Vitamin B Complexes

Vitamin B complexes are the type of water-soluble vitamin that plays a significant role in cell metabolism and synthesis of red blood cells. It has mainly been categorized into eight different vitamin B complexes such as vitamin B1, B2, B3, B5, B6, B7, B9, and B12. Vitamin B complexes help in releasing energy from carbohydrates and fat to breaking down amino acids and transporting oxygen and energy-containing nutrients around the body.

The Eight Vitamin B complexes

Thiamin – Vitamin B1

Thiamine is a water-soluble vitamin that plays a vital role in the growth and function of various cells. It helps the breakdown of the nutrients for energy and several basic cells function, a deficiency can lead to various problems in the brain and heart. Only a small amount of thiamine is stored in our liver, so the required amount is needed to intake from thiamine rich-food. It was discovered firstly for the Vitamin B complexes that why is B1 at the top. The body needs thiamine to make adenosine triphosphate (ATP) that transports energy within cells.

The function of vitamin B1 of B complexes

  • It helps to convert carbohydrates, fats, and protein into energy, or glucose. Therefore, B1 is beneficial to energy release.
  • It works in anti-stress and boosts the body’s immune system in times of stress. Thus, it is good works in immunity procedure.
  • Thiamine is needed to make adenosine triphosphate (ATP) that transports energy within cells. Hence, it is ideal for energy transportation to the cells.
  • B1 plays a role in the nervous system, and they are needed for good brain function. Hence, it is good for brain development.
  • It is necessary for keeping the liver, skin, hair, and eyes healthy. Therefore, taking thiamine is good for personal care.

Deficiency of vitamin B1

  • Beriberi, a condition that features problems with the peripheral nerves and wasting.
  • Weight loss and anorexia can develop.
  • Mental issues include confusion and short-term memory loss.
  • It can cause damage to the optic nerve, which may result in blurry or loss of vision.
  • It may cause a decrease in heart rate, resulting in increased fatigue and dizziness.
  • Muscle weakness
  • Lowered immunity

Sources of vitamin B1

  • Fortified breakfast cereals
  • Pork
  • Fish
  • Beans, lentils
  • Green peas
  • Enriched cereals, breads, noodles, rice
  • Sunflower seeds
  • Yogurt
  • Whole grains

 The Recommended Dietary Allowance (RDA) for men ages 19 and older is 1.2 mg daily, and for women in the same age range 1.1 mg daily. For pregnancy and lactation, the amount increases to 1.4 mg daily.

Polishing rice take out thiamine

Thiamin is destroyed with high-heat cooking or long cooking times. It also leaches into the water and will be lost in any cooking or soaking water that is thrown out. It may also be removed during food processing, such as with refined white bread and rice. This is why thiamin is enriched or added back, too many pieces of bread, cereals, and grains have undergone processing. 

Riboflavin – Vitamin B2

Riboflavin or Vitamin B2 is naturally present in foods, added to foods and available as a supplement. It comes second in the list of vitamin B complexes. Bacteria in the gut can produce small amounts of riboflavin, but not enough to meet dietary needs. Riboflavin is a key component of coenzymes involved with the growth of cells, energy production, and the breakdown of fats, steroids, and medications. 

  • Most riboflavin is used immediately and not stored in the body, so excess amounts are excreted in the urine.
  • An excess of dietary riboflavin, usually from supplements, can cause urine to become bright yellow.

The function of vitamin B2

  • Vitamin B2 helps break down proteins, fats, and carbohydrates. Riboflavin helps convert carbohydrates into adenosine triphosphate (ATP). The human body produces ATP from food, and ATP produces energy as the body requires it. The compound ATP is vital for storing energy in muscles.
  • Some research suggests that vitamin B2 may help prevent cataracts and migraine headaches, but further studies are needed to confirm this.

Deficiency of vitamin B2

A riboflavin deficiency most often occurs with other nutrient deficiencies, such as in those who are malnourished. Symptoms may include:

  • Cracked lips
  • Sore throat
  • Swelling of the mouth and throat
  • Swollen tongue (glossitis)
  • Hair loss
  • Skin rash
  • Anemia
  • Itchy red eyes
  • Cataracts in severe cases

Groups at higher risk of deficiency:

  • Vegans/vegetarians due to a lower intake or complete exclusion of dairy and meat products.
  • Pregnant women, especially in those who consume little dairy (lactose intolerance) or meat, due to increased nutrient needs with a growing fetus.

Sources of Rivoflavin

Riboflavin is found mostly in meat and fortified foods but also in some nuts and green vegetables.

