Vitamin B12 Deficiency

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Definition Aetiology Pathophysiology Sign and Symptoms Investigations Management

Vitamin B12 deficiency refers to a condition characterised by low levels of vitamin B12 in the body. Vitamin B12, also known as cobalamin, is a crucial nutrient that plays a vital role in various bodily functions.

• Inadequate Dietary Intake: One of the leading causes of vitamin B12 deficiency stems from an inadequate dietary intake of this crucial vitamin. Vitamin B12 is primarily found in animal-derived products, such as meat, fish, eggs, and dairy. Therefore, individuals following strict vegan or vegetarian diets are at a higher risk of developing a deficiency if they fail to consume adequate alternative sources of vitamin B12, such as fortified plant-based products or supplements.

• Impaired Absorption: Even with an adequate dietary intake of vitamin B12, certain conditions can hinder the body's ability to absorb and utilise this nutrient properly. Pernicious anaemia is a prime example, wherein the body lacks a specific protein called intrinsic factor, necessary for the absorption of vitamin B12 in the small intestine. Without intrinsic factor, the body's ability to absorb this vitamin is significantly compromised, leading to a deficiency.

• Gastrointestinal Disorders: Various gastrointestinal disorders can interfere with the absorption of vitamin B12. Celiac disease, an autoimmune disorder triggered by gluten consumption, damages the lining of the small intestine, hampering the absorption process. Similarly, Crohn's disease, ulcerative colitis, and other inflammatory bowel diseases present chronic inflammation and damage to the intestinal tract that hampers the absorption of vitamin B12. Over time, these conditions can contribute to a deficiency.

• Gut Microbiome Imbalance: the gut has trillions of beneficial bacteria that aid in digestion and nutrient absorption. Disruptions in the balance of these gut bacteria, known as dysbiosis, can adversely affect the body's ability to absorb vitamin B12. Certain conditions, such as small intestinal bacterial overgrowth (SIBO), can result in bacteria outcompeting the host for vitamin B12, leading to a deficiency.

• Decreased absorption of vitamin B12 can be caused by factors like compromised stomach intrinsic factor in conditions like pernicious anaemia or autoimmune disorders, resulting in reduced absorption.

• Another significant cause of vitamin B12 deficiency is inadequate intake. Individuals following strict vegan or vegetarian diets without proper supplementation are at higher risk.

• Crohn's disease, celiac disease, or malabsorption syndromes, can contribute to reduced B12 absorption.

• One of the primary consequences is the impaired production of red blood cells, leading to megaloblastic anaemia. In megaloblastic anaemia, the bone marrow produces larger, immature red blood cells that are unable to function optimally. This impairs their oxygen-carrying capacity, resulting in fatigue, weakness, and shortness of breath.
  Furthermore, the nervous system also suffers significant consequences in vitamin B12 deficiency. The deficiency leads to demyelination and damage to peripheral nerves, resulting in neurological symptoms.

• Patients may experience tingling and numbness in the extremities, difficulty with balance and coordination, and even cognitive impairment. These neurological manifestations often represent the irreversible consequences of long-standing vitamin B12 deficiency, emphasizsng the importance of early detection and intervention.

• Moreover, vitamin B12 deficiency can also affect gastrointestinal health. Decreased production of stomach acid and intrinsic factor can lead to atrophic gastritis, characterised by inflammation and thinning of the stomach lining. This condition further impairs B12 absorption, creating a vicious cycle of worsening deficiency.

1. Fatigue and weakness: One of the primary signs of Vitamin B12 deficiency is persistent fatigue and weakness. When the body lacks sufficient B12, it affects the production of red blood cells, resulting in reduced oxygen-carrying capacity and energy levels.
2. Pale or jaundiced skin: Vitamin B12 is responsible for the production of healthy red blood cells. A deficiency can lead to a reduced number of red blood cells, causing a pale or even yellowish skin tone.
3. Shortness of breath: A lack of Vitamin B12 affects the transport of oxygen throughout the body. This can result in shortness of breath, even during mild physical activity.
4. Tingling sensation and numbness: Vitamin B12 deficiency can damage the nerves, leading to a sensation of pins and needles, numbness, or a "crawling" feeling in the hands and feet. This condition is known as peripheral neuropathy.
5. Balance and coordination problems: Because Vitamin B12 is involved in the health of the nervous system, a deficiency can lead to balance and coordination problems. Individuals may experience unsteady gait, difficulty maintaining balance, and an increased risk of falls.
6. Memory problems and cognitive decline: Adequate levels of Vitamin B12 are necessary for proper brain function. Deficiency in this vitamin can contribute to memory problems, difficulty concentrating, and even cognitive decline in severe cases.
7. Mood disturbances: Low levels of B12 can affect neurotransmitter production and cause changes in mood. It may lead to symptoms such as depression, irritability, and anxiety.
8. Digestive issues: Some individuals with Vitamin B12 deficiency may experience digestive problems such as diarrhoea, constipation, loss of appetite, or weight loss.
9. Enlarged or inflamed tongue: Known as glossitis, an inflamed or swollen tongue can be a sign of Vitamin B12 deficiency. It may appear red, smooth, or have a sore or tender sensation.

Lab Tests

The most common test is a blood test that measures the serum vitamin B12 levels. Usually, a low level of vitamin B12 in the bloodstream (below the reference range) indicates a deficiency.

Additional test include FBC ( which will show low HB and raised MCV).

Also check, the intrinsic factor (IF) antibody test may be checked. This test checks for the presence of antibodies that attack the intrinsic factor, a protein required for vitamin B12 absorption. Positive results in this test may suggest an autoimmune condition called pernicious anaemia as the cause of the deficiency, as it impairs vitamin B12 absorption.

• Depending on the blood test result, patients will be treated with either IM hydroxocobalamin 3 monthly for chronic or oral ( 50-100 mcg OD).

  Follow local guidelines.

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