Vitamin B complex is a group of essential nutrients that play a key role in maintaining energy levels, brain function, and cell metabolism. These vitamins also support the health of the skin, hair, digestive system, and immune response.
Found in many everyday foods, vitamin B complex includes eight different B vitamins that work together to keep the body functioning properly. Because they are water-soluble, these vitamins need to be replenished regularly through diet or supplementation.
Vitamin B complex is especially important during periods of growth, stress, or illness when the body’s nutritional needs increase. A deficiency in any of these vitamins can lead to symptoms like fatigue, irritability, and weakened immunity.
List of B-complex vitamins
The following sections explain the role of each B vitamin, including the main food sources and recommended daily intake.
Vitamin B1 – Thiamine
Vitamin B1, or thiamine, helps regulate energy production in the body and supports cell growth, development, and function.
Where to find it: The main sources of vitamin B1 include meats, brewer’s yeast, wheat germ, beans, and sunflower seeds.
Recommended intake: The daily recommended amount of vitamin B1 varies based on age and sex. For women aged 19 and older, the recommended intake is 1.1 mg per day. For men aged 19 and older, it's 1.2 mg per day.
Deficiency symptoms: A lack of vitamin B1 can cause tingling sensations in the body, increased heart rate, loss of appetite, weakness, low immunity, drowsiness, and memory problems. Severe deficiency may lead to beriberi, a disease that causes symptoms like muscle wasting, numbness in the hands and feet, and cramps.
Vitamin B2 – Riboflavin
Vitamin B2, or riboflavin, helps convert carbohydrates, fats, and proteins from food into energy and supports the formation of red blood cells, promoting oxygen transport throughout the body.
Where to find it: Vitamin B2 is mainly found in meats and fortified foods. It's also present in milk and dairy products, almonds, and fortified cereals, cakes, and breads.
Recommended intake: The recommended intake of vitamin B2 is 1.1 mg per day for women aged 19 and older and 1.3 mg per day for men aged 19 and older.
Deficiency symptoms: A deficiency in vitamin B2 may lead to anemia, cracks or sores on the lips and tongue, increased sensitivity to light, vaginal and anal dermatitis, and conjunctivitis.
Vitamin B3 – Niacin
Vitamin B3, or niacin, plays a role in converting nutrients from food into energy. It also helps produce hormones, fats, and cholesterol and protects DNA.
Where to find it: Foods rich in vitamin B3 include red meat, chicken, fish, brown rice, Brazil nuts, beans, broccoli, potatoes, and tomatoes.
Recommended intake: The recommended daily intake is 16 mg for men and 14 mg for women aged 19 and older.
Deficiency symptoms: Vitamin B3 deficiency may lead to pellagra, a condition characterized by dermatitis, headaches, mental confusion, and diarrhea.
Vitamin B5 – Pantothenic acid
Vitamin B5, or pantothenic acid, helps produce hormones and fats and supports the conversion of carbohydrates into energy.
Where to find it: This vitamin is present in nearly all foods. The best sources include beef, chicken, organ meats such as liver and heart, fortified cereals, and sunflower seeds.
Recommended intake: For children aged 9 to 13 years, the recommendation is 4 mg per day. For men and women aged 14 and older, it's 5 mg per day.
Deficiency symptoms: Lack of vitamin B5 may lead to headaches, muscle weakness, cramps, nausea, and vomiting.
Vitamin B6 – Pyridoxine
Vitamin B6, also known as pyridoxine, supports the proper functioning of the nervous system, strengthens immune function, and may help reduce the risk of cardiovascular disease.
Where to find it: Good sources of vitamin B6 include brewer’s yeast, organ meats like liver and gizzard, chicken, soybeans, and whole grains.
Recommended intake: For men aged 14 to 50 years, the recommendation is 1.3 mg per day. For women aged 19 to 50 years, it's also 1.3 mg per day.
Deficiency symptoms: A vitamin B6 deficiency may cause skin lesions around the nose and mouth, irritability, depression, low immunity, and seizures.
Vitamin B7 – Biotin
Vitamin B7, also known as biotin or vitamin H, helps metabolize carbohydrates, proteins, and fats. It also supports skin and hair health and helps the body absorb other vitamins in the intestines.
