Colon-cancer risk in young people linked to one amino acid, small study finds

Scientists have identified molecules in the blood that could potentially be used to identify young adults at risk of developing colorectal cancer and thus flag them for preemptive screening.

Colorectal cancer predominantly affects people over 50, but it's on the rise in younger people in the U.S. — in 1992, the diagnosis rate was 8.6 in 100,000 people under 50, but in 2018, it rose to 12.9 in 100,000.

In a recent study, published in July in the journal NPJ Precision Oncology, researchers found that patients diagnosed with colorectal cancer before age 50 have higher levels of specific metabolites in their blood, compared with colorectal cancer patients over 60. Metabolites are byproducts of digestion, cellular activity and drug breakdown that circulate in the blood.

The younger patients had higher levels of metabolites related to the production and breakdown of an amino acid, or protein building block called arginine. The body makes its own arginine, and the substance is also naturally found in protein-rich foods, such as meat and nuts. It's involved in many cellular processes, including protein production and the urea cycle — how the body gets rid of toxic byproducts left over from protein metabolism, namely ammonia.

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In addition to arginine, the younger cancer patients had higher levels of metabolites related to the urea cycle than did the over-60s. According to the study authors, the findings suggest that having more arginine in the blood and unusually high activation of the urea cycle may drive colorectal cancer in young people.

They say that the finding could help doctors identify younger people who are at highest risk of developing the cancer. The idea is that these individuals could be put forward for regular screenings, including colonoscopies and stool-based tests. These are usually reserved for people over age 45 who have an average risk of the disease, or slightly younger people with a family history of the condition.