The body depends on healthy cell repair to prevent mutations. When B12 levels stay low for years, DNA copying errors may become more frequent.
Researchers believe this is one possible reason why B12 deficiency may indirectly increase cancer risk.
A growing number of studies have explored this relationship. One important area of focus has been colorectal cancer, where long-term nutritional imbalance, chronic inflammation, and poor DNA repair often overlap.
According to research published by the US National Library of Medicine, deficiencies involving folate and B12 may contribute to genomic instability, a process linked to cancer development.
But there is another side to this story.
Some studies have also observed that extremely high levels of B12 in the blood are found in certain cancer patients. This created confusion for years. Did high B12 trigger cancer, or was cancer itself changing B12 levels in the body?
Recent evidence suggests the second explanation is more likely.
Doctors now believe elevated B12 often acts as a warning sign rather than a direct cause. Tumours, liver disease, or blood disorders can sometimes alter how B12 circulates in the bloodstream.
This means unusually high B12 levels without supplementation should not be ignored. They deserve medical evaluation.