High-protein diets, also known as low-carbohydrate diets, are generally used for weight reduction. Many forms of high-protein diets exist. Examples include Atkins and the Zone diets. These diets emphasize the intake of high levels of protein and fat--in the form of meat, eggs, fish, most dairy products and low-carb vegetables--while minimizing carbohydrate intake. While on these diets, some people experience frequent urination.
Metabolism and Body Chemistry
The increase in available protein in the body causes metabolic and body chemistry changes. These changes produce waste products in the form of water, urea and ketones that, over time, build up within the bloodstream. As they increase, the body will attempt to eliminate them by excreting them through urine.
Glycogen Metabolism
When a high-protein diet is started, and carbohydrate intake is significantly reduced, the body will begin to metabolize stored glycogen as fuel. Glycogen holds large quantities of water. As the amount of glycogen in the body is reduced, that water is released into the bloodstream. Consequently, the body will eliminate that water through the kidneys, and the frequency of urination increases.
Urea Nitrogen Production
The increase in protein in the diet can also result in higher blood urea nitrogen levels. The body will then do its best to eliminate this waste product by increasing the level of output from the kidneys. This results in increased urinary frequency and may even lead to dehydration in extreme cases.
Ketone Production
Another effect of high-protein diets is the production of ketones, which are chemicals that result from the breakdown of fat stored in the form of triglycerides within fat cells. These ketones can be used as fuel for most of the body. The brain and nervous system, however, run exclusively on glucose. Protein within the body, in the form of food and muscle, is then broken down to obtain glucose. This will also trigger ketones to continue to increase in the body, producing a condition called ketosis. The increase in ketones is irritating to the kidneys. To reduce this irritation, the kidneys will increase urinary output, resulting in more frequent urination.
Risks
Excessive nitrogen and ketones in the bloodstream from high-protein diets have been shown to cause kidney damage. The risk of kidney stones can also increase. Individuals with kidney disease should consult with a physician before beginning a high-protein diet.
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