Vitamin B12, scientifically termed cobalamin, is an essential nutrient mainly consumed through animal products. It can also be consumed as a supplement or added to foods. Vitamin B12 plays a role in producing red blood cells and DNA and helps in the proper functioning and growth of the human brain and nervous system.

Consuming an adequate amount of nutrients is necessary to function the human body optimally. For example, knowing the right amount for consumption and the negative repercussions of not consuming enough Vitamin B12 is equally essential. This article briefly discusses vitamin B12 deficiency, including the causes, treatment, and more, which everyone should be aware of and share among their colleagues.

How much is Vitamin B12 “too much”?
The maximum daily amount that is unlikely to cause undesirable side effects in the general population is the Tolerable Upper Intake Level (UL). There is no defined hazardous level for vitamin B12; hence there is no upper limit. However, according to some data, supplementation with 25 mcg or more per day may raise the risk of bone fractures. Also, there exists a lower limit beyond which the deficiency of VitaminB12 can occur, rendering individuals diseased and symptomatic.

So how much Vitamin B12 should you consume in a day?
The RDA (Recommended Dietary Allowance) for males and females aged 14 and above is 2.4 micrograms (mcg) per day. During pregnancy and lactation, the dose increases to 2.6 mcg and 2.8 mcg per day.

Do you think you are at risk for developing Vitamin B12 deficiency? Let’s find out!
Up to 15% of the general population suffers from Vitamin B12 deficiency, and there are several reasons behind developing Vitamin B12 deficiency.

Here are important factors that result in Vitamin B12 deficiency:

  • Low/absent intrinsic factor:
    As the intrinsic factor helps absorb Vitamin B12, the lack of it will result in Vitamin B12 deficiency. Pernicious anemia is an inflammatory illness that attacks and damages the gastrointestinal cells, preventing the release of intrinsic factors, thus preventing the absorption of vitamin B12. In this case, taking a high-dose B12 supplement also won’t help.
  • Vegetarian/ Vegan diet:
    Since animal products have vitamin B12 in suitable amounts, people who do not consume meat, fish, poultry, or dairy are thus at risk of becoming Vitamin B12 deficient. In addition, studies have found the blood levels of vitamin B in vegetarians lower than non-vegetarians.
    As a result, vegetarians and vegans should supplement their diets with B12-fortified foods or take a B12 supplement. This is especially crucial for pregnant women because the fetus requires sufficient vitamin B12 for neurologic development, and a deficit can result in irreversible neurological impairment.
  • Malabsorption/ gastrointestinal diseases:
    The intrinsic factor is released in the stomach while vitamin B12 is absorbed in the distal part of the ileum. Therefore, any illnesses affecting these two areas may result in Vitamin B12 deficiency, for example, Crohn’s disease, malabsorption syndromes, etc.
  • Undergone stomach / intestinal surgery:
    People who have undergone stomach / intestinal surgery, for example, weight loss surgery, might develop vitamin B12 deficiency.
  • Old age (above 50 years):
    Stomach acid is essential in absorbing Vitamin B12 from the food we consume. However, in people aged above 50, due to a lack of acid secretion, the risk of getting Vitamin B12 deficiency becomes more common. Also, older people who take proton-pump inhibitors, H2 blockers, or other antacids daily to treat illnesses like gastroesophageal reflux disease (GERD) or peptic ulcer disease may have trouble absorbing vitamin B12 from meals. These medications can either slow or stop the production of stomach acid. Hence it is essential to watch this population for developing Vitamin B12 deficiency and fortify food with B12 enriched foodstuffs and supplements as and when required.

Signs and symptoms of Vitamin B12 deficiency:

  1. Anemia
    Anemia basically means a low healthy red blood cell count. Vitamin B12 helps produce RBCs, which help transport oxygen throughout the body. Your tissues and organs won’t get enough oxygen if you don’t have enough red blood cells. Your body won’t work at an optimum level if you don’t have adequate oxygen, and you’ll end up feeling lethargic. Anemia can be of 2 types:
    1. Megaloblastic anemia is a disorder characterized by larger-than-normal red blood cells and a lower-than-normal number of the same.
    2. Pernicious anemia occurs due to the lack of intrinsic factors.
  2. Weakness, fatigue
  3. Tingling sensation and numbness in the hands and legs
  4. Confusion

How is Vitamin B12 deficiency diagnosed?

The CBC, vitamin B12, and folate levels diagnose vitamin B12 deficiency. Megaloblastic anemia is usually detected by a complete blood count (CBC).
People should not think of Vitamin B12 deficiency and folate insufficiency as the same disease. People with folate deficiency have an elevated homocysteine level. However, people with Vitamin B12 deficiency have a high level of homocysteine and MMA. Therefore, folate supplementation can mask vitamin B12 deficiency and ameliorate megaloblastic anemia while allowing neurologic impairments to continue or accelerate. In addition, other diagnostic tests can be performed if:

  • Clinical diagnosis suggests vitamin B12 deficiency
  • vitamin B12 level is low to normal (200-350 pg/mL [145-260 pmol/L]), or the hematologic indices are normal.

Other tests include assessing serum methylmalonic acid, homocysteine, and transcobalamin levels. Physicians may also go for Schilling tests in adults and younger populations, especially those with pernicious anemia.

How is Vitamin B12 deficiency treated?

Vitamin B12 supplements of 1000-2000 mcg are given orally to patients suffering from mild symptoms. In case of severe symptoms, Vitamin B12 1 mg intramuscular (IM) is administered 1 to 4 times a week until hematologic abnormalities are resolved. Post resolution, a Vitamin B12 injection is given once a month. Unfortunately, the resolution of hematologic abnormalities occurs quicker than neurological manifestations. Therefore, unless the pathophysiologic mechanism underlying the shortage is rectified, the patient should continue with vitamin B12 medication for the rest of their life as per the physician’s advice.

Can you prevent Vitamin B12 deficiency?

It is crucial to diagnose and treat Vitamin B12 deficiency early to avoid suffering from significant health complications and irreversible neurological manifestations. In addition, a proper diet with the advice of a nutritionist or physician can prevent Vitamin B12 deficiency.
If you’re a committed vegetarian or vegan, you should eat vitamin B12-fortified bread, cereals, and other grains or take a daily supplement as directed by the physician. A regular multivitamin has six micrograms, more than enough to meet the average person’s daily requirements.
Pregnant vegan mothers should take Vitamin B12 supplements regularly as prescribed by the doctor. Supplemental vitamin B12 should also be given to vegan mothers’ babies from the moment they are born to avoid deficiency in them.
Always take medications after consulting a medical practitioner.


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