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What is vitamin B12?
What foods provide vitamin B12?
What is the recommended dietary intake for vitamin B12?
When is a deficiency of vitamin B12 likely to occur?
Do pregnant and/or lactating women need extra Vitamin B12?
Who else may need a vitamin B12 supplement to prevent a deficiency?
Drug : Nutrient Interactions
Caution: Folic Acid and vitamin B12 deficiency
What is the relationship between vitamin B12 homocysteine, and cardiovascular disease?
Do healthy young adults need a vitamin B12 supplement?
What is the health risk of too much vitamin B12?
Selecting a healthful diet

What is vitamin B12?
Vitamin B12 helps maintain healthy nerve cells and red blood cells [1-4]. It is also needed to help make DNA, the genetic material in all cells. Vitamin B12 is also called cobalamin because it contains the metal cobalt [1-4].

Vitamin B12 is bound to the protein in food. Hydrochloric acid in the stomach releases vitamin B12 from proteins in foods during digestion. Once released, vitamin B12 combines with a substance called intrinsic factor (IF). This complex can then be absorbed by the intestinal tract.

What foods provide vitamin B12?
Vitamin B12 is naturally found in foods that come from animals, including fish, meat, poultry, eggs, milk, and milk products. Fortified breakfast cereals are a particularly valuable source of vitamin B12 for vegetarians [5-7]. Table 1 lists a variety of food sources of vitamin B12.

Table 1: Selected food sources of vitamin B12 [5]


Micrograms (μg)
per serving


Mollusks, clam, mixed species, cooked, 3 ounces



Liver, beef, braised, 1 slice



Fortified breakfast cereals, (100%) fortified), ¾ cup



Trout, rainbow, wild, cooked, 3 ounces



Salmon, sockeye, cooked, 3 ounces



Trout, rainbow, farmed, cooked, 3 ounces



Beef, top sirloin, lean, choice, broiled, 3 ounces



Fast Food, Cheeseburger, regular, double patty & bun, 1 sandwich



Fast Food, Taco, 1 large



Fortified breakfast cereals (25% fortified), ¾ cup



Yogurt, plain, skim, with 13 grams protein per cup, 1 cup



Haddock, cooked, 3 ounces



Clams, breaded & fried, ¾ cup



Tuna, white, canned in water, drained solids, 3 ounces



Milk, 1 cup



Pork, cured, ham, lean only, canned, roasted, 3 ounces



Egg, whole, hard boiled, 1



American pasteurized cheese food, 1 ounces



Chicken, breast, meat only, roasted, ½ breast



*DV = Daily Value. DVs are reference numbers developed by the Food and Drug Administration (FDA) to help consumers determine if a food contains a lot or a little of a specific nutrient. The DV for vitamin B12 is 6.0 micrograms (μg). Most food labels do not list a food's vitamin B12 content. The percent DV (%DV) listed on the table indicates the percentage of the DV provided in one serving. A food providing 5% of the DV or less is a low source while a food that provides 10% to 19% of the DV is a good source. A food that provides 20% or more of the DV is high in that nutrient. It is important to remember that foods that provide lower percentages of the DV also contribute to a healthful diet. For foods not listed in this table, please refer to the US Department of Agriculture's Nutrient Database Web site: http://www.nal.usda.gov/fnic/cgi-bin/nut_search.pl.

What is the recommended dietary intake for vitamin B12?
Recommendations for vitamin B12 are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine of the National Academies [7]. Dietary Reference Intakes is the general term for a set of reference values used for planning and assessing nutrient intake for healthy people. Three important types of reference values included in the DRIs are Recommended Dietary Allowances(RDA), Adequate Intakes(AI), and Tolerable Upper Intake Levels(UL). The RDA recommends the average daily intake that is sufficient to meet the nutrient requirements of nearly all (97% to 98%) healthy individuals in each age and gender group [7]. An AI is set when there is insufficient scientific data available to establish an RDA. AIs meet or exceed the amount needed to maintain a nutritional state of adequacy in nearly all members of a specific age and gender group [7]. The UL, on the other hand, is the maximum daily intake unlikely to result in adverse health effects [7]. Table 2 lists the RDAs for vitamin B12, in micrograms, for children and adults.

Table 2: Recommended Dietary Allowances (RDA) for vitamin B12 for children and adults [7]


Males and Females



















19 and older




Information on vitamin B12 is insufficient to establish an RDA for infants. Therefore, an AI has been established that is based on the amount of vitamin B12 consumed by healthy infants who are fed breast milk [7]. Table 3 lists the AIs for vitamin B12, in micrograms, for infants.

Table 3: Adequate Intake (AI) for vitamin B12 for infants [7]


Males and Females

0-6 months


7-12 months


When is a deficiency of vitamin B12 likely to occur?
Results of two national surveys, the National Health and Nutrition Examination Survey (NHANES III-1988-94) [8] and the Continuing Survey of Food Intakes by Individuals (CSFII 1994-96) found that most children and adults in the United States (US) consume recommended amounts of vitamin B12 [6-8]. A deficiency may still occur as a result of an inability to absorb vitamin B12 from food and in strict vegetarians who do not consume any foods that come from animals [9]. As a general rule, most individuals who develop a vitamin B12 deficiency have an underlying stomach or intestinal disorder that limits the absorption of vitamin B12 [10]. Sometimes the only symptom of these intestinal disorders is subtly reduced cognitive function resulting from early vitamin B12 deficiency. Anemia and dementia follow later [1,11].

Signs, symptoms, and health problems associated with vitamin B12 deficiency:
  Characteristic signs, symptoms, and health problems associated with vitamin B12 deficiency include anemia, fatigue, weakness, constipation, loss of appetite, and weight loss [1,3,12].
  Deficiency also can lead to neurological changes such as numbness and tingling in the hands and feet [7,13].
  Additional symptoms of vitamin B12 deficiency are difficulty in maintaining balance, depression, confusion, dementia, poor memory, and soreness of the mouth or tongue [14].
  Signs of vitamin B12 deficiency in infancy include failure to thrive, movement disorders, delayed development, and megaloblastic anemia [15].

