![\"Default](\"https:\/\/www.newsbeep.com\/nz\/wp-content\/uploads\/2026\/09\/1789086503_711_author_avatar.png\"){kind=avatar}
<\/p>\nRoutine blood testing may hold hidden clues to colorectal cancer before age 45<\/p>\n
<\/p>\n
When you have blood drawn during a routine doctor\u2019s visit, some of the markers that get tested could hold unexpected clues to how likely you are to develop colorectal cancer at a young age, new research suggests.<\/p>\n
Related video above: Report examines increase in colorectal cancer rates among younger people<\/p>\n
Adults younger than 45 who had lower levels of two liver enzymes \u2014 aspartate transaminase, or AST, and alanine transaminase, or ALT \u2014 were more likely to be diagnosed with early-onset colorectal cancer compared with their peers in an analysis released Wednesday by Epic Research<\/a>, which is owned by the healthcare software company Epic.<\/p>\n \u201cThe direction was a little counterintuitive. Clinically, we tend to watch for high liver enzymes, so seeing that low AST and ALT were associated with a higher likelihood of early-onset colorectal cancer stood out,\u201d said Kersten Bartelt, a clinician and researcher at Epic Research who worked on the new analysis.<\/p>\n But doctors say younger adults with low AST or ALT should not panic and that there is no change to colon cancer screening recommendations.<\/p>\n The new research highlights an association but does not mean that low levels cause cancer or that people should rush to get an early colonoscopy due to low levels alone. Rather, the findings \u2014 which have not been published in a peer-reviewed journal \u2014 suggest an area to investigate to better understand the potential underlying factors in the rise in colorectal cancer among younger adults.<\/p>\n \u201cOur study shows the association but wasn\u2019t built to uncover why,\u201d Bartelt said. \u201cClinically, low AST and ALT can reflect things like lower muscle mass, frailty or nutritional factors. It\u2019s one of the questions we hope this work prompts others to investigate.\u201d<\/p>\n The new findings are striking since higher levels of AST and ALT are sometimes a sign of an unhealthy liver, and certain conditions such as liver diseases or infections can cause elevated levels. These markers are often included in routine blood testing because elevated liver enzymes may serve as early warning signs of liver injury, inflammation or disease, even before symptoms appear.<\/p>\n \u201cAST and ALT aren\u2019t values we\u2019d advise anyone to try to raise,\u201d Bartelt said.<\/p>\n \u201cAnd nothing in our study suggests that changing them would change a person\u2019s cancer risk,\u201d she said. \u201cThey likely reflect underlying physiology like muscle and nutritional status, so the focus should be on overall health in partnership with your clinician, not on moving a single lab number.\u201d<\/p>\n Along with examining AST and ALT levels, Bartelt and her colleagues examined triglyceride and cholesterol levels, as well as levels of potassium. They found that none of the other routine labs were associated with early-onset colorectal cancer.<\/p>\n Cancer rising among younger ages<\/p>\n The question of why colorectal cancer cases are increasing among younger adults has been an ongoing one within medicine. Colorectal cancer has surpassed other types to become the leading cause of cancer deaths among people under 50 in the United States.<\/p>\n \u201cWhenever there\u2019s a focus on colon cancer, particularly early-onset colon cancer, we need to figure out why. There\u2019s definitely been an increase in early-onset colon cancer, and if there are markers that point us towards the right patients to screen, that\u2019s great,\u201d said Dr. Marc Fenster, a gastroenterologist at Episcopal Health Services<\/a> in New York who was not involved in the new research.<\/p>\n \u201cThe broader conversation surrounding early-onset colorectal cancer has focused on family history and genetics, obesity and metabolic health, diet, physical inactivity, the microbiome, antibiotic exposures, and delays in recognizing symptoms in younger patients. However, none of these factors fully explains the increase in cases,\u201d Fenster said. \u201cThis study may broaden the discussion by suggesting that routinely collected metabolic and nutritional markers could contain useful clues.\u201d<\/p>\n Fenster added that although the research points to a \u201csignal\u201d and is \u201chypothesis-generating,\u201d it does not establish low AST or ALT as risk factors for early-onset colorectal cancer.<\/p>\n \u201cThe study should encourage research, but it should not change how an individual patient is screened,\u201d he said.