Why you shouldn’t be wary of B12

Vegans who “don’t believe” in supplements may have found themselves celebrating lately. It’s been reported that high levels of vitamin B12 (which vegans are advised to supplement with) might be linked to an increased risk of cancer.

The most recent news challenges the long-held view many of us have had for years, ostensibly based on science, that keeping your vitamin B12 (and folate) levels up could help reduce  your cancer risk. Type “vitamin B12 and cancer” into an internet search, and you’ll see plenty of authoritative sites telling you just that.

And it’s not just cancer. B12 might also reduce your risk of heart disease and Alzheimer’s. But science is rarely black and white. Dig a bit deeper, and you’ll see studies that suggest the exact opposite, especially when it comes to folate—or at least its synthetic, oxidized form, folic acid.

But in the last few months, B12 has been starting to get something of a bad rap, following in the wake of its closely related B vitamin partner, folate. The news has even gotten to some European government regulators, who
are trying to pull high-dose
(500 mcg and higher) B12 off
the shelves.

Because it’s the vitamin that vegans are most deficient in, those vegans who don’t take supplements to boost their levels may find this news reassuring. Are they actually better off, long-term, than those taking high-dose lozenges or even B12 intravenously or as injections?

Could we really increase our cancer risk if we up our B12 levels with supplements? The short answer is a resounding “No.”   

At the heart of the confusion are two studies, one good, the other suspect. Together, they’re akin to “two plus two makes five,” and are leading to some serious confusion among the public, healthcare professionals and some regulators.

The first study, the good-quality one, is by researchers from the Department of Clinical Epidemiology at Aarhus Hospital in Denmark and based on data from Danish medical registries between the years 1998 and 2014.1 

They looked at circulating vitamin B12 (cobalamin) levels in around 25,000 people one year prior to a cancer diagnosis and compared them  with around 60,000 cancer patients in whom circulating B12 levels hadn’t been measured.   

What they found was enough to put a shiver up the spine of any die-hard B12 lozenge-lover or IV addict: sky-high levels of B12 in those who died the fastest.

But, as with all medical research, you have to look beneath the surface. There you’ll find that the study’s authors are at pains to say these very high levels of B12 have absolutely nothing to do with dietary intake or any other external sources of B12.

Instead, what they discovered is an anomaly linked to what happens when people get cancer. B12 reserves in the liver, it seems, become mobilized, and that’s what you find in the bloodstream of people with cancer.

Why? Because B12, for the same reason as folate, is a nutrient involved in one-carbon metabolism. That means the body needs it to make new cells.

So, when the body moves into tumor-creation mode, itself a complex imbalance relating to multiple systems, it redirects metabolism in ways that allows it to draw in the nutrients it needs.

You’ve probably all heard of sugar being one of them. Well, you can add folate and B12 to that list. Just remember: the B12 can’t create cancer—in fact, it can act as a one-carbon nutrient to help multiple other systems, too, including the immune and mitochondrial systems, both of which are especially greedy for nutrients when they’re firing on all cylinders.

The other study, the suspect one,  is a re-analysis of the UK Vitamins and Lifestyle (VITAL) cohort.2 The researchers observed an association between lung cancer and those taking multivitamins that contain over 55 µg/day of vitamin B12 and over 20 mg/day  of vitamin B6, another one-carbon nutrient.

They concluded that, based on this observation, the multivitamins are not protective and may even be harmful, inducing more cancer.

The thing is, the data source (a questionnaire with a 23 percent response rate) included so many uncontrolled sources of variance and bias, without any supporting blood measurements, that it’s impossible to draw the conclusions the scientists did.

Fortunately, an astute peer-reviewed response to the paper published in the same journal the following year painted these findings for what they really were: speculation.3 

The long and short of it is that you must draw conclusions based on the overall evidence. You’ll now perhaps appreciate how the 2017 analysis of the VITAL cohort, coupled with a misreading of the Danish study in 2016, has caused a fair number of people  to add two plus two incorrectly.

So don’t be fearful of B12, other than being concerned you might not be getting enough of the stuff. And if you’ve chosen to limit meat from your diet, it’s especially important you get additional B12—at levels a few thousand percent over those recommended by governments.

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