Many of these symptoms are very general and can result from a variety of medical conditions other than vitamin B12 deficiency. It is important to have a physician evaluate these symptoms so that appropriate medical care can be given.
Do pregnant and/or lactating women need extra Vitamin B12?
During pregnancy, nutrients travel from mother to fetus through the placenta. Vitamin B12, like other nutrients, is transferred across the placenta during pregnancy. Breast-fed infants receive their nutrition, including vitamin B12, through breast milk. Vitamin B12 deficiency in infants is rare but can occur as a result of maternal insufficiency [15]. For example, breast-fed infants of women who follow strict vegetarian diets have very limited reserves of vitamin B12 and can develop a vitamin B12 deficiency within months of birth [7,16]. This is of particular concern because undetected and untreated vitamin B12 deficiency in infants can result in permanent neurologic damage. Consequences of such neurologic damage are severe and can be irreversible. Mothers who follow a strict vegetarian diet should consult with a pediatrician regarding appropriate use of vitamin B12 supplements for their infants and children [7]. They should also discuss with their personal physician their own need for vitamin B12 supplements.
Who else may need a vitamin B12 supplement to prevent a deficiency?
  Individuals with pernicious anemia or with gastrointestinal disorders may benefit from or require a vitamin B12 supplement.
  Older adults and vegetarians may benefit from a vitamin B12 supplement or an increased intake of foods fortified with vitamin B12.
  Some medications may decrease absorption of vitamin B12. Chronic use of those medications may result in a need for additional vitamin B12.

Individuals with pernicious anemia
Anemia is a condition that occurs when there is insufficient hemoglobin in red blood cells to carry oxygen to cells and tissues. Common signs and symptoms of anemia include fatigue and weakness. Anemia can result from a variety of medical problems, including deficiencies of vitamin B12, vitamin B6, folate and iron. Pernicious anemia is the name given more than a century ago to describe the then-fatal vitamin B12 deficiency anemia that results from severe gastric atrophy, a condition that prevents gastric cells from secreting intrinsic factor. Intrinsic factor is a substance normally present in the stomach. Vitamin B12 must bind with intrinsic factor before it can be absorbed and used by your body [7,17-18]. An absence of intrinsic factor prevents normal absorption of vitamin B12 and results in pernicious anemia.

Most individuals with pernicious anemia need parenteral (deep subcutaneous) injections (shots) of vitamin B12 as initial therapy to replenish depleted body stores of vitamin B12. Vitamin B12 body stores can then be managed by a daily oral supplement of vitamin B12. A physician will manage the treatment required to maintain the vitamin B12 status of individuals with pernicious anemia.

Individuals with gastrointestinal disorders
Individuals with stomach and small intestine disorders may be unable to absorb enough vitamin B12 from food to maintain healthy body stores [19]. Intestinal disorders that may result in malabsorption of vitamin B12 include:

  • Sprue, often referred to as celiac disease (CD), is a genetic disorder. People with CD are intolerant to a protein called gluten. In CD, gluten can trigger damage to the small intestines, where most nutrient absorption occurs. People with CD often experience nutrient malabsorption. They must follow a gluten-free diet to avoid malabsorption and other symptoms of CD.
  • Crohn's disease is an inflammatory bowel disease that affects the small intestines. People with Crohn's disease often experience diarrhea and nutrient malabsorption.
  • Surgical procedures in the gastrointestinal tract, such as surgery to remove all or part of the stomach, often result in a loss of cells that secrete hydrochloric acid and intrinsic factor [7,20-21]. Surgical removal of the distal ileum, a section of the intestines, also can result in the inability to absorb vitamin B12. Anyone who has had either of these surgeries usually requires lifelong vitamin B12 supplements to prevent a deficiency. These individuals would be under the routine care of a physician, who would periodically evaluate vitamin B12 status and recommend appropriate treatment.

Older adults
Hydrochloric acid helps release vitamin B12 from the protein in food. This must occur before vitamin B12 binds with intrinsic factor and is absorbed in your intestines. Atrophic gastritis, which is an inflammation of the stomach, decreases the secretion of gastric juices, including hydrochloric acid. Less hydrochloric acid decreases the amount of vitamin B12 separated from proteins in foods and can result in poor absorption of vitamin B12 [10,22-26]. Decreased hydrochloric acid secretion also results in growth of normal bacteria in the small intestines. The bacteria may take up vitamin B12 for their own use, further contributing to a vitamin B12 deficiency [27].

Up to 30 percent of adults aged 50 years and older may have atrophic gastritis, an increased growth of intestinal bacteria, and be unable to normally absorb vitamin B12 in food. They are, however, able to absorb the synthetic vitamin B12 added to fortified foods and dietary supplements. Vitamin supplements and fortified foods may be the best sources of vitamin B12 for adults older than age 50 years [7].

Researchers have long been interested in the potential connection between vitamin B12 deficiency and dementia [28]. A recent review examined correlations between cognitive skills, homocysteine levels, and blood levels of folate, vitamin B12 and vitamin B6. The authors suggested that vitamin B12 deficiency may decrease levels of substances needed for the metabolism of neurotransmitters [29]. Neurotransmitters are chemicals that transmit nerve signals. Reduced levels of neurotransmitters may result in cognitive impairment. In 142 individuals considered at risk for dementia, researchers found that a daily supplement providing 2 milligrams (mg) folic acid and 1 mg vitamin B12, taken for 12 weeks, lowered homocysteine levels by 30%. They also demonstrated that cognitive impairment was significantly associated with elevated plasma total homocysteine. However, the decrease in homocysteine levels seen with the use of vitamin supplements did not improve cognition [30]. It is too soon to make any recommendations, but is an intriguing area of research.

