What Is Vitamin B12 Deficiency?

Photo by Harold Julian

If you don’t eat meat, you’re probably used to fielding the same questions over and over again—like “Is it boring to eat only plants?” and “Where do you get your protein from?” If you’ve been eating plant-based for a while, you also probably have your responses on lock: “No, there’s a ton of variety” and “I get my protein from whole grains, beans, and nuts.”

As annoying as those well-intentioned questions can get, there may be another one worth considering—one that’s rarely asked but much more important than the rest: “How much vitamin B12 do you get?”

Because while dietary boredom and protein deficiency aren’t all that common in the United States and other developed nations, vitamin B12 deficiency is—especially among those who don’t eat animal products. But you don’t have to be vegan to be at risk: Studies show that it can affect anywhere from 1.5 to 15% of the population.

Since a lack of vitamin B12 can cause serious conditions like anemia, vision loss, and an inability to walk or talk—not to mention depression, fatigue, irritability, and brain fog—it’s well worth everyone’s while to do a little check-in. With that in mind, here’s everything you need to know about vitamin B12 deficiency.

First, what is vitamin B12?

Vitamin B12, also known as cobalamin, is a water-soluble micronutrient that supports the nervous system by transporting oxygen to your blood cells. “It helps keep your body’s blood and nerve cells healthy,” explains Jacey Folkers, BS, DC, a functional-medicine practitioner whose great uncle Karl Folkers, MD, happens to be the scientist who made the first major contributions to the identification and isolation of the vitamin. “B12 plays an essential role in red-blood-cell formation, cell metabolism, nerve function, and the production of DNA, the molecules inside cells that carry genetic information.”

In other words, it’s essential for keeping your entire body working optimally.

Where does vitamin B12 come from?

Despite vitamin B12’s all-important role in our health, our bodies can’t make it by themselves. That’s where diet comes in: “The main source of vitamin B12 is animal protein such as meat, fish, eggs, and dairy,” says Eva Pena, a nutritionist and the founder of Wellness+ Studio on New York’s Upper East Side.

But if you don’t eat animal protein, there are still a few ways to get vitamin B12 through your diet. Some foods, like breakfast cereals, soy milk, and almond milk, are commonly fortified with it, while some whole-plant foods like mushrooms and nori contain small amounts. The best vegetarian option, however, is probably nutritional yeast, a deactivated yeast with a savory flavor that can be easily sprinkled on everything from salads to popcorn. Studies have found that consuming two tablespoons per day of nutritional yeast provides sufficient amounts of vitamin B12 in adults. Yet another option is to take an oral supplement, either in the form of a B-complex pill or high-quality multivitamin.

How much vitamin B12 is enough?

The adequate amount of vitamin B12 you need varies depending on age, diet, sex, lifestyle, and specific medical conditions. Most healthy adults need 2.4 mcg of vitamin B12 on average—the equivalent of consuming two cups of 2% milk, a can of tuna, a three-ounce piece of salmon, or four and a half eggs. But if you’re pregnant or breastfeeding, you’ll want a little more, between 2.6 and 2.8 mcg.

In terms of supplements, most oral multivitamin capsules or general B-complex pills contain much more B12 than the recommended dose, usually around 5 to 1000 mcg. But the percentage your body can absorb from a high dose of B12 in supplement form is only about 10 mcg—so no need to worry about taking too much; your body will eliminate what it doesn’t need through your urine.

The ability to absorb vitamin B12 is key when it comes to getting an adequate amount. As we age, it becomes harder for our bodies to absorb the nutrient, so people over 60 are often at higher risk of developing a deficiency. In addition, anyone who has had stomach surgery, has a thinned stomach due to atrophic gastritis, or has a condition that affects the small intestine—like Crohn’s disease, celiac disease, a parasite, or an overgrowth of gut bacteria—may also have trouble with absorption. Same goes for those with immune disorders like Grave’s disease and lupus. Heartburn medications with proton-pump inhibitors or diabetes medications like metformin can also have an impact on the body’s B12 uptake.

There’s also a rare autoimmune disease called pernicious anemia, which prevents the intestine from being able to absorb vitamin B12. In cases of pernicious anemia, the body lacks a certain protein called intrinsic factor that is an essential element in processing vitamin B12.

It’s worth noting that even moderate amounts of alcohol consumption can affect the body’s ability to absorb vitamin B12. This is because alcohol inflames the stomach, thinning its lining and preventing intrinsic factor from doing its job—all the more reason to cut back on alcohol.

What happens if you don’t get enough vitamin B12?

“People who are deficient in vitamin B12 can experience hematological and neurological disorders,” Pena says. “The health risks include anemia, cramps, and numbness or tingling due to the lack of capacity to regenerate blood cells.” She also notes that low blood oxygen can contribute to symptoms like fatigue, depression, headaches, and difficulty concentrating.

Folkers says that other symptoms to look out for are a sore and red tongue, mouth ulcers, problems with your vision, anxiety, confusion, and problems with memory or comprehension. “Left untreated, a vitamin B12 deficiency can also lead to muscle weakness, intestinal problems, nerve damage, and mood disturbances,” he says, noting that some of the damage may not be reversible.

Bottom line? Make sure you’re getting enough vitamin B12—either through your diet or with supplements. If you’re concerned that you are not, or if you are experiencing the symptoms above, schedule an appointment with your doctor. A quick blood test will tell you where your B12 levels stand, and if they’re low, early detection makes treatment much easier. It may be as simple as being prescribed an oral supplement or receiving a series of subcutaneous or intramuscular injections; there are even nasal sprays and gels.

And if you’re feeling fine? Consider this information your permission to order the three-egg omelet at brunch and sprinkle on the nutritional yeast. Your blood cells will thank you.

This article was originally published on Vogue.com

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