According to a new study, the consumption of vitamin B6 and B12 supplements, which was previously thought to protect against cancer, is actually linked to a higher risk of lung cancer.
As discovered by the researchers at the Ohio State University, the risk is higher only in men, especially smokers. Considering the fact that a lot of people are consuming these vitamins, should we be concerned?
More than 77,000 people took part in this research. The researchers asked them how often they take B vitamins and in which doses, and about their normal diet in the past 10 years. However, the accuracy of the information over such a long time is questionable because we usually cannot remember our diet and supplements for the last couple of days let alone for 10 years.
Moreover, we don’t know whether the researchers compared the information from their questionnaires with the gold-standard method of dietary assessment i.e. a weighed-food record. And the formulation of the supplements may have also changed during those 10 years.
After six years of consuming vitamin supplements, the researchers checked the participants to see if they developed lung cancer and discovered a 30% increase linked with the consumption of vitamin B12 and a 40% increase linked with the consumption of vitamin B6 (as individual vitamins). The effect was not seen for B vitamins as part of multivitamins. Other factors that may influence the development of cancer were also included.
The results showed that the consumption of vitamin B supplements did not increase the risk of cancer in women, only in men. And those men that consumed higher doses of supplements had even higher risk of cancer. The risk was also higher for smokers.
According to the study, doses higher than 20 mg (milligrams) of vitamin B6 per day and 55μg (micrograms) of vitamin B12 per day, increase the risk of lung cancer. These are very high doses in comparison to the ones found in average multivitamin tablets (1.4mg for B6 and 1.5μg for B12, according to the recommended daily intakes for adult males in the UK). These doses are actually very close to the maximum allowed dose in over-the-counter supplements (25 mg per day).
The vitamin supplements are linked to higher risk of cancer, but they are not the cause of it
This is also a very important thing to remember because studies like this one usually don’t provide proof of causation. Moreover, although the researchers included other factors that may influence the risk of cancer, such as history of lung diseases or age, there may also be other additional factors that affect the risk of cancer and are not connected to the vitamin supplement usage.
A randomized controlled trial is needed in order to prove that these vitamin supplements directly cause cancer.
However, you should be careful when taking vitamin supplements because vitamins that are very healthy when taken through food may be dangerous when taken as supplements. Such example is beta-carotene – the precursor form of vitamin A which when consumed through food can help you prevent cancer, but when taken as a supplement (in high doses) can increase the risk of lung cancer in smokers.
The World Cancer Research Fund also recommends consuming vitamins through diet, and not through supplements. Moreover, it is very easy to get the needed dosages of vitamin B6 and B12 through foods such as fish, pork, chicken, liver, milk, eggs, soybeans, whole grains, walnuts and peanuts.