The popularity of vegetarian diets has risen along with an interest in avoiding meat and meat products for environmental, philosophical, and health reasons. However, the term vegetarianism is subject to a wide range of interpretations. Some people consider themselves to be vegetarian when they avoid red meat. Others believe that vegetarianism requires avoidance of all products that come from animals, including meat, poultry, fish, eggs, and dairy foods. The most commonly described forms of vegetarianism include:
  "lacto-ovo vegetarians", who avoid products that come from meat, poultry, and fish but consume eggs and dairy foods;
  "strict vegetarians", who avoid meat, poultry, fish, eggs, and dairy foods; and
  "vegans", who avoid meat, poultry, fish, eggs, and dairy foods and also do not use products that come from animals such as honey, leather, fur, silk, and wool.

Strict vegetarians and vegans are at greater risk of developing vitamin B12 deficiency than lacto-ovo vegetarians and nonvegetarians because natural food sources of vitamin B12 are limited to foods that come from animals [7]. Fortified cereals are one of the few sources of vitamin B12 from plants, and are an important dietary source of vitamin B12 for strict vegetarians and vegans. Strict vegetarians and vegans who do not consume foods that come from plants that are fortified with vitamin B12 need to consider taking a dietary supplement that contains vitamin B12 and should discuss the need for vitamin B12 supplements with their physician.

It is widely believed that vitamin B12 can be consistently obtained from nutritional yeasts. Consumers should be aware that these products may or may not contain added nutrients such as vitamin B12. Dietary supplements are regulated as foods rather than drugs, and companies that sell supplements such as nutritional yeasts fortified with vitamin B12 can legally change their formulation at any time. If you choose to supplement, select reliable sources of vitamin B12 and read product labels carefully.

When adults adopt a strict vegetarian diet, deficiency symptoms can be slow to appear. It may take years to deplete normal body stores of vitamin B12. However, breast-fed infants of women who follow strict vegetarian diets have very limited reserves of vitamin B12 and can develop a vitamin B12 deficiency within months [7]. This is of particular concern because undetected and untreated vitamin B12 deficiency in infants can result in permanent neurologic damage. Consequences of such neurologic damage are severe and can be irreversible. There are many case reports in the literature of infants and children who suffered consequences of vitamin B12 deficiency. It is very important for mothers who follow a strict vegetarian diet to consult with a pediatrician regarding appropriate use of vitamin B12 supplements for their infants and children [7].
Drug : Nutrient Interactions
Table 4 summarizes several drugs that potentially influence vitamin B12 absorption.

Table 4: Important vitamin B12/drug interactions


Potential Interaction

  Proton pump inhibitors (PPIs) are used to treat gastroesophageal reflux disease (GERD) and peptic ulcer disease. Examples of PPIs are Omeprazole (Prilosec©) and Lansoprazole (Prevacid©)

PPI medications can interfere with vitamin B12 absorption from food by slowing the release of hydrochloric acid into the stomach [31-33]. This is a concern because acid is needed to release vitamin B12 from food prior to absorption. So far, however, there is no evidence that these medications promote vitamin B12 deficiency, even after long-term use [34].

  H2 receptor antagonists are used to treat peptic ulcer disease. Examples are Tagamet©, Pepsid©, and Zantac©

H2 receptor antagonists can interfere with vitamin B12 absorption from food by slowing the release of hydrochloric acid into the stomach. This is a concern because acid is needed to release vitamin B12 from food prior to absorption. So far, however, there is no evidence that these medications promote vitamin B12 deficiency, even after long-term use [34].

  Metformin© is a drug used to treat diabetes.

Metformin may interfere with calcium metabolism [35]. This may indirectly reduce vitamin B12 absorption because vitamin B12 absorption requires calcium [35]. Surveys suggest that from 10% to 30% of patients taking Metformin have evidence of reduced vitamin B12 absorption [35].

In a study involving 21 subjects with type 2 diabetes, researchers found that 17 who were prescribed Metformin experienced a decrease in vitamin B12 absorption. Researchers also found that using calcium carbonate supplements (1,200 mg/day) helped limit the effect of Metformin on vitamin B12 absorption in these individuals [35].

Although these medications may interact with the absorption of vitamin B12, they are necessary to take for certain conditions. It is important to consult with a physician and registered dietitian to discuss the best way to maintain vitamin B12 status when taking these medications.
Caution: Folic Acid and vitamin B12 deficiency
Folic acid can correct the anemia that is caused by vitamin B12 deficiency. Unfortunately, folic acid will not correct the nerve damage also caused by vitamin B12 deficiency [1,36]. Permanent nerve damage can occur if vitamin B12 deficiency is not treated. Folic acid intake from food and supplements should not exceed 1,000 μg daily in healthy individuals because large amounts of folic acid can trigger the damaging effects of vitamin B12 deficiency [7]. Adults older than 50 years who take a folic acid supplement should ask their physician or qualified health care provider about their need for additional vitamin B12.
What is the relationship between vitamin B12 homocysteine, and cardiovascular disease?
Cardiovascular disease involves any disorder of the heart and blood vessels that make up the cardiovascular system. Coronary heart disease occurs when blood vessels which supply the heart become clogged or blocked, increasing the risk of a heart attack. Vascular damage can also occur to blood vessels supplying the brain, and can result in a stroke.

