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Vitamin B12 Deficiency: Causes, Symptoms, and Treatment & More

Vitamin B12 is a water-soluble vitamin. Also known as cobalamin, vitamin B 12 is an essential vitamin out of the eight B group vitamins. The body does not store this vitamin for long and therefore Vitamin B12 deficiency can occur that can cause several health problems. That is why it is essential to keep its levels at an optimum.

B12 vitamin is involved in many metabolic processes in the body. These include fatty acid and amino acid metabolism. The vitamin is a cofactor in DNA synthesis. It also plays a role in the maturation of red blood cells in the bone marrow and the synthesis of the myelin sheath of the nerve cells.

Animal foods are some of the best sources of vitamin B12. These include

  • Meat
  • Organ meat as animal kidneys and liver
  • Fish as salmon, sardines, tuna, clams, and trout
  • Eggs
  • Poultry
  • Milk and other dairy products
  • Fortified non-dairy milk
  • Fortified non-nutritional yeast
Vitamin B12 Deficiency Causes, Symptoms, and Treatment

Owing to the importance of this vitamin in our body and the fact that we consume a nutrient-deficient diet, some food items, as cereals or flour, are fortified with vitamin B12 to overcome any deficiency. The vitamin is available in supplement form as well as B12 shots are also available.

Causes of vitamin B12 deficiency

Besides all the availability of products to keep up with its levels, vitamin B12 deficiency is prevalent. The underlying cause is either;

  • Inability to absorb the vitamin from the digested food, or
  • Insufficient amounts of B12 in dietary sources

Vitamin B12 deficiency is more prevalent in some high-risk cases. These include;

  • The elderly cohort
  • Strict vegetarians
  • Intake of the anti-diabetic drug metformin
  • Long-term use of antacids and proton pump inhibitors (used for gastric ulcers)
  • Smokers
  • Alcoholics

Some medical conditions associated with vitamin B12 deficiency include;

  • Pancreatic insufficiency
  • Small intestinal bacterial overgrowth (SIBO)
  • Parasite infections
  • Autoimmune disorders (which cut back on the production of intrinsic factor; a substance that binds vitamin B12 and facilitates its absorption in the intestine)
  • Post-surgery involving resection of part of the small intestine

Signs and symptoms of vitamin B12 deficiency

The unfortunate part is that any deficiency of the vitamin takes years to show its signs and symptoms. Then folate and B12 deficiency often co-exist. Folate deficiency is easy to diagnose, and correcting the mineral levels often masks the Vitamin B12 deficiency. This further hinders the accurate diagnosis of vitamin B12 deficiency.

However, some signs indicate dropping vitamin B12 levels. Here is a look at them.

1. Pale or Jaundiced Skin

Vitamin B12 contributes to red blood cell metabolism. In its deficiency, this function is compromised. The presenting sign in such a case is pale skin. The skin takes on a yellowish tinge, a sign that also affects the conjunctiva of the eye (the white portion).

DNA contains the code required to complete metabolic processes in the body, including red blood cell metabolism. In the case of B12 deficiency, the instructions from DNA are lacking, resulting in disturbance in the synthesis of red blood cells.

Vitamin B12 deficiency causes megaloblastic anemia, a deficiency of functional red blood cells. The RBCs produced are large in size and fragile. They are unable to perform their function and break away easily. This results in an increase in the by-products of RBCs destruction in the blood, namely bilirubin. It also results in a decreased number of functional red blood cells in the circulation, which explains the pale appearance of the skin in such patients.

The increasing levels of bilirubin cause the skin and eyes to become yellowish or jaundiced.

2. Chronic fatigue

Other symptoms that follow decreased red blood cell production include fatigue, lethargy, and unexplained weakness.

This happens because the blood lacks red blood cells that adequately perform their function, i.e., carrying oxygen to every body cell. The result is feeling of tiredness all the time.

3. Tingling sensations

Undoubtedly, the most damaging effect of vitamin B12 deficiency is nerve damage. This is dangerous because nerve damage is irreversible.

