First, why do we need B12 anyway?
B12 is a nutrient that helps DNA and other genetic material, but it also helps keep our blood and nerve cells healthy. It also helps prevent a certain type of anemia called megaloblastic anemia. If you have this condition you likely feel tired or weak. So, B vitamins are often touted to give you more energy. But taking extra B vitamins will not give you extra energy unless you were deficient to begin with.
How do we get B12?
Today most people get it from the animal foods that they eat. But animals don't make their own B12; they get it from the ground. B12 is actually from a bacteria. Animals eat "dirty" food, ingest the bacteria, and their bodies store the nutrient produced in the animal's flesh. But humans used to get plenty of B12 just by doing things like gardening, and drinking from steams or springs. Now that we have outsourced these jobs, and sterilized our environment it is more difficult for vegans to get a reliable source of B12 without supplementation. For more detailed information see Dr. Klaper's video link below in the resources.
Depending on the resource you are citing, about 15% to as much as 40% of the population are not getting enough B12. So, it is not just vegans (only about 3.2% of the U.S. population) that can be deficient! This may be due to the fact that the first step in absorption starts in the stomach. If you have low, or weak stomach acid your body will struggle to break the nutrient down. So it is suggested that people 50 and older also supplement.
How much do we need? How do we know if we are getting enough?
The Recommended Daily Allowance (RDA) for men is 2.4 micrograms, and 2.6 for women. The only way to know for sure is to get your doctor to test your blood.
So should I take a supplement? What kind should I take?
If you are a vegan, then the answer is yes! The word that keeps popping up in my research is 'reliable.' There are no reliable sources of B12 in the sterilized environment that most of us live in today other than supplements. And, based on the statistic that I shared earlier it appears that vegans are not the only ones that should consider a supplement for a reliable source!
There is some research that shows that taking a B-complex is the best way to go since they work synergistically and there is evidence to suggest that absorption may improve when taken together. But, I am going to recommend that you talk to your doctor about your test results before making a final decision. B vitamins are water-soluable, so it is difficult to over dose since you will likely excrete any excess, but it is dangerous to exceed the upper limit (B6 is apparently the one to watch out for).
There are other considerations when choosing a supplement. In general, any of the many forms of B12 out there will be fine. But if you are one of the individuals mentioned previously that have digestive issues, or are over 50, you may want to consider a sublingual (under the tongue) form in order to bypass your digestive system. I, personally, have chosen a B12 tablet that goes under the tongue that I try to remember to do once a week. Again, please check with your doctor to determine what is right for you.
Dr. Klaper: https://www.facebook.com/rawfoodforlife.org/videos/1265738773542051/
Vegan Society: https://www.vegansociety.com/resources/nutrition-and-health/nutrients/vitamin-b12/what-every-vegan-should-know-about-vitamin-b12
National Inst. of Health (chart of RDAs): https://ods.od.nih.gov/factsheets/VitaminB12-Consumer/
B Educated: www.livenaturallymagazine.com