Long-term study shows increased risk, especially for male smokers

Men: whoever takes the vitamins B6 or B12 for a long time, can increase his lung cancer risk significantly. This is indicated by a US study with a good 77,000 participants, in which the intake of these vitamins increased the lung cancer rate in men by twice, in male smokers even by three to four times, as the researchers report. In women, this previously unrecognized side effect strangely failed to materialize.

Many vitamin supplements are much too highly dosed. Long-term intake of B6 and B12 may promote lung cancer risk. © The Ohio State University Comprehensive Cancer Center

Vitamins are vital to us. But it is not always the case that "much helps a lot" - to the contrary. For example, Vitamin D, which has been praised as a bone vitamin, can promote food allergies and increase the risk of falling in older people. Too much vitamin E damages the bone, and even vitamin C can promote kidney stones if the overdosage is massive.

B6 and B12 - harmless nerve vitamins?

So far, the vitamins B6 and B12 were regarded as harmless. Both are advertised as "nerve vitamins" and as a "booster" for mental fitness. In fact, a lack of vitamin B12 can weaken the ability to concentrate, and even increase the risk of dementia in old age, as studies suggest. To avoid this, many elderly people take these vitamins in highly dosed form as food supplements.

But this can have serious consequences - at least for men - as Theodore Brasky of Ohio State University and his colleagues report. They have analyzed the data from a long-term US study on vitamins and lifestyle. For 77,000 participants between 50 and 76 years, they determined whether and at what dosage they had taken vitamin B6 or B12 in the last ten years and examined the number of lung cancer cases.

Two to four times higher risk

The result: The male participants, who had taken vitamin D6 or B12 over a long period of time, suffered lung cancer twice as often as the men without vitamins. Potential factors such as lifestyle, age, smoking or hereditary and environmental pollution were already calculated here.

Even greater was the risk of lung cancer for male smokers who had taken a multiple of the recommended daily dose of these vitamins for ten years.

With these smokers, the risk was increased by three to four times, Brasky reports.

In women, however, whether smoking or not, the researchers were unable to detect any increased lung cancer caused by vitamin intake.

Dosages of the pills often much too high

The RDA for vitamin B6 is for adult men at 1.5 milligrams, for B12 the daily dose at around three micrograms. However, in many sold dietary supplements significantly more vitamin B6 and B12 is included.

They are sold in doses up to 5000 micrograms per tablet - which exceeds the recommended daily allowance by far, said Brasky.

The doctors therefore advise a "hands of" of highly dosed vitamin B preparations.

We get enough vitamin B through meat, chickpeas or even cereals with vitamin supplements, the researcher said. As a rule, there is therefore no reason to take these vitamins high doses or to take them additionally - and in any case not for years.

Especially the elderly should take high doses of B6 and B12 only in consultation with their doctor, according to the recommendation of the experts. They have already begun two studies to further investigate the relationship between lung cancer and vitamin B6 and B12. They also want to find out why the negative effect does not appear in women.

Source: Journal of Clinical Oncology, 2017