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Vitamin B12, also known as cobalamin, is an essential nutrient with several important roles in the body. While it might not be as famous as some other vitamins, its importance to our health cannot be ignored. Vitamin B12 is involved in healthy red blood cell formation, nervous-system function, DNA synthesis and normal metabolism.
What Is Vitamin B12?
Vitamin B12 is a water-soluble vitamin that the body needs but cannot produce in sufficient amounts on its own. It is naturally present mainly in animal-based foods and is also added to some fortified foods and dietary supplements.
Getting enough vitamin B12 is particularly important because deficiency can affect both the blood and nervous system.
Health Functions and Benefits of Vitamin B12
Supports Healthy Red Blood Cell Formation
Vitamin B12 is essential for normal red blood cell formation. When the body does not have enough vitamin B12, abnormal red blood cells can develop and a type of anemia known as megaloblastic anemia may occur.
Vitamin B12 deficiency can cause symptoms such as fatigue, weakness and pale skin. However, these symptoms may also have many other causes, so a healthcare professional may use blood tests to determine whether B12 deficiency is present.
Supports the Nervous System
Vitamin B12 is important for the development, myelination and normal function of the nervous system.
A significant vitamin B12 deficiency can cause neurological symptoms including numbness or tingling in the hands and feet, difficulty with balance and other nerve-related problems.
Neurological problems can sometimes occur even when anemia is not present, which is one reason persistent symptoms should be medically evaluated.
Helps With DNA Synthesis
Vitamin B12 is involved in the synthesis of DNA, the genetic material found in our cells. It therefore plays an important role in normal cell formation and function.
Supports Normal Energy Metabolism
Vitamin B12 participates in normal metabolism and helps the body process nutrients from food.
However, taking additional vitamin B12 does not normally provide an energy boost to people who already have adequate B12 levels. People who are deficient may feel less tired after the deficiency is appropriately treated.
Vitamin B12 and Mental Health
Vitamin B12 is important for normal neurological function, and vitamin B12 deficiency can sometimes be associated with neurological or psychological symptoms.
Research has also examined relationships between low B12 levels and conditions such as depression and cognitive decline. However, this does not mean that vitamin B12 supplements treat depression, dementia or other mental-health conditions in people who already have adequate B12 levels.
Vitamin B12 and Homocysteine
Vitamin B12 is involved in the metabolism of homocysteine, an amino acid found in the blood. Low vitamin B12 status can contribute to elevated homocysteine levels.
Although supplements containing vitamin B12 and other B vitamins can reduce homocysteine levels, clinical research has not shown that taking these vitamins for this purpose reliably prevents heart disease or stroke.
Vitamin B12 and Healthy Aging
As people age, their ability to absorb vitamin B12 naturally present in food may decrease.
Older adults are therefore among the groups more likely to develop low vitamin B12 levels, particularly when conditions affecting the stomach or intestines interfere with absorption.
Maintaining adequate B12 status is important, but vitamin B12 supplements should not be promoted as a treatment that prevents normal age-related cognitive decline.
Vitamin B12 and Pernicious Anemia
Pernicious anemia is an autoimmune condition that interferes with the body's ability to absorb vitamin B12 because of a lack of intrinsic factor, a protein needed for normal B12 absorption.
Therefore, simply consuming more vitamin B12 in food does not prevent the underlying autoimmune condition.
People diagnosed with pernicious anemia require appropriate medical treatment. Vitamin B12 injections are commonly used, although healthcare professionals may use high-dose oral B12 in some circumstances.
Foods That Provide Vitamin B12
Vitamin B12 occurs naturally mainly in animal-based foods. Good dietary sources can include:
- Fish and shellfish
- Meat and poultry
- Eggs
- Milk and dairy products
- Fortified breakfast cereals
- Fortified nutritional yeast and other fortified foods
Plant foods do not naturally provide reliable amounts of vitamin B12 unless they have been fortified.
How Much Vitamin B12 Do Adults Need?
According to the U.S. National Institutes of Health, the recommended daily amount for most adults is 2.4 micrograms (mcg).
The recommended amount increases to 2.6 mcg per day during pregnancy and 2.8 mcg per day while breastfeeding.
Who Is at Greater Risk of Vitamin B12 Deficiency?
Some people are more likely to have inadequate vitamin B12 intake or difficulty absorbing it.
- Older adults
- People with pernicious anemia
- People with certain stomach or intestinal disorders
- People who have undergone some types of gastrointestinal surgery
- People following vegan diets without adequate fortified foods or supplements
- Some vegetarians with low intake of B12-containing foods
Certain medicines can also affect vitamin B12 status. For example, long-term use of metformin or some medicines that reduce stomach acid can interfere with B12 absorption in some people.
Can Vitamin B12 Supplements Be Harmful?
Vitamin B12 is generally considered to have a low potential for toxicity. The U.S. Food and Nutrition Board has not established a tolerable upper intake level for vitamin B12 because available evidence indicates that it is generally safe even at relatively high doses.
This does not mean that everyone needs high-dose supplements. Taking more B12 than required has not been shown to provide additional energy or health benefits for people who already have adequate vitamin B12 status.
People who believe they may have a deficiency, have a medical condition, are pregnant, or regularly take medicines that can affect B12 absorption should discuss their individual needs with a qualified healthcare professional.
Important Note About Vitamin B12 During Pregnancy
Adequate vitamin B12 intake is important during pregnancy. The recommended amount is slightly higher during pregnancy because B12 contributes to normal cell and neurological development.
Pregnant women should not avoid vitamin B12 because of claims that B12 itself causes autism. Supplement choices and doses during pregnancy should instead be discussed with a doctor or other qualified healthcare professional, particularly when a deficiency or special dietary requirement is present.
Conclusion
Vitamin B12 is a small but mighty nutrient that plays an important role in our health and well-being. It supports healthy red blood cell formation, normal nervous-system function, DNA synthesis and normal metabolism.
Most people can obtain vitamin B12 through an appropriate diet, but older adults, people with absorption problems and those eating little or no animal-derived food may need fortified foods or supplements.
If vitamin B12 deficiency is suspected, it is better to obtain appropriate medical testing and treatment rather than simply taking increasingly large supplement doses without knowing the cause.
Sources and Further Reading
National Institutes of Health, Office of Dietary Supplements — Vitamin B12 Fact Sheet
National Heart, Lung, and Blood Institute — Vitamin B12-Deficiency Anemia
Disclaimer: This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment.
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