Bone Fractures, Lung Cancer, and Vitamin B12 Supplements?

Bone Fractures, Lung Cancer, and Vitamin B12 Supplements?

Vitamin B12 Supplementation: Understanding Its Impact on Cancer Risk, Bone Health, and Longevity

Vitamin B12 is an essential nutrient crucial for maintaining nerve health, red blood cell production, and DNA synthesis. Unlike plants and animals, vitamin B12 is not naturally produced by these organisms but is synthesized by microbes that inhabit the earth. Historically, humans likely obtained sufficient B12 by consuming water from natural sources such as mountain streams or wells, where these beneficial bacteria thrived. However, modern water treatment practices, particularly chlorination, have significantly reduced the presence of these microbes in our water supplies. While this sanitization helps prevent waterborne diseases like cholera, it inadvertently decreases our natural intake of vitamin B12. Studies indicate that vegetarians in developing countries who consume purified water are at a higher risk of B12 deficiency compared to those living in less sanitized environments. Conversely, vegetarians residing in impoverished areas of less developed regions often face fewer B12-related issues, highlighting the complex relationship between hygiene and nutrient intake. Unlike humans, great apes such as gorillas obtain their necessary B12 by consuming their own feces, a natural method of recycling essential nutrients. Given the challenges of obtaining adequate B12 from diet alone in sanitized environments, supplementation emerges as a preferred and reliable solution for maintaining optimal B12 levels.

High-Dose Vitamin B12 and Hip Fracture Risk

In 2019, a study titled “Association of High Intakes of Vitamins B6 and B12 from Food and Supplements with Risk of Hip Fracture Among Postmenopausal Women in the Harvard Nurses’ Health Study” was published. The study found that only the combined high intake of vitamins B6 (≥35 mg/day) and B12 (≥20 mcg/day) was associated with an increased risk of hip fractures. Notably, high doses of vitamin B6 alone have been previously linked to a 40 percent higher risk of hip fractures over a decade-long period. However, high intake of vitamin B12 alone did not show an increased risk. In fact, some observational studies suggest a slightly lower fracture risk at high B12 blood levels. Interventional studies, where participants are randomized to receive B12 supplements, have not demonstrated an increased fracture risk among those given B12, reinforcing the safety of high-dose vitamin B12 supplementation concerning bone health.

Vitamin B12 and Cancer Risk

Concerns about vitamin B12 supplementation extend to its potential association with cancer risk. In 2017, a study found that men taking vitamin B12 supplements appeared to have an increased risk of lung cancer. This association was not observed in women and was primarily seen among men who smoked, raising questions about whether B12 could be feeding budding tumors. However, replication of these findings in additional prospective studies is necessary. When considering all observational studies, there is no significant correlation between lung cancer and blood levels of B12, regardless of smoking status. In fact, many studies trend towards higher B12 levels being protective against cancer.

The Role of Confounding Factors and Reverse Causation

Observational studies often face challenges such as confounding factors and reverse causation, which complicate the interpretation of results. A confounding factor, or “lurker variable,” can be a third factor associated with both higher B12 levels and cancer, potentially obscuring the true relationship. For instance, individuals with higher B12 levels often consume more meat and dairy, which are significant contributors to serum B12. Increased meat consumption is also associated with a higher risk of lung cancer, suggesting that B12 levels might merely be a marker for meat intake rather than a direct cause of cancer.

Reverse causation adds another layer of complexity, where instead of high B12 levels leading to cancer, the presence of cancer may cause elevated B12 levels. Approximately 75 percent of patients diagnosed with cancer exhibit elevated B12 levels, indicating that high B12 might be a marker of underlying health issues rather than a cause. Additionally, elevated B12 levels can result from liver problems, kidney issues, bone marrow disorders, and cancer itself, further complicating the association.

Randomized Controlled Trials on B12 Supplementation

To address the uncertainties posed by observational studies, randomized controlled trials (RCTs) provide more definitive insights. Over a dozen RCTs involving thousands of participants have investigated the effects of high-dose daily vitamin B12 supplementation (up to 2,000 mcg) on cancer incidence, death due to cancer, and overall mortality. The findings from these trials consistently show that vitamin B12 supplementation does not increase the risk of fractures, cancer incidence, or mortality. In fact, some studies indicate that B12 supplements may lower the risk of the most dangerous forms of skin cancer. These results are crucial in dispelling myths about the potential carcinogenic effects of vitamin B12 and highlight its safety when used appropriately.

Conclusion: The Safety and Necessity of Vitamin B12 Supplementation

Vitamin B12 supplementation is essential, particularly for individuals on plant-based diets, those over the age of 65, and individuals with certain medical conditions that impair B12 absorption. High-dose vitamin B12 supplementation has not been shown to increase the risk of fractures or cancer, according to randomized controlled trials. Observational studies suggesting an association between B12 and cancer risk are likely influenced by confounding factors and reverse causation, rather than a direct causal relationship.

Maintaining adequate vitamin B12 levels through supplements or fortified foods is crucial for preventing a wide range of health issues, including neurological disorders, cognitive impairments, and psychiatric symptoms. Given the modern challenges of obtaining sufficient B12 from natural sources due to sanitized water supplies, supplementation remains a reliable strategy for ensuring optimal health and longevity.

Key Takeaways

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Update from Michael Greger, on 2024-12-19Source