Vitamin B is a major group of nutrients that have important functions in the body’s use of energy . The B vitamins are water-soluble—that is, they dissolve readily in water and in such watery fluids as blood and urine . For this reason, B vitamins are readily removed from the body in urine. The body cannot store B vitamins in large amounts, so individuals should eat foods that contain them daily.
Grains are good sources of B vitamins. However, the vitamins are lost when the husk and bran layer of the grain are removed, as happens in the refining of wheat into white flour . White flour must therefore be enriched with B vitamins.
There are eight different B vitamins. They are known collectively as the B complex.
Vitamin B
also called thiamine, functions in breakdown of substances such as glucose (blood sugar) for energy. It also plays an important role in the functioning of the nervous system . Sources of thiamin include legumes (members of the pea family), organ meats, pork, fish, whole grains, and enriched flour and fortified breakfast cereals.
People who do not get enough of a particular nutrient can develop a deficiency disease. Thiamin deficiency most often occurs among the elderly; people who are physically stressed, including athletes; and people who are dependent on alcohol . Alcohol hinders the absorption of thiamine, producing a deficiency called Wernicke-Korsakoff syndrome.
Thiamine deficiency causes a disease called beriberi . It occurs in two different types, called dry and wet. Dry beriberi is caused by poor nutrition and calorie intake. Symptoms include confusion, muscle wasting, and nerve damage. Wet beriberi results in edema (fluid buildup) and lung congestion due to heart failure, caused by a lack of energy supplied to heart muscle.
Vitamin B
also called riboflavin, functions in the use of glucose and fat for energy. Food sources include whole grains, enriched flour, fortified breakfast cereals, milk, cheese, and meat.
Riboflavin deficiency often occurs in combination with deficiencies of other B vitamins. Symptoms occur in tissues with rapid cell division, such as the lips, tongue, mouth, and eyes. They include cracks in corners of mouth and a magenta color to the tongue.
Vitamin B
is also called niacin, nicotinamide, and nicotinic acid. It functions in reactions that release energy from carbohydrates , protein , and fat. Niacin also functions in the formation of glycogen , the chief form of stored carbohydrate in animals. Food sources of niacin include whole grains, enriched flour, fortified breakfast cereals, meat, and legumes.
Niacin deficiency is called pellagra . It often occurs with riboflavin deficiency.
Pantothenic acid
functions in the production of cholesterol, certain fats, and important substances called steroids . Because pantothenic acid is found in all plant and animal tissue, deficiency is rare. It is only seen in severely malnourished people. Deficiency symptoms include fatigue and nerve problems. Extremely large doses of pantothenic acid can be harmful, causing diarrhea .
Biotin
functions in the creation and breakdown of important substances called fatty acids. Bacteria that normally live in intestines produce some biotin, which can help meet daily requirements. Biotin is also widespread in foods, and deficiency is rare. Deficiency can be caused by consuming large amounts of avidin, a protein in raw egg white, or by alcohol abuse. Avidin binds to biotin, making it unavailable to the body. Excessive alcohol consumption often occurs with reduced nutritional intake, leading to biotin deficiency. Deficiency symptoms include hair loss, dermatitis (skin inflammation), and nerve disorders.
Vitamin B
also called pyridoxine, can be stored in muscle tissue. Vitamin B6 is needed in the processing of amino acids (the building blocks of proteins) and of hemoglobin (the red pigment in blood cells). It also plays a role in the breakdown of glycogen and in the functioning of the immune system .
Vitamin B6 is widespread in foods, including meat, poultry, seafood, fortified breakfast cereals, starchy vegetables, and some fruits. Deficiency is rare. It is occasionally seen among alcohol abusers or elderly people with health problems and poor nutrition. Vitamin B6 deficiency results in a weakened immune response and in abnormalities of the skin and the central nervous system (the brain and spinal cord). Deficiency in infants can cause irritability and convulsions . Prolonged consumption of extremely high doses of vitamin B6 can lead to severe nerve damage.
Folate
is also known as folic acid and folacin. This B vitamin is needed in amino acid production and in the formation of red and white blood cells . It is also important for the formation of DNA (deoxyribonucleic acid). DNA is the molecule that governs each cell’s activities.
Folate is widely available in foods, but much of it is destroyed by cooking. Good sources of folate include liver, beans, fresh dark-green leafy vegetables, oranges, and fortified grains and cereals. Folate deficiency was common in the United States before 1998. That year, the United States began requiring that folate be added to white flour.
Physicians advise all women who may become pregnant to take folic acid supplements or to eat foods fortified with folate daily. This advice is intended to reduce the risk of a serious birth defect called spina bifida .
Low levels of folate can lead to high levels of a substance called homocysteine in the blood, a risk factor for heart disease. Low folate levels affect rapidly dividing cells, leading to anemia and to disturbances of the gastrointestinal (digestive) tract. Anemia is a condition in which the number of healthy red blood cells falls below normal.
Vitamin B
also called cobalamin, functions in the activation of folate. A deficiency of either of these two vitamins produces anemia. Both vitamins are needed to produce DNA and myelin . Myelin is a fatty substance that surrounds parts of some nerve cells and assists in the transmission of nerve signals.
Vitamin B12 is reused by the human body, and some is stored in the liver. Sources of vitamin B12 include meat, poultry, seafood, milk, cheese, eggs, and fortified breakfast cereals. Most plant foods do not naturally contain vitamin B12. Vegetarians and especially vegans must be careful to ensure that their diets provide sufficient B12 or must take supplements.
A protein produced in the stomach, called intrinsic factor, is necessary to absorb vitamin B12. Production of intrinsic factor declines with age. The elderly are thus at risk for low levels of the vitamin due to poor absorption. Other conditions—including a disease called pernicious anemia, reduced levels of stomach acid, and gastrointestinal surgery—may also result in poor vitamin B12 absorption.
Vitamin B12 deficiency may take five to six years to appear. Symptoms include anemia, neurological changes, gastrointestinal disorders, and high homocysteine levels. Neurological changes associated with vitamin B12 deficiency include numbness of the hands and feet, depression , and dementia . Doctors use injections of vitamin B12 to treat deficiency in cases of inadequate intrinsic factor.
