Your Guide to Vitamin B12: Do You Need to Take It On a Plant-Based Diet?

Vegan diets often get criticized for being short in certain nutrients, like protein and iron, but both are easily attained through eating protein-rich foods like tofu, lentils, and all kinds of beans. The next on the list that gets singled out is vitamin B12. That’s because this nutrient is most commonly found in animal products, and if you’re not eating animals, you may assume you’re not getting enough B12.

While anyone can be deficient in B12 if they’re not careful, not only plant-based eaters. “People who are taking metformin, or having malabsorption issues, or eating a vegetarian diet are at highest risk for vitamin B12 deficiency,” says Kim Rose, R.D.N., certified diabetes care, and education specialist and dietitian for the weight loss app Lose It!. Older adults are also at risk of a B12 deficiency.

So how can you make sure you’re getting the B12 you need if you’re following a plant-based diet? Here is everything you need to know to eat plant-based and get the B12 you need.

Vitamin B12 is a water-soluble vitamin that’s made by microorganisms in the soil and water. Although the soil was once a rich source of B12, soil quality has declined, making it tough to get B12 from, and any B12 remaining on produce is often washed off. Instead, B12 today comes mainly from two sources: Foods that have been fortified with vitamin B12 and animal products, namely because B12 is added to supplement animal feed. Farmed animals also accumulate it throughout their lives.

One reason you need B12? To convert an amino acid called homocysteine into methionine, another amino acid. “High levels of homocysteine in the blood are associated with the development of heart disease,” Rose says.

B12 also has other roles in the body, including DNA synthesis, normal red blood cell formulation, and proper neurological function. And for pregnant women, it’s a critical nutrient for the baby's growth and brain development, especially early. “Adequate intake of B12 is key to a healthy pregnancy, as it’s important in avoiding brain and spinal cord birth defects,” says Brittany Dunn, M.S., R.D., C.D., performance dietitian and chef in Philadelphia.

Whether you’re eating plant-based or not, the Recommended Dietary Allowance for people aged 14 years and older is 2.4 micrograms (mcg) daily. If, though, you’re pregnant or lactating, you need 2.6 to 2.8 mcg a day, Dunn says.

A B12 deficiency can take time to physically show up in your body, namely because your body stores it. “Adults with normal stomach function store about 50 percent of dietary vitamin B12 in their liver, and because the body can store it for when it’s needed, the physical manifestations of a deficiency don’t occur immediately,” Rose says.

When a deficiency does occur, though, symptoms are vast and can include anemia, fatigue, weakness, poor appetite, constipation, mouth or tongue soreness, and weight loss, Dunn says. You might also have neurological issues, including numbness or pain in your extremities, depression, dementia, confusion, and trouble with memory and balance.

One thing to know? “Some problems can occur with or without symptoms, especially in cases concerning neurological issues,” Dunn adds. It’s also possible that a folate deficiency may be masking a B12 deficiency.

If you’re having these symptoms or suspect you may be deficient in Vitamin B12, one of the earliest detections tools is a blood test that assesses levels of holotranscobalamin II, the primary delivery protein for B12, Rose says. Ask your doctor about getting tested.

You don’t need animal products to get your B12, as there are numerous B12-fortified foods, including cereals, plant-based milks, and some soy products. Here are some examples from Dunn:

There is, however, one hitch with relying on fortified foods. “Not all B12-fortified foods are reliable sources,” Dunn says. She points to nutritional yeast, which most people assume contains B12. Yet not all companies add it to their nutritional yeast so make sure you’re checking labels frequently to see if it’s there.

If you’re a plant-based eater, you can get enough B12 through food, but you have to be conscious about it and eat a variety of fortified foods on a daily basis, Rose says. According to NutritionFacts.org, you should eat B12-fortified foods three times a day, making sure that each serving contains at least 4.5 mcg. To get what you need, you would have to eat roughly the equivalent of two teaspoons three times a day of B12-fortified nutritional yeast.

Yet because it’s challenging and not always convenient to get the B12 you need from food alone, it’s a wise idea to add a supplement to your diet if you’re eating vegetarian or vegan, Dunn says. Follow the advice of Michael Greger, M.D., founder of NutritionFacts.org and author of How Not to Die and How Not to Diet, who recommends adults up to age 65 supplement with at least 2,000 mcg of cyanocobalamin, found to be the most effective form, once a week. (If you’re 65 or older, that increases to 1,000 mcg a day, largely because your body has a tougher time absorbing B12.) You can also take it daily at a dose of 50 mcg. Choose a supplement that can be chewed, taken sublingually, or is in liquid form, and take it on an empty stomach.

The one caveat? Gastrointestinal issues can prevent the absorption of B12, which is why oral supplementation may not be enough, Rose says. If this is the case, talk with your doctor about receiving an intramuscular injection of B12.

You can opt for foods fortified with B12 or choose a B12 supplement. If you're choosing a supplement, be sure to consult your doctor first.