Why is B12 difficult to absorb and does B12 oral sprays work?

Vitamin B12 plays a vital role in many body systems, such as the production of cellular energy and the synthesis of DNA. A series of factors can affect the absorption rates of vitamin B12, which can result in the occurrence of vitamin B12 deficiency. To remedy this, individuals can take a variety of supplements, such as B12 oral sprays.

Cobalamin, more commonly known as B12, is a water-soluble vitamin that comes in a variety of forms, such as hydroxyl, cyano, deoxyadenosyl and methyl-cobalamin. Cyanocobalamin is generally present at low concentrations in animal products, such as eggs, dairy products and red meat, and is used in supplements.

Foods rich in vitamin B12 (cobalamin). Image Credit: bitt24 / Shutterstock

Vitamin B12 is bound to protein molecules contained in foods and can only be absorbed into the body after being separated from the protein by hydrochloric acid in the stomach. In order to absorb vitamin B12 in the terminal ileum, the parietal cells of the stomach produce a glycoprotein called intrinsic factor (IF). Free cobalamin binds to an R protein that is eliminated during pbadage into the duodenum, allowing cobalamin to bind to the SI, thereby allowing its active absorption. The B12-IF complex then moves into the small intestine where the ileal receptors ingest it by phagocytosis.

B12 is a pretty big molecule, and the process by which the body absorbs it is long and depends on the availability of the IF. Vitamin B12 absorption problems can occur at different points in the process and may be more influenced by certain coexisting medical conditions or certain medications. The unavailability of the IF is a serious problem because it limits the absorption of B12 (by diffusion) to about 1-2%.

The researchers discovered that many diseases can lead to malabsorption of vitamin B12 outside a low vitamin B12 diet. These include Crohn's disease and a gastrectomy.

Pernicious anemia (PA) is a type of autoimmune disease that can affect the absorption capacity of vitamin B12. In this situation, autoantibodies are synthesized and cause damage to the parietal cells of the stomach, causing their atrophy. As a result, the cells lose the ability to generate IF as well as hydrochloric acid.

In other AP subtypes, autoantibodies are synthesized, which affects the SI function by preventing its binding to B12. Normally, signs of vitamin B12 deficiency may be delayed because the liver stores excess vitamin B12 and it is suggested that these reserves are sufficient to provide the body with adequate levels of vitamin for about 3 to 5 years. However, people with FI deficiency will have difficulty absorbing not only the new vitamin B12, but also that released by the liver.

Some drugs have been found to alter the absorption of vitamin B12. Proton pump inhibitors are often used to treat heartburn and indigestion by reducing the amount of acid produced by the stomach. However, by reducing the acidity of the gastric lumen, these drugs also inhibit the body's ability to absorb vitamin B12 by preventing its separation from the molecules of the carrier protein.

As the body ages, the amount of hydrochloric acid produced by the stomach naturally decreases, resulting in similar effects. In some cases, this may promote the proliferation of intestinal bacteria dependent on vitamin B12, further decreasing the proportion of the vitamin available for absorption.

To cure vitamin B12 deficiency, doctors often prescribe supplements to be taken by various routes, including oral sprays. The use of oral sprays allows vitamin B12 to be delivered directly into the mouth, in order to penetrate the highly vascular tissue of the mucous mucosa. As a result, the vitamin can enter the bloodstream directly. This route of administration is particularly useful in patients who have difficulty taking B12 in tablet or liquid form.

In terms of efficacy, research suggests that, compared to tablets, sprays have a faster turnaround time because they do not need to wait for dissolution. In addition, sprays allow the vitamin to enter the systemic circulation by avoiding the intestinal vessels. This reduces the delay between administration and absorption, which is usually longer when you take other oral forms such as tablets.

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