Vitamin B12: Benefits, Immune Support and How Much You Need

Vitamin B12 is the vitamin that keeps your blood and nerve cells healthy and helps your body make DNA [1]. It's found naturally only in animal foods, and your body needs help from your stomach to absorb it. That's why some people run low without realizing it [1].

What is vitamin B12?

Vitamin B12 is a water-soluble vitamin that's found naturally in some of the foods we eat, added to others, and yes, available as a supplement [1]. Because it contains the mineral cobalt, the different forms of vitamin B12 are called cobalamins. Your body uses two of them as its active forms: methylcobalamin and adenosylcobalamin [1].

Most supplements use a form called cyanocobalamin, but you'll also see methylcobalamin, adenosylcobalamin and hydroxycobalamin on labels [1]. Here's something interesting about B12: your body stores 1,000 to 2,000 times as much as you'd typically eat in a day. That's why a shortfall can take several years to show up [1].

What does vitamin B12 do for the body?

Vitamin B12's best-known job is helping your body make healthy red blood cells [1].

Vitamin B12 is important to four things inside the human body: the blood, the nerves and brain, your DNA, and the immune system. Let's take each one individually.

• The blood: B12 helps your body make healthy red blood cells. Without enough of it, you can develop megaloblastic anemia, a blood condition that leaves people tired and weak [1].
• The nerves and brain: B12 is needed for your central nervous system to develop and work properly, including building myelin, the protective coating around your nerves [1].
• Your DNA: B12 helps make DNA, the genetic material inside every one of your cells [1].
• The immune system: And the last one. B12 helps your body keep healthy numbers of key germ-fighting cells, including CD8 T cells and natural killer cells [2] [3].

Why is vitamin B12 important for the human body?

Without enough vitamin B12, you may feel tired and weak, and you can develop pale skin, a racing heartbeat, numbness or tingling in your hands and feet, balance problems and trouble with memory [1]. A B12 shortfall can damage the nervous system even before anemia shows up, so it's important to catch and correct it early [1].

Low B12 is especially common as we get older, affecting somewhere between 3% and 43% of older adults [1]. Here's why. Your body absorbs B12 from food in two steps. First, stomach acid frees B12 from the protein it's attached to. Then it joins with a protein your stomach makes, called intrinsic factor, so your body can absorb it. Many older adults don't make enough stomach acid for that first step [1].

Vitamin B12 also connects to the two processes research links to declining health with age: increased oxidative stress, which is damage from excess free radicals, and chronic inflammation [4]. Together with folate and vitamin B6, B12 helps keep a compound called homocysteine in check. High homocysteine, along with oxidative stress and inflammation, has been linked to heart disease [5].

To be fair to the evidence, B vitamin supplements do lower homocysteine, but studies haven't shown that they lower the risk of heart disease or stroke [1]. Still, research-based formulas include a full set of B vitamins above the RDA, because they work as a team [6]. Vitamin B12 does its best work as part of that team, not by itself.

How does vitamin B12 support immune function?

Vitamin B12 supports immune function mainly by helping your body keep healthy numbers of CD8 T cells and active natural killer (NK) cells, two of your most important germ-fighting cells [2] [3]. In people who are low in B12, these cells drop, and restoring B12 brings them back toward normal [2] [3].

Think of your immune system as having two jobs: responding strongly when a threat shows up, and calming back down once the job is done. Let's look at how B12 helps.

• First-line (innate) defense: This is your body's rapid-response team, and natural killer cells are a big part of it. People with low B12 tend to have weaker NK cell activity, and it improves once their B12 is restored [2] [7].
• Targeted (adaptive) defense: This is the part of your immune system that learns and remembers specific threats. CD8 T cells, which seek out and destroy infected cells, run low when B12 is low and rise again after treatment [2] [3].
• Antibodies: B12 also supports the B cells that make antibodies. Antibody levels rose after B12 treatment in people who were deficient [2] [7].

One honest note: most of this research comes from people who were truly low in B12, often because of a condition called pernicious anemia. It shows that B12 helps restore normal immune function, not that extra B12 boosts it beyond normal [3].

