Vitamin supplements are also widely used in many European countries. However, a US study showed that vitamins B6 and B12, taken as individual nutritional supplements, may have a role in male lung cancer incidence.
Previous studies had already provided the medical community with initial, mostly ambivalent findings on B vitamins and their relation with human tumors. However, since B vitamins have become one of the world's most popular dietary supplements, the slightest suspicion that they may promote tumors is reason enough for their review.
Brasky et al used data on lung cancer risk from the Vitamin and Lifestyle Cohort (VITAL). Their current work investigated the influence of long-term vitamin B supplements on lung cancer risk in male and female 77.118 participants.
All study participants were between 50 to 76 years old and were recruited between 2000 and 2002. The study authors were particularly interested in the daily dose of B-vitamins and multivitamin preparations during a 10-year observation period. A total of 808 cases of primary invasive lung cancer occurred.
As a result, vitamins B6 and B12 had no effect on lung cancer risk in the studied women cohort. In men, however, the intake of B6 and B12 as individual supplements led to a 30% to 40% higher risk of lung cancer. Multivitamin preparations, which also contained vitamins B6 and B12, did not appear to increase the risk of tumors in men either.
The effects of the individual supplements over 10 years were particularly pronounced for a daily dose of > 20 mg/day vitamin B6 (HR 1.82; 95% CI, 1.25 - 2.65) and > 55 µg/day vitamin B12 (HR 1.98; 95% CI, 1.32 - 2.97).
From these daily rations, the risk of tumors doubled compared to people who never took vitamin supplements. Brasky and colleagues also showed that smoking increased this risk even more. Interestingly, there was a link between the vitamins and the histological type of lung tumor, with the exception of adenocarcinoma, which is much less frequently associated with smoking.
This study shows once again that vitamins B6 and B12 are unlikely to be suitable for chemoprevention in lung cancer. Rather, these vitamins - taken over a longer period of time in the form of high-dose preparations - could even be harmful to men and increase their risk of lung cancer.
Vitamin supplements are actually unnecessary for the majority of patients enjoying a balanced nutrition. However, such preparations from drugstores and pharmacies are often used without properly controlled intake at home.
Doctors should, therefore, look with greater care on the topic of vitamin supplements and provide their patients with updated, exhaustive information. Indications, such as vitamin B12 deficiency, should be discussed with the patient and the effectiveness of supplementation monitored by a doctor.
Brasky TM et al., Long-Term, Supplemental, One-Carbon Metabolism–Related Vitamin B Use in Relation to Lung Cancer Risk in the Vitamins and Lifestyle (VITAL) Cohort. J Clin Oncol 2017; 35(30): 3440-3448.