Vitamin B Supplements and Lung Cancer: What the Research Really Shows

Explore the latest evidence, controversies, and expert recommendations about vitamin B supplements and their potential link to lung cancer risk.

By Medha deb

Created on Sep 25, 2025

Explore the latest evidence, controversies, and expert recommendations about vitamin B supplements and their potential link to lung cancer risk.

Vitamin B supplements have long been marketed as beneficial for energy, nerve health, and metabolism. However, studies in recent years have raised important questions about the safety of high-dose vitamin B6 and B12 supplementation, especially with regard to lung cancer risk. This comprehensive review dives deep into the scientific evidence, examines potential mechanisms, and shares practical recommendations for consumers.

What Are B Vitamins?

B vitamins are a group of water-soluble nutrients essential for many bodily processes, including cellular energy production, DNA synthesis, and nervous system health. The B vitamin family includes:

B1 (thiamine)
B2 (riboflavin)
B3 (niacin)
B5 (pantothenic acid)
B6 (pyridoxine)
B7 (biotin)
B9 (folate or folic acid)
B12 (cobalamin)

Each vitamin plays distinct roles. While most people can get adequate B vitamins through a balanced diet, supplements are widely available and often used for perceived health boosts.

The Link Between Vitamin B Supplements and Lung Cancer

Interest in a possible connection between vitamin B use and cancer risk began because of the role these vitamins play in cell growth, DNA methylation, and repair. Several large-scale studies have examined whether high intake of B vitamins affects the risk of developing lung cancer.

Key Research Findings

Some research indicates a higher risk of lung cancer, particularly among men who take high doses of vitamin B6 and B12 supplements over long periods.
The increased risk appears most pronounced in current smokers and recent former smokers.
The effect is less clear or not present for those taking multivitamins or in nonsmokers and women.

Why Are B Vitamins Studied in Cancer?

B vitamins—especially B6, B9 (folate), and B12—are involved in one-carbon metabolism, a pathway crucial for DNA synthesis and repair. Disruptions in this process may contribute to cancer by allowing the accumulation of DNA damage or promoting abnormal cell growth.

Notable Studies on Vitamin B and Lung Cancer Risk

Vitamins and Lifestyle (VITAL) Cohort

The landmark VITAL study is one of the most influential investigations in this field. It followed over 77,000 adults aged 50 to 76 in Washington State for up to 10 years. Scientists analyzed supplement use and tracked cancer rates over time.

Men who took high doses of vitamin B6 (over 20 mg per day) or vitamin B12 (over 55 µg per day) from individual supplements—not multivitamins—had a 30% to 40% increased risk of developing lung cancer compared to nonusers.
For men who smoked at the study’s outset, the risk was almost doubled for those using these high-dose supplements.
No significant risk increase was found for women or for those taking multivitamins containing B vitamins.
The elevated risk was generally present across different types of lung cancer except for adenocarcinoma, which is less closely tied to smoking.

Dietary Vitamin B and Cancer Risk

A population-based study among over 63,000 Singaporean Chinese individuals examined vitamin B12 intake from food sources. After nearly 18 years of follow-up:

Those in the highest quintile of B12 intake had about an 18% higher risk of developing lung cancer compared to those in the lowest quintile, after accounting for factors like age, sex, and smoking status.
The risk increased most in men, especially for those developing lung cancer in the early years of the study.
Findings paralleled results from studies of supplement users, although intake from supplements tended to be higher and risk increments greater.

**Summary of Key Research on B Vitamin Supplementation and Lung Cancer Risk**
Study	Population	Main Exposure	Key Findings
VITAL	77,118 U.S. adults, 50–76 yrs	B6 & B12 supplements (high dose) (from individual supplements, not multivitamins)	30–40% higher lung cancer risk in men; risk doubled in male smokers
Singapore Chinese Health Study	63,257 Chinese adults, 45–74 yrs	Dietary B12 intake (from food)	18% higher lung cancer risk in highest vs. lowest intake; stronger in men
Randomized Trials (Norway)	6,837 adults	B12 + folic acid supplementation	Increased overall cancer risk, mainly for lung cancer

Potential Mechanisms: How Might B Vitamins Affect Cancer Risk?

The biological reasons why high-dose B6 and B12 supplementation may increase lung cancer risk are not yet fully understood. Researchers have proposed several mechanisms:

Enhanced cell growth: B vitamins are vital for DNA synthesis and cell proliferation. High intake could foster rapid cell division, including of precancerous or cancerous cells.
DNA methylation changes: Disruption of this gene-regulating process can lead to mutations or unscheduled cell growth.
Pro-oxidant effects: In high concentrations, vitamins might act more like pro-oxidants than antioxidants, potentially promoting cell damage in some individuals.
Synergy with smoking: Tobacco smoke damages lung tissue and DNA. High doses of certain B vitamins may further accelerate harmful cell changes in the at-risk environment created by smoking.

