Association between Vitamin B12 Levels and Colon Cancer Survival
February 2026. Authored by Drs. Chang-gu, Khanipov, Golocko, and D'Andrea in Cancer Research Communications.
This article compared the association between B12 levels and adverse outcomes in colon cancer. Patients had had a B12 level within 1 year of diagnosis. Of 37,000 patients with a colon cancer diagnosis, 64% had normal B12 levels, 14% had low B12 levels, and 18% had elevated levels. Patients with elevated B12 levels had higher metastatic involvement and tumor stage at diagnosis and shorter survival when vitamin B12 levels were above 1000 mcg. Survival when B12 was >1000 mcg was 59.4 months, compared to 129.8 months among those who had normal levels. There are currently no data that can distinguish whether this exaggerated level affects normal cells adversely or cancer cells, but elevated B12 levels are strongly associated with decreased survival and possibly could be a marker of an adverse outcome.
When colon tumors were examined, researchers found significantly higher activity in the MTR gene, which requires folate (and, in addition, B12) and provides instructions to create an enzyme that helps in DNA synthesis. It was theorized that aggressive tumors may be hijacking B12 and using it to fuel their own rapid growth, rather than that high B12 levels were causing the development of cancer in healthy cells. Similar survival findings were reported in people with high levels of B12 who were on immunotherapy and in oral cancer patients.
Vitamin B12, cobalamin, is an essential vitamin for:
The production of red blood cells.
It affects nervous system functions by helping to maintain the insulating layer around nerve axons, myelin, that allows electrical impulses to respond.
It is needed in the production of thymidine/purines for DNA synthesis and can affect the on/off switch for gene regulation.
It is found naturally in meat, fish, eggs, and dairy, but with a normal diet it is very difficult to ingest too much. However, people with digestive dysfunction or on a vegetarian diet may require supplementation.
B12 is an essential vitamin, as is folate, B9, and both are needed for the methylation cycle. This cycle uses the active form of folate along with B12 to convert the amino acid methionine to SAM-e, S-adenosyl methionine. This is the body's primary methyl donor, which is utilized by DNA to produce proteins and neurotransmitters, and glutathione for detoxification. In recent years, genetic testing for MTHFR (methyltetrahydrofolate reductase) enzyme variants was seen as a method to provide information which, if abnormal, could indicate diminished folate utilization and poor methylation.
This testing has become popular in the integrative medicine community and tests the gene needed to process inactive folate, 5,10-methyltetrahydrofolate, to active 5-methyltetrahydrofolate for use in the methylation cycle. If there is a genetic MTHFR variant which diminishes folate conversion to its active form, practitioners believe they must aggressively replace folate, and the assumption is that B12 will also be deficient and needs replacement. Interestingly, practitioners assume an MTHFR variant means poor methylation, but often it does not signify a clinically significant disorder. By measuring a byproduct of this pathway, homocysteine, if it is normal, methylation is normal, and unless homocysteine is elevated, an abnormal MTHFR variant is unlikely to require treatment. This example illustrates that while there may be a genetic susceptibility for a problem, it does not mean that there is an abnormal expression in terms of function.
But if high doses of vitamin B12 are not needed, especially given consideration of its potential harm as recognized in colon cancer survival, this should be discussed. Especially since B12, homocysteine, and folate can be measured before prescribing.
In a broader sense, an awareness that a nutrient insufficiency can cause health issues requires consideration for possible treatment, but also that an excess of a nutrient may be harmful. So just because Dr. Google says B12, or any nutrient, is essential and should be taken regularly, look for yourself at the available information from reliable sources and make choices based on its effect on your health. Search out the optimum amount needed to maintain normal levels without risking the potential of something being beneficial turning out not to be so. Obviously, if testing suggests you are lacking a nutrient, a supplement may be needed to help correct the issue, but it should not necessarily be taken indefinitely without reassessment.