What Epic found. Epic Research looked at 11,469 US adults aged 18 to 44 who had a first colorectal cancer screening between January 2017 and March 2025, matching each case to controls on age, sex, lab timing and screening year. An AST below 14 U/L was linked to a 65% higher likelihood of an early-onset colorectal cancer diagnosis, and an ALT below 14 U/L to a 68% higher likelihood, compared with values of 14 to 29 U/L. Values of 30 U/L or higher went the other way: 22% lower for AST and 29% lower for ALT. A rise in either enzyme over three years was associated with roughly 26% to 27% lower likelihood.
Read the design before the percentages. Everyone in the study had a screening, so the comparison is between screened people, not between people with and without cancer in the general population. The page gives no absolute rates and does not say why each person was screened. It reports relative likelihood only. The 14 and 30 U/L cut points are the analysts’ categories. They are not laboratory reference limits, and the page does not say whether it was peer reviewed.
The authors name their own explanation problem. Epic writes that low AST and ALT can be markers of other underlying conditions, such as reduced muscle mass or poor nutritional status, and that accounting for them cannot fully rule that possibility out. The analysis adjusted for age, sex, BMI, weight trajectory, smoking, alcohol use disorder, diabetes, hypertension, fatty liver disease, malnutrition, insulin use, statin use, race and ethnicity, and insurance type. A low enzyme may be marking a person’s muscle and nutritional state, and the study cannot separate that from a link to the tumor itself.
The direction is not new, and neither are the caveats. In a 2020 UK Biobank cohort study in the International Journal of Cancer, He and colleagues followed 375,693 people for a median of 10 years and recorded 2,662 colorectal cancers. Higher ALT, AST, GGT, total protein and albumin, largely within the normal range, went with lower risk. Epic’s under-45 result points the same way. Both are observational, and neither shows that changing an enzyme changes risk.
What a low ALT looks like on your report. Our comprehensive metabolic panel guide gives a typical laboratory reference of ALT below 40 U/L. A 12 U/L sits under that limit and prints as normal. This study is not a reason to treat that number as a finding.
What to do with it. Do not try to raise your enzymes. The study did not test that, and an association in either direction cannot show it would help. The NHS lists bleeding from the bottom or blood in the stool, a lasting change in bowel habit, abdominal discomfort or a lump, bloating, unexplained weight loss, and feeling very tired or short of breath. Any of those is a reason to see a GP, whatever your ALT says. If your enzymes are low and you feel well, nothing in this study asks you to do anything.
To see how ALT and AST are normally read, including the high side, see the liver function test guide. For the blood test the FDA has approved for colorectal cancer screening, see what the SimpleScreen approval does and does not catch.