July 18, 2024

Health Supplements

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What Happens to Your Body When You Take B-Complex Vitamins

11 min read

How many times per week have you heard: I am so tired! from a friend, family member or out of your own mouth. About 1 in 5 adults complain of general fatigue, and constantly being tired is, well, tiring. Plus, according to a recent consumer survey, the most sought-after benefit from food, nutrients and beverages across all generations is—you guessed it—energy and less fatigue. This may prompt someone to march down the supplement aisle in search of a much-needed energy boost. A popular supplement on shelves today—and the one many of us associate with more energy—is a B-complex vitamin.

B vitamins are a group of eight water-soluble vitamins, including B1 (thiamine), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate) and B12 (cobalamin). “A B-complex supplement formula will package all of these together in one pill or capsule,” says Jenna Braddock, RDN, a performance dietitian, certified personal trainer and owner of Make Healthy Easy and Rhythm Sports Nutrition. 

These eight B vitamins are grouped together because they have related, but different responsibilities in the body. “B vitamins are important because they play a role in energy production and functions that impact your heart, brain and cells,” explains Bonnie Taub-Dix, RDN, host of the Media Savvy Podcast and author of Read It Before You Eat It: Taking You from Label to Table

In this article, we’ll explore what vitamin B complex is, highlight its health benefits and discuss how much you need per day. We’ll also discuss which foods contain B vitamins, how to pick out a B-complex supplement, and who may or may not benefit from taking one.

What Is Vitamin B Complex?

Vitamin B complex is made up of the following eight water-soluble vitamins. Each B vitamin has different functions within the body:

  • Vitamin B1 (thiamine): Thiamine essential for energy metabolism and converting food into energy. It also supports cell growth, development and function.
  • Vitamin B2 (riboflavin): Riboflavin also plays a role in cell development, growth and function. It also contributes to energy production and the metabolism of fats and medications.
  • Vitamin B3 (niacin): Niacin is involved in more than 400 cellular metabolic processes, helping convert food into energy.
  • Vitamin B5 (pantothenic acid): Pantothenic acid helps turn food into energy and metabolize fat.
  • Vitamin B6 (pyridoxine): Vitamin B6 supports hundreds of metabolic reactions. It also plays a role in brain development and immune function.
  • Vitamin B7 (biotin): Biotin plays a role in metabolism, gene regulation and cell signaling.
  • Vitamin B9 (folate). Folate is crucial for DNA synthesis, amino acid metabolism and formation of red blood cells. 
  • Vitamin B12 (cobalamin): Vitamin B12 is essential for central nervous system development and function, red blood cell formation and DNA synthesis.

Health Benefits of Vitamin B Complex

1. Boosts Energy

Almost all B vitamins play a part in how our bodies make energy. Therefore, we need to have an adequate supply of all B vitamins on hand to keep energy production chugging along smoothly. Any shortage, such as a deficiency or being low in a B vitamin, could disrupt this process. Studies have shown that supplementing with B vitamins can alleviate feelings of fatigue and help improve energy levels.

2. Supports Brain Health

We all want to keep our minds sharp, and B vitamins can help. Research has found that supplementing with B vitamins benefits cognitive function and slows cognitive decline. There’s also scientific evidence suggesting that a higher intake of folate in people over 50 years old is associated with lower risk of dementia.

3. Prevents Anemia

“Anemia is a condition in which your blood produces fewer than normal healthy red blood cells, affecting nearly 3 million Americans,” says Kunal Lal, M.D., a board-certified internal medicine physician based in Miami. “Your body isn’t able to get enough oxygen, which can lead to you feeling tired and weak, experiencing symptoms like headaches, dizziness, shortness of breath and—at times—chest pain,” he explains. Getting enough folate and vitamin B12 is important to prevent anemia.

4. Improves Mood and Reduces Stress

At times we could all use a little mood boost and, good news: B vitamins can help in that department. “Supplementing with B-complex vitamins could have a positive effect on mood and mental health, even when a deficiency is not present,” says Braddock. Research indicates that taking a B vitamin supplement may improve mood and reduce feelings of stress in healthy people.