Cardiovascular disease is the most common cause of death in industrialized countries such as the United States, and is on the rise in developing countries. The National Heart, Lung, and Blood Institute of the National Institutes of Health has identified many risk factors for cardiovascular disease, including an elevated LDL-cholesterol level, high blood pressure, a low HDL-cholesterol level, obesity, and diabetes [37]. In recent years, researchers have identified another risk factor for cardiovascular disease: an elevated homocysteine level. Homocysteine is an amino acid normally found in blood, but elevated levels have been linked with coronary heart disease and stroke [38-47]. Elevated homocysteine levels may impair endothelial vasomotor function, which determines how easily blood flows through blood vessels. High levels of homocysteine also may damage coronary arteries and make it easier for blood clotting cells called platelets to clump together and form a clot, which may lead to a heart attack [43].

Vitamin B12, folate, and vitamin B6 are involved in homocysteine metabolism. In fact, a deficiency of vitamin B12, folate, or vitamin B6 may increase blood levels of homocysteine. Recent studies found that vitamin B12 and folic acid supplements decreased homocysteine levels in subjects with vascular disease and in young adult women. The most significant drop in homocysteine level was seen when folic acid was taken alone [48-49]. A significant decrease in homocysteine levels also occurred in older men and women who took a multivitamin/ multimineral supplement for 8 weeks [50]. The supplement taken provided 100% of Daily Values (DVs) for nutrients in the supplement.

Evidence supports a role for folic acid and vitamin B12 supplements for lowering homocysteine levels, however this does not mean that these supplements will decrease the risk of cardiovascular disease. Clinical intervention trials are underway to determine whether folic acid, vitamin B12, and vitamin B6 supplements can lower risk of coronary heart disease. It is premature to recommend vitamin B12 supplements for the prevention of heart disease until results of ongoing randomized clinical trials positively link increased vitamin B12 intake from supplements with decreased homocysteine levels AND decreased risk of cardiovascular disease.
Do healthy young adults need a vitamin B12 supplement?
It is generally accepted that older adults are at greater risk of developing a vitamin B12 deficiency than younger adults. One study, however, suggests that the prevalence of vitamin B12 deficiency in young adults may be greater than previously thought. This study found that the percentage of subjects in three age groups (26-49 years, 50-64 years, and 65 years and older) with deficient blood levels of vitamin B12 was similar across all age groups but that symptoms of vitamin B12 deficiency were not as apparent in younger adults. This study also suggested that those who did not take a supplement containing vitamin B12 were twice as likely to be vitamin B12 deficient as supplement users, regardless of age group. However, people who did not use supplements but did eat fortified cereal more than 4 times per week appeared to be protected from deficient blood levels of vitamin B12. Better tools and standards to diagnose vitamin B12 deficiencies are needed to make specific recommendations about the appropriateness of vitamin B12 supplements for younger adults [51].
What is the health risk of too much vitamin B12?
The Institute of Medicine of the National Academies did not establish a UL for this vitamin because vitamin B12 has a very low potential for toxicity. The IOM states that "no adverse effects have been associated with excess vitamin B12 intake from food and supplements in healthy individuals" [7]. In fact, the IOM recommends that adults older than 50 years get most of their vitamin B12 from vitamin supplements or fortified food because of the high incidence of impaired absorption in this age group of vitamin B12 from foods that come from animals [7].
Selecting a healthful diet
As the 2000 Dietary Guidelines for Americans states, "Different foods contain different nutrients and other healthful substances. No single food can supply all the nutrients in the amounts you need" [52]. For more information about building a healthful diet, refer to the Dietary Guidelines for Americans (http://www.cnpp.usda.gov/Publications/DietaryGuidelines/2000/2000DGProfessionalBooklet.pdf) [52] and the US Department of Agriculture's MyPyramid food guidance system (http://www.nal.usda.gov/fnic/Fpyr/pyramid.html) [53].



