Vitamin B12 is an essential vitamin that supports everything from energy levels, cognitive function, and mood. It plays a key role in several essential functions in your body, and you can only find it in animal-based foods.
Deficiencies in vitamin B12 are common, and become increasingly likely the fewer animal-based foods you have in your diet.
B12’s benefits are among the most wide-ranging of any supplement. Our research team has dug into the scientific research on the biology of vitamin B12 and highlighted the following ways B12 can benefit your health and wellness.
Vitamin B12 benefits
1. Vitamin B12 can only be found in animal sources
There are no plant-based sources of vitamin B12, other than foods that are fortified with added B12 (1).
Lower levels of vitamin B12 can cause anemia and fatigue, so it’s very important to keep high levels of this vitamin.
2. Vitamin B12 can give you more energy
B12 is also often used as an energy supplement, which is why it’s included in many different energy drinks (2). Users often report a rush of energy after taking B12, which is why you’ll find it in both energy supplements and nootropic supplements.
3. A lack of vitamin B12 can cause weakness, dizziness, pale skin, and constipation
These problems are common among people in groups with B12 deficiency, like older adults, vegetarians, and vegans (3).
4. Vitamin B12 deficiency is a leading cause of anemia
A lack of vitamin B12 can limit your levels of red blood cells which supply oxygen to your muscles. This will manifest as weakness, fatigue, and poor performance during exercise (4).
5. One quarter of adults have low B12 levels
Close to six percent of older adults are B12 clinically deficient, and an additional 20% of people have “marginal” B12 levels, meaning they are right on the edge of low vitamin B12 (5).
6. B12 supplements can fix B12 deficiency, but it can take up to six months
That’s according to research published in the New England Journal of Medicine, which followed people with B12 deficiency after they started taking a B12 supplement (6). Even with steady supplementation, it takes time to build up depleted stores of B12 in your body.
7. Low levels of vitamin B12 might prevent cognitive decline
One study identified low B12 as a significant risk factor for Alzheimer’s disease and dementia (7).
The researchers found that low levels of vitamin B12 increased Alzheimer’s disease by 4.5-fold. The core role of B12 in cognitive function might explain why this vitamin appears to be protective against cognitive decline.
8. B12 deficiency is associated with depression
When compared to healthy subjects, people with depression are more likely to have lower B12 levels, according to a study in Rotterdam (8). As with the link between vitamin B12 and cognitive function, the essential role of B12 in cells in your brain might explain the connection.
9. Cardiovascular health is closely associated with vitamin B12.
The benefits of B12 aren’t limited to your brain: a study published in Circulation showed that higher blood levels of vitamin B12 was protective against cardiovascular disease too (9).
10. Vitamin B12 is essential for children and women who are pregnant
While folate gets a lot of the attention during pregnancy, B12 matters too.
A working group from the World Health Organization reports that deficiencies in B12 during pregnancy increase the risk of neural tube defects, a serious birth defect (10).
Some research also supports an association between low maternal levels of B12 and other birth defects too, but the evidence is not as strong.
11. The importance of B12 for health doesn’t end after birth
Children who are deficient in vitamin B12 suffer developmental delays, and may not ever fully recovery.
Among schoolchildren, the working group noted that lower levels of B12 correlated with worse grades and lower scores on tests of cognitive ability.
12. Weight loss surgery can cause vitamin B12 deficiency
Getting bariatric surgery, like a lap band or gastric bypass, can be a life-changing procedure for people who are very obese.
However, one of the unexpected side effects of these procedures can be B12 deficiency, which can be treated with supplementation (11).
Vitamin B12 side effects
Vitamin B12 is safe for most people, even at high doses. While short-term use of vitamin B12 has no immediate side effects, even at very high doses, taking high doses over a long period of time does seem to be linked to an increased risk of lung cancer, but only in men.
Long-term B12 use in smokers might increase lung cancer risk. A study from the Ohio State University found that men taking high doses of vitamin B12 had two to four times the incidence of lung cancer compared to men who didn’t take high doses of B12 (12).
This risk needs to be weighed against the benefits of B12 supplementation and the risks of B12 deficiency.
Vitamin B12 dosage
B12 supplementation has pretty firm recommendations on dosage for restoring proper B12 levels.
Aim for 500 to 1000 mcg per day to address B12 deficiency. This number comes from a study that tested doses of 2.5 to 1000 micrograms per day of vitamin B12 over the course of several weeks to see which doses elicited the most rapid restoration of B12 levels (13).
Doses of 2-2.5 mcg per day are sufficient during pregnancy if you are not B12 deficient. Later, you can lower your intake to maintain your levels (for example, during pregnancy you need a much smaller minimum of 2-2.5 mcg per day (14) if you are not already deficient).
Vitamin B12 benefits FAQ
Q: What foods are high in vitamin B12?
A: The list of foods that are high in B12 is surprisingly short. Beef, salmon and other fish, milk, cheese and other dairy products, and eggs more or less round out the significant sources of natural B12.
While other foods like breakfast cereals are often listed as being high in vitamin B12, these foods are fortified with supplemental vitamin B12.
Q: Is it okay to take B12 as a vitamin supplement?
A: Yes, vitamin B12 is extremely safe. No significant adverse effects have been associated with acute intake of vitamin B12, according to the National Institute of Health’s Office of Dietary Supplements (15).
As noted in the side effects section of this article, one study found an association between long-term use of vitamin B12 and an increased risk of lung cancer, though more research is needed to replicate this finding.
People who smoke or who are otherwise at high risk for lung cancer may want to talk to their doctor before taking a vitamin B12 supplement long-term, but aside from this, it’s okay to take a B12 supplement.
Q: Can you overdose on vitamin B12?
A: No. B12 is one of the safest vitamin supplements you can take. B12 is a water-soluble vitamin, so any excess is simply eliminated in urine.
There have been no documented cases of overdose on vitamin B12, and indeed, you’ll find many examples of supplements that provide massive doses of vitamin B12 with no apparent ill effect.
Q: What are the symptoms of B12 deficiency?
A: Vitamin B12 deficiency can manifest as tingling, pins and needles sensations, fatigue, continual tiredness, and pale skin.
Not all of the symptoms are easily observable physical symptoms, though. B12 deficiency can also manifest as mood changes, depression, forgetfulness, and other memory problems.
You may feel as though you are in a constant “mental fog” for no apparent reason. If you have these symptoms, it’s worth getting your vitamin B12 levels checked.
It’s particularly important to do so if your diet is pretty healthy—there may be an underlying medical cause for B12 deficiency, like celiac disease and other gastrointestinal disorders.
Q: Can you get vitamin B12 naturally?
A: Yes, but only from animal foods. The only natural source of vitamin B12 is from foods like beef, eggs, dairy, and fish.
While plants are great sources of many other vitamins and minerals, you won’t be able to get even trace amounts of natural vitamin B12 from any plant based food.
Some foods—particularly breads, breakfast cereals, and rice—are often fortified with vitamin B12, so these foods can make appearances on lists of top sources of vitamin B12, but these are not naturally occurring sources of B12.
Related: Our best vitamin B12 picks
Vitamin B12 is an essential vitamin that you can only get from animal-based foods. Up to a quarter of the population has lower-than-optimal vitamin B12 levels, indicating that many peoples’ diets are not sufficiently high in vitamin B12.
If you have B12 deficiency, a supplement can help. Even with a good vitamin B12 supplement, it might take several weeks to rectify low B12 levels. However, given the potential links between vitamin B12 and cognitive health, mental wellness, and heart health, keeping your vitamin B12 levels high is well worth it.