The group of B vitamins is comprised of eight, water-soluble vitamins that are essential to cellular health, both catabolic and anabolic metabolism. While vitamins B6, folate (B9), and B12 are the most commonly known B vitamins, all eight are interrelated and hold an important function in the human body. Each of the B vitamins are numbered and named; however, vitamins B6 and B12 are generally known in their numerical format, whereas the remainder of the B vitamins tend to be referred to by their name. The eight B vitamins include:1
- Vitamin B1: thiamin
- Vitamin B2: riboflavin
- Vitamin B3: niacin
- Vitamin B5: pantothenic Acid
- Vitamin B6: pyridoxine
- Vitamin B7: biotin
- Vitamin B9: folate
- Vitamin B12: cobalamin
How Do B Vitamins Support Cellular Health?
The B vitamins are coenzymes, meaning they support enzyme activity in several processes essential to the healthy functioning of cells. These processes include: 2
- Production of energy via catabolic metabolism
- Synthesis of important molecules via anabolic metabolism, including amino acids and the methyl groups necessary for biochemical reactions within the cells
- Transport of oxygen and energy
In addition, B vitamins have been found to have significant effects on brain health and neuronal function. Research has indicated that deficiency in one or multiple B vitamins is linked to psychiatric disorders, such as depression and anxiety, cognitive impairment, and dementia.2-4 There is a lot of overlap in B vitamins’ individual functions and signs of deficiency.
Thiamin: Vitamin B1
Thiamin’s primary functions include converting food into energy, reducing cellular oxidative stress, and playing a role in cellular growth and development.5 Inadequate thiamin intake can result in mild symptoms of weight loss, anorexia, muscle weakness, and neurological and cardiovascular disorders. While severe deficiency is rare, it can lead to conditions like beriberi and Wernicke-Korsakoff syndrome.6
Riboflavin: Vitamin B2
Riboflavin plays a significant role in energy production, cellular growth, development, metabolism of fats, drugs, and steroids, and the maintenance of healthy homocysteine levels in the blood.7 Riboflavin also contributes to antioxidant activity and is involved in the pathogenesis of chronic conditions including cancer, cardiovascular disease (CVD), metabolic bone disorders, inflammation, and infection.5 A riboflavin deficiency may cause skin disorders, angular stomatitis (lesions in the corners of the mouth), hair loss, and itchy and red eyes. In severe cases, riboflavin deficiency may lead to liver and nervous degeneration. Riboflavin may be involved in cancer prevention and reduction of migraine headaches.7
Niacin: Vitamin B3
In body tissues niacin is converted to its metabolically active form coenzyme nicotinamide adenine dinucleotide (NAD), which can be then converted to coenzyme nicotinamide adenine dinucleotide phosphate (NADP). NAD is required for reactions that transfer energy from macronutrients (carbohydrates, fats, and proteins) to adenosine triphosphate (ATP), as well as functions related to genome integrity, gene expression, and communication between and within cells. NADP plays a role in synthesizing cholesterol and fatty acids and maintaining the antioxidant function of cells.8
Niacin deficiency may lead to pellagra, also known as the “three D disease,” characterized by bouts of diarrhea, dermatitis, and dementia. Niacin is essential to neuronal health and is recognized as a factor in dementia, neurological deficits, psychiatric disorders, and neuronal injury. Niacin has extensive benefits to the central nervous system including, but not limited to, inflammatory and immune gene modulation, reduced oxidative stress, reduced DNA damage, increased mitochondrial biogenesis, and mitochondrial function restoration.9
Pantothenic Acid: Vitamin B5
Pantothenic acid participates in the synthesis of coenzyme A (CoA) and the acyl carrier protein, both of which are essential for the production and degradation of fatty acids as well as many other anabolic and catabolic processes. Historically, pantothenic acid deficiency is associated with numbness and burning in the hands and feet, fatigue, irritability, disturbed sleep, restlessness, and gastrointestinal disturbances in anorexics, as observed in studies of World War II prisoners of war. Pantothenic acid may benefit the reduction of lipid levels in individuals with hyperlipidemia.10
A recent study has found severely deficient cerebral levels of pantothenic acid in patients with Alzheimer’s disease. Researchers observed worsened pantothenic acid deficiency in regions of the brain known to experience damage from Alzheimer’s disease such as the hippocampus, middle temporal gyrus, and entorhinal cortex. Ultimately they concluded that cerebral pantothenic acid deficiency may be linked to both neurodegeneration and dementia seen in Alzheimer’s disease, which may be prevented or possibly reversed in early stages with oral pantothenic acid supplementation. In addition to pantothenic acid, thiamin, niacin, vitamin B6, folate, and vitamin B12 are known to be associated with an increased risk of dementia or psychiatric disorders.3
Vitamin B6: Pyridoxine
Vitamin B6 is one of the more known and better researched of the B vitamin group. Vitamin B6 is involved in over 100 different enzyme reactions, extremely versatile, and has numerous functions:11-12
- Breakdown of proteins, carbohydrates, and fats
- Maintenance of health homocysteine levels
- Support of immune function
- Brain health including cognitive development
- Gluconeogenesis and glycogenolysis
- Hemoglobin formation
Vitamin B6 supplementation has been shown to reduce symptoms of premenstrual syndrome, relieve morning sickness in pregnant women, and improve cognitive function and memory. Vitamin B6 is also linked to disease prevention, including cancer prevention and the reduced risk of cardiovascular disease because of B6’s ability to maintain homocysteine levels. Individuals with kidney disease, autoimmune intestinal or inflammatory disorders, and alcoholism may be at an increased risk for vitamin B6 deficiency.11-12
Biotin: Vitamin B7
Biotin acts as a cofactor for five carboxylases, which are critical to catalyzing various steps of the metabolism of fatty acids, glucose, and amino acids. In addition, biotin plays a significant role in the modification of histones, regulation of genes, and cell signaling. Biotin deficiency is uncommon, but signs of deficiency include hair thinning, scaly and red rash around openings of the body, keto-lactic acidosis, skin infection, depression, and brittle nails, among others.13 Biotin deficiency is typically accompanied by other B vitamin or nutrient deficiencies. Biotin is often used to support hair, nail, and skin health, and it can be found in many beauty products.
