Scientists are raising new questions about vitamin B12 and cancer

Vitamin B12 has long been seen as a health hero, helping the body make red blood cells, repair DNA, and keep nerves functioning properly. But scientists are discovering that the story may be more complicated than simply “more is better.” While too little B12 can damage DNA and raise cancer risk, some studies suggest that extremely high levels — especially from long-term high-dose supplements — may also be linked to certain cancers or poorer outcomes in cancer patients.