A recent study links high levels of vitamin B12 to an increased risk of cancer. This study will help inform recommendations for vitamin intake.
Vitamin B12 is widely considered beneficial to health. However, a recent study has shown that excessively high blood levels of this vitamin may increase the risk of certain cancers and worsen the condition of cancer patients. This new information will help inform recommendations regarding vitamin supplementation.
The study revealed a U-shaped relationship between vitamin B12 intake and cancer risk. The risk increased with both deficiency and excess of the vitamin. This vitamin promotes cell growth in general. Theoretically, this means that if precancerous cells are present, increased B12 levels could support their growth. However, there is no direct evidence of a causal relationship at this time.
According to the results of studies conducted in 2022 and 2024, vitamin B12 levels are often elevated in cancer patients as a "secondary phenomenon"—that is, a side effect of the disease. One of the reasons is liver damage, which stores large amounts of the vitamin.
Furthermore, some tumors increase the amount of vitamin-binding proteins in the blood, leading to elevated levels in tests.
Scientists discovered in a new study conducted in 2026 that patients with colorectal cancer had very high levels of vitamin B12 and lived half the lifespan of patients with normal vitamin levels.
