IF YOU KNOW anyone who's deficient in a B vitamin, you may see them taking a vitamin B-complex supplement. They're being touted as a cure to all your vitamin B related needs—but do you really need it?

“Vitamin B-complex is a group of essential micronutrients, which are made up of water-soluble B vitamins. [They] require regular replenishment to maintain overall bodily functions,” says Amy Shapiro, M.S., R.D. “These micronutrients are critical for maintaining your energy level because of their roles in metabolic processes.”

Vitamin B-complex also plays a pretty big role in your brain and nervous system health. It’s made up of eight smaller vitamins: thiamine (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), pantothenic acid (vitamin B5), pyridoxine (vitamin B6), biotin, folic acid, and cobalamins (vitamin B12).

“They are called the ‘B complex’ because, although they are different vitamins, their functions in the body are so similar that they are grouped into one category,” says Destini Moody, R.D., a sports performance dietitian. “Our metabolism does not work optimally without enough vitamins from the B complex.”

Ahead, what you should know about these vital nutrients.

What Is Vitamin B-Complex?

As we mentioned above, the vitamin B-complex is a group of B vitamins that help our bodies function. These vitamins are water-soluble, “meaning they dissolve in water and are not stored in our body,” says Shapiro. Intake from our daily diet is required to maintain the levels of these vitamins, and B vitamins work best together.

What Are the Benefits of the Vitamin B-Complex?

They’re responsible for anabolic (building up) and catabolic (breaking down) processes in the body, including the release and breakdown of carbohydrates, fats, and amino acids. They also transport oxygen and energy-containing nutrients around the body.

There’s more: B vitamins act as coenzymes that help speed up these processes, especially those within the brain and nervous system, says Shapiro. They’re even associated with improved mental health and cognitive performance.

Separately, each specific vitamin has its own specialized job. For example, Moody says that vitamin B12, in particular, helps maintain red blood cells and provides some of the coating on our nerves that help conduct nerve impulses. Most of the other vitamins in the complex act as coenzymes to help the body generate enough energy—powering everything from getting out of bed to crushing your pick-up basketball game. This is why you typically find B vitamins in energy and sports drinks.

“Simply put, B vitamins are vital to our health because they act as the sidekicks of all the other hormones and enzymes that control our metabolism and other bodily processes that we do not consciously control,” says Moody. They’re the “ultimate background players of our bodies.”

What Are There Risks of Getting Too Much of the Vitamin B-Complex?

Yes, you need all the B vitamins. And yes, as with most things in life, there can be too much of a good thing.

“Getting too many B vitamins from supplements is possible. The first thing you will notice after getting a very high dose of B vitamins is neon yellow urine, but this is harmless,” Moody says. B vitamins are water-soluble, so the body will usually excrete the excess if you take too much.

Supplementing with very high doses may overwhelm your kidneys and liver to the point that they cannot clear the compounds safely, though, so still take the recommended dose when supplementing. More serious implications of taking too much are vomiting, diarrhea, and liver damage.

“There are only three B vitamins that have upper limits for daily consumption. The upper limit for folic acid is set due to the fact that increased folic acid intake could mask vitamin B12 deficiency. The upper limit for niacin is ascribed because it could potentially cause temporary flushing of skin over intake of 100mg,” says Shapiro. “Lastly, excessive vitamin B6 intake could possibly lead to reversible sensory neuropathy, but more research is needed to understand the association.”

What Foods Can You Get B Vitamins From?

You’re probably getting enough B vitamins from what’s on your plate.

“In general, the majority of men are getting enough B vitamins in their diet, but there is a possibility that they may be deficient in some cases,” says Moody. Men who follow restrictive diets may not get enough vitamins, especially if they’re vegan. B12 is found naturally only in animal foods, but some foods like cereal, plant-based milk, and nutritional yeast are fortified with it. Men who have an excessive alcohol intake, as alcohol depletes the body of B vitamins, may also be deficient.

Moody shares that B vitamins can be found naturally in a wide range of foods, including milk, eggs, seafood, beef, chicken, turkey, fortified cereal, and most vegetables.

How Much Vitamin B-Complex Do You Need?

This is a bit of a complicated question, since the amount you need depends on each of the eight vitamins individually. You don’t need to memorize the numbers, but you might want to scan your food and/or supplement labels to ensure you're getting 100 percent of the daily value of these vitamins, especially if you’re vegan or vegetarian. The most common B-complex deficiency is B12, which you can find in animal products and fortified breakfast cereals or milks.

How Do You Know If You're Deficient in B-Complex Vitamins?

Shapiro says that symptoms of deficiency include fatigue, weakness, and slow reflexes. More specific signs depend on which B vitamin is lacking in the diet or not being absorbed. Since you depend on B vitamins to function daily, you’ll generally know if something is up with your uptake of them.

“Due to B vitamins’ role in generating energy, creating red blood cells, and helping with the transmission of nerve impulses, you'll see the signs in these body systems when you don’t get enough of these vitamins,” says Moody. “You may get numbness or tingling in your extremities, muscle weakness, anemia, or irregular heartbeat.”

More serious deficiencies have more extensive effects on the body. Some can be permanent depending on how severe the deficiency is and how long you have been deficient. “These effects include depression, memory loss, confusion, reduced motor function, or paranoia,” says Moody.

What to Know About Picking Out Vitamin B-Complex Supplements:

As always, consult with your primary care physician or registered dietitian to see if a vitamin B-complex supplement may be right for you. A blood test will be able to tell you if you’re getting enough B12 and other nutrients.

One general guideline to keep in mind when shopping for any vitamin is to ensure it’s third party tested, says Shapiro. The FDA does not regulate supplements and therefore supplement companies aren’t required to tell you exactly what you’re getting. Examples of these third party lab companies include Consumer Labs, NSF, or Informed Choice.

“These labs test supplements for purity, safety, and potency, and dietitians always recommend consumers rely on products that have gone through this process for optimal results,” Moody says. Specifically for B-complex supplements, ensure all the B vitamins are included in the product and check the specific dosage depending on your body’s needs.

Watch for supplements with excessive amounts of vitamins, such as a DV of 500% or more. “You should also be sure that there is sufficient Vitamin B12 above all else. Besides being one of the most essential B vitamins in the complex, it's also one of the most common ones to be deficient in, thus holding the most need for supplementation,” she says.

Remember, though—unless you’ve been told by your doctor to supplement, you likely don’t need to be wasting your money.

“As long as one adheres to a healthy diet with a good balance of lean protein and vegetables, there’s no need to take B-complex supplements,” says Moody. “Like vitamin C, B-complex vitamins are water-soluble. As a result, they cannot be stored for later use. The body will use what it needs, and the rest is excreted as waste in the urine.”

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Perri O. Blumberg

Perri is a New York City-born and -based writer; she holds a bachelor’s in psychology from Columbia University and is also a culinary school graduate of the plant-based Natural Gourmet Institute, which is now the Natural Gourmet Center at the Institute of Culinary Education. Her work has appeared in the New York Post, Men's Journal, Rolling Stone, Oprah Daily, Insider.com, Architectural Digest, Southern Living, and more. She's probably seen Dave Matthews Band in your hometown, and she'll never turn down a bloody mary. Learn more at VeganWhenSober.com.