High Vitamin B12 Signals Poorer Cancer Survival, With Median 5 Years vs Nearly 11
Updated
Updated · SciTechDaily · May 20
High Vitamin B12 Signals Poorer Cancer Survival, With Median 5 Years vs Nearly 11
3 articles · Updated · SciTechDaily · May 20
A 2026 study found colon cancer patients with very high B12 levels survived a median of about five years, versus nearly 11 years for patients with normal levels.
Researchers say elevated B12 often appears to be a marker rather than a cause of cancer, with 2022 and 2024 studies tying high readings to liver disruption or tumor-driven increases in B12-binding proteins.
Similar links between high B12 and worse outcomes have also been reported in oral cancer and among patients receiving immunotherapy, strengthening interest in B12 as a progression signal.
Doctors say persistent, unexplained high B12—especially without supplements—should prompt checks for liver disease, blood disorders or hidden cancer, while deficiency remains the more common nutritional problem.
The findings add context to a 2025 Vietnamese study that suggested a U-shaped cancer risk from both low and high B12 intake, reinforcing advice to avoid long-term megadoses unless medically indicated.
High B12: A cause of cancer, or just a warning sign of a hidden disease?
Is your daily multivitamin secretly increasing your cancer risk?
Vitamin B12 and Cancer: Why Both Low and High Intake Raise Risk—Lessons from the Vietnamese U-Shaped Study
Overview
A major 2024 study from Vietnam examined nearly 3,800 cancer patients and almost 3,000 controls, finding a U-shaped link between vitamin B12 intake and cancer risk. This means both very low and very high B12 intake were associated with higher cancer risk, while moderate intake was linked to lower risk. The study used food questionnaires to estimate long-term B12 intake, but as an observational study, it could only show associations, not prove cause and effect. These findings highlight the importance of balanced B12 intake and suggest that both deficiency and excess may be problematic for cancer risk.