Define the Bioavailability of cyanocobalamin?

Vitamin B₁₂ is widely available. Availability is more from non-vegetarian foods as described earlier under the food sources section. Atrophic gastritis, loss of intrinsic factor (IF), surgical manipulations of the gastrointestinal tract including total and partial gastrectomy, gastric bypass operations, ileal resections, parasitic infection with  fish tapeworm and jejunal bacterial overgrowth cause malabsorption of vitamin B₁₂.  Bioavailability decreases with age. A common problem is that of hypochlorhydria associated with atrophic gastritis, where there is a progressive reduction with age of the ability of the parietal cells to secrete hydrochloric acid. The absence of acid in the stomach is postulated to prevent the release of protein bound vitamin B₁₂contained in food but not to interfere with the absorption of the free vitamin B₁₂found in fortified foods or supplements.

Drugs like nitrous oxide, metforrnin and stomach acid blockers decrease availability.

Other factors that destroy this vitamin are sunlight, alcohol, oestrogen -the female hormone. Calcium and protein-rich foods greatly help the absorption of this vitamin in the intestine. Hence, remember these practical tips discussed above to ensure good vitamin B₁₂ status.