Nutritional Pearls: B Vitamin Supplements Linked to Lung Cancer
Your patient is a 56-year-old man concerned about his risk of cancer. When asked about his diet, he admits that he probably does not eat as healthy as he should but tells you that he does take “a lot of vitamins,” including vitamin C, B6, and B12.
(Answer and discussion on next page)
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Answer: Vitamins are best sourced from food, not supplements.
An analysis of data from a large-scale study of long-term dietary supplement use and cancer shows a strong link between long-term consumption of certain B vitamins and the risk of lung cancer.
A study known as the VITAL cohort (VITamins And Lifestyle) began recruitment in 2000 in several counties of Washington State in the United States and continued recruitment through 2002, enrolling a total of over 77,000 men and women between the ages of 50 and 76 years. The period used for analysis ended in December of 2007, when the authors assessed the supplement-taking habits of those who developed lung cancer over the course of the study and compared them to those who did not develop lung cancer.
At the start of the study, the participants reported their intake of multivitamins, vitamin supplements, and vitamin supplement combinations (such as combinations of B vitamins or antioxidant mixtures of A, C, and E). The study's initial questionnaire established not only which vitamins the participant took regularly, but also for how long. Further questionnaires looked at diet, health history, and cancer risk factors such as smoking and alcohol intake.
For this article, the authors focused on 3 B vitamins: B6, B9 (folic acid), and B12. Using the participants' questionnaires, which asked for specific formulations of these vitamins, the authors could stratify B vitamin intake in increasing levels, from no use of supplements to very high doses taken daily over 10 years. (For reference, a moderately high dose of B6 was considered to be 20 milligrams per day: the recommended daily allowance for men over 50 is about 1.7 milligrams per day and for women over 50 is about 1.5 milligrams per day.) In their stratification, the authors made certain that those who were simply taking an amount of B vitamins similar to that in a daily multivitamin were not considered to be in the higher levels of intake.
For their analysis of lung cancer risk, the authors were careful to take into account smoking status, classifying participants as those who had never smoked, those who had smoked in the past but had quit over 10 years before, those who had quit less than 10 years before, and those who were still smoking. Similarly, they considered the participants' family history of lung cancer as well as whether the female participants were utilizing hormone therapy for menopause.
The researchers found that although women tended to take higher doses of B vitamins from supplements than men, only men saw increased risk of lung cancer from taking B6 or B12 supplements. When the authors calculated an average 10-year daily dose of B vitamins for the participants, those taking the highest levels of B6 and B12 supplements were as much as 2 and nearly 3 times as likely to develop lung cancer than those who did not take B vitamin supplements at all. When the authors looked at shorter periods of intake, similar bad news applied: men who took individual B6 or B12 supplements had a 40% or 33% increase in risk of lung cancer, respectively.
What’s the Take-Home?
This research supports the notion that vitamins are best sourced from food, not supplements. Good dietary sources of vitamin B6 include garbanzo beans (chickpeas), fatty fish like tuna or salmon, fortified cereals, and even bananas. Sources for B12 also include fortified cereals as well as clams, trout, salmon and tuna, milk, and eggs.
Brasky TM, White E, Chen CL. 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.