Vitamin B12 is one of eight B vitamins that play essential roles in your health. B12 is needed for neurological function, red blood cell production, metabolism, and DNA synthesis. Having a vitamin B12 deficiency can impact health in a number of ways.
B12 is naturally concentrated in animal products like meat, fish, and eggs, and is also added to some plant-based foods, like fortified breakfast cereals.
Even though B12 is found in many commonly consumed foods, some people need to supplement with B12 in order to maintain healthy levels of this nutrient.
Here’s everything you need to know about B12 supplements, including health benefits, safety, side effects, and how to choose the best B12 supplement for your needs.
Benefits of B12
B12 is a water-soluble nutrient. This means that your body doesn’t store B12 in large amounts and excretes whatever it doesn’t need through the urine. Because B12 isn’t readily stored, your body requires a steady supply of B12 in order to perform vital processes like energy production and normal nerve function.
Most healthy people following unrestricted diets consume enough B12 to maintain optimal blood levels. However, certain medical conditions, medications, dietary restriction of B12-rich foods, and even normal aging can affect the body’s B12 levels and its ability to absorb B12 from food sources.
People who can’t maintain healthy B12 levels through diet alone need to take B12 supplements in order to meet their daily requirements for this vitamin.
Here are some ways in which B12 supplements benefit health.
Can Increase B12 Levels and Treat B12 Deficiency
One of the top benefits of B12 supplements is their ability to effectively increase B12 levels in the body.
There are several reasons why a person may be unable to maintain optimal levels of B12 on their own.
As many as 30% of older adults are unable to properly absorb B12 from food due to changes in stomach acid and decreased production of a protein called intrinsic factor, both of which are needed for B12 absorption.
Commonly prescribed medications such as acid reflux medications and antidiabetic drugs can deplete B12 levels. Additionally, people with certain medical conditions like inflammatory bowel disease and those who follow restrictive diets, such as vegan diets, often develop low B12 levels.
For people who are unable to maintain healthy B12 levels on their own, a B12 supplement can help increase blood levels of this important nutrient and protect against B12 deficiency-related health issues, including macrocytic anemia, a blood disorder that impacts red blood cell production.
Can Reduce Homocysteine Levels
Homocysteine is an amino acid naturally found in your body in low amounts. B12 helps break down homocysteine and turn it into other compounds that your body needs. If you don’t have enough B12 in your system, homocysteine builds up in your blood.
High homocysteine levels increase inflammation and oxidative stress, a condition caused when your body’s antioxidant defenses are overwhelmed by reactive oxygen species, which are substances that cause cellular damage when levels get too high in the body.
High homocysteine has been linked to an increased risk of several health conditions, including heart disease, cognitive decline, and depression.
Supplementing with B12, along with other nutrients involved in the regulation of homocysteine, like folate, can significantly reduce homocysteine levels and therefore reduce disease risk associated with high homocysteine.
A 2022 review of 8 studies found that supplementation with B12 , B6, and/or folic acid led to a 31.9% average reduction of homocysteine levels in people with mild cognitive impairment.
May Benefit People with Depression
B12 plays important roles in brain function and is necessary for the production of neurotransmitters like serotonin, γ-aminobutyric acid (GABA), and dopamine, which play important roles in mood regulation. What’s more, B12 keeps homocysteine levels in check, which is essential for healthy brain function.
Research shows that having low B12 levels increases the risk of developing depression.
A 2021 study in older adults found that having low or deficient levels of B12 increased the risk of developing depression by 51% over four years.
Supplementing with B12 may help prevent the onset of depression and improve symptoms in people with depression. A 2023 review concluded that supplementing with B12 may be effective for reducing depression symptoms and improving the effectiveness of antidepressant medications.
Supports Brain Health
Having low levels of B12 can negatively affect brain health by increasing homocysteine, which promotes nerve cell inflammation and oxidative stress. Supplementing with vitamin B12 may help protect against oxidative stress-related cellular damage, which has been linked to a number of chronic diseases, such as cognitive decline.
Studies suggest that supplementing with B12 may help preserve brain function and delay cognitive impairment in older adults.
A 2022 review found that B12 supplements helped slow cognitive decline in older adults, especially when people started taking the vitamin earlier in life.
Good Sources of B12
B12 is naturally concentrated in animal foods and is added to some plant-based foods, like cereals, through food fortification.
Here’s some of the best food sources of B12:
- Cooked beef liver: 23.5 mcg per ounce, or 981% of the DV
- Cooked clams: 17 micrograms (mcg) per 3-ounce serving, or 708% of the daily value (DV)
- Fortified nutritional yeast: 15mcg per 2 tablespoons, or 630% of the DV
- Cooked salmon: 2.6mcg per 3-ounce serving, or 108% of the DV
- Ground beef: 2.5mcg per 3-ounce serving, or 106% of the DV
- Whole milk Greek yogurt: 1.04mcg per 7-ounce container, or 43% of the DV
- Eggs: .5mcg per whole cooked egg, or 19% of the DV
Even though B12 is found in certain fortified foods, like nutritional yeast, plant-based milks, and breakfast cereals, people following strict plant-based diets may have a difficult time reaching their daily B12 needs through diet alone.
Studies show that people following vegan diets are much more likely to develop a B12 deficiency compared to people who consume animal products. If you’re following a vegan diet or a restrictive diet that limits most natural sources of B12, it’s recommended that you supplement with B12 or a B complex vitamin in order to prevent deficiency and maintain healthy B12 levels.
