Vitamin B12 – A Game Changer

Vitamin B12 – A Game Changer

B12 is hugely important for complex physiological functions of complex body systems such as synthesis of DNA and RNA, synthesis of red blood cells, and lipid synthesis and proper cell division.  

To sum up – this vitamin is essential for life.

B12 vitamin is not made by humans, nor is produced by animals. It is, in fact, made by microbes in animals’ gut, after ingesting bugs, dirt, and faces. This is why the omnivores put a strong emphasis on the role of animal proteins in the diet, arguing that we can get enough of this essential nutrient only by eating animals.

Drinking water wells and mountain groundwater may still have it, but as we today chlorinate our water to remove waterborne pathogens, this way we remove vitamin B12 as well.

Why eating eggs can’t provide enough of B12

For example, to get 47 micrograms of B12 (from eggs), we would have to eat hundreds of eggs a day, because the absorption of the vitamin is very low. To get enough of B12 from scrambled eggs, we need to consume 69,000 milligrams of cholesterol—practically the entire year amount every single day.

Although bacteria in the colon can make B12, it is unabsorbable because is just too far down the intestine to be absorbed (most of the nutrients are metabolized in the small intestine and a very small part in the colon).  

How vegetarians/vegans get enough vitamin B12?

Fortified foods (mainly cereals) and supplements are the safest and the most effective way to supply our body with the necessary amount of the vitamin. 

Interestingly, despite popular thinking that eating animal proteins can provide the right amounts of vitB12, the U.S. Framingham Offspring Study showed that one in six meat-eaters between ages 26 to 83 were, in fact, B12-deficient! 

Namely, the study found out that participants with the highest B12 levels weren’t those who eat animal proteins, but those taking supplements and fortified breakfast cereal. This means that eating animal proteins alone won’t save you from B12 deficiency, because there are other factors in play. 

Aging, for example, is another risk factor for developing B12 deficiency, because the body’s ability for B12 absorption declines with age.

However, eating fortified cereals, B12 supplements, and tiny amounts of dairy products, would be just enough to meet this need for B12.

B12 deficiency leads to serious conditions

The population at greater risk of lack of B12 are young children, vegans, vegetarians, and people over 50 years old. 

B12 deficiency can lead to serious health disorders such as megaloblastic anemia, oral fistulas, neurological manifestations (paranoid schizophrenia), vegetarian myelopathy, and irreversible degeneration of the spinal cord. B12 is also essential for arterial walls! In B12 deficiency homocysteine accumulates in the arteries and can damage their walls.

How much B12 supplements we should be taking?

How much of B12 supplements and how long, and whether we should take it daily or weekly, depends on many factors, including diet, gender, age, and pregnancy. If we are on a vegan or vegetarian diet the right amounts of B12 and other vitamins are vital for preserving good health. 

According to the NIH Office of Dietary Supplements recommended daily intake for Vit B12 is 2.4 micrograms per day for healthy individuals above the age of 14, and pregnant and lactating women slightly higher – 2.6 and 2.8 micrograms, respectively.

However, because the absorption of Vitamin B12 supplements is extremely low (only about 10 mcg of a 500 mcg oral supplement is actually absorbed in healthy people) here are the suggested doses that should provide you with the enough of vitB12:

  • At least 2500 micrograms of cyanocobalamin once a week, ideally as a sublingual supplement, aqueous solution, or chewable tablets. 
  • Or 250 micrograms per day 
  • Or 3 servings per day of vitamin B12 fortified foods.

If you are Vitamin B12 deficient, the best option is to talk to your doctor to determine the right dose to correct the anemia.

The tolerable upper limit (UL – maximum daily intake that is unlikely to cause adverse effects) for VitB12 is not established, and there is no evidence of adverse effects of supplements intake (in patients with B12 deficiency) of up to 1000 µg/day orally for prolonged periods (up to 5 years).

What to measure in the blood to find out about levels of B12?

Vegans may have a B12 deficiency, but their blood levels could, at first, seem completely normal. Because high levels of folic acid (naturally occurring B vitamin) for those on a vegan diet can mask lack of the nutrient.

If B12 deficiency is suspected, the best test is urinary MMA, not serum B12, because only increased MMA and homocysteine ​​are reliable signs of deficiency.

The latest test – holotranscobalamin, also measures its levels.

How long to take B12 supplements? Lifelong? Occasionally?

It is important to remember that mild B12 deficiency, which is commonly overlooked, can occur with almost any type of diet, but vegan and vegetarian dieters are most likely to develop severe manifestations and need to take the supplementation throughout the life-course.

It is good to know that those switching to vegan, or meatless diet, need not to worry about the levels of B12 in the near future. They will be having still their past reserves of vitB12 in place, even after a year or two, which might prevent the absorption of the supplementation taken (if we don’t need it). Plus, the vitamin is hydrosoluble which means that the surplus is excreted via urine.

Remember: whatever your age and type of a diet you consume, it is of paramount importance to check B12 levels in the blood, at least yearly, because deficiency of this vitamin is still commonly missed in many diagnoses, such as anemia for example, which sometimes takes months to resolve. As for vegetarians and vegans they need to take vitamin B12 regularly, preferably in the form of supplementation. Most importantly, consult your doctor, or nutritionist, to find out whether you should take dietary supplements in the first place, and on the correct dose, you might need.


  • Katherine L Tucker, Sharron Rich, Irwin Rosenberg, Paul Jacques, Gerard Dallal, Peter WF Wilson, Jacob Selhub, Plasma vitamin B-12 concentrations relate to intake source in the Framingham Offspring Study, The American Journal of Clinical Nutrition, Volume 71, Issue 2, February 2000, Pages 514–522,
  • European Food Safety Authority. Tolerable upper intake levels for vitamins and minerals.EFSA, February 2006.
  • National Institutes of Health. Office of Dietary Supplements. Vitamin B12.
  • Carmel R. How I treat cobalamin (vitamin B12) deficiency. Blood. 2008;112(6):2214-2221. DOI:10.1182/blood-2008-03-040253
  • Healton EB, Savage DG, Brust JC, Garrett TJ, Lindenbaum J. Neurologic aspects of cobalamin deficiency. Medicine (Baltimore). 1991;70(4):229-245. doi:10.1097/00005792-199107000-00001