  • Dairy milk
  • Yogurt
  • Cheese
  • Eggs
  • Lean beef and pork
  • Organ meats (beef liver)
  • Chicken breast
  • Salmon
  • Fortified cereal and bread
  • Almonds
  • Spinach

 The Recommended Dietary Allowance (RDA) for men and women ages 19+ years is 1.3 mg and 1.1 mg daily, respectively. For pregnancy and lactation, the amount increases to 1.4 mg and 1.6 mg daily, respectively.


A toxic level of riboflavin has not been observed from food sources and supplements. The gut can only absorb a limited amount of riboflavin at one time, and excess is quickly excreted in the urine. Therefore no more side effects occur.

Niacin- Vitamin B3

Niacin, or vitamin B3, is a water-soluble B vitamin found naturally in some foods, added to foods, and sold as a supplement. It comes third in the list of vitamin B complexes. The two most common forms of niacin in food and supplements are nicotinic acid and nicotinamide. The body can also convert tryptophan—an amino acid—to nicotinamide. Niacin is water-soluble so that excess amounts the body does not need are excreted in the urine. It works in the body as a coenzyme, with more than 400 enzymes dependent on it for various reactions. Niacin helps to convert nutrients into energy, create cholesterol and fats, create and repair DNA, and exert antioxidant effects.

The function of vitamin B3

  • It works in good blood circulation, normal functioning of the brain, and boosting memory. Hence, it enhances mental health.
  • Niacin increases high-density lipoprotein (HDL) cholesterol — the “good” cholesterol that helps remove low-density lipoprotein (LDL), the “bad” cholesterol, from your bloodstream.
  • It helps you to maintain a healthy digestive system and skin.
  • Vitamin B3 also helps in releasing energy from foods that we intake.

Deficiency of B3

  • It leads to pellagra, a condition that causes a dark
  • bright redness of the tongue
  • constipation/diarrhea
  • Depression
  • Headache
  • Fatigue
  • Memory loss
  • Hallucinations

Sources of niacin

  • Red meat: beef, beef liver, pork
  • Poultry
  • Fish
  • Brown rice
  • Fortified cereals and breads
  • Nuts, seeds
  • Legumes
  • Bananas 

Niacin is measured in milligrams (mg) of niacin equivalents (NE). One NE equals 1 milligram of niacin or 60 mg of tryptophan. The Recommended Dietary Allowance (RDA) for adults 19+ years is 16 mg NE for men, 14 mg NE for women, 18 mg NE for pregnant women, and 17 mg NE for lactating women.


Toxicity can occur from the long-term use of high-dose supplements. A reddened skin flush with itchiness or tingling on the face, arms, and chest is a common sign. Flushing occurs mainly when taking high-dosage supplements in the form of nicotinic acid, rather than nicotinamide.

  • Dizziness
  • Low blood pressure
  • Fatigue
  • Headache
  • Upset stomach
  • Nausea
  • Blurred vision
  • Impaired glucose tolerance and inflammation of liver in severe cases (at very high doses of 3,000-9,000 mg daily for several months/years)

Pantothenic acid- Vitamin B5

Pantothenic acid is naturally present in foods, added to foods, and available as a supplement. It is used to make coenzyme A (CoA), a chemical compound that helps enzymes to build and break down fatty acids as well as perform other metabolic functions, and the acyl carrier protein, which is also involved in building fats.

Pantothenic acid is found in a wide variety of foods. Bacteria in the gut can also produce some pantothenic acid but not enough to meet dietary needs.

The function of Vitamin B5

  • Pantothenic acid helps to break down fats, it has been studied for a potential role in reducing cholesterol levels in people who have dyslipidemia. Therefore, it may extremely beneficial for dyslipidemia patients.
  • It may have an antioxidant effect that reduces low-grade inflammation, which is present in the early stages of heart disease.
  • It can lower blood fats independently of (or enhance the cholesterol-lowering effects of) eating a heart-healthy diet.

Deficiency of Vitamin B5

  • Headache
  • Fatigue
  • Irritability, restlessness
  • Disturbed sleep
  • Nausea, vomiting, stomach cramps
  • Numbness or burning sensation in hands or feet
  • Muscle cramps

Sources of Pantothenic acid- B5

  • Fortified cereals
  • Organ meats (liver, kidney)
  • Beef
  • Chicken breast
  • Mushrooms
  • Avocado
  • Nuts, seeds
  • Dairy milk
  • Yogurt
  • Potatoes
  • Eggs
  • Brown rice
  • Oats
  • Broccoli

The Recommended Dietary Allowance (RDA) for men and women ages 19+ years is 5 mg daily. For pregnancy and lactation, the amount increases to 6 mg and 7 mg daily, respectively.


