Vitamin B12 is regarded as one of the most important B vitamins. Most of us are able to get this vitamin from our diet pretty easily, but there are a couple populations where deficiency is estimated to affect up to 90%! [1] It’s important to know if you’re at risk, because supplementation is an easy and effective way to prevent deficiency, and the side effects that come along with it.
Let’s first dig a little deeper into the functions of B12, because it has some pretty important roles in human health:
- – It is an essential component of the development and maintenance of the central nervous system, and is essential for our neurological health
- – Vitamin B12 helps create and maintain the health of red blood cells, which transport oxygen to the entirety of our body
- – It helps maintain the integrity of our skin, nails, and hair
- – B12 is also important for healthy division of DNA – it assists our cells in accurate replication, helping slow the occurrence of DNA mutations [2-6]
To optimize our health and daily functioning, it is essential for us to maintain a healthy vitamin B12 status, and to ensure that we are able to absorb it. Some key players in the absorption of vitamin B12 are two molecules, intrinsic factor and hydrochloric acid. What are these molecules, and why are they important for absorption? Let’s review.
A quick note on the physiology and anatomy of the stomach
The stomach is lined with cells that release a variety of secretions and molecules that help us break down the food we eat for digestion and absorption. One particular type of cell, called a parietal cell, secretes two molecules, intrinsic factor and hydrochloric acid, in the presence of food. As mentioned above, these two molecules are very important for the absorption of B12. It’s a two-step process. [2]
Step 1 – Breaking the Bond:
Vitamin B12 is tightly bound to the food we eat, and requires hydrochloric acid to break these bonds. The vitamin B12 we get from food would not be bioavailable if hydrochloric acid was not present. It’s also important to note that if B12 is fortified or supplemented, it does not require this separation like the food-bound form does.
Step 2 – Activation:
Once free from food sources, it needs the addition of intrinsic factor for transport. Intrinsic factor is a protein that binds tightly to the free B12 floating around in the stomach after digestion, and allows it to be transported through the rest of the body so it can go where it needs to go. [2]
So, now that we know a little more about the digestion and absorption of this nutrient, we can more easily understand why certain populations of individuals might be at higher risk for deficiency. Those who are at higher risk of deficiency might need to pay a little closer attention to their daily intake, and likely need to supplement to ensure a healthy level. Do you know whether or not you’re at risk of deficiency?
You might be at risk if you…
…have pernicious anemia
Pernicious anemia is an autoimmune condition that affects the mucosal layer of the stomach. This condition causes particular cells in the stomach, called parietal cells, to be inappropriately attacked by the immune system. The parietal cells are essential for B12 absorption, as they release a molecule called intrinsic factor, which binds with B12 in the stomach. Without intrinsic factor, an individual may become vitamin deficient, even if they are consuming enough dietary B12. [2]
…are of elderly age
While aging isn’t necessarily a cause of B12 deficiency, there are several risk factors that might increase the risk of deficiency in an elderly population. Decreased intake, gastritis, decreased production of intrinsic factor, and gastric infections may be a large factor in the increased rates of deficiency in elderly individuals. [7]
…follow a vegan or vegetarian diet
Vitamin B12 is primarily found in meat and animal products, such as beef, liver, fish, milk, and eggs. It is possible for vegans and vegetarians to get what they need from their diet, but it can be much more challenging. Those who follow plant based diets should identify fortified sources of vitamin B12 and/or supplement to prevent deficiency.
…are an infant with a vegan or vegetarian mother
If a mother is deficient in vitamin B12 during pregnancy and/or breastfeeding, the infant may experience deficiency as well. If a mother is deficient during pregnancy, little B12 is able to be passed on to the infant in the womb. This deficiency can be exacerbated if the mother remains deficient while breastfeeding. With less B12 stored, and limited additional B12 supplied by the diet, deficiency in infancy can be dangerous, resulting in neurological problems, failure to thrive, developmental delays, and anemia. [8]
…have a gastrointestinal disorders
Individuals with gastrointestinal disorders, like celiac disease or Crohn’s Disease may experience decreased absorption of many nutrients related to their condition. Even though individuals with gastrointestinal disorders
may eat enough vitamin B12, the inflamed and injured sections of the gastrointestinal tract may have decreased ability to absorb nutrients. Individuals with these conditions may be deficient in many nutrients, not just vitamin B12. [9]
…you’ve had gastrointestinal surgery
Certain gastrointestinal surgeries, like bariatric surgery, alter the anatomy and function of the stomach. This may decrease the number of parietal cells, which means a reduced concentration of hydrochloric acid and intrinsic factor. Without these two molecules available to digest and transport food-bound B12, individuals may be at risk of deficiency. [10]
Now, you may wonder, “I don’t fall into any of these populations, but how would I know if I’m B12 deficient?” It’s important to know the symptoms of B12 deficiency because they can easily be mistaken for other conditions and illnesses.
Citations
- Pawlak R, Lester SE, Babatunde T. The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature. Eur J Clin Nutr. 2014 May;68(5):541-8. doi: 10.1038/ejcn.2014.46. Epub 2014 Mar 26. Erratum in: Eur J Clin Nutr. 2016 Jul;70(7):866. PMID: 24667752.
- Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B(6), Folate, Vitamin B(12), Pantothenic Acid, Biotin, and Choline. Washington, DC: National Academies Press; 1998.
- Carmel R. Cobalamin (vitamin B12). In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:369-89.
- Allen LH. Vitamin B12. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:812-20.
- Allen LH. Vitamin B-12. Adv Nutr 2012;3:54-5. [PubMed abstract]
- Stabler SP. Vitamin B12. In: Marriott BP, Birt DF, Stallings VA, Yates AA, eds. Present Knowledge in Nutrition. 11th ed. Washington, DC: Elsevier; 2020:257-71.
- Wong CW. Vitamin B12 deficiency in the elderly: is it worth screening? Hong Kong Med J. 2015 Apr;21(2):155-64. doi: 10.12809/hkmj144383. Epub 2015 Mar 10. PMID: 25756278.
- Dror DK, Allen LH. Vitamin B-12 in Human Milk: A Systematic Review. Adv Nutr. 2018 May 1;9(suppl_1):358S-366S. doi: 10.1093/advances/nmx019. PMID: 29846529; PMCID: PMC6008958.
- Carmel R. Cobalamin (vitamin B12). In: Ross AC, Caballero B, Cousins RJ, Tucker KL, Ziegler TR, eds. Modern Nutrition in Health and Disease. 11th ed. Baltimore, MD: Lippincott Williams & Wilkins; 2014:369-89.
- Kornerup LS, Hvas CL, Abild CB, Richelsen B, Nexo E. Early changes in vitamin B12 uptake and biomarker status following Roux-en-Y gastric bypass and sleeve gastrectomy. Clin Nutr 2019;38:906-11.