Vitamin B12, also known as cobalamin, is an important B vitamin and the one most people supplement with. So, what is so special about vitamin B12 that causes people to take supplements or get vitamin B12 shots?
Vitamin B12 is a water-soluble vitamin found primarily in animal foods, meat, poultry, seafood, eggs, and dairy products, but people can also obtain it from fortified cereals and nutritional yeast. Vitamin B12 supports the normal function of nerve cells and the formation of red blood cells and DNA synthesis. It supports bone health, improves energy and mood, and protects against heart disease. Finally, studies show vitamin B12 helps prevent cognitive impairment and dementia.
Humans cannot make vitamin B12 and can only acquire it from their diet. On the other hand, animals obtain vitamin B12 from soil ingested while eating and grazing. Ruminant animals such as cows and sheep synthesize vitamin B12 from the bacteria in multiple compartments of their stomachs. The richest sources of vitamin B12 are from organ meats. Marketers state fermented soy products such as tempeh and miso are good plant sources of vitamin B12, but they contain compounds like vitamin B12 that do not function as B12 in the body. Since vegans obtain little B12 in their diets, they need to pay special attention of getting enough through fortified cereals (although not usually absorbed as well as animal sources) and nutritional yeast, and health care providers usually advise supplementation.
The recommended dietary allowance of vitamin B12 for adults is 2.4 µg/day and in the United States intake from the diet typically exceeds this amount. Adults who are healthy absorb about 50% of B12 from the foods they eat although the absorption of B12 is complex. First B12 binds to the protein in food and then hydrochloric acid (HCL) and gastric juices of the stomach release B12 from the proteins. The freed vitamin B12 then binds to intrinsic factor in the stomach which enhances its absorption.
Symptoms of deficiency are hard to detect but include chronic fatigue, muscle aches and weakness, joint pain, poor memory, mood changes, poor dental health, poor concentration, and digestive disorders such as nausea, diarrhea, or cramping.
So, what causes a person to become deficient in vitamin B12 and what are the consequences? There are specific reasons why a person may become deficient. First following a long-term vegan or vegetarian diet can lead to a deficiency. Another reason is limited production of HCL in the stomach often occurring in 10-30% of older adults. Gastric bypass surgery, the drug Metformin to treat type 2 diabetes, and medications that block stomach acid production can cause limited HCL production leading to improper absorption of B12.
An autoimmune disease called pernicious anemia causes malabsorption of vitamin B12 due to improper production of intrinsic factor in the stomach. Finally, studies show that people with IBD are more prone to vitamin B12 deficiencies and need to play close attention to their intake of this important nutrient.
There are consequences of vitamin B12 deficiency. If the deficiency is severe enough causing a reduction in red blood cell formation, anemia (Macrocytic) can occur leading to symptoms of fatigue, loss appetite, shortness of breath, tingling of the hands and feet. When there is poor intake of vitamin B12, folate, and vitamin B6 this can lead to high homocysteine (an amino acid found in the blood) levels which is a risk factor for heart disease, stroke, cognitive dysfunction, and fractures caused by osteoporosis. Research studies have not consistently shown supplementation with vitamin B12, B6, and folate to reduce the risk of heart disease, though homocysteine levels went down, but consuming sufficient vitamin B12, vitamin B6, and folate are necessary for good health and normal functioning of the body. Eating goods sources of vitamin B12 is important since even when a deficiency is not severe, often seen in older Americans, neurological problems and elevated blood homocysteine levels can occur.
As mentioned before, those with a vitamin B12 absorption problem either from surgery, IBD, medications, or pernicious anemia, should consider vitamin B12 supplementation, but always check with your medical provider first. The best sources of vitamin B12 are beef liver, sardines, Atlantic mackerel, lamb, wild-caught salmon, nutritional yeast, feta cheese, grass-fed beef, cottage cheese, and eggs.
For those requiring supplementation, there are three options. First, monthly injections of vitamin B12 to bypass the GI tract, vitamin B12 nasal gel, or extremely high oral doses (1-2 mg per day) in which the body absorbs a small amount without the need of intrinsic factor.
For those who begin following a vegetarian or vegan diet, deficiency may not occur immediately since the liver stores vitamin B12 but need to pay special attention to obtaining proper vitamin B12 in their diet. Vegetarians can consume dairy products, eggs, and foods fortified with vitamin B12 along with supplementation. Vegans should also take a vitamin B12 supplement, consume fortified foods, and nutritional yeast. If you have IBD, ensuring you are getting enough vitamin B12 is essential, and this is where we can help!
References
https://draxe.com/nutrition/vitamin-b12-benefits/
Byrd-Bredbenner C, Moe G, Berning J. Perspectives in Nutrition. Eleventh edition. McGraw Hill. 2019.
Park YF, Park SJ, Park JJ, et al. Incidence and risk factors of micronutrient deficiency in patients with IBD and intestinal Behçet’s disease: folate, vitamin B12, 25-OH-vitamin D, and ferritin. BMC Gastroenterol. 2021; 21(32). https://doi.org/10.1186/s12876-021-01609-8.
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