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Is There a Link Between High B12 and Lung Cancer?

Here at Xandro, we were recently asked by a customer about high dosages of B vitamins leading to cancer, in particular, an overdose of vitamin B12 and lung cancer.

Let’s go over what we know.

Can Vitamin B12 Cause Lung Cancer? — The Studies

There have been inconsistent findings about the association between dietary vitamin B12 intake and lung cancer, so in 2021, a study by Luu et al. came out from an ongoing study of 63,257 Singaporean Chinese men and women, aged 45 to 74 when they started, between 1993 and 1998.

The trial went for up to 25 years and at a mean follow-up of 17.64 years, it was found that 2,001 participants developed lung cancer. The study concluded that high dietary intake of vitamin B12 (from food sources) was associated with an increased risk of lung cancer.

While the study is well conducted, has a large sample size and is run across a long timeframe, it does have its flaws. The study shows that high levels of vitamin B12 from dietary sources are only associated with lung cancer risk, with the authors not showing any causal links. It's also important to note that this study was only conducted on the Singaporean Chinese population, many of these being men who smoked and drank more than 7 alcoholic drinks per week. These individuals also had a high intake of fried meat and fish, both high in B12.

This study built on findings from a 2009 study that found taking folic acid and vitamin B12 was linked to increased cancer outcomes in patients with ischemic heart disease in Norway, along with another large study that showed taking vitamin B6 and B12 supplements was linked with lung cancer, but only for men. This latter study was also only conducted in the elderly, compared to the larger age range in Luu et al, so yes, there may be a link between elderly men taking high doses of vitamin B12 and lung cancer.

The Luu et al. study, however, did not find a link between high B12 and lung cancer in women, but only in men. This correlates to another study examining over 71,000 women in China that didn’t find a connection between lung cancer and B vitamins.

What’s more, a 2022 review of studies on vitamin B12 and cancer from 2005 and 2022 found that a link between the two is inconsistent, except for liver cancer, with no meaningful association between B12 and cancer, regardless of whether this is through the foods we eat or from supplements. High plasma levels of vitamin B12 due to genetics were likely to be associated with cancer, but cancer patients typically had low plasma levels of vitamin B12.

What Happens If Your B12 Is Too High?

If you have too much vitamin B12 in your body, the excess gets flushed out through your urine. This is because B vitamins are water-soluble, so they don’t get stored in your fat like fat-soluble vitamins.

The recommended daily dose of vitamin B12 for adults is 2.4mcg and if your body is lacking and needs more, if you’re taking more than this, it will absorb what it needs and then excrete the rest.

Vitamin B12 also has a low potential for toxicity, even at large doses, as the body doesn’t store it, so it’s generally considered to be safe.

One study showed that smoking men who supplemented with 23 times the recommended daily amount of vitamins B6 and B12 over 10 years had a 30 to 40 per cent increase of lung cancer. There is no need to take this much of any vitamin, especially since excess B vitamins, which are water-soluble, simply get flushed out in your urine instead of being stored in your body. Taking slightly higher doses of vitamin B12 may help some people, though, with low potential for toxicity even at these higher doses.

Does high B12 mean cancer? A 2013 study found that high vitamin B levels were linked with a subsequent cancer diagnosis, which was similarly found in a 2020 study that showed that high levels of serum B12 could be linked with the development of solid cancers (tumours). This needs further research and it’s unknown whether it was high levels of vitamin B12 causing the cancer or if the cancer caused high levels of vitamin B12. Also, it’s important to note that vitamin B12 from food does not have a large effect on serum B12, as the 2020 study noted.

High levels of vitamin B12 may suggest other issues, such as types of liver diseases, blood cancer or blood disorders, due to vitamin B12 levels rising in the disease process.

How do you know if you have a vitamin B12 overdose? If you notice yourself being weak and fatigued, having headaches, nausea, vomiting, diarrhoea or tingling in your hands and feet, you may have high levels of vitamin B12, so make sure to speak with your doctor if this is you.

Who Should Not Take B12?

Some individuals should speak with their doctor before taking vitamin B12 supplements, as they may interact with certain medications. For example:

• Metformin: This is a treatment for prediabetes and diabetes which may reduce the absorption of vitamin B12 as well as significantly reduce your levels of serum vitamin B12.
• Gastric acid inhibitors: Medications such as Prilosec, Prevacid and Zantac may interfere with vitamin B12 absorption by slowing the release of gastric acid into the stomach, which can lead to vitamin B12 deficiency.
• Anti-inflammatories: Taking colchicine, a drug used to prevent and treat gout, may lower your body’s ability to absorb vitamin B12.
• Vitamin C: Taking vitamin C and vitamin B12 together may reduce the amount of vitamin B12 in your body. It’s best to take vitamin C at least 2 hours after taking a vitamin B12 supplement.

Should you take B12 if you have cancer? Vitamin B12 for cancer patients is something you should speak with your doctor about, but some studies show it may reduce pain. Vitamin B12 and chemotherapy should be avoided though, as this may reduce the effectiveness of chemotherapy. More studies are needed to confirm any results, so speak with your doctor before making any decision about vitamin B12 and cancer patients.

If you’re a vegan or vegetarian, an older adult, have a gastrointestinal disorder or have pernicious anaemia, you might have a vitamin B12 deficiency. This can be easily treated with supplementation if you’re not getting enough in your diet. If it’s incredibly severe, you can have B12 injected.

End Note

So, what does this mean for vitamin B12 and lung cancer?

There’s no strong verdict from studies showing that high doses of vitamin B12 cause cancer. While some may show associations, it’s important to note that numerous other studies are showing no link whatsoever.

More studies are needed to figure out how vitamin B12 and other B vitamin levels may affect cancer risk.

Unless your doctor recommends it, stick with the recommended daily dosage of vitamins and minerals. You might need to get a blood test to check your levels, especially if you haven’t been feeling like yourself as of late, which you can then work on improving your health.

Stay informed with Xandro Lab in your biohacking journey. Check out our research and blog pages to learn more!