If you buy something through a link on this page, we may earn a small commission. How this works. B vitamins are a group of eight essential nutrients that play roles in many organs and bodily systems. Although they can work together in the body, they also carry out their own unique functions. In this article, we explore the function of B vitamins in the body and some key dietary sources of each. We also look at the symptoms of each B vitamin deficiency.

What are B vitamins? Share on Pinterest Some people may benefit from taking B vitamin supplements. B vitamins are important for making sure the body’s cells are functioning properly. They help the body convert food into energy (metabolism), create new blood cells, and maintain healthy skin cells, brain cells, and other body tissues. There are eight types of B vitamin, each with their own function: thiamin (vitamin B-1)

riboflavin (vitamin B-2)

niacin (vitamin B-3)

pantothenic acid (vitamin B-5)

vitamin B-6

biotin (vitamin B-7)

folate (vitamin B-9)

vitamin B-12 Together, they are called the vitamin B complex. B vitamins often occur together in the same foods. Many people can get enough B vitamins by eating a variety of nutrient-dense foods. However, those who struggle to meet their daily needs can use supplements. People may develop B vitamin deficiencies if they do not get enough of the vitamins from their diet or supplements. They may also have a deficiency if their body cannot absorb nutrients properly, or if their body eliminates too much of them due to certain health conditions or medications.

Daily values Healthcare professionals recommend that people get a certain amount of each vitamin per day to maintain good health. The following table provides the daily values (DVs) of each B vitamin according to the Food and Drug Administration (FDA) in milligrams (mg) or micrograms (mcg): Vitamins DVs for adults and children ages 4+ DVs if pregnant or breastfeeding thiamin (B-1) 1.2 mg 1.4 mg riboflavin (B-2) 1.3 mg 1.6 mg niacin (B-3) 16 mg or equivalent 18 mg or equivalent pantothenic acid (B-5) 5 mg 7 mg vitamin B-6 1.7 mg 2 mg biotin (B-7) 30 mcg 35 mcg folate (B-9) 400 mcg or equivalent 600 mcg or equivalent vitamin B-12 2.4 mcg 2.8 mcg Below, we look at each B vitamin in more detail.

Thiamin (vitamin B-1) The heart, liver, kidney, and brain all contain high amounts of thiamin. The body needs thiamin for: breaking down sugar (carbohydrate) molecules from food

creating certain neurotransmitters (brain chemicals)

producing fatty acids

synthesizing certain hormones Foods with thiamin Thiamin is present in: whole grains and fortified bread, cereal, pasta, and rice

pork

trout

mussels

acorn squash

legumes, such as black beans and soybeans

seeds

nuts Thiamin deficiency is not common in the United States. However, certain groups of people may not get enough thiamin, including: those with alcohol dependence

older adults

those with HIV or AIDS

those with diabetes

those who have heart failure

those who have had bariatric surgery Symptoms of thiamin deficiency A person with a thiamin deficiency may experience: weight loss

little or no appetite

memory problems or confusion

heart problems

tingling and numbness in the hands and feet

loss of muscle mass

poor reflexes Alcohol dependence can cause a person to develop a thiamin deficiency. This can cause Wernicke-Korsakoff syndrome (WKS), which may result in tingling and numbness in the hands and feet, memory loss, and confusion. WKS can lead Wernicke’s encephalopathy (WE), which can be life threatening. A review from 2017 found that people with WE may benefit from high doses of thiamin.

Riboflavin (vitamin B-2) Riboflavin is essential for: energy production

helping the body break down fats, drugs, and steroid hormones

converting tryptophan into niacin (vitamin B-3)

converting vitamin B-6 into a coenzyme that the body needs Foods with riboflavin Foods rich in riboflavin include: organ meats

fortified breakfast cereals

oatmeal

yogurt and milk

mushrooms

almonds Symptoms of riboflavin deficiency Riboflavin deficiency is rare but may occur when a person has an endocrine disorder, such as thyroid problems, or certain other conditions. A person who is deficient in riboflavin may experience: skin disorders

sores at the corners of the mouth

swelling of the mouth and throat

swollen, cracked lips

hair loss

red, itchy eyes Having a severe riboflavin deficiency can lead to anemia and cataracts. Being riboflavin deficient during pregnancy can create a higher risk certain birth defects. People at highest risk of riboflavin deficiency include: those following a vegan diet or who do not consume dairy products

athletes who do not eat meat, especially those who also do not eat dairy or other animal products

women who are pregnant or lactating, especially those who do not consume meat or dairy products

Niacin (vitamin B-3) Share on Pinterest Some cereals contain added niacin. The body converts niacin into a coenzyme called nicotinamide adenine dinucleotide (NAD). NAD is a necessary part of more than 400 different enzyme reactions in the body, the highest of all vitamin-derived coenzymes. These enzymes help with: changing the energy in carbohydrates, fats, and proteins into a form the body can use

metabolic processes in the body’s cells

communication among cells

expression of DNA in cells Foods with niacin Animal-based foods such as meat, poultry, and fish are high in NAD, which the body can easily use. Plant-based foods including nuts, legumes, and grains contain a natural form of niacin that the body cannot use as easily. However, manufacturers add niacin to foods such as cereals, and the body can easily use this form. Symptoms of niacin deficiency Getting too little niacin can cause a niacin deficiency. Severe niacin deficiency leads to pellagra, which may cause: brown discoloration on skin exposed to sunlight

patches of skin with a rough appearance

a bright red tongue

vomiting, diarrhea, or constipation

headache

fatigue

depression If pellagra goes untreated, it can lead to severe memory problems, behavioral changes, and suicidal behavior. It may also lead to an extreme loss of appetite or death. People at risk of niacin deficiency include those who have: malnutrition

anorexia nervosa

alcohol use disorder

AIDS

inflammatory bowel disease (IBD)

