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Why Can't You Get B12 From Plants?


When CNN’s  documentary The Last Heart Attack premiered—documenting Bill Clinton’s attempt to reverse his heart disease through diet—pundits were eager to point out the downsides. Yes, eating a healthy plant-based diet may make us “heart attack proof“—but, some ask, what about vitamin B12?

So on one hand, there’s the possibility of eliminating the greatest killer in our country, which decimates the lives and families of more than 100,000 Americans every year, at an annual cost in the hundreds of billions. But, on the other hand, we risk vitamin deficiency? Are the defenders of the status quo seriously trying to stack a documented cure for heart disease (not to mention the reversal of diabetes, obesity, and hypertension) against some obscure B vitamin?

It’s true, plants don’t make B12.  Animals don’t make it either. B12 is made by microbes that blanket the earth. These bacteria grow in the guts of animals, which is why their bodies and products can be a source of this vitamin. Our herbivore primate cousins get all they need ingesting bugs, dirt, and feces, and we may once have gotten all we needed by drinking out of mountain streams or well water. But now we chlorinate our water supply to kill off any bugs. So we don’t get a lot of B12 in our water anymore, but we don’t get a lot of cholera either—that’s a good thing!

So in our modern, sanitized world, those eating plant-based diets must ensure a regular, reliable source of vitamin B12. 

Make no mistake: vitamin B12 is important. But so is keeping our perspective, given the millions who are crippled and die from the onslaught of chronic disease that could be prevented, stopped, and reversed with a B12-fortified, plant-based diet.

-Michael Greger, M.D.


Which Type of Vitamin B12 is Best–Cyanocobalamin, Methylcobalamin, or Hydroxycobalamin?

Question: Which B12 is best?


Answer: Unless you’re a smoker, have kidney failure or base your diet around cassava root, cyanocobalamin should be fine. That’s what I take!


- Michael Greger M.D


If you do have kidney failure, smoke, or consume cassava root, then stick with methylcobalamin.  Per, "Fred Bloem, M.D., a holistic physician in Maryland, states that methylcobalamin is a more bio-available form of vitamin B-12, while cyanocobalamin is cheaper. Your body must convert cyanocobalamin to methylcobalamin. A small amount of cyanide is released during the conversion process, but this isn't a concern if you are healthy, according to Dr. Bloem."

How Much B12 Do We Need And Where Do We Get It?

According to the National Institutes of Health, adults require just 2.4 micrograms of B 12 daily. If you’re breast-feeding, the requirement inches up to 2.8 micrograms. A benefit of breast-feeding is that your baby gets B12 from you. A bottle-fed baby needs 0.4 microgram through age 6 months, 0.5 micrograms from 7 to 12 months, and 0.9 micrograms from age 1 to 3 years.


Individuals following a vegan diet can easily meet their vitamin B12 needs by taking a daily multivitamin. B12 is also found in fortified breakfast cereals, soymilk, and meat analogues. Some brands of nutritional yeast, such as Red Star Vegetarian Support Formula, are a reliable source for this vitamin.


-Neal Barnard, M.D.

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