<\/p>\n \u201cI don\u2019t want people to think they have a low AST or ALT, then all of a sudden, that means they\u2019re going to have colon cancer or they even need to do anything differently,\u201d he said. \u201cIf you don\u2019t have a family history, if you\u2019re having zero symptoms, if you\u2019re healthy, you\u2019re not losing weight, you\u2019re not having rectal bleeding, then this study doesn\u2019t change my approach to that.\u201d<\/p>\n In the United States, the clinical guidance is that everyone at average risk starts screening for colorectal cancer at age 45. People at higher risk \u2014 because of things like their own health history, a family history or symptoms \u2014 may start screening earlier. And blood testing is already an option to screen for colorectal cancer.<\/p>\n In May, for the first time, the American Cancer Society added blood-based screening tests to its list of recommended choices for adults 45 and older who are at average risk of colorectal cancer and who have not completed or who have declined visual exams and stool tests.<\/p>\n The blood-based screening test the group recommends is the Shield test<\/a>, which is not a part of routine blood work.<\/p>\n Colonoscopies are still considered the gold standard for screening, and blood testing is not the first choice for patients. Also, a positive Shield blood test is not a final diagnosis; the patient must follow up with a timely colonoscopy.<\/p>\n Blood-based tests \u201cdo not replace colonoscopy in any way,\u201d Fenster said.<\/p>\n Generating \u2018worthwhile\u2019 questions<\/p>\n To uncover what routine lab results may be associated with early-onset colorectal cancer, Bartelt and her colleagues analyzed health data on more than 11,000 people between the ages of 18 and 44 across the United States. Each adult had their first colorectal cancer screening test between 2017 and 2025 and had at least one AST or ALT test in the three years prior to screening.<\/p>\n But since regular screening for colorectal cancer is not recommended until age 45, it was unclear why patients included in the analysis had a colonoscopy or other screening test. It could have been due to a family history, symptoms or other factors putting them at high risk.<\/p>\n \u201cI would suspect that these patients are coming in with some sort of symptom, and they\u2019re having a diagnostic colonoscopy other than a screening colonoscopy,\u201d Bartelt said.<\/p>\n The researchers analyzed the data from adults who were diagnosed with colorectal cancer within a year of the screening and compared it with data from the adults who were not diagnosed with the disease.<\/p>\n The analysis showed that adults whose AST levels fell below 14 units per liter of blood had a 65% higher likelihood of an early-onset colorectal cancer diagnosis compared with peers who had levels in the range of 14 to 29. Similarly, adults whose ALT levels were below 14 had a 68% higher likelihood than their peers.<\/p>\n In contrast, higher AST levels \u2013 30 or above \u2013 were associated with a 22% lower likelihood of being diagnosed with colorectal cancer, and ALT levels of 30 or above were associated with a 29% lower likelihood.<\/p>\n The researchers said they used the levels of 14 to 29 as comparison values because they fell within the midrange of the levels observed in the new analysis.<\/p>\n \u201cClinically, these enzymes vary from person to person and can shift over time with things like activity level, muscle mass, illness or medications,\u201d Bartelt said.<\/p>\n The researchers also looked closely at AST and ALT levels that shifted over time, specifically those that rose in the three years before the adults were screened for cancer.<\/p>\n The data showed that rising AST was associated with a 27% lower likelihood of colorectal cancer and a rising ALT with a 26% lower likelihood, compared with adults whose values held steady. Decreasing AST or ALT levels showed no significant association in either direction with colorectal cancer.<\/p>\n Still, what are considered \u201cnormal\u201d levels of AST or ALT can vary within medicine in general.<\/p>\n While each diagnostic lab may have its own reference range for how \u201cnormal\u201d levels of AST and ALT are measured, \u201cthe AST and ALT levels described as \u2018low\u2019 in this study would generally be regarded clinically as normal values,\u201d Dr. Daniel Sussman, leader of the gastroenterology high-risk prevention clinic at the University of Miami Health System\u2019s Sylvester Comprehensive Cancer Center<\/a>, said in an email.<\/p>\n \u201cThat makes me particularly cautious about suggesting that these laboratory results represent an abnormality or a meaningful colorectal cancer risk marker,\u201d wrote Sussman, who was not involved in the new research. \u201cUnexpected findings can certainly generate worthwhile research questions, but they also require particularly careful validation.\u201d<\/p>\n Could the liver hold clues?<\/p>\n