Scientists Raise New Questions About the Relationship Between vitamin B12 and Cancer

🧬 Brief Summary

Recently, scientists have raised questions about the relationship between vitamin B12 and cancer. Vitamin B12, also known as cobalamin, is essential for overall health, especially in supporting blood functions, the nervous system, and DNA repair processes. However, recent studies indicate that taking very high amounts of this vitamin, or having high levels in the blood, may be associated with an increased risk of some types of cancer. But vitamin B12 is not necessarily the cause; it may instead be a warning sign of a specific disease. Balance in the levels of this vitamin is key, and caution should be exercised against overusing supplements without medical advice.

🧪 The Vital Role of Vitamin B12 in the Body

Vitamin B12 plays a critically important role in several bodily functions:

• It helps produce red blood cells.
• It supports the central nervous system.
• It helps accurately copy and repair deoxyribonucleic acid DNA during cell division.

These processes are essential for maintaining cell health and preventing mutations that can lead to chronic diseases.

Natural sources of vitamin B12 include animal foods such as meat, fish, eggs, milk, and dairy products. There are also foods fortified with this vitamin, such as some breads and cereals, which play an important role especially for groups that follow a strict vegan diet or suffer from absorption problems such as older adults.

🧠 The Relationship Between Vitamin B12 and Cancer: A New Perspective

The body constantly works to produce new cells through precise cell division that depends on proper DNA copying. Vitamin B12 is necessary to ensure the accuracy of this process. In cases of deficiency, problems occur in DNA structure, which may lead to mutations associated with a higher risk of certain cancers such as colon cancer.

But matters are not simple when talking about high B12 levels. A study conducted by researchers in Vietnam in 2025 linked vitamin B12 intake in a U-shaped relationship, where the study showed that both lower and higher intake of the vitamin were associated with an increased risk of cancer. This means that balance in vitamin levels is more important than excessive intake.

Despite the understandable idea that more vitamin B12 boosts cell health and thus reduces cancer risk, the matter is more complex. Vitamin B12 generally stimulates cell growth, not only healthy cells, which raises concern that very high levels may cause faster growth in cells that may be in a precancerous stage. However, this possibility has not yet been conclusively proven in humans.

🩺 Research Findings on Long-Term B Vitamin Supplements

Multiple studies so far have shown that the use of B vitamin supplements, especially at high doses and for long periods, has not been proven to reduce cancer incidence rates or cancer-related deaths.

• No general protection from cancer has been shown with high-concentration B vitamin supplements.
• In the case of melanoma, one study observed a lower risk of disease, but this remains a special case and is not sufficient evidence of prevention.
• Some observational studies linked high-dose supplements of vitamins B6 and B12 to a slight increase in lung cancer risk, especially among men and smokers, but they do not prove a direct causal relationship.

🌱 Elevated Vitamin B12 in the Blood of Cancer Patients: Cause or Result?

Doctors have long noticed unusually high levels of vitamin B12 in the blood of many cancer patients. Recent research suggests that this elevation may not be the cause of the disease, but rather a secondary result of the presence of cancer or its effect on the body.

In 2022, a study concluded that elevated vitamin B12 in cancer patients is often an epiphenomenon, meaning a concomitant phenomenon and not proof that the vitamin is causing the disease.

Possible mechanisms that explain elevated B12 in the blood during cancer include the following:

• The liver, which stores large amounts of the vitamin, is affected, leading to excess release when it is damaged or under stress.
• An increase in the production of certain proteins related to B12 in the blood by some tumors, which may lead to high readings in blood tests without an actual increase in cellular uptake.

🧬 Vitamin B12 as a Biomarker of Disease Progression

It seems that elevated vitamin B12 levels, especially when there is no clear reason such as supplement use, may be an important indicator of the presence of disease or the progression of a patient’s health condition.

A large 2026 study showed that colon cancer patients with very high blood B12 levels had a lower average survival of about 5 years compared with those who had normal levels, who lived about 11 years.

Similar patterns were also observed in oral cancer and in patients receiving immunotherapy, where elevated B12 was associated with worse outcomes. Therefore, persistently high B12 without a clear reason should be taken into account for early detection of liver disease, blood disorders, or cancer.

🧪 Balance and Caution: The Health Conclusion 🌿

For healthy people who eat a balanced diet containing meat, fish, eggs, and dairy products or fortified foods, getting vitamin B12 is sufficient and healthy without the risk of excessive increase. Meanwhile, deficiency remains the greater challenge in terms of negative health impact.

The greater concerns are linked to taking B12 supplements at high doses for long periods without medical supervision, or the appearance of elevated blood levels without a known cause. This requires careful medical follow-up.

The most important message from recent research is that “more is not always better.” There is no single vitamin that prevents cancer on its own; rather, a balanced lifestyle, healthy food, physical activity, and avoiding risks such as smoking are what ensure overall health.

🩺 General Advice on Taking Vitamin B12

People who rely on a strict vegan diet, older adults, or those who suffer from digestive system problems should monitor their vitamin B12 levels and compensate when needed through supplements.

However, using very high doses is not recommended unless after consulting a doctor and conducting the appropriate tests.

With vitamin B12, as with most nutrients, the goal is to reach the optimal level and no more. This ensures the vitamin’s role in maintaining health without turning it into a potential risk factor.

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