Dr. Nuria Roda / Alberto Tejero
Dietary trends are leaning toward greater sustainability, among which vegan and vegetarian diets can be found. However, these diets are not complete from a nutritional standpoint since some vitamins are found only in products of animal origin. This is the case for vitamin B12, essential for the functioning of the nervous system, the formation of red blood cells, or cellular energy production.
In a world where dietary trends lean toward greater sustainability, people are choosing vegan and vegetarian diets. However, these rapidly growing dietary patterns are not entirely complete from the standpoint of the human body’s nutritional needs. Ovo-lacto-vegetarian patterns are not as lacking, but if a vegan lifestyle is followed, there is an essential nutrient that must not be forgotten. This is vitamin B12 or cobalamin, and it is essential for the functioning of the nervous system, red blood cell formation, and cellular energy production, among other functions that will be discussed in this article. This vitamin is not found in the plant kingdom since it is produced by certain bacteria in the gastrointestinal tract of animals; therefore, vegans and certain types of vegetarians must resort to obtaining it through supplements or fortified foods. On the other hand, there is another group of people who will also need to rely on this vitamin: bariatric surgery patients. This occurs because this vitamin has the unique characteristic of requiring an intrinsic factor necessary for its absorption, which is located in the stomach. If part of the stomach has been removed to reduce its capacity and lose weight, this factor or the surface area where it is located may have been lost, meaning the vitamin cannot be absorbed. The elderly are also prone to deficiency because, during aging, the stomach lining is less capable of producing intrinsic factor. In addition, older people use antacids more often, which further complicates absorption. A final important group to highlight is pregnant women, since a deficiency in the mother is linked to a higher risk of premature birth, neural tube defects, and low birth weight infants.
The form in which we take this vitamin is very important, as they are not exactly identical in their structure, absorption, and biological function. The active form is methylcobalamin, making it the option of choice for effective treatment and better absorption. The functions of this vitamin are detailed below:
- Hematopoiesis: Vitamin B12 plays a fundamental role in erythropoiesis—that is, the formation of red blood cells or erythrocytes in the bone marrow. Specifically, it contributes to DNA synthesis necessary for the rapid proliferation and maturation of erythrocytes. Vitamin B12 deficiency impairs the synthesis and maturation of these erythrocytes, leading to anemia. During pregnancy, vitamin B12 has been linked to maternal and infant health. For example, vitamin B12 deficiency in pregnant women causes megaloblastic anemia, but it is also associated with various congenital malformations, such as congenital heart defects and neural tube defects. Megaloblastic anemia also occurs in adults; however, it must be kept in mind that there is another type of anemia also due to a lack of B12—pernicious anemia, caused by the lack of intrinsic factor in the stomach.
- Cellular Metabolism: Vitamin B12 plays a fundamental role in humans. Although it does not act as a direct stimulant, it actively participates in the metabolic processes that allow the body to generate energy from the nutrients we consume. Specifically, B12 intervenes in the Krebs cycle, facilitating the conversion of carbohydrates, fats, and proteins into ATP, the main energy molecule in the organism. Additionally, it acts as a cofactor in the conversion of homocysteine into methionine, a reaction that contributes to amino acid metabolism and the production of S-adenosylmethionine (SAMe), a key substance for cellular methylation and neurological balance. This relationship explains why B12 deficiencies are associated with depressive disorders, anxiety, or impairments in memory and concentration.
- Maintaining a Healthy Nervous System: Vitamin B12 plays a fundamental role in the maintenance and proper functioning of the central and peripheral nervous systems. Its importance lies in its participation in several essential neurometabolic processes, especially in myelin synthesis, neurotransmitter formation, and protecting neurons from cellular damage.
First, B12 acts as a cofactor in the conversion of methylmalonyl-CoA to succinyl-CoA, an indispensable reaction for fatty acid metabolism. When this process is disrupted by a B12 deficiency, methylmalonic acid accumulates, which can alter lipid synthesis and compromise the integrity of the myelin sheath, the protective layer covering nerve fibers. The resulting demyelination causes neurological symptoms such as numbness, tingling, loss of balance, muscle weakness, and cognitive decline.
Adequate levels of B12 also appear to have a neuroprotective effect. Recent studies suggest that its deficiency may increase the risk of brain degeneration and dementia, especially in older adults. In this regard, maintaining an optimal intake of vitamin B12 not only prevents the neurological manifestations of pernicious anemia, but can also contribute to preserving long-term cognitive function and mental well-being.
- Protecting the Cardiovascular System: Vitamin B12 plays a key role in cardiovascular health, primarily due to its involvement in the metabolism of homocysteine—an amino acid that, at elevated levels, is associated with a higher risk of heart disease, stroke, and vascular damage. Along with vitamins B6 (pyridoxine) and B9 (folic acid), B12 acts as a cofactor in converting homocysteine into methionine, a process that maintains plasma homocysteine levels within a healthy range. When there is a B12 deficiency, this reaction is disrupted, causing an accumulation of homocysteine, which can damage the vascular endothelium, increase the oxidation of LDL cholesterol, and promote the formation of atherosclerotic plaques.
In addition to this indirect effect, vitamin B12 can contribute to cardiovascular well-being through its influence on red blood cell production and oxygen transport, optimizing tissue oxygenation and heart function. In individuals with megaloblastic anemia due to B12 deficiency, the heart must work harder to make up for the lack of oxygen, which can cause palpitations, tachycardia, or heart enlargement in severe cases. Several observational studies have shown that patients with higher baseline concentrations of vitamin B12 who took high doses of vitamins had the best outcomes, whereas those with lower baseline concentrations of vitamin B12 who took low doses of vitamins presented the worst outcomes regarding stroke, mortality, and coronary events, suggesting that some patients might require higher doses of vitamin B12.
In conclusion, vitamin B12 is an essential micronutrient whose influence extends far beyond the prevention of anemia, and multiple population groups (vegans, the elderly, bariatric patients, or pregnant women) are susceptible to deficiency.
Bibliographical References:
- Kumar, R., Singh, U., Tiwari, A., Tiwari, P., Sahu, J. K., & Sharma, S. (2023). Vitamin B12: Strategies for enhanced production, fortified functional food products and health benefits. Process Biochemistry, 127, 44-55.
- National Institutes of Health (NIH). Vitamin B12 – Fact Sheet for Health Professionals. Office of Dietary Supplements. Updated 2022. https://ods.od.nih.gov/factsheets/VitaminB12-HealthProfessional/
- Stabler, S. P. (2013). Vitamin B12 deficiency. New England Journal of Medicine, 368(2), 149–160. DOI: 10.1056/NEJMcp1113996
- Refsum, H., Ueland, P. M., Nygård, O., & Vollset, S. E. (1998). Homocysteine and cardiovascular disease. Annual Review of Medicine, 49, 31–62. DOI: 10.1146/annurev.med.49.1.31
- Spence, J. D., Bang, H., Chambless, L. E., & Stampfer, M. J. (2005). Vitamin intervention for stroke prevention trial: an efficacy analysis. Stroke, 36(11), 2404-2409.