Vitamin B12 is an essential element of fatty acid metabolism. Fatty acids are an essential constituent of the myelin, a sheath covering the nerves in the brain and elsewhere. Myelin acts as an insulation and protective covering for the nerves.

Disturbance in myelin sheath synthesis causes irreversible damage to the nerves, which cannot perform their function. This malfunctioning presents itself as paresthesia or sensations of pins and needles in the affected part of the body. Most often, the pricky sensation is felt in the hands and feet.

The neurological symptoms of vitamin B12 deficiency may or may not accompany anemia.

4. Changes in functional ability

In addition to the sensory complaints, the neurological symptoms of vitamin B12 deficiency progress to cause disturbances in the motor functional abilities of your body as well. These usually appear of the condition is overlooked for a long time.

Vitamin B12 deficiency results in disturbing your walk, ability to balance yourself and coordinate different movements. The condition also makes you more prone to falls and injuries because of a lack of balance and coordinated moves.

This sign is more prominent in the elderly, where supplementation with the vitamin improves mobility. The mobility issues may also occur in young people suffering from severe and untreated deficiency of vitamin B12.

5. Glossitis and Mouth Ulcers

Glossitis is inflammation of the tongue. The tongue becomes red and swollen, making talking and eating painful and difficult. The tongue appears smooth as the taste buds stretch and disappear. There may be associated gum bleeds in such patients.

Glossitis is another sign indicating a lack of vitamin B12. It is one of the earliest signs of the subject vitamin deficiency.

Symptoms like mouth ulcers may also accompany glossitis. Pin and needle sensations and burning and itching of the tongue may follow in severe cases.

6. Breathlessness and Dizziness

Since the red blood cells cannot serve their function effectively in B12 deficiency, you may feel occasional dizziness. You may also find yourself short of breath upon slight exertion if the anemia is severe enough. Breathlessness with heart palpitations shows that the heart tries to compensate for the malfunction of blood oxygen-carrying capacity.

The deficient supply of oxygen to the cells is the underlying cause of these symptoms. Any unusual breathlessness should be consulted with your doctor as it is a sign of other medical conditions.

7. Disturbed Vision

Long-standing vitamin B12 deficiency may involve the optic nerve in the eye. If the myelin sheath of the optic nerve gets damaged, its function of relaying messages also becomes compromised. You may experience disturbed vision as blurred images.

This condition is also called optic neuropathy and can complicate to cause blindness in severe cases of deficiency. The condition is reversible with optimal vitamin B12 replacement, so supplementing with the subject vitamin is helpful.

It is also seen that vitamin B12 is vital for reducing the risk of age-related macular degeneration. This is particularly true in the elderly cohort, where supplementation might contribute to preserving eye health.

8. Mood Changes

B12 deficiency is often associated with mood changes. The deficiency of B12 has a strong link with depression and dementia. This is because of slow or delayed nerve impulses in the brain—the nerve synapses malfunction, resulting in signs and symptoms of low mood. The same is responsible for symptoms as loss of concentration, poor focus, and memory decline.

The underlying cause is related to high homocysteine levels, which happen when vitamin B12 levels go down. The damage to brain tissue results in a disturbance of nerve signaling mechanisms to and fro from the brain. This results in mood and behavioral changes.

9. Temperature dysregulations

Rarely vitamin B12 deficiency results in a high body temperature. Clinical evidence points out that supplementing with B12 reverses the fever-like condition of the body.

However, increased body temperature is usually linked to some infectious process in the body, so a proper diagnosis should be sought in this regard.

10. Weight gain

The evidence of vitamin B12 deficiency regarding weight changes is insufficient. However, some observational studies point out a low B12 as the cause of weight changes.

Obese people or who are overweight are observed to have low levels of vitamin B12 in their bodies. Some studies have concluded that obesity is more associated with B12 deficiency than a normal BMI index.

