Out of the 13 vitamins our bodies need to function, eight are part of the B vitamin complex. All eight are vital to the functionality of our bodies. Some get more attention than others (B6, B9). But don’t forget about B12.

Vitamin B12 is a vital nutrient that helps everything from your heart to your brain. Most young American adults consume enough B12 in their diet. But as you age, your ability to absorb vitamin B12 decreases, which is likely why vitamin B12 deficiency is more common in older adults.

Low B12 can trigger symptoms ranging from a lack of energy and pins and needles to stomach problems, memory issues and shortness of breath.

Ahead, experts provide a lowdown on the nutrient and how much you need to stay healthy.

What Is Vitamin B12?

Vitamin B12 is a multifaceted nutrient, says Brian St. Pierre, RD, CSCS, director of performance nutrition at Precision Nutrition.

It’s good for your brain, improving focus and memory. Vitamin B12 also helps your red blood cells and nerves function. Plus, B12 also plays a crucial role in DNA production.

Vitamin B12 being important for your body is an understatement. With that said, don’t let supplement companies try to sell you on a megadose of vitamin B12. They will, if you let them. Unless you have major dietary restrictions, you should be able to get all the B12 you need from the food you eat.

How Much Vitamin B12 Do You Need Per Day?

The NHS says adults (aged 19 to 64) need 1.5 micrograms of vitamin B12 a day.

“Vitamin B12 requirements are low because we can store up to 2,500 micrograms in the liver,” says Ryan D. Andrews, RD, CSCS, principal nutritionist at Precision Nutrition.

Most meat-eating men consume about 5 micrograms of B12 daily and pee out what they don’t need. But if you’re vegan or have a GI condition, you’re at a greater risk of deficiency.

Granted, B12 is tough to track unless you use an app that tallies milligrams and micrograms of specific vitamins and minerals.

How Age Affects B12 Absorption

If you’re 50 years or older, you may need a little more vitamin B12 than the general health guidance. That’s because vitamin B12 absorption decreases with age because of changes in our digestive tract, says registered dietitian Avery Zenker.

“Vitamin B12 absorption requires adequate stomach acid, saliva, digestive enzymes, and other essential digestive components,” she says. “Older adults are more likely to have impaired ability to digest food-bound vitamin B12.”

One study in people over 70 found 22% of men were B12-deficient compared to 8% of women. Still, Zenker notes that vitamin B12 deficiency often starts younger, as 10-30% of adults over 50 develop atrophic gastritis: inflammation in the stomach lining. Atrophic gastritis reduces stomach acid and digestive enzymes like pepsin, which normally helps with separating B12 from food proteins it’s bound to so it can be absorbed.

According to the NHS, vitamin B12 deficiency and folate deficiency affect around 1 in 10 people aged 75 or over and 1 in 20 people aged 65 to 74.

For this reason, Zenker says adults over 50 should continue eating fortified foods and consider a B12 supplement. It might sound counterintuitive that whole foods aren’t the optimal source of B12, but it’s a special exception when an older adult’s digestive system cannot efficiently separate B12 bound to protein in food.

What Foods Contain Vitamin B12?

Nutritional yeast

If you eat animal products, St. Pierre advises aiming for four palm-sized portions a day. Beef, chicken, pork, eggs, and seafood are good sources. Two small mussels provide a day’s worth of vitamin B12 along with Greek yogurt and cottage cheese.

If you’re vegan or restricting your meat consumption, turn to fortified cereals, nondairy milk, or nutritional yeast – a vegan standby that has a cheesy taste and contains 100% of your daily dose of B12 in just one tablespoon, says Dana Hunnes, PhD, MPH, RD, adjunct assistant professor at UCLA Fielding School of Public Health.

Wait, what’s ‘fortified cereal?’ It’s basically most boxed cereals. Food manufacturers have added minerals and vitamins, including B12, to products like cereal (fortifying them) for almost 100 years. And yes, sugary cereals are also fortified. No, that doesn’t make them healthy.

What Are the Symptoms of Vitamin B12 Deficiency?

Deficiency isn’t common, but it can produce some scary side effects when it does happen. Lack of vitamin B12 can cause megaloblastic anaemia – a condition characterised by larger-than-normal red blood cells in a smaller-than-normal amount. This causes fatigue, paleness in the skin, nerve problems, and memory loss.

Pernicious anaemia, or Addison’s anaemia, is an autoimmune disease that decreases red blood cell count, caused by the body’s inability to properly absorb vitamin B12. It can cause diarrhoea, pale skin, lightheadedness, shortness of breath, swollen and red tongue, and bleeding gums.

Other symptoms of vitamin B12 deficiency include headaches, indigestion, loss of appetite, palpitations, problems with your vision and pins and needles.

When to Take a Vitamin B12 Supplement

Consider a supplement if you can’t get enough B12 from real foods and your dietary restrictions or age is making you deficient. While your fatigue might have you suspecting B12 deficiency, a blood test is the only way to know for sure.

If you do need to get B12 in supplement form, talk to your doctor about the best kind and dosage to take. They will be able to take into consideration your age and what B12-rich foods you already eat. You may not even need a megadose. Hunnes recommends a supplement of no more than 500 micrograms.

Jocelyn Solis-Moreira, MS is the associate health & fitness for Men’s Health and has previously written for CNN, Scientific American, Popular Science, and National Geographic before joining the brand. When she’s not working, she’s doing circus arts or working towards the perfect pull-up.

Cassie Shortsleeve is a Boston-based journalist with more than a decade of experience reporting for some of the nation’s largest print and digital publications, including Women’s Health, Men’s Health, Medscape, Parents, Conde Nast Traveler, and others. She also writes the best-selling Substack newsletter Two Truths and is a co-founder of the non-profit Chamber of Mothers. 

Cori Ritchey, C.S.C.S., is the fitness editor at Women’s Health, as well as a certified strength and condition coach and group fitness instructor. She’s reported on topics regarding health, nutrition, mental health, fitness, sex, and relationships for several years. You can find more of her work in Men’s Health, HealthCentral, Livestrong, Self, and others.