Folate: Vitamin B9
Folate is well known for its role in megaloblastic anemia and its popularity as a prenatal supplement for pregnant mothers. Folate plays many key roles in the human body including in the synthesis of nucleic acids (DNA and RNA), cell division, the metabolism of amino acids, and the production of red blood cells.14-15 Due to folate’s role in nucleic acid synthesis and the increased demand of nucleic acid synthesis during pregnancy, pregnant women often need to increase their folate intake. Folate deficiency during pregnancy has been linked to increased risk of low birth weight, fetal growth retardation, preterm delivery, and birthing a baby with neural tube defects.15
Vitamin B12: Cobalamin
Similar to folate, vitamin B12 is necessary for the formation of red blood cells and DNA. Vitamin B12 also plays a role in brain and nerve cell development and function.16 As a result of its role in blood formation, megaloblastic and pernicious anemia are signs of deficiency. Vitamin B12 deficiency can cause many additional symptoms, including:16-17
- Fatigue and weakness
- Nerve damage resulting in tingling and numbness in the hands and feet
- Memory loss, dementia, and confusion
- Difficulty maintaining balance
One study found low levels of B12 to be associated with an increased risk of cognitive dysfunction, cardiovascular disease, and osteoporosis.18 Like folate, vitamin B12 deficiency tends to coexist with other nutrient or mineral deficiencies.
What are Good Sources of B Vitamins?
While the B Vitamins are commonly found in animal food sources, there are many plant-based sources of the eight B vitamins as well. The B vitamins are found naturally in foods but are also added to fortified foods like breads, cereal, pasta, and rice.
|B Vitamin||Animal-based Sources||Plant-based Sources|
|Thiamin (B1)||Pork, trout, tuna, mussels, beef, yogurt, liver, eggs||White rice, brown rice, black beans, acorn squash, sunflower seeds, barley, whole grains|
|Riboflavin (B2)||Eggs, organ meats (kidneys, liver), beef, salmon, clams, cheese, milk, yogurt||Oats, mushrooms, almonds, quinoa, spinach, apples, kidney beans, legumes|
|Niacin (B3)||Beef liver, chicken, turkey, salmon, tuna, pork, ground beef||Legumes, mushrooms, peanuts, rice, potato, sunflower seeds, pumpkin seeds, soymilk, bananas|
|Pantothenic Acid (B5)||Beef liver, chicken breast, tuna, milk, eggs||Shiitake and white mushrooms, sunflower seeds, avocados, potatoes, broccoli|
|Vitamin B6 (pyridoxine)||Beef, tuna, salmon, chicken, turkey, cottage cheese||Legumes, bananas, chickpeas, dark leafy greens, papayas, oranges, cantaloupe, rice, onion|
|Biotin (B7)||Eggs, salmon, pork, tuna, cheddar cheese, milk, yogurt, beef liver||Sunflower seeds, sweet potato, almonds, spinach, broccoli, oatmeal, bananas, apples|
|Folate (B9)||Seafood, eggs, beef, poultry||Dark leafy green vegetables like spinach, asparagus, Brussels sprouts, citrus fruits, nuts, beans, peas, grains|
|B12 (c0balamin)||Salmon, trout, tuna, beef, liver, ham, chicken, turkey, eggs, milk, milk products||Enriched soy or rice milk, fortified nutritional yeast, and breakfast cereals|
The information in this table was obtained from the National Institutes of Health: Office of Dietary Supplements Data Base on Strengthening Knowledge and Understanding of Dietary Supplements.