5. Supports Heart Health

B vitamins may keep our heart healthy. “B vitamins help produce new red blood cells in your body, which perfuses our organs and tissues with oxygen,” says Lal. And more blood flow is a good thing, he says: “This ultimately aids in circulation in our body, and theoretically improves cardiovascular health.”

6. Supports a Healthy Pregnancy

Pregnant people are advised to take prenatal vitamins, which are packed with B vitamins to support their growing baby and their own bodies. B vitamins play a crucial role in supporting a healthy pregnancy by forming red blood cells, maintaining the nervous system and helping prevent birth defects. Additionally, B vitamins support the baby’s growth and development.

And there’s one bonus benefit. Science suggests that supplementing with vitamin B6 may help alleviate nausea and morning sickness in some pregnant women.

7. May Reduce Migraines

If you experience migraines, you know the debilitating impact they can have. Studies have shown B vitamins can have promising potential. Taking 400 milligrams of riboflavin per day over three months has shown significant improvement on migraines. Research found a significant reduction in the number of migraine days, duration, frequency and pain levels experienced during attacks.

8. Supports Gut Health

Our gut bacteria produce small amounts of B vitamins, says Braddock. These B vitamins play a critical role in shaping a healthy and diverse gut flora. A deficiency in any B vitamin can disrupt both gut bacteria and overall intestinal health.

Food Sources of Vitamin B Complex

B vitamins are found in many different food groups, including:

  • Whole grains like brown rice, barley, oats, whole-wheat bread  
  • Dark leafy greens like spinach, kale, collard greens
  • Beans and lentils 
  • Milk, yogurt, cheese, eggs
  • Nuts and seeds
  • Chicken and beef 
  • Fish like salmon, tuna
  • Fortified breakfast cereals

Tips for Incorporating Vitamin B-Rich Foods into Your Diet

  • Whip up a batch of one of our most popular overnight oat recipes, use brown rice, quinoa or bulgur in grain bowls, toss farro, buckwheat or barley into salads, soups or chili.  
  • Blend dark leafy greens into smoothies (we promise you can’t even taste them), stuff them into a pita, wrap or sandwich, add greens into stir-fries and pasta dishes or try one of our healthy green salad recipes. 
  • Grab a handful of your favorite nuts or seeds to munch on at snack time, roll them into a batch of energy balls, sprinkle them on top of salads for crunch or use them in place of breadcrumbs as a crust when baking salmon or chicken.  
  • Incorporate beans and lentils into your day by whipping them up into dips, stuffing them into veggies, making them into burgers or adding them to tacos or fajitas.

How Much Vitamin B Complex Do You Need?

The recommended daily intake for B vitamins varies depending on age, sex and health conditions. Pregnant people and those who are breastfeeding have higher needs of certain B vitamins. People with certain health conditions or deficiencies may also require either higher or lower amounts.

If you’re taking a B-complex supplement, you’ll get several or all of these B vitamins, often at levels that exceed 100% of your Daily Value. Check the label on your product to see what vitamins (and the dosages) are included in yours.

 Recommended Daily Intake (RDA)  Adult Males  Adult Females
 Vitamin B1 (Thiamine)  1.2 mg  1.1 mg
 Vitamin B2 (Riboflavin)  1.3 mg  1.1 mg
 Vitamin B3 (Niacin)  16 mg  14 mg
 Vitamin B5 (Pantothenic acid)  5 mg  5 mg
 Vitamin B6 (Pyridoxine)  1.3 mg  1.3 mg
 Vitamin B7 (Biotin)  30 mcg  30 mcg
 Vitamin B9 (Folate)  400 mcg  400 mcg
 Vitamin B12 (Cobalamin)  2.4 mcg  2.4 mcg

How to Know If You Have a Vitamin B Deficiency

There’s a range of symptoms you may experience depending on which B vitamin you are low on or deficient in. Signs and symptoms you may have a vitamin B deficiency include:

  • Fatigue
  • Weakness
  • Depression
  • Nausea
  • Constipation or diarrhea
  • Shortness of breath
  • Skin rashes

Health conditions associated with B vitamin deficiencies include: 

  • Cardiovascular disease 
  • Cognitive problems
  • Neurological symptoms
  • Vision problems
  • Psychological problems
  • Anemia
  • Digestive issues

Should You Be Taking Vitamin B-Complex Supplements?

