Man developed memory loss for 3 months. The real culprit? Not dementia, but a nutrient deficiency, shares CMC Vellore doctor

Memory problems often spark fear of dementia, but not all cognitive decline signals irreversible disease. A 50-year-old man experiencing memory loss for three months recently discovered this firsthand. Dr Sudhir Kumar, an Apollo Hyderabad neurologist trained at CMC Vellore, highlighted how a routine blood test uncovered the surprising cause of his symptoms. The case underscores the importance of identifying treatable conditions early, showing that sometimes a simple nutritional deficiency, rather than a serious neurological disorder, can be behind alarming memory lapses.

The culprit?

The patient’s initial blood work revealed abnormally large red blood cells, a condition known as macrocytosis. This finding prompted doctors to test vitamin B12 levels, which turned out to be severely deficient. His strict vegan diet, lacking animal-derived foods, was identified as the underlying reason for the deficiency.

After beginning a course of vitamin B12 injections, the man’s memory started improving within weeks. Dr Kumar emphasised that vitamin B12 deficiency can closely mimic dementia, causing memory loss, nerve damage, and anaemia. Recognising early clues, such as a high MCV on a complete blood count, can lead to a swift diagnosis and treatment, reversing symptoms before permanent damage occurs.



This case serves as a critical reminder for both patients and doctors: not every memory problem is Alzheimer’s disease. Reversible causes, including vitamin deficiencies, should always be investigated to ensure appropriate care. Prompt identification and treatment of such conditions can restore cognitive function and improve quality of life, demonstrating that simple interventions can sometimes have life-changing results.

How does Vitamin B12 work in our body?

Vitamin B12 plays a crucial role in overall health, particularly in maintaining nerve function and supporting brain health. According to a Harvard Medical School Special Health Report, B12 is water-soluble, meaning the body excretes what it does not use. It contributes to the production of DNA and RNA, while working in tandem with other B vitamins to support essential bodily functions. For example, B12 and folate (B9) collaborate to produce healthy red blood cells, while B12, B6, and B9 together help regulate blood levels of homocysteine, an amino acid linked to potential heart disease when elevated.

Vitamin B12 deficiency symptoms

A deficiency in B12 can present in a variety of ways. Common early symptoms include fatigue, dizziness, nervousness, and tingling or numbness in the fingers and toes. If left unaddressed, severe, long-term deficiency can lead to mobility issues, difficulty walking, and even memory loss, highlighting the importance of early detection and treatment.

Vitamin B12-rich foods

Incorporating B12-rich foods into the diet is one of the most effective ways to prevent deficiency. Some of the best sources include 100% fortified breakfast cereals, trout, salmon, canned tuna, fortified soy milk, and certain types of chocolate (with labels checked for fortification). Other options include nonfat plain Greek yoghurt, eggs, and roasted chicken breast. Regularly including these foods can help maintain adequate B12 levels and support both cognitive and physical health.