How to Take B12
B12 can be taken at any time of day and can be taken with or without food. However, some research suggests that higher-dose supplements should be taken on an empty stomach to maximize absorption.
There are different forms of B12 supplements, including liquids, sprays, capsules, and lozenges. All of these forms are effective for raising B12 levels, so you should choose a product best suited for your needs and preferences. You can take B12 as a single supplement or in a B-complex supplement, which also contains other important B vitamins like folate and B6.
Keep in mind that while B12 supplements are effective for increasing low B12 levels, some people with vitamin B12 deficiency may require B12 injections in order to effectively increase their B12 levels. Your healthcare provider will decide which method is best for you.
B12 supplements can contain different forms of B12, such as cyanocobalamin, adenosylcobalamin, and methylcobalamin. Some research suggests that natural forms of B12 that are bioidentical to the B12 found in our bodies and in food—like adenosylcobalamin and methylcobalamin—are more bioavailable to the body compared to cyanocobalamin, which is a synthetic form of B12.
Some experts suggest that people with genetic polymorphisms that impact B12 metabolism choose natural forms of B12, like methylcobalamin, to improve their B12 status more efficiently.
The current recommended daily B12 intake for adult men and women is 2.4mcg. Pregnant and breastfeeding women need 2.6 and 2.8mcg of B12 per day, respectively.
B12 supplements usually provide very high doses of B12. Most B12-only supplements provide 500mcg or more of B12 per serving, which is over 20,000% of the DV. However, your body only absorbs very small amounts of supplemental B12 doses that exceed 2mcg. For example, while your body absorbs around 50% of B12 doses between 1-2mcg, you only absorb around 2% of B12 in doses of 500mcg.
Even though people with B12 deficiency or low B12 levels may need to supplement with high-dose B12 supplements, most healthy people looking to support their B12 intake should opt for lower-dose supplements.
Is B12 Safe?
B12 is generally considered safe, even at high doses. The body excretes extra B12 through the urine, so it doesn’t have the ability to build up in the body. Plus, you only absorb small amounts of B12 from dietary supplements.
In fact, there’s currently no Tolerable Upper Intake level (UL) established for B12 due to its low level of toxicity. The UL refers to the maximum daily dose of a vitamin unlikely to cause harm in the general population.
Some studies have reported that high-dose B12 therapy may exacerbate or cause acne in some people. However, in general, B12 supplements aren’t associated with adverse side effects.
Cyanocobalamin supplements may not be safe for some people, including those with kidney failure and people with Leber optic nerve atrophy, an inherited condition that causes vision loss.
Potential Drug Interactions
B12 supplements aren’t known to interact with many medications. However, a number of medications can deplete B12 levels in the body by impacting the body’s ability to absorb B12.
Here’s a list of medications known to deplete B12 levels:
- Proton pump inhibitors: Proton pump inhibitors like Prilosec that are prescribed to treat acid reflux can interfere with B12 absorption and cause B12 deficiency.
- Histamine 2-receptor antagonists: These medications inhibit gastric acid secretion and can cause low B12 levels.
- Metformin: The antidiabetic drug Metformin can reduce B12 absorption from food, which can cause low blood levels of B12.
Keep in mind that these medications are known to decrease the absorption of B12 from food, but not from B12 supplements. This is because the B12 found in food depends on stomach acid secretion for absorption. Stomach acid is not required for the absorption of B12 from dietary supplements.
What to Look For
When shopping for a B12 supplement, there’s a few things to keep in mind. First, you’ll want to choose high-quality products from trusted supplement brands. Some supplement manufacturers are certified by organizations like UL, USP, and NSF International. These organizations set strict standards for supplement quality and safety.
You’ll also want to choose a form of B12 that works best for your preferences. If you can’t tolerate pills, you may want to choose a liquid supplement or a dissolvable lozenge.
You can choose to take a B12-only supplement or take a B-complex vitamin that contains all eight B vitamins. You can also find B12 in multivitamin supplements.
Can You Take Too Much B12?
Because B12 is a water soluble vitamin, it’s generally considered safe, even at high doses.
Extremely high doses of up to 2mg (2,000mcg) have been safely used to treat pernicious anemia, an autoimmune condition that impacts B12 absorption. However, this doesn’t mean you should take megadoses of B12. Most people do not need to supplement with high-dose B12.
Side Effects of B12
B12 supplements are generally considered safe and aren’t associated with many side effects.
A certain form of B12 called cyanocobalamin may cause allergic reactions in some people and may cause the following side effects when used in high doses, such as when a person is being treated for B12 deficiency by a healthcare provider:
- Shortness of breath
- Swollen tongue
- Low blood potassium levels
Keep in mind that B12-related side effects are usually associated with very high dose replacement therapy such as B12 injections. If you experience any side effects when taking oral B12 supplements, stop taking the supplement and contact your healthcare provider for advice.
A Quick Review
Vitamin B12 is a nutrient that’s naturally found in certain animal-based foods and added to some plant-based products. Some people need to supplement with B12 for various reasons, such as low dietary intake and medical conditions that impact the body’s ability to absorb B12 from food.
B12 supplements are generally considered safe and can help people who are low or deficient in B12 reach and maintain optimal levels. If you're interested in taking B12, your healthcare provider can assess your needs and recommend a high-quality supplement if needed.
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