Anyone who has a deficiency or is at risk of being deficient would benefit from taking vitamin B complex. Older adults and pregnant and breastfeeding people need higher amounts of B vitamins in their diet, therefore are at greater risk of a B vitamin deficiency. Those with certain medical conditions, such as Crohn’s disease or celiac disease, have malabsorption issues that put them at risk for a deficiency. In addition, it’s important to consider your diet. “Vegetarians and vegans may also be at great risk of vitamin B12 [deficiency] since this vitamin is more prevalent in animal products,” Taub-Dix explains.

Who Should Avoid Taking a B Vitamin Supplement?

Not everyone needs a B-complex supplement, and some people would be better off without one. “Those who suffer from liver disease, renal disease, diabetes, alcohol dependence and certain allergies should not supplement with B vitamins without the advice of a health care provider, ” says Taub-Dix. She says B vitamins may also interfere with certain medications, such as antibiotics or anti-seizure medications. Even though B-complex products are available over-the-counter, it’s still important to check with your health care provider before beginning a new supplement.

What to Look For in a Vitamin B-Complex Supplement

Here are six things to look for and consider when picking out a vitamin B-complex supplement:

  1. Look for third-party testing by reputable organizations like USP, NSP or Consumer Lab and certified seals on the label.
  2. Check for supplements free from additives, fillers, artificial flavors and colors. Avoid any that have proprietary blends, formulas or complexes listed as an ingredient.
  3. Make sure the supplement has all eight B vitamins listed.  
  4. Look for one that provides close to 100% Daily Value for most B vitamins.
  5. Check with your doctor to determine the recommended dosage and timing.
  6. Taking a B vitamin complex with food may enhance absorption of certain B vitamins.

Potential Downsides and Precautions

B vitamins are water-soluble, which means that you’ll urinate out any excess you consume. However, in certain instances, taking too much can cause problems. “High doses of B vitamins, niacin in particular, can cause unpleasant side effects like nausea, diarrhea, vomiting, flushing, numbness, tingling and potentially liver and nerve damage,” says Lal.

Frequently Asked Questions


  • Is it OK to take vitamin B complex every day?

    A dose of 100% Daily Value for each B vitamin is generally safe for most people to consume daily. It’s always best to check first with your physician before starting a supplement.


  • Should you stop taking vitamin B if your urine is yellow?

    You don’t need to stop taking vitamin B if your urine turns yellow. It is a common side effect of taking B vitamins and not considered dangerous. B vitamins are water-soluble vitamins, therefore excess will be excreted in your urine.


  • Who should not take vitamin B complex?

    People with certain medical conditions like liver disease, renal disease, diabetes and alcohol dependence, should not take a B-complex vitamin, unless directed by their health care provider. People taking other medications or supplements should check with their health care provider to learn if B-complex is safe for them to take.


  • What happens if you take too much vitamin B complex?

    Most likely, you will eliminate excess B vitamins through your urine. However, excessive intake of B vitamins can cause nausea, vomiting, diarrhea, flushing, numbness and tingling. Nerve or liver damage could also occur.

The Bottom Line

B vitamins are essential for many bodily functions, including energy production, brain health, supporting a healthy pregnancy, heart health and gut health. A B-complex vitamin provides all eight B vitamins in one supplement. Certain groups may be more susceptible to being low or deficient in B vitamins and should consult with their health care provider on supplement recommendations. You may not need a B-complex vitamin. Eating a well-balanced diet full of whole grains, dairy products, chicken, fish, dark leafy greens, beans, nuts and seeds can also help you meet your daily vitamin B needs.

EatingWell.com, June 2024

EatingWell uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable and trustworthy.
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