21 Important Facts About Vitamin B12 Deficiency

Vitamin B12 is a powerhouse. It helps make DNA, nerve and blood cells, and is crucial for a healthy brain and immune system. Your metabolism wouldn't run smoothly without it. But B12 isn't like other vitamins. It's only found in animal products like eggs, meat, shellfish, and dairy. Up to 15% of people don't get enough B12, and they're more likely to be vegetarians, have celiac disease or other digestive issues, or be an adult over 50. The signs of vitamin B12 deficiency include exhaustion, rapid heartbeat, brain fog, and other symptoms, Maggie Moon, RD, a Los Angeles–based nutritionist and owner of Everyday Healthy Eating, tells Health. Read on to find out more about the causes, symptoms, and cures for a vitamin B12 deficiency.

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Vitamin B12 occurs naturally in animal products. So if your diet largely consists of plant-based foods such as fruits, veggies, beans, and soy, you're at risk for deficiency. "Vegetarians who consume eggs and dairy should aim to include at least one source a day from both of these food groups," Stephanie Middleberg, RD, nutritionist at Middleberg Nutrition in New York City, tells Health. Vegans—who by definition consume no animal products—need to take a supplement or consume vitamin B12–fortified foods, such as breakfast cereal and grains. Other foods fortified with B12 include nondairy milks and meat substitutes. But not all of these foods are fortified, so check the label first to make sure.

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As you age, your stomach produces less acid, and stomach acid is key for B12 absorption, says Middleberg. About one in 31 adults over 50 are deficient, estimates the Centers for Disease Control and Prevention. "Older individuals also often have poorer appetites and food intakes, and they may be on medications (such as heartburn meds) that can further reduce stomach acid levels," she says. In fact, some seniors actually lose the ability to absorb vitamin B12 from food completely, and they must get it via supplements or, if the deficiency is severe, injections.

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B12 isn't nicknamed the energy vitamin for nothing. Inadequate B12 intake makes a dent in red blood cell production, and some of the earliest signs of a deficiency include feeling dragged, confused, and weak. Problem is, says Middleberg, these clues are so vague, and not everyone experiences them the same way. And since they can be attributed to so many other possible triggers, most people don't think to be tested. If these symptoms hit and stick around for weeks, it's best to consult your doctor and rule out other causes, she says. Similar tip-offs include dizziness, impaired thinking, and confusion.

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Some prescription heartburn drugs suppress the production of stomach acid, which is needed to absorb vitamin B12. A study from JAMA backs this up. Researchers found that taking meds called proton pump inhibitors (like Prilosec and Nexium) for more than two years was linked to a 65% higher risk of vitamin B12 deficiency. And two years or more using H2 receptor blocker drugs (such as Pepcid and Zantac) is associated with a 25% boost in deficiency odds. A If you take these regularly, talk to your doctor about steps you can take to protect yourself.

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"Symptoms of a deficiency often mimic those of dementia, such as memory loss, disorientation, and difficulty thinking and reasoning," says Middleberg. It can be hard distinguishing deficiency from dementia, especially since older folks are at risk for both. And the two conditions often overlap: 75% to 90% of B12 deficient people also have neurological complications such as dementia, says Moon. But even when a B12 shortage strikes younger people, it still typically resembles dementia. Experts aren't exactly sure of the relationship between the two, but patients with unexplained cognitive decline should be tested for B12 deficiency, suggests Moon.

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"Women who have been on oral contraceptives for extended periods of time tend to have issues absorbing vitamin B12," says Middleberg. "Studies show that pills that are higher in estrogen are more strongly associated with B12 and folate (folic acid, or vitamin B6) deficiencies, leading to the assumption that the estrogen in the pill is the reason for this impaired absorption." If you're on the pill, talk to your doctor about the risks, and if you should take B12 supplements as a backup.

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Beef liver and clams are tops in B12, according to the National Institutes of Health. If you're not a fan of either, plenty of good options abound. Ground beef, oysters, trout, and salmon are B12 superstars; a serving of each delivers close to or more than 100% of your RDA (2.4 micrograms for men and women over 14, going up to 2.6 and 2.8 for pregnant and breastfeeding women respectively, says Moon). Eggs (0.6 micrograms per egg, 10% of daily value) and milk (1.2 micrograms per cup of low-fat, 18% of daily value) are also solid sources.

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Both can help vegans, vegetarians, older adults, and others who are unable to absorb naturally occurring B12, says Moon. When absorption is an issue, "simply loading up on foods naturally high in B12 may not solve the problem," she says. "The synthetic form of B12 is more readily absorbed." Best places to find it in food: fortified cereals, many of which have 100% of your RDA.

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More than a few drinks on average each day can cause gastritis, or irritation of the stomach lining, and this can lead to low stomach acid and reduced B12 absorption, says Middleberg. Alcohol plays a role in deficiency in another way, too. B12 is stored in the liver, and alcohol consumption can impair liver function and deplete B12 stores or make it harder for the liver to use it.

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Vitamin B12 deficiency even affects the Pap test you get at your regular gyno checkup to screen for cervical cancer. Low B12 levels can change the way some cervical cells look, potentially triggering a false positive, according to the National Institutes of Health. Yet another reason to shore up your intake of the nutrient.

