Vitamin B12's importance for energy, memory, potency

- and much more

Deficiencies of vitamin B12 are widespread due to plant-based diets, aging processes, poor absorption, and certain types of medication. A B12 deficiency can cause anemia, fatigue, poor memory, infections, reduced fertility, impotence, and neurological diseases such as neuropathy, according to an article published in Cureus.

A deficiency of vitamin B12 (cobalamin) is a global health problem affecting three billion people. The number is increasing, especially due to the growing elderly population and campaigns promoting plant-based diets, as vitamin B12 is only found in animal-based foods. It is also important to note that it can take months or even years for a deficiency to manifest because the vitamin is stored in the liver. The absorption of vitamin B12 also requires sufficient stomach acid and the carrier protein intrinsic factor, which transfers vitamin B12 into the bloodstream from the last part of the small intestine. Pernicious anemia, a severe form of life-threatening anemia, is caused by the inability to absorb vitamin B12 from food. This is because pernicious anemia is an autoimmune disease in which antibodies attack the cells in the stomach lining that produce intrinsic factor. Certain gastrointestinal diseases, such as Helicobacter pylori infection, celiac disease, and Crohn’s disease, as well as local surgical procedures, also impair absorption. Additionally, medications such as PPIs for excessive stomach acid and metformin for type 2 diabetes further hinder absorption and utilization. Overall, many people are at risk of developing a vitamin B12 deficiency.

Sources of vitamin b12, requirements, metabolism, and functions

Vitamin B12 is only found in animal-based foods such as meat, liver, fish, eggs, and dairy products. The daily recommendations/RI are set at 2.5 micrograms. It is also estimated that only about half of the vitamin B12 in food is absorbed into the bloodstream. As mentioned, low stomach acid, medication, and several other factors can further impair absorption, meaning that individual vitamin B12 requirements may vary significantly. Once absorbed into the bloodstream, the transport protein transcobalamin ensures that vitamin B12 reaches the cells. It is well known that vitamin B12, together with folic acid, is essential for the formation of red blood cells, which is crucial for maintaining normal energy levels and cellular activity. Moreover, vitamin B12 plays a frequently overlooked role in the nervous system, cognitive functions, and immune system. Within the cells, vitamin B12 is specifically involved in the synthesis of the amino acid methionine after the breakdown of homocysteine. In this process, homocysteine levels must not become too high, as excess homocysteine has a toxic effect and can damage the circulatory system. Vitamin B12 is also important for the synthesis of RNA and DNA and normal cell division.

Cause of vitamin b12 deficiency — Examples

Low intake — Plant-based diet, elderly, and alcoholics
Autoimmune diseases — Pernicious anemia
Poor absorption — Chronic gastritis, stomach infection with Helicobacter pylori, celiac disease, and Crohn’s disease
Genetic disorders — Seen in individuals who lack the transport protein transcobalamin
Surgical procedures — Seen in individuals who have undergone stomach or intestinal surgery
Medicine — Seen in people being medicated with metformin or PPIs

Vitamin b12 deficiency harms blood formation and the nervous system

A deficiency of vitamin B12 can impair blood formation and the nervous system, leading to mild to severe symptoms. Two types of anemia can develop – pernicious anemia and megaloblastic anemia. Anemia itself can cause fatigue, paleness, sensitivity to cold, heart palpitations, reduced fertility, and numerous other symptoms due to a lack of cellular energy. If pernicious anemia is not treated in time, symptoms can become debilitating, and nerve damage may become irreversible. The condition can also be life-threatening. Hematological damage due to vitamin B12 deficiency can also include altered red blood cell volume and a reduced number of white blood cells (neutrophils) and platelets. Reduced quality of white blood cells increases the risk of infections and immune disorders. Neurological damage due to vitamin B12 deficiency includes peripheral neuropathy, which is associated with pain or sensory disturbances in the hands, arms, legs, and feet. Individuals with diabetes are also at high risk of developing foot ulcers and requiring amputations. Neurological damage may also lead to erectile dysfunction and spinal cord degeneration. Neuropsychiatric damage due to vitamin B12 deficiency includes cognitive decline, Alzheimer’s disease, depression, mania, and delirium. There is no clear link between hematological and neurological damage. A person may therefore have anemia without neurological damage and vice versa. It is also a fact that neurological and neuropsychiatric damage is often underdiagnosed, that patients are misdiagnosed, and that the condition often worsens with irreversible neurological complications. Some data suggest that patients with vitamin B12 deficiency are more susceptible to osteoporosis. Additionally, pernicious anemia appears to increase the risk of other autoimmune diseases, such as Hashimoto’s disease, which causes hypothyroidism, as well as type 1 diabetes and vitiligo. If pregnant women lack vitamin B12, their child is at risk of developing anemia, stunted growth, and, in the worst case, mental retardation.

Clinical manifestations of vitamin B12 deficiency — Examples

Hematological — The patient may have low hemoglobin levels and anemia. Reduced number of white blood cells (neutrophils) and platelets. Altered red blood cell volume.
Neurological — The patient may suffer from peripheral neuropathy, erectile dysfunction, and spinal cord degeneration.
Neuropsychiatric  — The patient may suffer from cognitive decline, depression, delirium, mania, and Alzheimer’s disease

Treatment of vitamin b12 deficiency

If the deficiency is due to a plant-based diet, it is easy to treat with dietary adjustments or supplements. Vitamin B12 supplements should contain at least 2.5 micrograms, corresponding to the daily reference intake (RI). However, some supplements contain much larger doses, as many people have difficulty absorbing the vitamin. In this regard, lozenge supplements provide significantly better absorption, as vitamin B12 is then absorbed directly through the oral mucosa. In cases of severe deficiency, treatment can begin with injections, which often quickly alleviate various symptoms. Treatment of pernicious anemia requires continued vitamin B12 injections due to the lack of intrinsic factor, which, as mentioned, is necessary for intestinal absorption.

References:

Sakshi S Jajoo et al. Etiology, Clinical Manifestations, Diagnosis, and Treatment of Cobalamin (Vitamin B12) Deficiency. Cureus 2024

Vitamin B12 deficiency: NICE guideline summary. BMJ 2024

Simone Passarelli et al. Global estimation of dietary micronutrient inadequacies: a modeling analysis. The Lancet Global Health 2024