Getting the most from vitamin B12

If you want to get the most out of vitamin B12, here are five things the research points to.

• Know your form: The Micro Daily EMF formula uses methylcobalamin, one of the two active forms of B12 your body uses [1] [8]. To be fair, the NIH notes that research hasn't shown any one supplement form to be better than the others [1].
• Mind the amount: Micro Daily EMF provides 10 mcg of B12 a day, 416% of the Daily Value [8]. That fits the approach of including B vitamins above the RDA [6]. B12 hasn't been shown to cause harm even at high doses, and your body absorbs only a small share of large amounts anyway [1].
• Over 50? Lean on fortified foods or supplements: Because many older adults make less stomach acid, the NIH suggests people over 50 get most of their B12 from fortified foods or supplements, which don't need stomach acid to be released [1].
• Don't take it alone: B12 works as a team with folate and vitamin B6, and research-based formulations combine them with antioxidants and minerals [4] [6].
• Take your formula twice a day: Comprehensive formulas are designed to be split into a morning dose and an evening dose. That's because many of a formula's nutrients leave the body within hours. B12 is a partial exception, since your body stores it, so here it simply comes along for the ride [9] [10].

One last thing to keep in mind: some common medications can lower your B12. These include metformin, used for diabetes, and acid reducers such as omeprazole [1]. If you take either, it's worth asking your healthcare provider about checking your B12.

Frequently asked questions about vitamin B12

How much vitamin B12 do I need each day?

Teens and adults need 2.4 mcg a day. During pregnancy that rises to 2.6 mcg, and while breastfeeding to 2.8 mcg. Children need 0.9 to 1.8 mcg, depending on age [1]. No upper limit has been set, because B12 hasn't been shown to cause harm even at high doses [1].

What foods are high in vitamin B12?

Beef liver is one of the richest sources, with about 70.7 mcg in 3 ounces, and 3 ounces of cooked clams have about 17 mcg. Fortified nutritional yeast can provide 8 to 24 mcg per quarter cup. Three ounces of salmon, canned light tuna or ground beef each give you about 2.4 to 2.6 mcg, and a cup of milk about 1.3 mcg [1].

What's the difference between methylcobalamin and cyanocobalamin?

Cyanocobalamin is the most common form in supplements. Methylcobalamin is one of the two forms your body actually uses to do its work [1]. Both raise your B12, and so far research hasn't shown that any one supplement form is better than the others [1].

Who is most likely to be low in vitamin B12?

The groups most at risk are older adults, people with pernicious anemia or atrophic gastritis, and people who've had stomach or intestinal surgery, including weight-loss surgery. People with celiac or Crohn's disease, vegetarians and vegans, and babies breastfed by vegan mothers are also at higher risk [1].

What are the signs of low vitamin B12?

Common signs include tiredness, weakness, pale skin, a racing heartbeat, and numbness or tingling in the hands and feet. Some people also have balance problems, memory trouble, low mood or a sore tongue [1]. Because your body stores so much B12, these signs can take years to appear [1].

Does vitamin B12 give you more energy?

Only if you're low. B12 supplements are often marketed for energy and endurance, but they don't provide these benefits in people who already get enough B12 from their diet [1]. If you're low, though, correcting it can help with the tiredness that comes with a shortfall.

Explore more micronutrients

Vitamin B12 works alongside other nutrients. Folate partners with B12 to make DNA and red blood cells, and iron carries the oxygen in them. Learn more about vitamin D, magnesium, calcium, zinc and potassium.

Key sources: NIH Office of Dietary Supplements, Vitamin B12 Fact Sheet [1]; Tamura J, et al., "Immunomodulation by vitamin B12," Clinical and Experimental Immunology, 1999 [2]; Prasad KN, Micronutrients in Health and Disease, CRC Press, 2019 [4]. Every numbered citation links to its full entry on our References page.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure, or prevent any disease. Talk with your healthcare provider before starting any supplement, especially if you are pregnant, nursing, taking medication or have a medical condition.