Where to find it: Liver is the main source of biotin. It can also be found in smaller amounts in meats, eggs, avocados, salmon, walnuts, and almonds.
Recommended intake: For adults aged 30 and older, the recommended intake is 30 mcg per day.
Deficiency symptoms: Signs of biotin deficiency may include dermatitis around the eyes, nose, and mouth, hair loss, conjunctivitis, and brittle nails.
Vitamin B8 – Choline
Vitamin B8, or choline, is essential for brain development and the production of acetylcholine, a neurotransmitter involved in memory, muscle control, and mood.
Where to find it: Choline is found in meats, fish, dairy products, eggs, whole grains, nuts, and seeds such as flaxseed, pumpkin seeds, and chia.
Recommended intake: The recommended daily amount is 425 mg for women and 550 mg for men aged 19 and older.
Deficiency symptoms: Choline deficiency can lead to liver and muscle damage.
Vitamin B9 – Folic acid
Vitamin B9, also known as folic acid or folate, supports the production of new cells and the formation of hemoglobin, a protein in red blood cells. It’s also important for fetal development and growth.
Where to find it: Foods high in vitamin B9 include yeast, dark leafy greens, organ meats like liver and gizzards, eggs, peanuts, and whole grains.
Recommended intake: For both men and women aged 14 and older, the recommended intake is 400 mcg per day. Pregnant women should aim for 600 mcg per day.
Deficiency symptoms: A deficiency in vitamin B9 may cause irritability, fatigue, headaches, hair loss, diarrhea, and anemia. During pregnancy, it may also increase the risk of complications like high blood pressure, miscarriage, and premature birth. In newborns, folate deficiency can lead to malformations such as spina bifida and cleft palate.
Vitamin B12 – Cobalamin
Vitamin B12, or cobalamin, helps form blood cells and supports the metabolism of proteins and carbohydrates. It also promotes physical and mental energy and supports central nervous system development and function.
Where to find it: Vitamin B12 is mainly found in animal-based foods, including seafood, meat, eggs, cheese, and milk. While plant-based foods don’t naturally contain B12, some breakfast cereals, plant-based milks, and nutritional yeast may be fortified with this vitamin.
Recommended intake: For children aged 9 to 13, the recommendation is 1.8 mcg per day. For adolescents and adults aged 14 and older, the recommended intake is 2.4 mcg per day.
Deficiency symptoms: Vitamin B12 deficiency may cause numbness in the hands and feet, a red and sore tongue, appetite loss, fatigue, dizziness, and headaches.
When to take B-complex supplements
B-complex supplements should only be taken when there’s an increased nutritional need or a confirmed deficiency, which can occur due to:
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Low intake of foods that contain B vitamins
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Pregnancy and breastfeeding
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Excessive alcohol consumption
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Intestinal malabsorption, as seen in bariatric surgery, celiac disease, or Crohn’s disease
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Low consumption of dairy and meat
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Long-term use of medications like antibiotics, anticonvulsants, or oral contraceptives
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High consumption of raw egg whites, which contain avidin, a protein that interferes with biotin absorption
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Genetic disorders that impair vitamin absorption
These supplements are available in capsules, tablets, chewable gummies, or liquid forms, and should always be taken with meals. Some B vitamins may also be available in injectable form.
However, it is important to note that B-complex supplementation should only be done under the guidance of a healthcare provider, as excessive intake can also be harmful.
Possible side effects
Taking high doses of B-complex supplements may cause side effects such as diarrhea, liver issues, light sensitivity, nausea, vomiting, abdominal cramps, skin redness, and irregular heartbeat.
Who should not take it
This supplement is not recommended for people with Parkinson’s disease who are taking levodopa.
People with diabetes who are on medications, as well as pregnant or breastfeeding women, should speak with a doctor before starting B-complex supplements.
Does B-complex make you gain weight?
B-complex vitamins do not cause weight gain because they don’t contain calories. However, a deficiency in certain B vitamins can decrease appetite, potentially leading to weight loss. Supplementing with B-complex vitamins helps regulate levels in the body and may restore appetite, which could contribute to weight gain.