Low Liver Enzyme Levels May Signal Higher Colorectal Cancer Risk In Adults Under 45
This finding lands at a moment when colorectal cancer rates have been climbing in adults under 50 by close to 3% every year, even as rates have declined slightly in older populations. Data shows 1this rise has been building since the 1990s across the U.S. and other high-income countries, in contrast with the steady decline in cases among people over 50. The U.S. Multi-Society Task Force on Colorectal Cancer2 even the recommended screening age to 45 for people at average risk, a shift also reflected in current CDC guidance3.
In light of this, researchers have been on the hunt for anything that might flag risk sooner, and a new analysis of more than 11,000 adults under 45 found it in an unexpected place: the standard liver panel.
A quick primer on the liver panel
AST (aspartate aminotransferase) and ALT (alanine aminotransferase) are two enzymes measured on the liver panel that comes with routine bloodwork. Most people don't give them a second thought unless a value comes back high, which is typically read as a sign of liver stress.
This analysis looked specifically at these two molecules, considering anyone in the range of 14 to 29 U/L to be part of the control group, and anyone under 14 U/L to be in the low, variable group. The authors note that a low reading of these live enzymes often reflects reduced muscle mass or poor nutritional status rather than anything about the liver itself.
What the new data shows
The Epic Research analysis included 11,469 U.S. adults ages 18 to 44 who were undergoing their first colorectal cancer screening. Among this group, having a pre-screening AST level below 14 U/L was linked to a 65% higher likelihood of an early-onset colorectal cancer diagnosis. Having an ALT level below 14 U/L was linked to a 68% higher likelihood.
Those comparisons come from actual diagnoses, not screening results alone. Researchers compared enzyme levels drawn in the three years before screening against those who went on to receive a CRC diagnosis within one year of that screening. Participants in the study had both lab results and a completed screening on file, which may tilt the group toward people who see a doctor more often and limits how widely the numbers apply.
Still, this comes as a surprise, since we're used to hearing that elevated liver enzymes are the ones worth worrying about. A link running in the opposite direction is worth some attention, even if this analysis only found an association between CRC diagnoses and liver enzymes, not a biological reason that shows these enzymes cause cancer.
What to actually do with this information
One lab value on one blood panel isn't a diagnosis, and low AST or ALT by itself isn't cause for alarm. Liver enzymes should be treated as one more piece of information within a bigger risk profile when it comes to CRC, especially for those under 45. Here are some other things to think when it comes to preventing early-onset CRC:
- Know your family history: A parent or sibling with colorectal cancer, or a personal history of inflammatory bowel disease, raises risk regardless of age.
- Don't dismiss symptoms because of your age: Persistent changes in bowel habits, rectal bleeding, unexplained abdominal pain, or unintended weight loss, are symptoms worth bringing to a doctor at any age.
- Ask about screening timing: If you're approaching 45, or you have risk factors that might warrant earlier screening, talk to your doctor about when to start.
- Watch how diet patterns matter: Emerging research on diet and colon cancer risk suggests what you eat plays a role in risk, even before age 50.
- Bring up your labs: If your AST or ALT levels come back low, mention it to your doctor rather than assuming it's a non-issue, especially if you have other CRC risk factors.
The takeaway
While high values are typically flagged on blood work panels and lab reports, this study shows us low values deserve the same curiosity. And remember, results from a single blood draw are rarely enough to make a sweeping health claims. Patterns found in panels done across several years tells you more than any single draw.
If you are concerned about colorectal cancer or notice low liver enzyme number, ask your doctor to walk you through your full liver panel and how those numbers have shifted at your next appointment. Know that liver numbers have a place in the prevention conversation alongside symptoms and family history, and that science in this area is moving quickly. The options we have to prevent, diagnose, and treat colorectal cancer are evolving everyday.