People who develop colorectal cancer at a younger age show different patterns of DNA methylation compared to those who develop it later in life, and these differences are linked to long-term environmental factors like smoking, lower education levels, and diets that are not Mediterranean.

We analyzed the available evidence and found that people who develop colorectal cancer at a younger age tend to have different DNA methylation patterns than those who develop it later in life. These differences in methylation — which are chemical changes that affect how genes are turned on or off — appear to be connected to long-term lifestyle and environmental exposures, such as smoking, lower levels of education, and diets that don’t follow a Mediterranean pattern [1]. What we’ve found so far is based on 39 studies or assertions that point to this association, with no studies contradicting it. DNA methylation isn’t something you can see or feel — it’s a biological marker that can change over time due to things you’re exposed to, like what you eat, whether you smoke, or even your social and economic environment. The patterns we’ve seen suggest that early-onset colorectal cancer may be shaped by different life experiences than later-onset cases. This doesn’t mean one group is more at risk than another, or that these factors cause cancer. It simply shows that the biological signatures in tumors from younger patients look different, and those differences line up with known lifestyle patterns. We don’t yet know if these methylation changes happen early in life and contribute to cancer development, or if they’re a result of the cancer itself. The evidence we’ve reviewed leans toward the idea that early-onset colorectal cancer is biologically distinct in ways that reflect long-term environmental influences. For now, this suggests that prevention strategies might need to consider how lifestyle factors in younger adults could be shaping cancer risk at a molecular level — even before symptoms appear.