Vitamin B12: Absorption, Deficiency and Neurological Consequences

B12 deficiency is one of the genuinely reversible causes of cognitive symptoms, and one of the more commonly missed.

The absorption pathway

B12 absorption is unusually elaborate. Dietary B12 bound to protein is released by stomach acid and pepsin, binds to haptocorrin, is transferred to intrinsic factor produced by gastric parietal cells, and the complex is absorbed in the terminal ileum via specific receptors. Each step is a potential failure point, which is why B12 deficiency arises from so many different causes rather than from dietary shortfall alone.

Who is at risk

People eating no animal foods, since B12 comes from animal sources or fortification. Older adults, because reduced stomach acid impairs release of protein-bound B12 - which is why fortified foods and supplements, where B12 is not protein-bound, are absorbed better than food B12 in this group. People on long-term proton pump inhibitors or metformin. People with pernicious anaemia, an autoimmune condition destroying intrinsic factor production. People after gastric or ileal surgery, or with Crohn's disease or coeliac disease.

The neurological picture

Neurological consequences can appear before or without anaemia, which is a critical clinical point. They include peripheral neuropathy with numbness and tingling, cognitive changes, mood symptoms, and in severe untreated cases subacute combined degeneration of the spinal cord. Early treatment can reverse much of this; prolonged deficiency can leave permanent damage. High folate intake can mask the haematological signs while neurological damage progresses, which is a documented concern.

A note on Cognizil

We publish this blog on the Cognizil official website, so treat anything we say about our own product as coming from an interested party. What we can do is be specific: Cognizil is a liquid dropper supplement taken once daily, and it makes no claim to treat, cure or prevent any disease. It also contains St. John’s Wort, so if you take any prescription medicine, read our interaction guide before the sales page. If you want the drawbacks first, start with Cognizil reviews and complaints.