Missing out on an essential vitamin could be the cause of debilitating symptoms for many people, according to reports.

Vitamin B12 is an essential nutrient and lack of it can affect the body in all sorts of ways, including its cognitive function. As The Express reports, this is lesser known symptom of B12 deficiency.

We need the vitamin, which is found mainly in the likes of meat, cheese and eggs, to help create healthy red blood cells to carry oxygen around the body. A deficiency can cause anaemia and anaemia-like symptoms with side effects such as extreme tiredness, muscle weakness and dizziness or lightheadedness.

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And cognitive function can be affected too. It adds that according to an article published this year in the British Medical Journal, there are five issues which are seen in 85% of patients with a B12 deficiency. These are:

• Memory problems
• Cognitive impairment
• Nominal aphasia (a language disorder that leaves a person unable to communicate effectively)
• Learning problems
• Headaches and migraines

The BMJ says these issues are far more common than any other type of symptom experienced with a B12 deficiency, adding: “However, in many people, neurological and neuropsychological or cognitive symptoms are the main presenting symptom.

“Anaemia is present in fewer than 20% of people with B12 deficiency.” While other symptoms associated with the deficiency might be cleared quickly, the cognitive impact can be longer lasting.

“Neurological symptoms resulting from B12 deficiency may take several months or even years to resolve completely,” the article says.

It lists a range of symptoms that can affect someone who is low in B12.

Brain function: 'Brain fog', memory problems, cognitive impairment, insomnia, headaches (especially migraine), behavioural changes, learning problems, nominal aphasia.

Mood: Mood swings, irritability, depression, anxiety, hallucinations, delusions, psychosis.

Sensory: Peripheral paraesthesia (pins and needles), numbness, neuropathic pains, poor balance, reduced vibration sense or proprioception (joint position), tinnitus, ataxia, taste impairment, sometimes myelopathy.

Constitutional: Fatigue, anaemia (either macrocytic, or normocytic when also iron deficient or associated with thalassaemia minor), other cytopenia, abdominal complaints, malabsorption, failure to thrive, weight loss, diarrhoea, hyperpigmentation, glossitis, (aphthous) stomatitis, infertility, urinary tract infections.

Motor: Muscle weakness, altered reflexes (increased in degeneration of the spinal cord, reduced when peripheral neuropathy dominates), spasticity, seizures, cardiomyopathy.

Autonomic: Urinary and/or faecal incontinence, postural hypotension or dizziness, erectile dysfunction.

Note: Anyone who thinks they may be deficient in B12 should ask for a test from your GP. Sometimes diet changes may be enough to address the problem, for instance by eating more meat, fish, cheese and butter, eggs, nutritional yeast (including Marmite) and fortified foods such as cereal.

However, if your deficiency is more severe you might need to take daily supplements or even receive injections from your doctor.