Lithocholic Acid (LCA), % of Bile Acids

This result reports lithocholic acid as a percentage of the bile acids measured in your stool. It describes the composition of that sample. The percentage can change because the amount of lithocholic acid changes, because other bile acids change, or both.

Human studies have linked altered stool bile acid profiles to inflammatory bowel disease, cirrhosis and bowel transit. But interpreting this particular percentage remains exploratory. There is no established health target or evidence that adjusting treatment to raise or lower it improves outcomes.

What the Percentage Reflects

Your liver makes primary bile acids that help you absorb fat. Most are reabsorbed in the intestine and returned to the liver. Gut bacteria transform some of those that remain into secondary bile acids. Specialized bacteria produce lithocholic acid from the primary bile acid chenodeoxycholic acid.

The bacterial step that produces LCA removes a specific chemical group from its precursor. Only some gut bacteria have the machinery for this reaction. Other bacteria can then transform LCA into related compounds, so the amount left in stool reflects several processes, including production, further breakdown and absorption.

This test uses LC-MS to separate and quantify bile acids before reporting LCA's percentage. Ordinary LCA, its glycine- or taurine-linked forms, and isolithocholic acid are distinct compounds. Findings about one cannot automatically be applied to another.

The percentage also depends on which bile acids the laboratory includes in its total. It can rise even when the LCA concentration stays unchanged, if other bile acids fall. Although expressing a result as a percentage can reduce the effect of simple dilution, it does not remove the effects of bowel transit, absorption or differences in sample preparation. It is not a direct measure of how efficiently your bacteria convert incoming bile acids.

Inflammatory Bowel Disease

A study of 62 people with inflammatory bowel disease and 17 healthy controls found a lower stool LCA percentage in the combined disease group. In ulcerative colitis, LCA concentrations were associated with looser stools and higher blood C-reactive protein. Associations with stool calprotectin involved the combined secondary bile acid pool and particular related compounds, rather than a consistent association with LCA itself.

These findings connect bile acid changes with bowel disease, but they do not establish a diagnostic role for this percentage. Inflammation, altered bacteria and faster transit can occur together. A low percentage cannot identify which process accounts for your result.

Cirrhosis and Advanced Liver Disease

A study comparing 47 people with cirrhosis and 14 controls found lower stool secondary bile acid concentrations and lower ratios of secondary bile acids to their primary precursors, especially in advanced disease. The LCA-to-chenodeoxycholic-acid ratio was associated with the abundance of some gut bacteria.

That precursor ratio is a different measurement from LCA's percentage of all measured bile acids. The findings support an association between cirrhosis and altered intestinal bile acid metabolism. They do not establish that this percentage can diagnose cirrhosis, grade its severity or distinguish reduced bile delivery from altered bacterial activity. Medicines used in advanced cirrhosis also complicate the comparison.

Fatty Liver Disease

The direction differs across studies. A study of 32 children with fatty liver disease and 36 controls found lower stool LCA concentrations, a smaller secondary bile acid fraction and a lower LCA-to-precursor ratio in the disease group.

A separate study included 199 adults with biopsy-confirmed fatty liver disease and 88 controls. Stool LCA concentrations were higher in the disease groups, but did not clearly distinguish mild from advanced liver scarring. After adjustment for body size and insulin resistance, LCA was not among the bile acids that independently distinguished advanced fibrosis.

These studies involved different populations and mostly examined concentrations or other ratios. They do not establish a desirable direction for your LCA percentage. Age, disease stage, diet, medicines and the rest of the bile acid mixture can all complicate comparisons.

Aging and Gut Barrier Function

A study comparing 100 younger adults with 100 older adults found higher stool LCA concentrations in the older group, alongside differences in gut bacteria and blood markers associated with inflammation and intestinal barrier function. It compared different people at one time, so it could not show how an individual's result changes with aging or whether LCA caused the other findings. It also measured concentrations, not this percentage. The study does not establish age-specific targets.

Colorectal Cancer

A systematic review of observational studies found no statistically clear pooled difference in stool LCA concentrations between the compared colorectal cancer risk groups. The included studies varied in design and measurement methods. This result neither settles LCA's biological role in cancer nor supports its use as a screening test.

Research in 228 colorectal tumor samples found differences in LCA between tumor locations, particularly among men. Those measurements came from tumor tissue in people who already had cancer. They do not show that an LCA percentage in stool predicts whether you will develop it.

Constipation and Diarrhea

Bile acids differ in their effects on the intestine, so a larger total amount and a larger LCA percentage are different findings. In a study of constipation-predominant irritable bowel syndrome, about 15% of the affected participants had reduced total fecal bile acid excretion. The constipation group also had a higher LCA proportion. That proportion came from a timed stool collection under a specified diet, which limits direct comparison with a routine stool sample.

Another study compared 55 people with diarrhea-predominant irritable bowel syndrome and 28 controls. It found lower stool LCA concentrations in the diarrhea group, with lower concentrations associated with more frequent stools. This was a concentration finding, not evidence that a particular percentage diagnoses diarrhea or explains its cause.

When Results Can Be Misleading

• The rest of the bile acid mixture: a change in other bile acids can change the percentage even if the LCA concentration is stable.
• Stool consistency and transit: loose stools and faster transit can accompany altered bacterial conversion and bile acid absorption. These are biological changes, not automatically false results. A low percentage in firm stool still does not prove that particular bacteria are missing.
• Medicines and recent treatment: antibiotics and bile acid medicines can substantially change the stool bile acid profile. A result obtained during or after treatment may describe that treatment period, and cannot establish what your untreated profile would have been.
• LC-MS sample preparation: extraction, calibration and separation of similar compounds affect accuracy. Other material in stool can suppress the instrument's signal unless the laboratory's method adequately controls for it.
• Which compounds are counted: laboratories may measure different sets of bile acids. Research on fatty-acid-linked bile acids largely concerns related compounds such as isolithocholic acid; it does not establish that routine assays miss a fixed fraction of ordinary LCA.
• Collection and handling: stool is unevenly mixed, and laboratories use specific sampling and preservation procedures. Differences in collection or processing can complicate comparisons.

Changes Over Time

In a study of 136 adults sampled six months apart, stool LCA concentrations varied within individuals despite good laboratory repeatability. This supports caution about interpreting one sample, but the study examined concentrations rather than this percentage.

Repeated measurements can describe a changing profile when collection and analysis are comparable. They have not been shown to establish recovery of the microbiome, measure treatment success or improve care when used to track this percentage. A trend still needs to be interpreted alongside symptoms, medicines and established tests.