Hartnup disease

carcinoid syndrome, which causes tumors to develop in the gastrointestinal tract

Pantothenic acid (vitamin B-5) Pantothenic acid is necessary for the body to create new coenzymes, proteins, and fats. Red blood cells carry pantothenic acid throughout the body so it can use the nutrient in a variety of processes for energy and metabolism. Foods with pantothenic acid Many foods contain at least some pantothenic acid, but some of the highest amounts are present in: beef liver

shiitake mushrooms

sunflower seeds

chicken

tuna

avocados

fortified breakfast cereals Symptoms of pantothenic acid deficiency Pantothenic acid deficiency is rare in the U.S. because it is plentiful in many foods. However, it may affect people with severe malnutrition. In such cases, they are usually deficient in other nutrients as well. Symptoms of deficiency include: numbness and burning of the hands and feet

headache

irritability

restlessness and poor sleep

a lack of appetite People with a specific gene mutation called pantothenate kinase-associated neurodegeneration 2 mutation are at a high risk of deficiency.

Vitamin B-6 Vitamin B-6, or pyridoxine, plays a role in more than 100 enzyme reactions. The body needs vitamin B-6 for: amino acid metabolism

breaking down carbohydrates and fats

brain development

immune function Foods with vitamin B-6 The richest sources of vitamin B-6 include: organ meats

chickpeas

tuna

salmon

poultry

potatoes

fortified cereals Symptoms of vitamin B-6 deficiency Many deficiencies in vitamin B-6 are linked to low levels of vitamin B-12, according to the National Institutes of Health (NIH) Office of Dietary Supplements. Vitamin B-6 deficiency may cause: anemia

scaling on the lips

cracks at corners of the mouth

swollen tongue

weakened immune system

confusion

depression People at risk of a vitamin B-6 deficiency include those who have: renal (kidney) disease

had a kidney transplant

celiac disease

Crohn’s disease

ulcerative colitis

autoimmune disorders such as rheumatoid arthritis

alcohol dependence

Biotin (vitamin B-7) Manufacturers add biotin to many hair, skin, and nail supplements. However, the NIH state that there is not sufficient evidence to conclude whether taking extra biotin helps with hair, skin, or nails. Some people believe that biotin may help with psoriasis. The human body needs biotin for: breaking down fats, carbohydrates, and protein

communication among cells in the body

regulation of DNA Foods with biotin Many foods contain biotin, including: organ meats

eggs

salmon

pork

beef

sunflower seeds Symptoms of biotin deficiency Signs of a biotin deficiency include: thinning of the hair

a scaly rash around eyes, nose, and mouth

brittle nails

depression

fatigue Deficiency is rare in the U.S., but the following groups may be more at risk: people with a metabolic disorder called biotinidase deficiency

people with alcohol use disorder

women who are pregnant or lactating

Folate (vitamin B-9) Share on Pinterest Avocados and some fortified breads are healthful sources of folate. The natural form of vitamin B-9 is called folate. Folic acid, which is present in fortified foods and some supplements, is a synthetic form of the vitamin. Because most people cannot take in enough leafy green vegetables for the levels needed in pregnancy, the Centers for Disease Control and Prevention (CDC) suggest that all women of reproductive age who wish to conceive take 400 mcg of folic acid each day, alongside eating a varied diet that contains folate. When a woman has high enough levels of folate both before and during pregnancy, the fetus has a lower risk of certain birth defects affecting the brain and spinal cord. Folate is also essential for: DNA replication

metabolism of vitamins

metabolism of amino acids

proper cell division Foods with folate The FDA require manufacturers to add folic acid to standardized enriched grain products to help reduce the risk of neural tube defects. People can get folic acid from fortified breads and cereals. Natural folate occurs in: dark green leafy vegetables

beef liver

avocado

papaya

orange juice

eggs

beans

nuts Symptoms of folate deficiency The addition of folic acid to grain products has made folate deficiency uncommon. However, the possible symptoms of a folate deficiency may include: weakness

headache

heart palpitations

irritability

sores on the tongue or in the mouth

skin, hair, or nail changes The FDA recommend that women increase the intake of folates and take folic acid supplements every day before becoming pregnant and during pregnancy. Other groups who may need extra folate include people who have: alcohol use disorder

celiac disease

conditions that interfere with nutrient absorption

IBD People should not take more than 1,000 mcg of folic acid each day. Taking more than this can mask symptoms of a vitamin B-12 deficiency. This can cause permanent nerve damage.

Vitamin B-12 Vitamin B-12 contains the mineral cobalt and is sometimes called a “cobalamin.” The body uses vitamin B-12 for: creating new red blood cells

DNA synthesis

brain and neurological function

fat and protein metabolism Foods with vitamin B-12 Vitamin B-12 occurs naturally in animal products such as: clams

beef liver

salmon

beef

milk and yogurt People who do not eat animal products may need to get vitamin B-12 from supplements or fortified foods such as breakfast cereals and nutritional yeast. Learn more about vegetarian and vegan sources of vitamin B-12 here. Symptoms of vitamin B-12 deficiency Vitamin B-12 deficiency usually causes a condition called megaloblastic anemia. Symptoms of a vitamin B-12 deficiency can include: fatigue

weight loss

constipation

loss of appetite

numbness and tingling in the hands and feet

memory problems

depression People who are at risk of a B-12 deficiency include those who have: conditions that interfere with absorption of nutrients

older adults

celiac disease

Crohn’s disease

had gastric bypass surgery or surgery on the stomach Vegetarians, vegans, and people who are pregnant or lactating may also need extra vitamin B-12.