DNA methylation patterns in blood and tumor samples can be used to estimate a person's past exposure to environmental factors like smoking, education level, and diet in studies of colorectal cancer.

We analyzed the available evidence and found that DNA methylation patterns in blood and tumor samples may help estimate past environmental exposures in colorectal cancer studies. Specifically, these patterns have been linked to factors like smoking, education level, and diet [1]. What we’ve found so far is that 39 studies or assertions support the idea that changes in DNA methylation can reflect a person’s history of environmental influences. None of the evidence we reviewed contradicts this. DNA methylation refers to chemical tags added to DNA that can turn genes on or off without changing the underlying code. These tags can be influenced by lifestyle and environment, and they sometimes remain detectable over time. In colorectal cancer research, scientists have observed consistent associations between these methylation changes and exposures such as long-term smoking or dietary habits. However, we cannot say these patterns directly measure exposure, nor can we say they are precise enough to predict individual risk. The evidence we’ve reviewed suggests that methylation scores might serve as useful indicators in group-level studies, but their reliability for personal assessment remains unclear. We also don’t know if these changes are caused by the exposures themselves or by other related factors. Our current analysis shows that while methylation patterns are frequently used in this context and appear consistently linked to environmental factors, the full picture is still being built. More research is needed to understand how stable, specific, and causal these links truly are. For now, if you’re reading about DNA methylation in relation to colorectal cancer risk, it’s likely being used as one of many clues — not a definitive record — of how your environment may have influenced your biology.