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absorption - In nutrition, the process of moving protein, carbohydrates, fats, and other nutrients from the digestive system into the bloodstream. Most absorption occurs in the small intestine.
Adequate Intake - AI. The recommended daily intake of a nutrient estimated by the Institute of Medicine to meet or exceed the amount needed to maintain adequate nutrition for most people in a particular life stage and gender group. An AI is established when not enough information is available from scientific research to determine a Recommended Dietary Allowance (a dietary intake level that is sufficient to meet the nutrient requirements of most people).
adverse effect - An unwanted side effect.
amino acid - A chemical building block of protein.
anemia - A condition in which the number of red blood cells in the blood, or the amount of hemoglobin in them, is lower than normal, causing a condition in which red blood cells are not able to supply enough oxygen to all the tissues in the body. Hemoglobin is the substance in red blood cells that carries oxygen to your body's cells.
atrophic gastritis - A long-lasting (chronic) condition in which the linining of the stomach is inflamed. Gradually the lining wastes away, destroying the glands that make stomach acid.
atrophy - A weakening, decrease in size, or wasting away of a tissue, organ, or part of the body. For example, the muscles of a leg that has been in a cast for some time will atrophy because they are not being used, causing them to become smaller and weaker.
bacteria - Single-celled organisms that are too small to be seen without a microscope. Bacteria are found everywhere and may be helpful or harmful.
blood vessel - A tube through which blood circulates in the body. Blood vessels include a network of arteries, arterioles, capillaries, venules, and veins.
body stores - The amount of a nutrient that stays in the body after eating and is available for future use. The size and location of this extra supply differs depending on the nutrient. For example, iron is stored in the liver.
calcium - A mineral found throughout the body. Calcium is required for normal growth and strength of bones and teeth, for nerves and enzymes to function properly, and for blood clotting.
calcium carbonate - A chemical compound naturally found in chalk, some seashells and other substances. Calcium carbonate is used in antacid drugs to treat indigestion and as a source of calcium to supplement the diet.
cardiovascular disease - CVD. A general term referring to disorders of the heart and blood vessels. CVD includes coronary artery disease, heart failure, atherosclerosis, high blood pressure, peripheral artery disease, and stroke.
cardiovascular system - The heart, blood, and blood vessels.
case report - A detailed record of the diagnosis, treatment, and follow-up of an individual patient. Case reports also contain some information about the patient (such as age, gender, and ethnic origin).
celiac disease - An autoimmune disorder in which eating gluten (a protein found in wheat, rye, and barley) causes the immune system to damage the small intestine, making it unable to absorb nutrients. It is a genetic disease that sometimes becomes active for the first time after surgery, pregnancy, childbirth, viral infection, or extreme stress. Also called sprue.
cell - The individual unit that makes up the tissues of the body. All living things are made up of one or more cells, which are the smallest units of living structure capable of independent existence.
chronic - Happening for a long time, persistently, or repeatedly.
cobalamin - A group of chemical compounds that works as vitamin B12 in the body. Cobalamin is required to maintain healthy nerve cells and produce normal red blood cells. It is involved in making DNA (the genetic material in all cells), and in the metabolizing of foods containing carbohydrate, fat, or protein. Cobalamin is found in foods that come from animals and in fortified breakfast cereals. Also called vitamin B12.
cobalt - An organic substance found in the earth and needed in very small amounts. It is also a necessary component of vitamin B12. A cobalt deficiency leads to anemia; too much cobalt can lead to a greater than normal number of red blood cells.
cognition - The intellectual and mental ability to be aware, think, learn, imagine, remember, reason, have perceptions, and make judgments.
cognitive function - Mental awareness and judgment.
cognitive skills - Mental and intellectual capabilities such as language, reading, math, reasoning, and critical thinking.
constipation - A condition in which stool becomes hard, dry, and difficult to pass and bowel movements happen infrequently. Other symptoms may include painful bowel movements and feeling bloated, uncomfortable, and sluggish.
Continuing Survey of Food Intakes by Individuals - CSFII. A nationwide survey conducted by the US Department of Agriculture that collects information about the kinds and amounts of foods Americans eat. The information is used to study the nation's food supply, including learning whether the foods available to consumers contain enough of the nutrients needed to maintain a healthy diet, finding out how much the foods provided by food assistance programs (such as Food Stamps) contribute to a person's nutrition needs, and calculating the amount of a pesticide that can be used on a crop while providing a safe food product. In 2002, CSFII was incorporated into the ongoing National Health and Nutrition Examination Survey.
coronary heart disease - A disease in which the blood vessels (coronary arteries) that carry blood and oxygen to the heart are narrowed or blocked, which can cause chest pain, shortness of breath, and heart attack. It is usually caused by a build-up of fat and cholesterol deposits inside the arteries (atherosclerosis). Also called heart disease.
Crohn's disease - A long-lasting (chronic) disease that causes severe irritation in the gastrointestinal tract. It usually affects the lower small intestine (called the ileum) or the colon, but it can affect any part of the digestive tract from the mouth to the anus. It is painful, causing severe watery or bloody diarrhea, and may lead to life-threatening complications. Crohn's disease is a form of inflammatory bowel disease.
Daily Value - DV. A term used on a food or dietary supplement product label to describe the recommended levels of intake of a nutrient. The percent Daily Value (% DV) represents how much of a nutrient is provided in one serving of the food or dietary supplement. For example, the DV for calcium is 1,000 mg (milligrams); a food that has 200 mg of calcium per serving would state on the label that the % DV for calcium is 20%.
dairy food - Milk and products made with milk, such as buttermilk, yogurt, cheese, cottage cheese, and ice cream.
deficiency - An insufficient amount, a shortage, or an inadequacy.
delayed development - Failure of a child to reach physical or behavioral milestones (such as rolling over, crawling, walking, and talking) at expected ages.
dementia - Damaged brain function (thinking, learning, making decisions, remembering) that worsens over time. It disrupts activities of daily living such as bathing, dressing, and walking.
depression - A serious medical condition that can interfere with an individual's ability to work, study, sleep, and eat. Symptoms include ongoing feelings of sadness and despair, loss of energy, and loss of interest or pleasure in activities that were once enjoyed. A person who has depression may experience changes in eating or sleeping habits, and have thoughts of death or suicide.
diabetes - A disease in which blood sugar (glucose) levels are high because the body is unable to use glucose properly. Diabetes occurs when the body does not make enough insulin, which helps the cells use glucose, or when the body no longer responds to insulin.
diagnose - The process of using signs and symptoms to identify a disease.
diarrhea - Frequent and watery bowel movements.
Dietary Guidelines for Americans - Advice from the federal government to promote health and reduce the chance (risk) of long-lasting (chronic) diseases through nutrition and physical activity. The Guidelines are updated and published every 5 years by the US Department of Health and Human Services and the US Department of Agriculture.
Dietary Reference Intake - DRI. A term developed by the Institute of Medicine that refers to a set of recommendations used to plan and evaluate the nutrient intake of healthy people. The DRIs include the Estimated Average Requirement (an intake value estimated to meet the nutrient requirements of half of all people), the Recommended Dietary Allowance (a dietary intake level that is sufficient to meet the nutrient requirements of most people), Adequate Intake (a recommended nutrient intake that meets or exceeds the amount needed to maintain adequate nutrition in most people), and the Tolerable Upper Intake Level (the largest daily intake of a nutrient that is considered unlikely to cause harmful side effects for most people).
dietary supplement - A product that is intended to supplement the diet. A dietary supplement contains one or more dietary ingredients (including vitamins, minerals, herbs or other botanicals, amino acids, and other substances) or their components; is intended to be taken by mouth as a pill, capsule, tablet, or liquid; and is identified on the front label of the product as being a dietary supplement.
digestion - The process the body uses to break down food into simple substances for energy, growth, and cell repair.
distal ileum - The end of the small intestine that attaches to the large intestine.
drug - Any substance (other than food) that is used to prevent, diagnose, treat, or relieve symptoms of a disease or abnormal condition. Also, a substance that alters mood or body function or that can be habit-forming or addictive, especially a narcotic.
