5 science-backed benefits of vitamin B12 and how to get enough of it in your diet

Adults should consume 2.4 micrograms of vitamin B12 every day.Getty
  • Vitamin B12 has many health benefits from helping your body form red blood cells to possibly preventing dementia
  • The recommended daily intake for adults is 2.4 micrograms.
  • Vitamin B12 is found in foods such as meat, eggs, dairy, and fish. It can also be consumed via supplement, injection, or an IV.
  • This article was medically reviewed by Samantha Cassetty, MS, RD, nutrition and wellness expert with a private practice based in New York City.
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There are a myriad of vitamins you need to maintain a healthy mind and body. An important one to keep track of is B12. It's involved in everything from red blood cell production to nail growth.

Here's what you need to know about vitamin B12, from the science-backed health benefits to recommended daily intake.

Health benefits of vitamin B12

B12 plays a crucial role in the body's formation of red blood cells and neurological functioning. Therefore, it can boost overall health in a variety of ways and here are five of them:
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1. Helps form red blood cells

Red blood cells carry oxygen from our lungs to tissues throughout our body. They also carry carbon dioxide — a toxic by-product of cell functioning — from those tissues back to the lungs where it's then expelled.

"Vitamin B12 participates in the production of red blood cells," says Vikram Tarugu, MD, a gastroenterologist and CEO of Detox of South Florida. "If the rates of vitamin B12 are too poor, red blood cell output is impaired, inducing megaloblastic anemia."

Megaloblastic anemia refers to anemia — a lack of red blood cells — specifically caused by lack of B12. It "causes symptoms like fatigue, difficulty concentrating, clumsiness, and dry skin," says Megan Wong, a registered dietitian at AlgaeCal, a company providing information on bone health.
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While there are other reasons a person may develop anemia, such as excessive bleeding or low iron, maintaining healthy levels of vitamin B12 is one way to prevent it.

2. Might prevent dementia

Another benefit of vitamin B12 is that it can slow brain atrophy in the elderly. Brain atrophy means an overall shrinkage in brain volume and also a loss of neurons, which can cause diseases like Parkinson's and Alzheimer's making it difficult to function independently in society. A 2008 study published by the American Academy of Neurology with 107 participants over 61-years-old, found that the brain volume lost over five years was greater for people with lower B12 levels in the blood.
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"Vitamin B12 is crucial for a well-functioning brain and nervous system. Its role in the brain is so important that research suggests vitamin B12 might play a role in preventing dementia," says Wong.

However, there's no evidence that B12 supplements improve memory loss in those who are already suffering from Alzheimer's disease.

3. May improve mood and symptoms of depression

There is still debate over the extent of its impact, but research has shown a connection between vitamin B12 deficiency and neuropsychiatric manifestations. These include depression, obsessive compulsive disorder (OCD), and mood swings.
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"Vitamin B12 is required for serotonin development, which is a chemical that controls mood," says Tarugu. This link has led researchers to encourage vitamin B12 supplements as part of treatment plans for those with depression.

For example, in a study of 199 depressed individuals, 100% of those treated with antidepressants as well as injected vitamin B12 improved by at least 20%. Only 69% of people treated with antidepressants and not B12 reported similar improvements.

4. May prevent birth defects

People who are pregnant have a higher recommended dose of vitamin B12. That's because the compound may help prevent severe birth defects like partial paralysis and an undeveloped skull. "Adequate amounts of vitamin B12 are important for a successful pregnancy," says Tarugu.
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If someone with low levels of B12 becomes pregnant, they have a greater chance of giving birth to a child with neural tube defect. This class of birth defects includes anencephaly, a fatal condition where the baby's brain and skull are severely underdeveloped. Along with maintaining proper vitamin B12 levels, taking folic acid before and after conception can decrease the chances of a baby having neural tube defects.

5. Supports healthy hair, skin, and nails

Tarugu says maintaining healthy levels of vitamin B12 can also assist in hair, skin, and nail growth by providing oxygen to these tissues.

"However, if your [B12] levels are already adequate, consuming a supplement probably won't boost your health in those regions," he says.
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If you do have a vitamin B12 deficiency, it may manifest as vitiligo — a condition in which the skin has discolored patches, slower hair growth, or skin hyperpigmentation. In this case, adding vitamin B12 to your diet or taking a supplement may improve the condition.

How much vitamin B12 do I need?

The amount of vitamin B12 a person needs steadily increases as they age: Older individuals may want to up their vitamin B12 intake. "Around the age of 50, it becomes harder to absorb vitamin B12, so older adults should aim to eat more B12-rich foods or take a supplement if needed," says Wong.
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Where can I get B12?

"The best food sources [of B12] are meat, poultry, eggs, dairy, fish, and fortified cereals," says Wong.

B12 can be supplemented in four ways, says Taylor Graber, MD, physician and owner of ASAP IVs, a mobile IV hydration and wellness company:

  1. Orally, through eating foods rich in vitamin B12
  2. Taking a B12 supplement
  3. Injected into the muscle
  4. Through an IV drip
As vitamin B12 is found naturally in animal-based food products, vegetarians and vegans may not get enough of it in their diet and require supplements. Medical conditions may also require a person to seek out additional amounts of the vitamin.
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Vitamin B12 deficiency symptoms and causes

Between 1.5% and 15% of the general population is vitamin B12 deficient. Symptoms of vitamin B12 deficiency include megaloblastic anemia — in which abnormally sized or immature red blood cells are produced — weight loss, weakness, neurological changes like memory loss and depression, as well as fatigue.

Your small intestine helps absorb B12 with help from a substance secreted by the stomach known as intrinsic factor. This makes people with certain health conditions more susceptible to B12 deficiency.

"Without intrinsic factor, the free vitamin B12 in the digestive tract is unable to be absorbed," says Graber. "Deficiencies of this glycoprotein, or a shortening of the small intestine where the B12 is absorbed, can lead to an inadequate amount of dietary vitamin B12."
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People with Crohn's Disease, or complications due to intestine shortening from surgeries are often at risk of vitamin B12 deficiency, says Graber.

Side effects of too much B12

Vitamin B12 is a water-soluble vitamin meaning that your body only absorbs necessary amounts of B12, with the rest flushing out through your urine. That said, there can still be side effects of excess intake. These symptoms include headaches, anxiety, and nausea.

Vitamin supplements, such as B12, have previously been reported to interact with medicines and supplements, like colchicine and vitamin C supplements. Therefore, always consult your doctor before starting a new supplement or diet
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