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There's a specific type of anemia that's triggered by a B12 deficiency. Called pernicious (which means "dangerous," because it was potentially life-threatening in the past) anemia, it is a red blood cell deficiency that happens when the stomach doesn't make enough of a protein called intrinsic factor, which helps the intestine absorb B12, says Moon. Pernicious anemia can be the result of an autoimmune issue, a problem with the stomach lining, or even a congenital condition passed down through families. Treatment usually involves B12 shots, possibly combined with supplements.

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"Because the body can store B12 for three to five years, early symptoms of a deficiency usually appear gradually, so you're unlikely to notice them," says Middleberg. After initial clues like fatigue, weakness, and brain fog set in, says Middleberg, more advanced tip-offs show up, such as numbness and tingling of the limbs, depression, and paranoia, even hallucinations. The signs are so varied and they don't strike everyone, so it's tough to diagnose even at a later stage. "Which symptoms hit when depends also on what caused the deficiency—malabsorption, which could mean they are absorbing some B12 and the deficiency is occurring more slowly, or total lack of animal products, which would likely cause the deficiency to develop more quickly," says Middleberg.

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Blood levels of vitamin B12 less than 160 pg/mL (picograms/milliliter) are a sign of a possible deficiency, according to the National Library of Medicine. "Blood tests are generally accurate, but a false positive is possible related to certain cancers, oral contraceptives, folate (folic acid) deficiency, and pregnancy," says Moon. "False negatives are also possible, as sometimes seen in people with liver disease, poorly functioning kidneys, or certain blood cell disorders." Your GP or primary care physician can take care of testing you.

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"B12 plays an important role in white blood cell production, and white blood cells are essential for proper immune system functioning," says Middleberg. Not only can a lack of B12 lower your immunity, some immune system disorders can increase your likelihood of becoming deficient. Graves' disease, for example, an autoimmune condition of the thyroid causing hyperthyroidism, is a risk factor for developing pernicious anemia, which in turn leads to B12 deficiency.

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People who deal with GI issues are at a higher risk of a B12 shortage because digestive problems can make absorbing the nutrient more difficult, says Middleberg. "Those with gut issues, such as colitis, Crohn's disease, inflammatory bowel disease, and leaky gut syndrome are at a higher risk," she says. Celiac disease sufferers can also have problems with absorption. If you have any of these, talk to your doctor about supplements or B12 shots, since all the B12-rich food in the world won't help your body shore up its reserves if it can't be absorbed by the GI tract.

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"Some surgeries that affect the GI tract, like gastric bypass surgery, make it hard to absorb B12," says Moon. One reason has to do with the decrease in the body's ability to digest food; it's also the result of iffy levels of intrinsic factor, a protein that helps the body absorb B12. The absorption problem could be a permanent one, and people who undergo gastric bypass may need to take vitamin B12 supplements for the rest of their life or risk a shortage.

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Depletion of your vitamin B12 stores leads to nerve damage. No wonder pins and needles in your hands and feet, shaky body movements, and trouble walking are all consequences of long-term B12 deficiency, says Middleberg. Like so many other B12 deficiency signs, these can be attributed to other causes, including old age. The only way to know for sure is to see your doctor for a test.

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In infants, vitamin B12 deficiency is serious—it can lead to symptoms such as anemia, problems with movement, difficulty reaching developmental milestones, and failure to thrive, which may be fatal. Low B12 levels are rare in infants but it can happen if a baby is fed a strict diet free of any animal products, or if a breastfeeding mom is a vegan who doesn't take vitamin B12 supplements (and breast milk is the only source of nutrition.) Based on evidence that B12 supplementation can reverse the course, the American Academy of Family Physicians says women at high risk or known deficiency should take taking supplements with B12 during pregnancy or while breastfeeding.

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Pale skin, mouth sores, a red, swollen, beefy tongue—these are some of the visible signs of a B12 shortage. Caused by deficiency-related changes in blood flow, these signs can show up years after the depletion sets in, says Middleberg. A rapid heartbeat or heart palpitations is another blood flow-related sign, and sometimes bruising easily is also a result of a longstanding deficiency. But these seemingly unrelated signs don't show in all B12 deficient people, or they come on so slowly, it's hard to notice them, says Middleberg.

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Vitamin B12 deficiency that persists for years can cause severe, irreversible neurologic damage—think memory loss, disorientation, and an inability to concentrate. Other permanent side effects include nerve damage, insomnia, erectile dysfunction, even difficulty with bowel and bladder control, says Moon. The upside: "Many symptoms can be reversed if caught early and treated with B12," she adds.

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Unlike fat-soluble vitamins that accumulate in your body and can have side effects in excess, B12 is a water-soluble vitamin, meaning your body only absorbs a small amount and the rest is excreted through urine, says Middleberg. That's good news if you need to refill your stores of this nutrient but worry about taking too much. But keep in mind that large amounts of B12 at one time may cause diarrhea and all-over itchiness, she adds. If your doctor recommends supplements, read the label and take only the amount recommended by your MD.

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