Collagen is the most abundant structural protein, providing strength to skin, bones, and connective tissues. Many people consume collagen in supplement form to support these tissues as natural production declines with age. An unexpected result of this increased intake is a change in urine odor, leading many to question if the supplement is the direct cause of a stronger smell. The answer is not that collagen itself smells, but rather that the body’s natural process for handling the extra protein can alter the scent of waste products.
The Breakdown of Collagen in the Body
The large, complex structure of a whole collagen molecule cannot be absorbed directly into the bloodstream. Ingested collagen must first be disassembled by the digestive system, starting in the stomach and continuing in the small intestine. Digestive enzymes, such as proteases, break the protein down into its constituent parts.
Most commercial supplements are already “pre-broken” into shorter chains of amino acids, known as collagen peptides or hydrolyzed collagen, to increase bioavailability. These smaller fragments are efficiently absorbed through the intestinal lining. Once absorbed, these amino acids and short peptides enter the bloodstream and are distributed throughout the body to be used for various functions, including building new proteins. This process introduces a higher load of protein components into the body’s metabolic pathways.
Protein Metabolism and Changes in Urine Odor
The consumption of collagen supplements adds a significant amount of protein to the diet, and it is the subsequent processing of this excess protein that can influence urine odor. Protein is composed of amino acids, which all contain a nitrogen group. When the body has more amino acids than it needs for tissue repair or synthesis, it must break them down for energy or excretion.
This breakdown involves a process called deamination, where the amino group is removed from the amino acid. The carbon-containing skeleton can be used for energy, but the nitrogen component must be safely eliminated from the body. The removed nitrogen group is initially converted into ammonia, which is highly toxic in large concentrations.
To neutralize this compound, the liver quickly converts the ammonia into urea through a biochemical pathway known as the urea cycle. Urea is a less toxic, nitrogenous compound that the kidneys can safely filter out of the blood. The concentration of urea in the urine is directly proportional to the amount of protein that has been metabolized.
A higher intake of protein results in a greater amount of urea needing to be excreted. While urea itself is virtually odorless, it can decompose into ammonia once it is passed. This decomposition creates the pungent, “ammonia-like” odor associated with high protein diets. The stronger smell is a benign sign that the body is processing the extra protein load effectively and eliminating nitrogenous waste.
Non-Collagen Causes of Strong Urine Smell
While a high protein intake from collagen can change urine odor, many other factors unrelated to supplements can cause a strong or unusual smell. One of the most common causes is dehydration, which concentrates the urine and increases the ratio of waste products to water. When urine is highly concentrated, the natural ammonia component becomes much more noticeable.
Certain foods are well-known to alter urine odor due to the sulfur-containing compounds they release during digestion. Asparagus is the most famous example, as its asparagusic acid breaks down into volatile sulfur compounds that some individuals can smell shortly after consumption. Other pungent foods like garlic, onions, and coffee can also contribute to a distinct scent profile in the urine.
Additionally, various supplements can affect urine odor, most notably B vitamins, which are water-soluble and excreted in excess, often leading to a bright yellow color and a distinct, musty scent. Medications, particularly some antibiotics, can also temporarily impart a noticeable smell to the urine.
Medical Causes of Odor Changes
A persistent, unusually foul, or sweet odor may indicate a medical issue requiring professional attention. A sweet or fruity scent can signal uncontrolled diabetes due to the presence of ketones. A strong, ammonia-like or foul odor, sometimes accompanied by pain or increased frequency, can be a sign of a urinary tract infection (UTI). Consulting a healthcare provider is recommended if the change in odor is sudden, severe, or does not resolve with increased hydration.