarkers of Metabolic Syndrome: A Randomized Clinical Trial"
- Journal of the International Society of Sports Nutrition: "International Society of Sports Nutrition Position Stand: Protein and Exercise"