Interpreting the Evidence: Who Is Most at Risk?

Although the data suggest that high-dose supplementation of vitamin B6 and B12 increases the risk of lung cancer in some groups, it’s important to interpret the research carefully.

Risk Increase Is Dose-Dependent: The risk rises among those taking doses far above the recommended daily allowance (RDA), and especially with long-term use.
Strongest in Current and Recent Smokers: Men who smoke and use high-dose individual vitamin B supplements are at greatest risk.
No Significant Risk from Multivitamins: Standard multivitamin use, which typically contains lower doses of B vitamins, has not been associated with increased lung cancer risk.
Women and Nonsmokers: Consistent evidence of increased risk is lacking in these groups, although data are more limited.

Should You Worry About Getting B Vitamins from Food?

Moderate intake of B vitamins as part of a balanced diet has not been linked to cancer. Most experts consider food sources to be safe and adequate for most people, unless a medical condition affects absorption or a clinical deficiency exists.

Current Recommendations: Should You Stop Taking Vitamin B Supplements?

The consensus among medical organizations and research experts based on current data is as follows:

**Do not use high-dose vitamin B6 or B12 supplements for cancer prevention.**
**Those at higher risk for lung cancer**—such as current or former smokers, particularly men—should avoid high-dose vitamin B6 or B12 supplements unless directed by a healthcare professional.
**Individuals with confirmed B vitamin deficiencies** (e.g., from digestive disorders, dietary restrictions, or certain medications) should follow clinician guidance regarding supplementation, aiming for doses that restore but do not dramatically exceed normal levels.
**Standard multivitamins consumed at recommended dosages** have not been linked to increased lung cancer risk.
**Eating a balanced diet** rich in whole grains, lean proteins, fruits, and vegetables typically provides all essential B vitamins.

Who Might Need Vitamin B12 Supplements?

Vitamin B12 is found almost exclusively in animal products. Certain groups are more prone to deficiency and may require supplementation:

People over 50 (as stomach acid decreases with age)
Vegetarians and vegans
Individuals with gastrointestinal disorders (e.g., celiac, Crohn’s, gastric bypass surgery)
Those on specific medications that interfere with B12 absorption

Even for those who need supplementation, caution is advised to avoid doses far exceeding daily needs, unless otherwise prescribed.

Smoking, Supplements, and Lung Cancer: The Triple Threat

One of the most striking findings in the research is the pronounced risk for current and recent smokers who use high-dose vitamin B6 and B12 supplements. Smoking alone is the single largest risk factor for lung cancer. Combined with heavy B vitamin supplementation, the risk appears to rise further.

The combination of cigarette smoke’s carcinogens and enhanced cell growth from excess vitamin B may create an environment ripe for malignant transformation.
Quitting smoking remains the most effective way to reduce lung cancer risk. Supplements cannot offset the dangers posed by tobacco.

Limitations and Areas of Ongoing Research

While the association between high-dose B vitamins and lung cancer risk is concerning, several scientific uncertainties and gaps remain:

Most studies are observational; only a few large-scale, randomized trials exist.
It’s still unclear which doses are truly hazardous for all groups.
Potential genetic, gender, and lifestyle interactions are not yet fully understood.
Not all studies have carefully distinguished between sources, forms, or combinations of B vitamins.

More research, especially from controlled interventions, is needed to clarify these relationships and refine guidelines.

Key Takeaways for Consumers

Do not exceed recommended doses of vitamin B6 or B12, especially from individual supplement products.
Smokers and those at high risk for lung cancer should avoid high-dose B vitamin supplements.
Standard multivitamins at or below 100% of recommended daily intake appear safe for most people.
A balanced diet is usually the best way to meet B vitamin needs.
Discuss supplementation with a healthcare provider, particularly if you have special medical needs or concerns.

Frequently Asked Questions (FAQs)

Q: Which B vitamin supplements are linked to higher lung cancer risk?

A: Research most strongly links high-dose vitamin B6 and B12 supplements with increased lung cancer risk, particularly among men who smoke or recently quit smoking.

Q: What are considered high doses of these vitamins?

A: In studies, high risk was associated with daily intakes above 20 mg for B6 and 55 µg for B12 from individual supplements, taken over several years.

Q: Is it safe to get vitamin B from food instead of supplements?

A: Yes. There’s no evidence that typical dietary intake of B vitamins from food raises cancer risk in healthy adults. Supplements are potentially problematic when taken in high doses and over long periods.

Q: Are multivitamins a concern?

A: No significant increase in lung cancer risk has been demonstrated for those taking standard multivitamins at recommended dosages.

Q: Who should consider vitamin B supplementation?

A: Only people with a confirmed deficiency, absorption issues, specific diets (e.g., vegans), or as directed by their doctor should use supplements, preferably at the lowest effective dose.

Vitamin B Supplements and Lung Cancer: What the Research Really Shows

What Are B Vitamins?