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A common vitamin has a complicated link to cancer, and too much may not be harmless
By Jordan Joseph,
A blood test comes back showing high vitamin B12, and most people read it as a non-event, maybe even a sign the supplements are working. Deficiency is the thing doctors flag, the cause of anemia, numb hands, and foggy memory.
A reading at the top of the range almost never gets a second look. A new analysis of more than 37,000 colon cancer patients worldwide suggests it should, because a high B12 number near diagnosis carried a quiet warning about how long people lived.
High vitamin B12, decoded
Your body uses B12 to build red blood cells, insulate nerves, and copy DNA each time a cell divides. The liver stockpiles years’ worth, releasing the vitamin into the blood as needed.
Researchers had long suspected the high end of the scale hides something. One French study found that people whose blood B12 stayed above 1,000 nanograms per liter faced sharply higher odds of developing a solid tumor.
Nobody knew whether high levels said anything once colon cancer is already diagnosed. The disease ranks among the deadliest cancers on Earth, so even a rough warning sign would count.
Records search worldwide
Bruce Chang-Gu, an M.D.-Ph.D. student at the University of Texas Medical Branch (UTMB) in Galveston, took up that question with pharmacologist Kamil Khanipov.
Their tool was a network of anonymized records from 108 healthcare systems worldwide.
The team pulled every adult diagnosed with colon cancer who also had a B12 blood test within a year of diagnosis. The search returned 37,106 patients, the largest group ever assembled for this question.
Each patient landed in one of three buckets. Low meant under 300 picograms per milliliter, normal ran from 300 to 1,000, and high meant anything above that line.
