If your body doesn’t get enough vitamin B-12, your stomach might bloat and your feet could swell. Your skin might darken or yellow or even turn pale. You might get muscle cramps or have painful joints. You could be depressed. Or manic. Or delirious. Also: weak, confused, dizzy or short of breath. Your hands and feet might tingle or feel numb. You could become anemic. Men might experience erectile dysfunction. Scarier yet, you could end up blind or your organs could fail.
That’s a long, though (believe it or not) abridged, list of varied symptoms. In turn, vitamin B-12 deficiency, which is diagnosed via blood test, can be tricky to identify. To wit: Researchers have called vitamin B-12 deficiency “the great masquerader.”
But getting enough vitamin B-12 isn’t only about consuming the micronutrient. Also important: your body’s ability to absorb it.
On the upside, most of us have a bit of a buffer. If a typical person stops getting the micronutrient altogether, they have enough stored, mainly in their liver, to last at least three years, according to several scientific sources, including Merck Manuals. But to avoid relying on reserves, here’s the scoop:
Vitamin B-12 foods
We love fruits and veggies for many reasons. Containing vitamin B-12 isn’t one of them.
Foods that naturally contain vitamin B-12 are animal-based: fish, chicken, beef, eggs, milk and cheese, for example.
“Vitamin B-12 deficiency is becoming more and more common due to the prevalence of plant-based diets,” says Mitra Shir, RHN, a holistic nutritionist in Vancouver, Canada, and founder of Nutriholist.
To be sure, B-12 often is added to bread, breakfast cereals, non-dairy milks and nutritional yeast. That said, “the synthetic form of B-12 found in these plant-based foods is often added in small quantities and is poorly absorbed,” Shir notes. “Therefore, it is important for vegans to check the labels, and supplement if necessary.”
The U.S. National Institutes of Health recommends most adults get at least 2.4 micrograms of vitamin B-12 each day. To give you a sense for that amount, three ounces of sockeye salmon has 4.8 mcg, one cup of low-fat milk has 1.2 mcg, and one hard-boiled egg has .6 mcg, according to the NIH.
Vitamin B-12 absorption
Unfortunately, even if you consume enough vitamin B-12, your body might not absorb it sufficiently.
“Gastrointestinal (GI) disorders are another reason why people become deficient in vitamin B-12,” Shir says. “Those who lack sufficient levels of stomach acid, digestive enzymes or intrinsic factor (a protein that the stomach produces that is necessary for B-12 absorption) can’t properly digest and absorb the nutrients in foods.” A general tendency toward low levels of intrinsic factor is often hereditary.
While vegans and those who adhere to a strict plant-based diet are more at risk for vitamin B-12 deficiency due to inadequate consumption, the elderly are more at risk because of issues with absorption.
“In order for the body to absorb vitamin B-12, first it needs to be accessed and released from the protein in food using hydrochloric acid (HCl) and protease (protein-digesting enzymes) in the stomach,” Shir says. “Free B-12 is then combined with intrinsic factor and proceeds to the small intestine where it is absorbed. As people age, the stomach produces less HCl and intrinsic factor.”
Bowel diseases and other factors can inhibit absorption too.
When is taking a vitamin B-12 supplement critical?
Shir generally advises vegans to supplement with 500 to 1000 mcg of vitamin B-12, at least two to three times a week.
Those with GI disorders who have trouble absorbing vitamin B-12 from natural sources and people older than 50 who are deficient in B-12 should benefit from supplementing with about 1000 mcg daily or getting intramuscular B-12 injections, Shir says.
Healthy people’s bodies absorb only about 10 mcg of a 500 mcg oral supplement of the micronutrient, according to the NIH.
What does B12 do for your body?
The long list of awful symptoms at the start of this piece is reason plenty to prioritize vitamin B-12. But on a more granular level and one that illuminates macro implications, a deficiency of the micronutrient will impede your body’s ability …
Helps form red blood cells
We all know we need red (and white) blood cells. But knowing why we need red blood cells, specifically, sheds light on why not having enough of them can lead to those aforementioned awful symptoms: Red blood cells move oxygen throughout your body, and if your body doesn’t have enough of them, your tissues, organs and other anatomy become oxygen-starved. In turn, your body won’t work the way it’s supposed to, leading to illness, injury and physical breakdown.
Helps make DNA
Along with folic acid (vitamin B-9), vitamin B-12 is a building block for your body’s unique genetic code.
Helps protect your nerves
Vitamin B-12 maintains the protective cover (myelin sheath) around your nerves. Not having enough B-12 can cause nerve damage (neuropathy), leading to numbness, tingling and other atypical sensations in your skin.
Journalist Mitra Malek is taking a break from years of hard-news reporting, in favor of writing about wellness, which has been terrific given she’s also a longtime yoga teacher and former Yoga Journal editor. She was tickled to interview someone with the same uncommon Persian first name as herself.