(The following is taken in part from an excerpt from the FAQ Chapter in The "Plan A" Diet)
What is it?
Vitamin B12, also called cobalamin, is a compound produced by bacteria that can live in an environment without oxygen - such as dirt.
In days gone by, bacteria-based B12 found in the soil would be consumed by humans eating plants which still had a bit of dirt attached.
But because our society now fervently washes fruits and veggies to wipe out any trace of bacteria, we no longer get proper levels of B12 from our food—nor from our chlorinated water supply.
Why do we need it?
Vitamin B12 is important for the production of red blood cells, the formation of DNA, and for maintaining the normal function of the brain and nervous system. Animals and plants don’t have the enzymes to produce B12, but animal tissues do have the ability to store B12 when it’s consumed from foods—which is why meat, poultry, eggs, fish, and dairy foods are typically recommended as sources of B12.
Just as with calcium, animals have B12 in their systems because they’ve consumed it from their food.
So where does that leave those of us who only consume plant foods? Fortunately, our bodies can store B12 for several years too, so there’s no need to run out and immediately purchase supplements; but to be safe, it is important for plant-based eaters to take a vitamin B12 supplement.
Meat-eaters need it, too
Meat-eaters require supplementation just as much as plant-eaters do, as they often develop B12 deficiency for many reasons as well—poor absorption due to celiac disease, atrophic gastritis, weight loss surgery, Crohn’s disease, pancreas dysfunction, and the prolonged use of certain medications (Metformin, Prilosec, Prevacid, Tagamet, and Zantec, just to name a few).
For those reasons, B12 supplementation is recommended by the Institute of Medicine for all adults over the age of 50, regardless of their diet.
How much?
How much vitamin B12 should we take? The average adult needs only about 2.4 micrograms (mcg) per day, but you’ll notice that supplements are sold in much higher dosages.
The experts’ opinions vary on the appropriate dosage. The goal is to take enough B12 to keep our levels at a healthy range without incurring any side effects from taking too much.
Dr. John McDougall recommends taking 500 mcg weekly, in either the hydroxyl, methyl, or adenosyl forms; he suggests avoiding the cyano form due to possible toxicity issues.
Dr. Thomas Campbell recommends taking the smallest dosage in either cyano or methyl form, perhaps a couple of times a week, and having your blood checked to make sure it’s sufficient.
And because our bodies can only absorb a small amount of B12 in any pill, Dr. Michael Greger recommends 2000 mcg of the cyano form once a week, in a sublingual (under the tongue), chewable, or liquid supplement.
As you can see, the recommendations for B12 supplementation vary. I personally take 2000 mcg once per week and have had good results to date.
Should you get tested?
If you have health concerns that may affect your B12 absorption ability, please discuss the matter with your doctor.
For exclusively plant-based eaters, it's suggested by Dr. Thomas Campbell to get your B12 level checked every few years, particularly if you aren’t great about taking a supplement.
He also suggests checking your methylmalonic acid (MMA) level, which is more specific for testing to determine if you have enough active B12. Both are simple blood tests.
Another good way to assess your true B12 status is to measure total homocysteine. Methyl B12 is needed as a co-factor to convert homocysteine back into methionine. If you have normal B12 values, but high homocysteine levels, this may point to a deficiency or problem utilizing methyl B12.
Dr. Greger talks more about these two extra tests in this informative article.
What's normal?
Normal ranges of vitamin B12 vary by country and even within different labs. The lab that I personal use, Ulta Lab Tests, shows the lower limit of 200 picograms per milliliter (pg/mL), but recommends staying above 400 pg/mL to be safe. One plant-based doctor I recently interviewed said to shoot for 500-800 pg/mL.
There are many factors involved here. Overall health conditions, the use of medications, pregnancy, and other considerations. Get yourself tested to make sure you're in a normal range, and consider having your MMA and homocysteine levels checked as well since they're indicators of your functioning B12 levels.
Do your research and to make the best decisions 🙂