evidence - Information used to support the use of a particular screening procedure, treatment, or preventive measure. In medicine, evidence needed to determine effectiveness is provided by laboratory research, clinical trials, and other studies.
failure to thrive - A condition in which infants and children are dramatically smaller or shorter than other children of the same age and gender, and physical, mental, and social skills are significantly delayed. Causes include medical disorders, environmental factors, malnutrition, and neglect.
fatal - Deadly; causing death.
fatigue - Extreme tiredness and an inability to function due to lack of energy.
fetus - The developing human from 7 to 8 weeks after conception until birth.
folate - A general term for the various forms of folic acid, a B vitamin. Folate is needed to make DNA, RNA, and amino acids. It occurs naturally in foods and is found in leafy green vegetables (such as spinach and turnip greens), fruits (such as citrus fruits and juices), and dried beans and peas. The synthetic (manufactured) form of folate used in supplements and fortified foods is called folic acid.
folic acid - The form of folate (a B vitamin occurring naturally in food) that is manufactured and used in supplements and fortified foods.
Food and Drug Administration - FDA, Department of Health and Human Services. FDA is the Federal government agency responsible for ensuring that foods and dietary supplements are safe, wholesome and sanitary, and that drugs, medical devices, cosmetics, and food are honestly, accurately and informatively represented to the public. FDA regulates dietary supplements under a different set of regulations than those covering conventional foods and drug products (prescription and over-the-counter). The dietary supplement manufacturer is responsible for ensuring that a dietary supplement is safe before it is marketed. FDA is responsible for taking action against any unsafe dietary supplement product after it reaches the market. Generally, manufacturers do not need to get FDA approval before producing or selling dietary supplements.
fortify - To add nutrients to a food during food processing or to replace nutrients lost when a food product is produced or stored that may be lacking in the overall diet (such as folate, vitamins A and D, and calcium). This process is sometimes called enrichment. For example, when calcium is added to processed orange juice, the orange juice is said to be "fortified with calcium." Another example is adding folic acid to flour.
gastric - Having to do with the stomach.
gastric juice - The digestive fluid made by the stomach. It contains hydrochloric acid, enzymes, intrinsic factor, and mucus.
gastroesophageal reflux disease - GERD. A condition in which stomach acid leaks back into the esophagus because the muscle between the stomach and the esophagus does not close properly. It causes frequent heartburn and can lead to more serious health problems such as ulcers, swallowing difficulties, and cancer.
gastrointestinal - GI. Having to do with the gastrointestinal tract (the large, muscular tube that extends from the mouth to the anus, where the movement of muscles and release of hormones and enzymes digest food).
gene - The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.
genetic disorder - A disease or disorder caused by an alteration or variation (mutation) in a gene or group of genes in the cells of an individual. Examples of genetic disorders include breast cancer, cystic fibrosis, Parkinson's disease, and celiac disease. They can be inherited or can occur without a known cause.
gluten - A protein found in wheat, rye, and barley. Eating gluten damages the small intestine in people who have celiac disease (also called gluten intolerance, gluten-sensitive enteropathy, and sprue) and can cause abdominal pain, gas, diarrhea, and other symptoms.
H2 receptor antagonist - A medication that reduces the amount of acid made by the stomach. It is used to treat conditions such as stomach ulcer (peptic ulcer) and gastroesophageal reflux disease.
HDL cholesterol - High-density lipoprotein cholesterol. A type of protein that carries excess cholesterol through the blood to the liver to be excreted in the bile. Also called good cholesterol.
health care provider - A person who supplies health care services. Health care providers include individuals with professional training (including doctors, nurses, technicians, and aides).
heart attack - The blockage of an artery supplying blood and oxygen to the heart, resulting in the damage or death of a section of heart muscle.
hemoglobin - The substance inside red blood cells that carries oxygen from the lungs to the body's tissues.
high blood pressure - A blood pressure measurement of 140/90 mmHg (millimeters of mercury) or higher is considered high blood pressure. Blood pressure is the force of blood pushing against the walls of the arteries. Blood pressure measurements are written as two numbers, for example 120/80. The first number (the systolic pressure) measures the pressure when the heart beats and pumps out blood into the arteries. The second number (the diastolic pressure) measures the pressure when the heart is at rest between beats. High blood pressure is a condition that occurs when a person's blood pressure often measures above 140/90 or regularly stays at that level or higher. This condition usually has no symptoms but can be life-threatening. It damages the arteries and increases the chance of stroke, heart attack, kidney failure, and blindness. Also called hypertension.
homocysteine - An amino acid (a building block of protein). At high blood levels, it may increase the risk of developing coronary heart disease, heart attack, stroke, and Alzheimer's disease. Elevated homocysteine may also increase the risk of developing osteoporosis and bone fractures.
hydrochloric acid - An acid made in the stomach. It works with enzymes (substances that speed up chemical reactions in the body) to break down proteins during digestion.
incidence - The number of new cases of a disease diagnosed in a specific group of people during a specific period of time. For example, the annual incidence of childhood cancer is 14.6 cases per 100,000 children aged birth to 14 years.
infant - A child younger than 12 months old.
inflammation - Redness, swelling, pain, and/or a feeling of heat in an area of the body. It is a protective reaction to injury, disease, or irritation of tissues.
inflammatory bowel disease - IBD. Long-lasting (chronic) problems that cause irritation and ulcers in the digestive tract. The most common disorders are ulcerative colitis and Crohn's disease.
injection - Use of a syringe and needle to push fluids or drugs into the body. Also called a shot.
Institute of Medicine - IOM. A private nongovernmental organization that issues reports on biomedical science, medicine, and health as requested by government agencies, private industry, and foundations.
intestine - The section of the digestive tract below the stomach, including the small and large intestines, rectum, and anus.
intrinsic factor - A protein made by the stomach that is needed to absorb vitamin B12 in the large intestine.
iron - In nutrition, a mineral the body needs to make red blood cells, proteins, and enzymes; and for the control of cell growth and cell specialization. Iron is found in some foods, including red meats, fish, poultry, lentils, and beans.
LDL cholesterol - Low-density lipoprotein cholesterol. A type of protein that carries cholesterol to many tissues throughout the body. High levels of LDL cholesterol increase the risk of coronary heart disease. Also called bad cholesterol.
malabsorption - A reduced ability to properly absorb nutrients. It can be caused by injury to the digestive tract, a genetic disease, or other conditions. Malabsorption can lead to malnutrition.
megaloblastic anemia - A disorder in which red blood cells are larger than normal, immature, and few in number, which reduces the amount of oxygen that can be carried by the blood to the body's tissues. It is caused by a deficiency in folate or vitamin B12.
metabolism - All chemical changes that take place in a cell or an organism. These changes produce energy and basic materials needed for important life processes.
microgram - µg or mcg. A unit of weight in the metric system equal to one millionth of a gram. (A gram is approximately one-thirtieth of an ounce.)
milligram - mg. A measure of weight. It is a metric unit of mass equal to 0.001 gram (it weighs 28,000 times less than an ounce).
National Academies - A private nonprofit organization that brings together committees of experts in all areas of science, technology, and health policy to address important national issues and give advice to the federal government and the public. It consists of the National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine, and the National Research Council.
National Heart, Lung, and Blood Institute - NHLBI. An organization in the federal government that plans, conducts and supports research related to the prevention, diagnosis, treatment, and rehabilitation of patients suffering from diseases of the heart, blood vessels, and lungs; blood diseases; and sleep disorders. It also supports research on the clinical use of blood and management of blood resources. NHLBI is one of 27 Institutes and Centers that make up the National Institutes of Health.
National Institutes of Health - NIH. The main organization in the federal government responsible for conducting and supporting medical research. It is composed of 27 Institutes and Centers that provide financial support to researchers in the United States and throughout the world to investigate ways to prevent, treat, and cure common and rare diseases. NIH is part of the US Department of Health and Human Services.
neurologic - Having to do with nerves and the nervous system.
