About B Vitamins

B Vitamins - Foods Image

B vitamins are essential for good health. These water soluble nutrients play an important role in the healthy function of various organs and tissues in the body—including the heart, nerves, muscles , gastrointestinal tract, nervous system and endocrine system—and in the formation of red blood cells. B vitamins help regulate appetite and are necessary for proper growth, development, and metabolism.

Types of B vitamins include the following:

  • Vitamin B1 (thiamin)
  • Vitamin B2 (riboflavin)
  • Vitamin B3 (niacin)
  • Vitamin B5 (pantothenic acid)
  • Vitamin B6 (pyridoxine)
  • Vitamin B7 (biotin)
  • Vitamin B9 (folic acid, folate)
  • Vitamin B12 (cyanocobalamin)

Sources of B Vitamins

B vitamins can be found in a wide variety of foods—plant and animal sources—and in foods that are fortified with the vitamins. Some foods are high in just one type of B vitamin, and others contain several of the important nutrients. Levels of some B vitamins in food are affected by excessive cooking/heating. Multivitamin supplements often contain B vitamins.

Good food sources include:

  • Dairy products
  • Eggs
  • Fish and seafood (clams)
  • Fortified breads and cereals
  • Fruits (bananas, watermelon, grapefruit)
  • Leafy green vegetables
  • Legumes (beans, peas)
  • Liver
  • Meat (beef, veal, pork)
  • Nuts
  • Potatoes
  • Poultry
  • Whole grains
  • Yeast

B Vitamin Recommendations

Recommended daily allowances (RDA) for B vitamins vary according to age, overall health and other factors. Most people are able to get an adequate intake of these nutrients through a well-balanced diet.

People with malabsorption disorders (e.g., celiac disease) or other chronic health conditions, older adults, and people who abuse alcohol, have had gastric bypass surgery, or receive parenteral (e.g., intravenous) nutrition may require dietary supplements that contain B vitamins. Talk to your health care provider if you have concerns about your B vitamin intake. Supplements containing some B vitamins may interact with certain medications.

B vitamin recommendations for adults and children 4 years of age and older are as follows:

  • Thiamin—1.5 mg/day
  • Riboflavin—1.7 mg/day
  • Niacin—20 mg/day
  • Pantothenic acid—10 mg/day
  • Pyridoxine—2 mg/day
  • Biotin —300 mcg/day
  • Folic acid—400 mcg/day
  • Vitamin B12—6 mcg/day

RDA/AI (adequate intake) of B vitamins in infants/children younger than 4 are:

  • Thiamin—0.5/0.7 mg/day
  • Riboflavin—0.6/0.8 mg/day
  • Niacin—8/9 mg/day
  • Pantothenic acid—3/5 mg/day
  • Pyridoxine— 0.1–0.3/0.5 mg/day
  • Biotin—50/150 mcg/day
  • Folic acid—100/200 mcg/day
  • Vitamin B12—2/3 mcg/day

B vitamin recommendations for women who are pregnant or nursing include the following:

  • Thiamin—1.7 mg/day
  • Riboflavin—2.0 mg/day
  • Niacin—20 mg/day
  • Pantothenic acid—10 mg/day
  • Pyridoxine—2 mg/day
  • Biotin —300 mcg/day
  • Folic acid—800 mcg/day
  • Vitamin B12—8 mcg/day

B Vitamin Deficiency

B vitamins are water soluble—excess amounts are removed from the body in the urine. However, very large doses of B vitamins may cause high blood sugar, gout and skin problems and can lead to heart and liver problems. Specifically, high levels of niacin (vitamin B3) may cause blurred vision, nausea and vomiting and may worsen stomach ulcers, and a high intake of folic acid (vitamin B9) may interfere with the chemotherapy drug methotrexate.

If you're over the age of 50, or are at increased risk for vitamin B deficiency (for example, due to a medical condition), talk to your health care provider about taking a supplement that contains B vitamins. Symptoms of a B vitamin deficiency vary depending on which vitamin is lacking and include anemia (low red blood cell count), rash, mouth sores, fatigue, insomnia, irritability, memory problems and peripheral neuropathy (numbness or tingling of the hands or feet).

According to the Office of Dietary Supplements of the National Institutes of Health (NIH), vitamin B12 deficiency affects 1.5–15 percent of people in the United States. This important nutrient is found in animal food sources, so people who are vegetarian or vegan may have difficulty getting enough vitamin B12 without fortified foods and supplements. Conditions like pernicious anemia and certain gastrointestinal disorders prevent absorption of vitamin B12 and may require treatment with high doses of the vitamin or vitamin B12 shots.

Vitamin B12 deficiency causes a variety of symptoms and serious health problems, including the following:

  • Constipation
  • Fatigue
  • Loss of appetite
  • Mouth/tongue soreness
  • Megaloblastic anemia (characterized by a certain type of abnormal red blood cell)
  • Nervous system damage resulting in numbness and tingling of the hands and feet, weakness, balance problems, dementia, memory loss, confusion, depression
  • Weight loss

Infants with vitamin B12 deficiency may have failure to thrive, developmental delays and megaloblastic anemia.

Folic acid is a very important nutrient for women of childbearing age—vitamin B9 deficiency increases the risk for birth defects of the brain and spine like spina bifida. According to the American Cancer Society, low levels of folic acid (vitamin B9) also have been linked to higher rates of certain types of cancer, including colorectal cancer.

B Vitamin Testing

Vitamin B tests may be used to detect deficiencies in people with characteristic symptoms or screen for a deficiency in people who are at increased risk. B vitamin blood tests cannot determine if the deficiency is from an inadequate intake of the vitamin(s) or a problem with absorption of the nutrient(s).

More research is needed to evaluate the potential health benefits of B vitamins and learn more about the effects of these nutrients in the body.

Sources: National Institutes of Health (NIH), Taber's Cyclopedic Medical Dictionary

Publication Review By: the Editorial Staff at Healthcommunities.com

Published: 23 Jan 2013

Last Modified: 23 Jan 2013