Cancer is an umbrella term for a host of diseases characterised by the rapid and uncontrolled proliferation of cells. There are numerous factors known to kick start the deadly malignancy. While supplements are generally hailed for their protective effects against the disease, others may promote cancer. One study has highlighted the detrimental effects of taking high doses of B12 and B6 for certain men.
The study, published in Journal of Clinical Oncology, looked at a cohort of 77,000 adults, 800 of whom developed lung cancer during the study’s follow-up period of six years.
Although the team observed no increased risk among women taking B6 and B12 supplements, men who took more than 20 milligrams of B6 per day had an 82 percent greater chance of the disease, relative to those who didn’t.
Men who consumed more than 55 micrograms of B12 per day saw their risk of lung cancer increase by 98 percent relative to those who didn’t take B supplements.
What’s more, men who smoked at the outset of the study and consumed high levels of the B vitamins were three to four times more likely to develop lung cancer.
“There’s simply no scientific backing for these doses.”
The findings were deemed valid by the head of the genetics section with the International Agency for Research on cancer, Paul Brennan.
However, they were later challenged by conflicting results published in the Journal of the National Cancer Institute, which didn’t find any links between B6 intake and lung cancer.
Mr Brennan noted: “If anything, we found a small protective effect that was more apparent among men.
“There is still clearly no evidence that these vitamins have any substantial protective effects. Smokers taking these vitamins should quit smoking.”
Duffy McKay, senior vice president of the Council for Responsible Nutrition, urged consumers to “resist the temptation to allow sensational headlines for this […] study to alter their use of B vitamins.
“He noted: “The numerous benefits of B vitamins from food and dietary supplements – including supporting cognition, heart health and energy levels – are well-established.”
He highlighted some of the limitations of the study, which required participants to memorise what they had eaten over the past decade.
Vitamin B6 and B12, which can be sourced naturally by adhering to a balanced diet, can have other adverse effects when taken in high doses, according to the NHS.
Taking more than 200mg of B6 per day can lead to a loss of feeling in the arms and legs, known as peripheral neuropathy, according to the health body.
Although these effects are generally short-lived, they can become permanent in individuals who continuously take large doses of the supplement.
“The effect of taking vitamin B6 at doses between 10 and 200 mg is unclear,” adds the NHS. “So there’s not enough evidence to say how long these doses could be taken for safely.”