B12 on a Tightrope: Balancing Deficiency Risks and Cancer Signals

Vitamin B12 is essential for DNA copying and nerve health and is mostly obtained from animal foods, but its link to cancer is complex. Research suggests a U-shaped relationship where both low and very high intakes may associate with cancer risk; high-dose B12 has not shown clear protective effects and could potentially support pre-cancer cells, though proof in humans is lacking. Elevated B12 in cancer patients is often an epiphenomenon (liver release or binding proteins increasing blood levels) and can serve as a cancer marker rather than a cause. For most people, normal dietary intake or modest supplementation suffices; avoid megadoses and focus on balance, healthy habits, and routine screenings.