I was in the first graduating class of the ADAPT Program from the Kresser Institute. I would like to thank Chris Kresser for most of the information in this post.  

Vitamin B12 (also known as cobalamin as it contains cobalt) is essential because so many functions require it. It works with folate in the production of DNA and red blood cells. Its other essential functions are:

• The production of myelin which is critical for nerve conduction.

• The production of the amino acids methionine and cysteine.

• Methylation reactions which help regulate numerous bodily functions.

• Energy production.

• The production of nitric oxide and reduction of inflammation.

  
  
  

How Commonly Does Deficiency Arise?

Vitamin B12 deficiency is way more common than most conventional physicians are willing to admit. The literature states that only 7% of the population is deficient, but the current limit of 200 ng/ml is probably too low. Neurological symptoms can be experienced in the low-normal range, and western medicine ignores this fact. Using functional medicine standards, which are higher, nearly half of the population may be suffering from B12 deficiency. Data from the Tufts University Framingham Offspring Study suggests that 40 percent of people between 26 and 83 have plasma B12 levels in the low-normal range. Most surprising to the researchers was that low B12 levels were as common in younger people as in the elderly. This is alarming as children suffer irreparable neurological damage with chronic B12 deficiency.

 How is it Measured?

Most MD's only test blood level B12, which is inaccurate. Only the B12 inside cells matters. High levels of vitamin B-12 can actually be seen in liver disease, leukemia, or diabetes. High serum folate levels may mask vitamin B-12 deficiency and worsen the symptoms. (1)There are four vitamin B12 deficiency stages, and the clinical signs do not show up until stage four! In stages one and two, only the amount of B12 in cells is depleted. There is only one test called HoloTC that can pick up these stages. It is not commonly used by most physicians. In stages three and four, functional B12 imbalance is characterized by elevated homocysteine and urinary or serum MMA concentrations. MMA, HoloTC, and Homocysteine test are all important and should be used when B12 deficiency is suspected.

What are the Symptoms of Deficiency?

Low B12 status can mimic the signs and symptoms of diseases that are commonly associated with aging, such as Alzheimer's, dementia, cognitive disorders, multiple sclerosis, Parkinson's, and other neurological problems; mental illnesses such as depression and anxiety; cardiovascular disease; cancer; and low libido. B12 deficiency can take years to become clinically evident, and

the effects can be irreversible. Symptoms of B12 deficiency range from nonexistent when it's mild to severe and irreversible, and they include:

•  Weakness and fatigue.

• Numbness and tingling in the hands, legs, or feet.

• Difficulty walking, such as staggering or balance problems.

• Anemia.

• A swollen and inflamed tongue.

• Jaundice.

• Difficulty thinking and reasoning.

• Memory loss.

• Paranoia or hallucinations.

  
  
  

What Are the Causes of B12 Deficiency?

The most common cause of B12 deficiency is an inadequate intake, which is common in vegetarians and vegans. 68 percent of vegetarians and 83 percent of vegans test low, compared to just 5 percent for omnivores. Conventional testing is missing 61 percent of vegetarians and 31 percent of vegans who are B12 deficient!

Other causes include:

• Low stomach acid.

• Celiac disease.

• Crohn's disease.

• Other gastrointestinal conditions like SIBO and dysbiosis.

• Pernicious anemia. 

H. Pylori infections and proton pump inhibitors like Nexium cause low stomach acid, interfering with the absorption. The diabetes drug metformin has also been shown to deplete B12 levels. 

What Foods Contain B12?

Only animal-based foods and soil-based bacteria contain B12. There are reports that some vegetables (especially Spirulina, blue-green algae) contain B12, but these are unfounded. Because soil-based bacteria make B12, dirty vegetables can include some. The best sources are (once again) organ meat and shellfish. Meat is the second-best source and dairy third. If you are not eating organ meats or fish, there is a distinct possibility you are not getting enough B12.

How Much Should We Be Ingesting?

As you may already know from many previous posts, food sources are the best way to achieve adequate B12 levels. Research by Loren Cordain suggests that the average daily intake of hunter-gatherers was 17.6 micrograms per day, which is significantly higher than the U.S. RDA, which is only 2.4! For adults over 50 or adults with impaired absorption, the RDA increases to 150 to 200 micrograms per day. In those populations, less than 1 percent of oral B12 that is consumed is actually absorbed. I believe the studies that suggest an RDA of 7 micrograms per day in people without absorption issues are more realistic.

What About Supplements?

There are four types of supplemental B12 available: methylcobalamin, hydroxocobalamin, adenosylcobalamin, and cyanocobalamin. The first three are naturally present in foods.

Cyanocobalamin is a synthetic form that can be converted into adenosylcobalamin and methylcobalamin. Still, its bioavailability is low compared to the other forms. The best supplements should contain all three natural sources combined with folate. Since some people can't absorb B12 in their intestines, a sublingual dose is best. An excellent brand is Trifolamin by Designs For Health.

Conclusion

I have barely scratched the surface; there is a ton more information available about B12. The major takeaways are that many of us are deficient without knowing, even if tested. Vegans and vegetarians are most at risk, but unless you are eating shellfish and organ meat, you too are at risk. The young are just as likely to experience shortages, which can lead to irreversible damage. This post is not meant to diagnose, treat, or give any medical advice. If you suspect you may have a problem, contact a functional medicine practitioner in your area.