The most common cause of B12 deficiency

Often-cited as a shortcoming of a plant-based diet is deficiency of Vitamin B12, an essential nutrient made by bacteria in the intestines of animals (including humans). For many omnivores, this is reason enough to continue eating animal products.

You may be surprised that the most common cause of B12 deficiency is not lack of B12 containing-foods but intestinal disease, and the prevalence of B12 deficiency among vegans is not much different than in the overall population. Some estimate says 15% or more of people are deficient in B12, and with deficiency increasing with age, and the Institute of Medicine recommends everyone over age 50 supplement with B12.

I discovered I had B12 deficiency prior to becoming vegan when I visited a brain specialist at age 40 with symptoms including fatigue, loss of memory and attention deficit. My general practitioner had diagnosed me with pernicious anemia, but had never ordered tests for B12. All the more reason everyone has to take responsibility for his or her own health!

The brain doctor gave me samples of a popular medication for Alzheimers–which I’m happy to say I didn’t try–after reading about its alarming short and long-term side effects. After my blood tests results showed I was dangerously low in B12 (prolonged deficiency could lead to permanent nerve damage), I had a series of intramuscular B12 injections to restore my B12 to a normal level, and continued to supplement with monthly injections.

The reason oral B12 supplementation would liquid vitamin b12 not work is the same reason my B12 levels were low in the first place: I lack “intrinsic factor”, a co-enzyme produced in a normal stomach necessary for the B12 contained in foods (predominantly those that are animal-based) to be absorbed in the lower intestine.

Follow up blood testing after regular B12 supplementation confirmed my B12 remained within normal ranges. I also found my thinking, attention, memory, etc. clearer than it had ever been. B12 is the only nutritional supplement I take, as I rely on whole foods for everything else. For example, 1-2 Brazils Nuts satisfies your daily requirement of selenium, magnesium and zinc.

While there are a few reliable plant-based sources of B12 (i.e. seaweeds and probiotics), most vegans are advised to take a supplement, or eat B12 fortified foods such as Vegetarian Formula Nutritional Yeast.

I continued B12 injections until early last year, when I met Dr. Michael Greger (founder of the amazing, who informed me that sublingual B12 tablets would achieve the same result as injections (bypassing the digestive system and sending B12 into the bloodstream) more safely than injections. Dr. Greger’s website contains a series of very informative videos on B12, including this one where he states that “we’d have to eat 200-400 eggs/day to get enough B12” and recommends B12-fortified foods (such as breakfast cereal) for those wanting a cholesterol-free source of B12.

People with B12 deficiency should take sublingual tablets every day, while vegans without deficiency should take oral supplements once/week. The trick to tablets–compared to injections–is remembering to take them. According to Dr. John McDougall’s article Vitamin B12 Deficiency-the Meat-eaters’ Last Stand, most oral supplements contain many thousands times greater amounts of B12 than the 3 micrograms a day required. Fortunately, there does not appear to be a risk from overdose.

Though the pain of injections didn’t bother me, one concern I had was the form of B12 (scientific name “cobalamin”) I was using. “Cyanocobalamin” is a cynanide compound which apparently leaves traces of cyanide behind. Two other forms of B12 are “Hydroxycobalamin” and “Methylcobalamin”. A naturopathic doctor once told me that Methylcobalamin should be avoided if you have dental fillings containing mercury, though I’ve not been able to confirm that.

Overwhelmed, I consulted Dustin Rudolph, the Plant-Based Pharmacist who shares his vast knowledge on Dustin said he was not aware of any studies showing the cyanide metabolite in Cyanocobalamin would lead to toxic effects in the human body, but added that to be on the safe side, he uses Methylcobalamin to get the job done.

Dustin also says he recommends a B12 and vitamin D supplement for all people whether they are plant-based or not and then to follow up blood work to determine if they are meeting their normal B12 and D levels in their body.

“Ultimately, whole plant-based foods are the foods with all the fiber, macro and micronutrients needed to survive and thrive,” Dustin said, “but many vegans and vegetarians do not eat a truly health promoting diet. For example processed junk foods such as potato chips, sugary cereals, oils, sugary desserts, soda, alcohol, refined white flour products, etc., are just as dangerous to the human body as many animal foods.”

For those of you just beginning a plant based diet, rest assured that your B12 levels will not drop overnight, by any means. According to Dr. McDougall, “it takes, on average, 20 to 30 years to become deficient, and that is if no vitamin B12 were consumed-which is impossible, even on a strict vegan diet, because of bacterial sources of B12 from the person’s bowel, contaminated vegetable foods, and the environment.

McDougall goes on to say that there is “less than one chance in a million” that an otherwise healthy vegan following a sensible diet would develop a disease from B12 deficiency.

Meanwhile, if you’re feeling tired all the time and/or have neurological concerns related to attention and memory, ask your doctor to have your B12 tested. Dr. Greger recommends a urine MMA (methyl-malonic acid) test, which is superior to blood testing, as it provides early warning of B12 deficiency.

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