Vitamin B12 Balancing: The Hazards of Insufficiency and Excess


As personal trainers we occasionally dispense post-workout advice to curious clients; no doubt a significant majority of us suggest some brand or other of a hydrating “sports beverage”. Many clients whose eating habits may leave them deficient in key minerals and vitamins briefly read the beverage label and deem the quantity of vitamins sufficient for their active lifestyle. Could these individuals still harbor a risk for vitamin B12 deficiency? Conversely, what hidden culprits may result in a deleterious excess?

B Vitamin Basics

Water-soluble vitamin B12, also known as cobalamin, plays a key role in many biological functions, such as the immune system response, mitochondrial processes, production of myelin and red blood cells, and the synthesis of the neurotransmitters serotonin and dopamine.

Several characteristics set B12 apart from other B vitamins, namely the fact that it contains a metal ion. The presence of cobalt accounts for the name cobalamin.

A water-soluble vitamin will rarely reach the point of excess in the body. Our renal system (kidneys) filters the vitamin from blood and eliminates it along with water. Even if an occasional transient excess builds up, the ramifications remain largely innocuous: the body can store sufficient B12 in the liver, meaning those whose bodies contain a slight abundance can go years without needing to purposefully consume it.

B12 Deficiency Dilemma

In spite of the body’s capacity to store B12 in the liver, some individuals consistently present with low (often dangerously so) circulating levels in their blood. The serious effects of vitamin B12 deficiency include anemia, depression, dementia, and hallucinations. Tingling in the lower limbs often sets in, along with neuropathy, fatigue, and an accelerated heart rate. Irritability also ranks highly on the list of reported symptoms.F

Many factors exist to explain why some individuals have low B12 stores. Since the primary sources of the vitamin B complex group include animal-derived protein – beef, chicken, dairy, and fish – both vegans and vegetarians must find other B12-rich food sources. Fortified cereals and breads, along with plant-based milk substitutes and healthful seaweed can help to fulfill B12 requirements.

Additionally, certain gastrointestinal issues can lead to malabsorption of nutrients, including B12. Celiac disease, Crohn’s, leaky gut, and atrophic gastritis will all affect gut-related absorption. Age contributes to this problem as well; older individuals lose the ability to effectively absorb vitamin B as time goes on.


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Beware of Rare Excess

As mentioned above, the human body rarely accumulates an excess of circulating B12, certainly not to any degree of toxicity. Thus, when a consistently high value of vitamin B12 in one’s body presents itself, this generally indicates the presence of underlying illnesses, some of which need immediate medical attention. A damaged liver/liver disease, kidney failure, and a unique subset of blood cancers known as myeloproliferative disorders (most notably, myelocytic leukemia) can cause an excess build-up of this micronutrient.

In their very early stages, illnesses associated with high vitamin B12 often present with generally common symptoms, such as fatigue and loss of appetite. While such symptoms come and go at some point in all of our lives, persistent conditions create an urgency to consult a physician. A blood test will confirm a dangerous excess of vitamin B, and considering the potentially life-threatening nature of some of these illnesses, an early diagnosis makes all the difference.

One research study attempted to draw a correlation between levels of vitamin B12 in one’s system and death rates. The scientists observed that among the participants studied, those whose blood showed the highest levels of B12 also had a higher death rate. Science has yet to determine any definitive reason for this outcome; hopefully continued additional research will eventually yield answers.

Senior author Dr. Stephan J.L. Bakker, a professor of internal medicine at the University Medical Center Groningen in the Netherlands, refers to the data as “only an association, not a cause-and-effect relationship.” He adds, “High amounts of vitamin B12 are often taken without a medical indication.” Dr. Bakker goes on to say how excessive levels of B12 “might change the gut microbiota in ways that could be harmful — but no one really knows.”

Natural Steps to Safely Lower Excesses of B12

When an individual presents with greatly elevated circulating levels of B12, and physicians have ruled out any serious underlying comorbidity, several easy steps can help return the level to a normal range.

Engage in regular moderate exercise. The resulting heat generated by the body causes sweating, a natural mechanism for shedding water (and with it, water-soluble vitamin B12). Exercise also lends itself to an increase in water consumption which, in turn, will boost renal activity. Water remains the beverage of choice, since a majority of “sports drinks” contain added vitamins, including B12.

*With the growing popularity of intramuscular and intravenous high vitamin doses to restore “energy” clients who subscribe to these practices need to be reminded that movement and nutrient-dense diet is still necessary.

Consume a natural mild diuretic, such as coffee or tea. Once again, this causes a positive impact on the body’s renal system, thereby helping to filter out excess quantities of vitamin B12.

Shift meal planning to include more plant-based sources of protein. Reduce consumption of animal-derived foods, as they serve as a generous provider of B12.


Vitamin B12



Cathleen Kronemer is an NFPT CEC writer and a member of the NFPT Certification Council Board. Cathleen is an AFAA-Certified Group Exercise Instructor, NSCA-Certified Personal Trainer, ACE-Certified Health Coach, former competitive bodybuilder and freelance writer. She is employed at the Jewish Community Center in St. Louis, MO. Cathleen has been involved in the fitness industry for over three decades. Feel free to contact her at [email protected] She welcomes your feedback and your comments!