A toxic level of pantothenic acid has not been observed from food sources. With very large daily doses of 10 grams a day, stomach upset or mild diarrhea has been reported.

Pyridoxine- Vitamin B6

Vitamin B6, or pyridoxine, is a water-soluble vitamin found naturally in many foods, as well as added to foods and supplements. Pyridoxal 5’ phosphate (PLP) is the active coenzyme form and most common measure of B6 blood levels in the body. PLP is a coenzyme that assists more than 100 enzymes to perform various functions, including the breakdown of proteins, carbohydrates, and fats; maintaining normal levels of homocysteine (since high levels can cause heart problems); and supporting immune function and brain health. 

The function of Vitamin B6

  • It also plays a key role in gluconeogenesis and glycogenolysis, metabolism of nutrients, synthesis and function of histamines, hemoglobin, neurotransmitters, and also in the expression of genes. Hence, it may maintain the perfect body metabolism.
  •  It synthesizes amino acids and proteins and helps in the formation of the myelin sheath that surrounds the nerves.
  • Vitamin B6 plays a role to the body in breaking down food i.e. complex carbohydrates into simple forms of sugar i.e. glucose, fats, and proteins which in turn provide energy for carrying out various bodily activities. Hence, it accelerates the energy distribution and formation for the cells to perform better metabolism.

Deficiency of vitamin B6

  • Microcytic anemia
  • Skin conditions
  • Depression
  • Confusion
  • Lowered immunity
  • Kidney disease
  • Autoimmune intestinal disorders like celiac disease, ulcerative colitis, and Crohn’s disease
  • Autoimmune inflammatory disorders such as rheumatoid arthritis

Sources of vitamin B6

  • Beef liver
  • Tuna
  • Salmon
  • Fortified cereals
  • Chickpeas
  • Poultry
  • Some vegetables and fruits, especially dark leafy greens, bananas, papayas, oranges, and cantaloupe.

The Recommended Dietary Allowance (RDA) for men ages 14-50 years is 1.3 mg daily; 51+ years, 1.7 mg. The RDA for women ages 14-18 years is 1.2 mg; 19-50 years, 1.3 mg; and 51+ years, 1.5 mg. For pregnancy and lactation, the amount increases to 1.9 mg mcg and 2.0 mg, respectively. 


It is quite unlikely to reach a toxic level of vitamin B6 from food sources alone. Vitamin B6 is a water-soluble vitamin so that unused amounts will exit the body through the urine. However, a toxic level can occur from long-term very high dose supplementation of greater than 1,000 mg daily. Symptoms usually subside after stopping the high dosage. Symptoms include:

  • Neuropathy in feet and hands
  • Ataxia (loss of control of body movements)
  • Nausea

Biotin- Vitamin B7

Biotin or B7 is a water-soluble B vitamin found naturally in some foods and also in supplements. It plays a vital role in assisting enzymes to break down fats, carbohydrates, and proteins in food. It also helps to regulate signals sent by cells and the activity of genes.

The function of Biotin

  • Biotin metabolizes carbohydrates, fats, and amino acids, the building blocks of protein. Therefore, it helps to protein for better performance and repair cells as well.
  • It helps in the growth and development of hair and nails also helps in skin health. Hence, it is excellent for hair health and growth.
  • Biotin play role in normal embryonic growth, making them a critical nutrient during pregnancy. Therefore, it is particularly essential during pregnancy.

Deficiency of biotin

  • Loss of hair and thinning
  • Scaly skin rashes around eyes, nose, mouth
  • Brittle nails
  • Depression
  • lethargy
  • hallucination
  • Paresthesias of extremities

Sources of biotin

  • Beef liver
  • Eggs (cooked)
  • Salmon
  • Avocados
  • Pork
  • Sweet potato
  • Nuts, seeds
  • An RDA (Recommended Dietary Allowance) does not exist for biotin because there is not enough evidence to suggest a daily amount needed by most healthy people.
  • AI for biotin for men and women 19 years and older and for pregnant women is 30 micrograms daily. Lactating women need 35 micrograms daily.
  • UL: A Tolerable Upper Intake Level (UL) is the maximum daily dose unlikely to cause adverse side effects in the general population. There is no UL for biotin due to a lack of reports showing negative effects from very high intakes.


No evidence in humans has shown toxicity of biotin even with high intakes. Because it is water-soluble, any excess amount will leave through the urine. Hence, there is no established upper limit or toxic level for biotin.