Some other studies show a positive correlation between supplementing with vitamin B12 on weight loss. Participants of a study who took B12 supplements gained weight over the ten-year observational study period than those deficient in the subject vitamin.

Low vitamin B 12 levels are linked to decreased appetite. This observation is seen in some cases of vitamin deficiency. This probably explains the weight loss associated with the deficiency of the vitamin.

11. Insomnia

The deficiency of vitamin B 12 affects sleep directly or indirectly.

Firstly, it affects the production of melatonin, the sleep hormone responsible for maintaining the circadian rhythm in our bodies. Lack of B12 has a direct impact on melatonin production and sleep.

Some studies show that high levels of B12 are associated with sleep disruption and reduced sleep time. More evidence is required for explaining the definitive role of B12 in sleep.

Secondly, B 12 deficiency causes slowed brain functioning, low mood, and depression. Depression is another major cause of insomnia and sleepless nights.

12. Incontinence

The deficiency of vitamin B12 has its links to urinary as well as fecal incontinence. This is especially true in the elderly. Research is ongoing in this regard.

13. Increased risk of osteoporosis

Though more research is required in this regard, studies have proposed that low levels of vitamin B 12 may be responsible for low bone mass and an increased risk of osteoporosis.

How much B12 is enough for you?

Ensuring optimal food B12-rich resources in your diet caters to optimal levels of the vitamin. However, mega doses of the vitamin have their side effects as well. So what are optimal levels of vitamin B12 that maintain a balance on either side? Here is what we know.

Vitamin B12 is a water-soluble ingredient, so high levels are well tolerated by the body as any excess is excreted out or stored in the liver.

That is why no upper tolerable levels are described for B12.

Supplementing with vitamin B12 for extended periods may cause specific side effects. These include;

  • outbreaks of acne and rosacea (associated with high dose injections of B12)
  • disturbed blood sugar levels
  • kidney function disturbances (increased risk of diabetic nephropathy)
  • increased risk of cardiovascular ailments as stroke and heart attack
  • increased risk of autism spectrum disorder in a child born to mother supplementing with B12

Clinical evidence shows that supplementing with 2 milligrams of vitamin B12 suffices in people suffering from a deficiency of this vitamin.

This requirement may increase in pregnant and nursing mothers. The same is true for vegetarians and the elderly. 

The daily recommended dose of B12 is about 2.4 micrograms for both men and women. A high dose of 2000 micrograms is considered the safe upper level of vitamin B12 in deficient people.

However, it is always suggested not to take a high dose of B12 without consulting with your doctor.

Our body is adept at absorbing the required amount of vitamin B12. For example, if you take a 500 mcg dose of B12, only ten mcg gets absorbed in a healthy adult without any deficiency of the subject vitamin. So taking a mega dose might not do you any good.

Treatment of vitamin B12 deficiency

The deficiency of B12 is best treated by upgrading your dietary intake with B12 rich foods.

Some examples of food choices to improve any B12 deficiency include;

  • Liver: a quarter cup of the cooked liver (75 g) provides 881% of the RDI.
  • Beef kidney: a quarter cup of cooked organ meat (75 g) provides 311% of the RDI.
  • Trout: a quarter cup of fish (75 g) provides 61% of the RDI.
  • Ground beef: a quarter cup of cooked ground beef (75 g) provides 40% of the RDI.
  • Eggs: 2 large eggs provide 25% of the RDI.
  • Milk: a cup (250 ml) provides 20% of the RDI.
  • Chicken: a quarter cup (75 g) yields 3% of the RDI.

Oral and injectable supplements are also available for people who are at high risk for B12 deficiency. Either of the supplement forms is an equally effective source of the vitamin. However, people with malabsorption syndromes may benefit from an injectable vitamin B12 more than the oral one.

Abdur Rashid
Medically Reviewed By Abdur Rashid
MSC Public Health, MCSP, MHCPC
BSC (Hon) Physiotherapy
Consultant Neuro-spinal & Musculoskeletal Physiotherapist


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