The B vitamins are thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), vitamin B-6, biotin (B7), folate (B8), and vitamin B-12.
The B vitamins function as coenzymes, small molecules that interact with enzymes to enable the enzymes to function.
B vitamin deficiency symptoms typically occur in the brain and nervous system, skin, and GI tract.
Thiamin (vitamin B-1) is used to help release energy from carbohydrate. The thiamin deficiency disease is called beriberi, a disorder characterized by muscle weakness, loss of appetite, irritability, nervous tingling throughout the body, poor arm and leg coordination, and deep muscle pain in the calves. A person with beriberi often develops an enlarged heart and sometimes severe edema. Beriberi results when glucose, the primary fuel for brain and nerve cells, cannot be metabolized to release energy.
Major sources of thiamin include pork products, whole grains (wheat germ), ready-to-eat breakfast cereals, enriched grains, green beans, milk, orange juice, organ meats, peanuts, dried beans, and seeds.
The coenzyme forms of riboflavin participate in many energy-yielding metabolic pathways. Without it, body can’t digest and use proteins and carbohydrates.
The symptoms associated with riboflavin deficiency include inflammation of the mouth and tongue, dermatitis, cracking of tissue around the corners of the mouth (called cheilosis), various eye disorders, sensitivity to the sun, and confusion.
Riboflavin deficiencies probably do not exist by themselves. Instead, a riboflavin deficiency would occur with deficiencies of niacin, thiamin, and vitamin B-6 because these nutrients often occur in the same foods.
Major sources of riboflavin are milk and milk products, enriched grains, ready-to-eat breakfast cereals, meat, and eggs. Vegetables such as asparagus, broccoli, spinach are also good sources.
The coenzyme forms of niacin function in many cellular metabolic pathways. In general, when energy is being released from the energy nutrients and used by cells, a niacin coenzyme is used. The group of niacin deficiency symptoms is known as pellagra, which means rough or painful skin. The symptoms of the disease are dementia, diarrhea, and dermatitis (especially on areas of skin exposed to the sun). Later, death often results. Early symptoms include poor appetite weight loss, and weakness.
Major sources of niacin are poultry, ready-to-eat breakfast cereals, beef, wheat bran, tuna and other fish, asparagus, peanuts. Coffee and tea also contribute some niacin to the diet. Niacin is heat stable; little is lost in cooking.
Pantothenic acid helps release energy from carbohydrates, fats, and protein. Pantothenic acid is so widespread in foods that a nutritional defi ciency among healthy people who eat varied diets is unlikely.
Rich sources of pantothenic acid are sunflower seeds, mushrooms, peanuts, and eggs. Other sources are meat, milk and many vegetables.
In its coenzyme form, biotin aids in fat and carbohydrate metabolism. Symptoms of biotin deficiency include a scaly inflammation of the skin,
changes in the tongue and lips, decreased appetite, nausea, vomiting, a form of anemia, depression, muscle pain and weakness, and poor growth.
Cauliflower, egg yolks, peanuts, and cheese are good sources of biotin.
Intestinal bacteria synthesize and supply some biotin, making a biotin deficiency unlikely.
The coenzymes of vitamin B-6 are needed for the activity of many enzymes involvedin carbohydrate, protein, and fat metabolism. Vitamin B-6 is needed in many areas of metabolism, so a deficiency results in widespread symptoms, such as depression, vomiting, skin disorders, irritation of the nerves, and impaired immune response. Another important role of vitamin B-6 is the synthesis of many neurotransmitters. The vitamin B-6 coenzyme is important for the synthesis of hemoglobin and its function as the oxygen-carrying part of the red blood cell. Vitamin B-6 is also necessary for the synthesis of white blood cells, which perform a major role in the immune system. Major sources of vitamin B-6 are animal products, ready-to-eat breakfast cereals, potatoes,
and milk. Other sources are fruits and vegetables such as bananas, cantaloupes, broccoli and spinach.
Folic acid is the synthetic chemical form added to foods and present in supplements. Folic acid is more readily absorbed than natural forms of folate. A key role of the folate coenzymes is to supply or accept single carbon compounds.
Green, leafy vegetables, organ meats, sprouts, other vegetables, dried beans, and orange juice are the richest sources of folate. The vitamin C in orange juice also reduces folate destruction. Ready-to-eat breakfast cereals, milk, and bread also are important sources of folate for many adults.
Folate is susceptible to destruction by heat. Food processing and preparation destroy 50% to 90% of the folate in food.
Pregnant women need extra folate (a total of 600 micrograms DFE) to accommodate the increased rates of cell division and DNA synthesis in their own bodies and in the developing fetus.
Vitamin B-12 represents a family of compounds that contain the mineral cobalt. All vitamin B-12 compounds are synthesized by bacteria, fungi, and other lower organisms. Vitamin B-12 participates in a variety of cellular processes. The most important function is in folate metabolism. Vitamin B-12 is required to convert folate coenzymes to the active forms needed for metabolic reactions, such as DNA synthesis.
Without vitamin B-12, reactions that require certain active forms of folate
do not take place in the cell. Thus, a vitamin B-12 deficiency can result
in symptoms of a folate deficiency. Another vital function of vitamin
B-12 is maintaining the myelin sheaths that insulate neurons from each
other. People with vitamin B-12 deficiencies have destruction of segments
of the myelin sheaths. This destruction eventually causes paralysis
and, perhaps, death. Vitamin B-12 also participates in homocysteine
metabolism and certain minor metabolic pathways. In the past, the inability to absorb enough vitamin B-12 eventually led to death, mainly because it destroyed nerves. This phenomenon was called pernicious anemia. Some symptoms of pernicious anemia include weakness, sore tongue, back pain, apathy, and tingling in the extremities.
Major sources of vitamin B-12 include meat, milk, ready-to-eat breakfast cereals, poultry, seafood, and eggs. Organ meats (especially liver, kidneys, and heart) are especially rich sources of vitamin B-12.
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