Folate (folic acid)- Vitamin B9

Folate is the natural form of vitamin B9, water-soluble and naturally found in many foods. It is also added to foods and sold as a supplement in the form of folic acid; this form is better absorbed than that from food sources—85% vs. 50%, respectively. Folate helps to form DNA and RNA and is involved in protein metabolism.

The function of Vitamin B9-folate

  • It plays a key role in breaking down homocysteine, an amino acid that can exert harmful effects in the body if it is present in high amounts.
  • Folate is needed to produce healthy red blood cells. Hence, it plays a role in red cells formation.
  • It needed is critical during periods of rapid growth, such as during pregnancy and fetal development. Therefore, folate is important for women during pregnancy.

Deficiency of Vitamin B9

  • During pregnancy deficiency of folate caused redevelopment of the fetus.
  • Celiac disease and inflammatory bowel disease can increase due to lower consumption of folate.
  • Producing fewer red blood cells and larger than normal.
  • weakness
  • fatigue
  • irregular heartbeat
  • shortness of breath
  • difficulty concentrating
  • hair loss
  • pale skin
  • mouth sores

Sources of folate

  • Dark green leafy vegetables
  • Beans
  • Peanuts
  • Sunflower seeds
  • Fresh fruits, fruit juices
  • Whole grains
  • Liver
  • Seafood
  • Eggs

The Recommended Dietary Allowance for folate is listed as micrograms (mcg) of dietary folate equivalents (DFE). Men and women ages 19 years and older should aim for 400 mcg DFE. Pregnant and lactating women require 600 mcg DFE and 500 mcg DFE, respectively. People who regularly drink alcohol should aim for at least 600 mcg DFE of folate daily since alcohol can impair its absorption.


ULA Tolerable Upper Intake Level (UL) is the maximum daily dose unlikely to cause adverse side effects in the general population. The UL for adults for folic acid from fortified food or supplements (not including folate from food) is set at 1,000 mcg a day. 

The amount of folic acid in a typical multivitamin does not cause any harm—and may help prevent some diseases, especially among people who do not get enough folate in their diets, and among individuals who drink alcohol.

Cobalamin- vitamin B12

Cobalamin or Vitamin B12 is naturally found in animal foods. Vitamin B12 comes last in the list of vitamin B complexes. Vitamin B12 is needed to form red blood cells and DNA. It can also be added to foods or supplements. It is also a key player in the function and development of brain and nerve cells.

Vitamin B12 binds to the protein in the foods we eat. In the stomach, hydrochloric acid and enzymes unbind vitamin B12 into its free form. From there, vitamin B12 combines with a protein called intrinsic factor so that it can be absorbed further down in the small intestine.

The function of vitamin B12

  • It plays a role in the function and development of brain and nerve cells. Thus, cobalamin is good for brain function.
  • It helps in the production of red blood cells. Hence, we should maintain the level of this vitamin for the healthy production of red blood cells.
  • Vitamin B12 may play a vital role in your bone health. Accordingly, it is beneficial for bone health.
  • It plays a vital role in synthesizing and metabolizing serotonin, a chemical responsible for regulating mood. Consequently, you can enhance your mood by taking it into your diet.

Deficiency of vitamin B12

  • Lack of intrinsic factor
  • Inadequate stomach acid or medications that cause decreased stomach acid.
  • Intestinal surgeries or digestive disorders that cause malabsorption.
  • Megaloblastic anemia—a condition of larger than normal-sized red blood cells and a smaller than normal amount; this occurs because there are not enough vitamin B12 in the diet or poor absorption
  • Pernicious anemia—a type of megaloblastic anemia caused by a lack of intrinsic factors so that vitamin B12 is not absorbed
  • Fatigue, weakness
  • Nerve damage with numbness, tingling in the hands and legs
  • Memory loss, confusion
  • Dementia
  • Depression
  • Seizures

Sources of vitamin B12

  • Poultry
  • Dairy products such as milk, cheese, and yogurt
  • Fortified nutritional yeast
  • Fortified breakfast cereals
  • Enriched soy or rice milk
  • Fish, shellfish
  • Liver
  • Red meat
  • Eggs

 The Recommended Dietary Allowance for men and women ages 14 years and older is 2.4 micrograms (mcg) daily. For pregnancy and lactation, the amount increases to 2.6 mcg and 2.8 mcg daily, respectively. Therefore, take care of this vitamin level in your body during pregnancy.


vitamin B12 is a water-soluble vitamin that can easily maintain your vitamin B12 amount by existing out through urine. It is up to 1000 mcg a day of an oral tablet to treat a deficiency.

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