Vitamin B12 not only plays a vital role in healthy cell formation and neurological function, but it’s also been touted as a weight-loss aid and a natural energy boost. But do the vitamin B12 benefits live up to the hype? How much B12 do you need in a day? And how can you make sure you’re getting enough? Before you pop a B12 supplement, here’s what you need to know.
What Is Vitamin B12 and Why Is It Important?
Vitamin B12 is one of the eight vitamins known as the B-complex. You need vitamin B12 to make everything from red blood cells to nerves to DNA, so you definitely don’t want to miss out on your B12 benefits.
But while “eat your veggies” is great advice for getting many of the essential nutrients you need every day, vitamin B12 isn’t one of them — this water-soluble vitamin is found primarily in animal products and fortified grains.
Vitamin B12 naturally occurs in meat, poultry, eggs, shellfish, and dairy products. Foods with the highest amount of B12 per serving include clams, liver, trout, and salmon. If you’re vegan or vegetarian, that can make it challenging to get enough B12 in your diet — but fortified breakfast cereals are a good source of B12, and if you’re a fan of sushi, nori is a plant-based source of B12.
How Much B12 Do You Need?
The recommended dietary allowances (RDAs) for B12 vary by age and sex.
- Men and non-pregnant women: 2.4 micrograms per day
- Pregnant women: 2.6 micrograms
- Lactating women: 2.8 micrograms
Because the best sources of B12 are animal products, incidences of vitamin B12 deficiency are much higher among people who follow a vegan or vegetarian lifestyle.
Even if you’re lacto-ovo, you may not be getting enough B12. One 8-ounce glass of milk and an egg, for example, only provide about two-thirds of the RDA of vitamin B12, according to Melissa Majumdar, MS, RD, senior bariatric dietitian for Brigham and Women’s Center for Metabolic and Bariatric Surgery. For people who don’t regularly eat animal products, a B12 supplement could act as an insurance policy.
There are also B12 injections available, but that’s overkill for most people. “The only people who definitely need to take B12 shots are those with chronic pernicious anemia, a condition in which B12 is not absorbed in the gut,” says Mascha Davis, MPH, RDN, private practice dietitian at Nomadista Nutrition.
Can You Overdose on B12?
While taking too much B12 can cause dizziness, nausea, and vomiting, it’s not common to overdo it. “B12 toxicity is very rare, because our bodies are fairly good at getting rid of what we don’t need,” Davis says.
Can B12 Give You More Energy?
Vitamin B12 is often touted as a natural energy booster, but there’s no strong evidence to back up that claim. “B12 doesn’t have calories, so it doesn’t really supply actual energy to our bodies — it just helps the process move along,” Davis says.
Having low B12, however, can definitely sap your energy. Symptoms of B12 deficiency include irritability and fatigue. And vitamin B12 deficiency can lead to megaloblastic anemia, a type of anemia that causes weakness and tiredness.
But popping a B12 supplement probably won’t give you a jolt. “B12 is only helpful for boosting energy when a person is actually deficient in it,” Majumdar says. “It should not be considered a cure-all for poor energy.”
Can B12 Help You Lose Weight?
Unfortunately, there’s no evidence that connects B12 supplementation to weight loss.
Vitamin B12 plays a role in energy metabolism, which is your body’s ability to convert food into fuel — this is why fatigue is a common symptom of a B12 deficiency. But while correcting the B12 deficiency can help get your energy metabolism back to normal, you can’t burn extra calories by taking more B12 than you need. If it were really that easy, we’d all pop a multivitamin and call it a day.
Tips for Taking B12
If you think you may be lacking in the vitamin B12 department, talk to your doctor or dietitian to find out if supplements are right for you. They can also suggest the best type of B12 supplement for you.
When choosing a B12 supplement, you might notice the dosage sounds much higher than the RDA. That’s because your body absorbs a limited amount of B12 from dietary supplements — only about 10 mcg from a 500 mcg pill, according to the National Institutes of Health.
To get the most out of your B12 supplements, Davis suggests taking B12 separately from iron or vitamin C supplements, since iron and vitamin C can change B12 to a less absorbable form.
It’s also better to take B12 supplements daily rather than weekly. “Taking a smaller, daily dose — 350 to 500 micrograms — may be better absorbed than a weekly megadose, because absorption decreases with larger doses,” Majumdar says.
And last but not least, if you’re vegetarian or vegan, you don’t need to worry about whether your B12 supplement was derived from animal products. B12 supplements are often synthesized or derived from bacteria — so unless you’re concerned about the ethical treatment of bacteria, you’re good to go.