Vitamin B12 Deficiency: Potential Links to Cancer Explored

Vitamin B12 deficiency has been observed in some cancer patients, raising questions about the potential relationship between the two. However, it is still unclear whether the deficiency is a consequence of cancer or due to other underlying factors.

“Any micronutrient deficiency is going to affect your body. There could be a link between B12 and cancer, but we don’t have that definitive answer yet,” said Patty McDonnell, RD, CSO, CD, FAND, a clinical oncology nutrition advisor at Fred Hutch Cancer Center.

Vitamin B12, also known as cobalamin, is essential for producing red blood cells, forming cellular DNA, and maintaining nerve health. The body cannot produce B12 on its own, so it must be obtained from animal and dairy products, as well as fortified foods.

A B12 deficiency can occur for several reasons: inadequate dietary intake, malabsorption due to digestive issues, or increased bodily needs. Despite its correlation with cancer, a B12 deficiency is not classified as a cancer indicator.

“Vitamin B12 needs the stomach and intestines to work together for proper absorption. Any health condition affecting these organs may hinder B12 processing,” McDonnell added.

Risk factors for B12 deficiency include:

- Insufficient dietary intake, particularly in older adults and those following vegan diets.

- Digestive disorders such as gastritis, Crohn’s disease, or celiac disease.

- Gastric bypass surgery.

- Pernicious anemia, an autoimmune disorder affecting B12 absorption.

- Removal of part or all of the stomach.

- Poor nutrition and digestive damage from excessive alcohol use.

- Certain medications, like metformin and proton pump inhibitors.

- Specific family cancer syndromes and cancers affecting B12 absorption.

- Increased nutritional needs during pregnancy and breastfeeding.

Studies on the connection between vitamin B12 levels and cancer have yielded mixed results. Some research indicates lower B12 levels in patients with various cancers, including breast, cervical, liver, stomach, and colorectal cancers. However, a deficiency does not imply cancer causation, as digestive cancers can impair absorption.

Cancer treatments, such as chemotherapy and radiation therapy, can also affect B12 levels by damaging digestive tract cells. Conversely, elevated B12 levels have been noted in some cancer patients, but researchers are unsure of the reason.

“More research is needed to learn whether and how vitamin B12 is connected to cancer. If you have concerns about your B12 levels, talk with a registered dietitian or your healthcare provider,” advised Heather Greenlee, ND, PhD, MPH, an expert from the American Society of Clinical Oncology.

Diagnosis of B12 deficiency is typically done through blood tests. Current guidelines do not recommend routine screening; testing is usually suggested for individuals showing deficiency symptoms, which include anemia, fatigue, memory issues, balance problems, tongue inflammation, and numbness or tingling in extremities.

For individuals diagnosed with B12 deficiency, healthcare providers may recommend dietary changes to include more B12-rich foods or supplements. Meat, fish, and dairy are the best natural sources, while vegans may need fortified foods. If dietary adjustments are insufficient, supplementation methods such as sublingual, inhalation, or injections are available to enhance absorption.

The recommended daily intake for most adults is 2.4 micrograms, and exceeding this does not necessarily provide additional benefits according to McDonnell.

B12 levels typically improve within weeks of treatment initiation, although some symptoms, particularly neuropathy, may take longer to resolve. Long-term treatment may be required as the underlying cause of deficiency often persists.

“Supplements are not a silver bullet for lowering your cancer risk or treating cancer,” Dr. Greenlee emphasized, urging a holistic approach to diet and nutrition.