Researchers are raising new questions about the relationship between vitamin B12 and cancer, as studies have shown that high blood levels of the vitamin in some cancer patients are associated with disease spread and worse treatment outcomes.
Conversely, other research suggests that lower levels may also be associated with an increased risk of cancer, making the relationship between the two more complex than it appears.
Vitamin B12 is an essential vitamin for the body, as it is involved in the formation of DNA and contributes to maintaining healthy nerves, red blood cell production, and the metabolism of fats and amino acids. It is naturally found in foods of animal origin, so vegetarians and people with malabsorption issues are more prone to deficiency.
Researchers began studying the link between vitamin B12 and cancer because of its role in DNA building and repair. It was believed that a deficiency in the vitamin might hinder cellular DNA repair, potentially increasing the likelihood of cancer-related mutations.
However, subsequent studies revealed a striking paradox, as high levels of B12 were recorded in some patients with lung, breast, esophageal and colon cancers.
High blood levels of vitamin B12 do not necessarily mean a person is getting too much of it. Vitamin levels are affected by how the body stores, uses, and transports it. The liver stores large amounts of it, but tumors can interfere with these processes, and some cancers can increase the production of proteins that transport B12 in the blood.
Therefore, researchers believe that a high level of B12 may in some cases be a sign of the presence or development of cancer, rather than a cause of it.
A recent study published in the journal Cancer Research Communications supported this hypothesis, after researchers from the University of Texas Medical Branch analyzed data from 37,106 colon cancer patients, each of whom had a blood test for B12 levels near the time of diagnosis.
The analysis showed that patients with B12 levels exceeding 1000 picograms per liter had significantly worse outcomes. Their median survival was approximately five years, compared to approximately 11 years for patients with normal levels.
Those with high levels were also nearly twice as likely to die compared to those with low levels, and about 65% more likely than those with normal levels. Elevated B12 was also associated with an increased likelihood of being diagnosed with stage 4 cancer and of developing new metastases within a year, particularly in the liver.
The researchers didn't stop at blood tests; they also studied hundreds of colon tumors themselves and found high activity in the MTR gene, which is responsible for producing an enzyme that requires B12 in a process related to DNA synthesis. High activity in this gene was also associated with lower survival rates.
These results suggest that some tumors may be more able to use B12 in processes associated with rapid growth, but this does not prove that the vitamin feeds cancer or causes its development.
The picture isn't simply about high vitamin levels. A study conducted in Vietnam, involving 3,758 cancer patients and 2,995 healthy individuals, found a link between dietary B12 intake and cancer risk. Both low and high intakes were associated with an increased risk compared to moderate intake levels.
However, the study was observational and relied on dietary questionnaires, so it cannot prove a causal relationship.
The group with the highest B12 intake also consumed about 2.97 micrograms per day, a level close to the usual dietary recommendations of between 2.4 and 2.8 micrograms per day.
Current evidence points to a complex relationship between B12 and cancer, but there is not enough evidence to say that high or low levels of the vitamin directly cause cancer.
It is more likely that elevated blood levels of vitamin B12 in some cancer patients reflect, rather than cause, the changes the disease induces in the body. Therefore, further research is needed to determine the nature of this relationship and to understand whether vitamin B12 plays a direct role in tumor development or is merely an indicator of disease-related changes.