nutrient - A chemical compound (such as protein, fat, carbohydrate, a vitamin, or mineral) that is found in food. Nutrients are used by the body to function and maintain health.
nutrition - The process of eating, digesting, and absorbing nutrients (such as protein, carbohydrate, fat, vitamins, minerals, and water) in food to maintain the body, grow new cells, repair tissues, and supply energy. Nutrition is also the science of food, diet, and the health and disease consequences.
nutritional - Having to do with nutrition (eating, digesting, and absorbing the nutrients in food, and the health and disease consequences).
nutritional yeast - A food product or food additive made from yeast (a fungus). The yeast is pasteurized (heated) to prevent it from growing in a person's digestive tract. Nutritional yeast is used as a source of protein and B vitamins. Some (but not all) brands of nutritional yeast contain vitamin B12. Latin name: Saccharomyces cerevisiae.
obesity - A condition characterized by an excessive amount of body fat. Obesity can be determined by calculating the body mass index (BMI). (BMI is a number that estimates the amount of body fat on a person, based on his or her weight and height. It is calculated by multiplying weight [in pounds] by 703, dividing the answer by height [in inches] and dividing that answer by height [in inches]). In adults, a BMI of 30 or higher indicates obesity. Some people, such as bodybuilders or other athletes with a lot of muscle, can be overweight without being obese. See: overweight.
oral - By mouth; having to do with the mouth.
parenteral - Having to do with providing substances for the body without using the gastrointestinal tract. Examples include an intravenous infusion, an injection under the skin, or an injection into a muscle.
pediatrician - A medical doctor (physician) who specializes in the treatment of children.
peptic ulcer disease - A sore or hole in the lining of the stomach or the first part of the small intestine, causing burning pain in the gut. Most ulcers are caused by an infection with a type of bacteria called Helicobacter pylori (H. pylori); other causes include long-term use of nonsteroidal anti-inflammatory drugs (such as aspirin and ibuprofen), alcohol, and tobacco.
placenta - The organ that delivers nutrients and oxygen and takes away carbon dioxide and other metabolic wastes from the developing fetus in the uterus.
plasma - The yellowish fluid part of blood in which blood cells are found. The plasma contains proteins that form blood clots.
platelet - Fragments of bone marrow cells (megakaryocytes) that help prevent bleeding by causing blood clots to form. Also called a thrombocyte.
poultry - Birds that are raised for eggs or meat, including chickens, turkeys, ducks, and geese.
prescription - A written order from a health care provider for medicine, other therapy, or tests.
prevalence - In medicine, the percentage of a population that is affected with a specific disease at any one time.
prevention - In medicine, action taken to decrease the chance (risk) of developing a disease.
protein - A molecule made up of amino acids that is needed for the body to work properly. Proteins are the basis of body structures such as skin and muscle, and substances such as enzymes and antibodies.
proton pump inhibitor - PPI. A drug that reduces the amount of acid made by the stomach. It is used to treat peptic ulcer and gastroesophageal reflux disease.
randomized clinical trial - A study in which the participants are assigned by chance to separate groups that compare different treatments. Neither the researchers nor participants can choose which group participants are assigned to. Using chance to assign people means that the groups will be similar and the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.
Recommended Dietary Allowance - RDA. The daily dietary intake level estimated by the Institute of Medicine to meet the nutrient requirements of most healthy individuals in a particular life stage and gender group. For example, the RDA for vitamin C is 75 mg/day for women older than 18 years.
red blood cell - A cell that carries oxygen to and removes carbon dioxide from all parts of the body.
regulate - To govern, make uniform, and bring under the control of a rule, principle, or legal system. In the United States, the FDA has the authority to regulate dietary supplements.
risk - The chance or probability that a harmful event will occur.
risk factor - Something that may increase the chance of developing a disease. For example, a diet that is low in calcium and vitamin D is a risk factor for osteoporosis; smoking is a risk factor for lung cancer.
sign - An indication of disease that can be seen and/or measured. Examples include high fever, high blood pressure, infection, and coughing up blood.
small intestine - The part of the digestive tract that is located between the stomach and the large intestine.
species - The name of a category that is part of the scientific classification of all organisms. The category species is located in the classification system after kingdom, phylum, class, order, family and genus. Humans, for example, belong to the species sapiens and are identified by the scientific name Homo (genus) sapiens (species).
statistically significant - In medicine, a mathematical measure of difference between two or more groups receiving different treatments that is greater than what might be expected to happen by chance alone.
status - The state or condition.
stroke - A loss of blood flow to part of the brain. Strokes are caused by blood clots or broken blood vessels in the brain, and result in damage to a section of brain tissue. Symptoms include dizziness, numbness, weakness on one side of the body, and problems with talking or understanding language. The chance (risk) of stroke is increased by high blood pressure, older age, smoking, diabetes, high cholesterol, heart disease, a family history of stroke, and a build-up of fatty material inside the coronary arteries (atherosclerosis). See also NIH publication: Know Stroke. Know the Signs. Act in Time. http://www.ninds.nih.gov/disorders/stroke/knowstroke.htm
subcutaneous - Beneath the skin.
supplement - A nutrient that may be added to the diet to increase the intake of that nutrient. Sometimes used as a synonym of dietary supplement.
symptom - An indication of disease that an individual can feel, but that cannot be measured objectively by a health care professional. Examples include headache, fatigue, indigestion, depression, and pain.
synthetic - Made by combining parts to make a whole; usually having to do with substances that are artificial or manufactured.
tissue - A group or layer of cells in a living organism that work together to perform a specific function.
Tolerable Upper Intake Level - UL. The largest daily intake of a nutrient that is considered unlikely to cause harmful side effects for most people in a particular life stage and gender group. Taking more than the UL is not recommended and may be harmful. The amount is established by the Institute of Medicine. For example, the UL for vitamin A is 3,000 micrograms/day. Women who consume more than this amount every day shortly before or during pregnancy have an increased chance (risk) of giving birth to an infant with a birth defect.
toxicity - The state of being poisonous (toxic).
US Department of Agriculture - USDA promotes America's health through food and nutrition, and advances the science of nutrition by monitoring food and nutrient consumption and updating nutrient requirements and food composition data. USDA is responsible for food safety, improving nutrition and health by providing food assistance and nutrition education, expanding markets for agricultural products, managing and protecting US public and private lands, and providing financial programs to improve the economy and quality of rural American life.
vascular - Having to do with blood vessels.
vasomotor - Having to do with the narrowing and widening of blood vessels.
vegetarian diet - A diet based on foods that come from plants, such as vegetables, beans, fruits and grains. There are many types of vegetarian diets, some including foods that come from animals. A diet that also contains eggs and dairy products is called lacto-ovo vegetarian. Strict vegetarian and vegan diets include only foods made from plants. In addition, people who follow a vegan diet also may choose not to use products that come from animals such as honey, leather, fur, silk, and wool.
vegetarianism - The practice of avoiding all or most animal products for environmental, philosophical, and health reasons. Vegetarians (people who practice vegetarianism) eat a diet based on foods that come from plants and may include some dairy products and eggs. Some also may avoid wearing clothes made from animals or using other products that come from animals. See: vegetarian diet.
vitamin - A nutrient that the body needs in small amounts to function and maintain health. Examples are vitamins A, C, and E.
vitamin B12 - A group of chemical compounds that contain cobalt and are needed for certain chemical reactions in the body. Vitamin B12 is involved in maintaining healthy nerve cells and red blood cells. It is needed to make DNA (the genetic material in all cells), and is required for the metabolism (chemical changes that take place in the tissues to produce energy and the basic materials needed by the body) of carbohydrate, fat, and protein. Also called cobalamin. For more information see the NIH Office of Dietary Supplements Vitamin B12 fact sheet.
vitamin B6 - A group of water-soluble chemical compounds, including pyridoxine, pyridoxal, and pyridoxamine. It is involved in protein metabolism, is needed for the nervous system and immune system to work efficiently, and is needed to make hemoglobin (a molecule within red blood cells that carries oxygen to tissues). It also helps maintain blood glucose (sugar) within a normal range. For more information see the NIH Office of Dietary Supplements Vitamin B6 fact sheet.

Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.

About ODS
The mission of the Office of Dietary Supplements (ODS) is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an enhanced quality of life and health for the U.S. population.

General Safety Advisory
Health professionals and consumers need credible information to make thoughtful decisions about eating a healthful diet and using vitamin and mineral supplements. To help guide those decisions, registered dietitians at the NIH Clinical Center developed a series of Fact Sheets in conjunction with ODS. These Fact Sheets provide responsible information about the role of vitamins and minerals in health and disease. Each Fact Sheet in this series received extensive review by recognized experts from the academic and research communities.

The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

The Clinical Nutrition Service and the ODS thank the expert scientific reviewers for their role in ensuring the scientific accuracy of the information discussed in these fact sheets:
Ralph Carmel, M.D., Cornell University Medical College and New York Methodist Hospital
Leon Ellenbogen, Ph.D., Lederle Consumer Health Division of Whitehall-Robbins
Victor D. Herbert, M.D., J.D., (deceased) Mt. Sinai and Bronx VA Medical Center
Robert M. Russell, M.D., USDA Human Nutrition Research Center on Aging, Tufts University

Information Provided By:
Office of Dietary Supplements
National Institutes of Health
Bethesda, Maryland 20892 USA
Web: http://ods.od.nih.gov
E-mail: ods@nih.gov