Colorectal cancer cases are spiking, especially among younger adults, leaving scientists racing to uncover the hidden culprits behind this troubling trend. While poor diets, sedentary lifestyles, and environmental factors have long been in the spotlight, a new study reveals a surprising contributor, a condition that is both widespread and frequently missed.

Researchers have identified a striking link between non-alcoholic fatty liver disease (NAFLD), a silent condition that affects an estimated one in four people globally and millions of Americans, and a significantly increased risk of early-onset colorectal cancer (diagnosed before the age of 50). Despite its prevalence, NAFLD often goes undetected in routine medical care and progresses without obvious symptoms.

To understand the link between NAFLD and early-onset colorectal cancer, researchers conducted a large-scale, population-based cohort study using data from the Korean National Health Insurance Service involving over 4.6 million adults.

The participants were between the ages of 20 and 49 who underwent routine health checkups in 2009, with health outcomes tracked through 2019. NAFLD was identified using a validated measure known as the Fatty Liver Index (FLI), with scores of 60 or higher indicating the presence of NAFLD.

Participants were then grouped based on their FLI scores: those with NAFLD (FLI ≥ 60), borderline NAFLD (FLI between 30 and 59), and no NAFLD (FLI < 30). Cases of early-onset colorectal cancer were identified through national claims data. Over a median follow-up period of 9.3 years, 2,733 individuals were diagnosed with early-onset colorectal cancer.

Researchers noted that individuals with NAFLD had a 24% higher risk of developing early-onset colorectal cancer compared to those without fatty liver, while those in the borderline NAFLD category had a 12% increased risk.

Interestingly, the study also found a dose–response relationship between the severity of fatty liver and cancer risk in cancers, in those located in the left colon and rectum. The association was particularly strong among males, younger individuals aged 20–29, and those without diabetes, highlighting the need for targeted early screening and liver health monitoring in these higher-risk populations.

"These findings highlight the need for multifaceted preventive strategies, including lifestyle interventions and expanded screening for younger populations with NAFLD," the researchers wrote in the study published in the journal Clinical Gastroenterology and Hepatology.

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