In India, where a substantial portion of the population follows vegetarian diets, vitamin B12 deficiency is common yet frequently overlooked. Among its less recognized effects are neuropsychiatric symptoms such as memory lapses, irritability, mood changes, and poor concentration—even in the absence of anemia.

Vitamin B12 Role

Vitamin B12 (cobalamin) is a water-soluble vitamin essential for DNA synthesis, red blood cell formation, and neurologic integrity. Deficiency can harm nerve tissue, myelin integrity, and neuronal metabolism.

Vitamin B12 rich foods

Humans cannot synthesize B12; dietary intake and absorption are necessary. In nonvegetarian diets, B12 is found in animal products such as meat, fish, eggs, and dairy.

In vegetarian diets, vitamin b12 rich foods consist of dairy products (milk, cheese, yogurt), fortified foods like cereals and plant-based milks, nutritional yeast, and eggs. But strict vegetarian or vegan ones, dietary sources are limited. Fortified foods (fortified cereals, nutritional yeast) may supply some amount, they can also add Plant-Based Milks: Soy, almond with added Vit B12 but many vegetarians remain at risk of inadequate B12 intake.

Vitamin B12 Deficiency Symptoms

Based on published studies and clinical reports, common signs include:

• Persistent fatigue, weakness

• Pale or jaundiced (yellow-tinged) skin

• Numbness, tingling, or “pins and needles” in hands or feet (peripheral neuropathy)

• Impaired balance, coordination problems, unsteady walking

• Memory loss, difficulty concentrating, “brain fog” or other cognitive impairment

• Mood changes such as irritability or depression

• Glossitis (inflamed or sore tongue), mouth ulcers or sore mouth

• Breathlessness or dizziness during activity (due to low red blood cell count)

Severe B12 deficiency (for example in pernicious anemia) often causes obvious signs like enlarged red blood cells (megaloblastic anemia) and nerve damage. But milder or “subclinical” B12 deficiency—when there are metabolic signs without clear symptoms—may be more widespread and matters for public health. In India, low B12 levels have been linked to higher body fat, gestational diabetes in mothers, insulin resistance in their children, raised homocysteine (a compound associated with heart disease), and faster cognitive decline in older adults. ¹

Neurologist Dr. Sudhir Kumar recently shared a clinical scenario on social media: a 33-year-old IT professional presented with several years of progressive forgetfulness and irritability. He was otherwise healthy and had no overt systemic illness, yet the cognitive changes were affecting both his work and personal life.

On further inquiry, Dr. Kumar discovered that the patient followed a strict vegetarian diet and decided to check his active Vitamin B12 (holotranscobalamin) level. The result was profoundly low—10 pmol/L (normal > 70 pmol/L), indicating severe B12 deficiency. After initiation of intramuscular B12 injections, followed by maintenance therapy, the patient’s mood, concentration, and memory improved over weeks to months, according to Dr. Kumar’s report.

Vitamin B12 deficiency, especially among vegetarians, can manifest primarily with neuropsychiatric symptoms before hematologic signs like anemia appear.

Prevalence of Vitamin B12 deficiency in vegetarians and general population

In India, B12 deficiency is widely prevalent. One survey suggested that nearly 47% of the general population may have B12 deficiency (using a cutoff of <200 pg/mL). Among vegetarian Indians, prevalence estimates are even higher. In a study of vegetarian Indians, around 70% were found to have biochemical evidence of B12 deficiency (based on holotranscobalamin or total B12 criteria).² Other regional studies have confirmed a strong association between strict vegetarian diets and higher rates of deficiency.³

Because typical hematologic abnormalities may not be present early, diagnosing B12 deficiency in patients with neuropsychiatric symptoms requires a more nuanced approach.

Management and prognosis

When B12 deficiency is identified, prompt supplementation is standard. Common regimens include:

• Parenteral (intramuscular or subcutaneous) B12 injections, especially in severe deficiency, neurologic involvement, or when absorption is uncertain.

• Oral high-dose B12 supplementation can be effective in many patients with dietary deficiency and intact absorption pathways.

• Maintenance therapy with oral supplements or periodic injections, depending on the underlying cause and monitoring.

With early treatment, many neuropsychiatric symptoms, including memory and mood changes, can improve or reverse. Delayed diagnosis can lead to irreversible nerve damage or structural brain changes.

In Dr. Kumar’s reported case, mood and memory improved over weeks to months after initiation of therapy.

References

1. Andrès, Emmanuel, Bernard Loukili, Olivier Noel, et al. 2014. “Vitamin B12 (Cobalamin) Deficiency in Elderly Patients.” Monaldi Archives for Chest Disease 81 (2): 138-149. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4266598/.

2. Sashindran, V. K., and Sushil K. Sashindran. 2019. “Epidemiology of Vitamin B12 Deficiency in India.” Journal of Clinical & Diagnostic Research 13 (1): 1-6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6540890/.

3. Sharma, Ritambhara, Ajay D. Gupta, and Piyush Kumar. 2022. “Clinical and Nutritional Correlates of Vitamin B12 Status in Northern India.” Indian Journal of Medical Research 155 (3): 310-318. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9480660/.

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