Straighterline Intro to Nutri Chap 8 Vitamins

Name four types of ingredients that are classified as dietary supplements by the Dietary Supplement Health and Education Act.

-A vitamin -A mineral -An herb or another botanical -An amino acid

Describe three functions of choline in the human body.

-Cell Membrane Structure. -Nerve Function and Brain Development. -Lipid Transport.

retinoic acid

-acid form of vitamin A -acts as a hormone (cel differentiation, growth, embryonic development) -cannot be converted to retinol

B vitamins, including thiamin, riboflavin, and niacin, are called the "energy" vitamins because they

are part of coenzymes needed for release of energy from carbohydrates, fats, and proteins

1,25-dihydroxyvitamin D3 (calcitriol)

biologically active form of vitamin D

Avidin, a component of raw egg whites, may decrease the absorption of

biotin.

provitamin A

carotenoids that the body converts to vitamin A

Vitamin C is necessary for the production of

collagen

anencephaly

congenital deformity in which some or all of fetal brain is missing

Osteomalacia

disease marked by softening of the bone caused by calcium and vitamin D deficiency

Vitamin D is called the sunshine vitamin because

exposure to sunlight converts a precursor to vitamin D

The B vitamins

facilitate chemical reactions that yield energy from the macronutrients.

Vitamins are classified as

fat soluble and water soluble

A deficient intake of_____ has been shown to increase the risk of having a baby with a neural tube defect such as spinabifida.

folate

Consuming high doses of ______ can mask signs of a vitamin B-12 deficiency

folate

megadose

generally defined as 10 times the recommended amount of a vitamin or mineral

endometrium

inner lining of the uterus

hemoglobin

iron-containing protein in red blood cells that carries oxygen for delivery to cells

pernicious anemia

lack of mature erythrocytes caused by inability to absorb vitamin B12 into the bloodstream; it is pernicious because of associated nerve degeneration that can result in eventual paralysis and death.

macular degeneration

loss of central vision

All of the following forms of cancer are related to excessive calorie intake except

lung cancer.

neural tube defect

malformations of the brain, spinal cord, or both during embryonic development that often results in lifelong disability, spina bifida, or death

benign

mild, not cancerous

What are the consequences of vitamin A deficiency?

night blindness, xeropthalmia

What group of people is at very high risk of deficiency of B vitamins?

older adults who eat little food and in other people with poor dietary patterns.

Choline is an important component of

phospholipid

carotenoids

phytochemicals, that is, chemicals within plants that have health-promoting properties for humans. Carotenoids, which are precursors of vitamin A, have profound antioxidant properties. Because carotenoids can be turned into vitamin A, they are termed provitamin A.

7-dehydrocholesterol

precursor of vitamin D found in the skin

vitamin D3 (cholecalciferol)

previtamin form found naturally in some animal sources, including fish and egg yolks

Which of the B vitamins is sensitive to and can be degraded by light?

riboflavin

ariboflavinosis

riboflavin deficiency that causes sore throat and swollen mucous membranes

Bowed legs, an enlarged and misshapen head, and enlarged knee joints in children are all symptoms of

rickets.

retinyl

storage form of vitamin A

retinol

the alcohol form of vitamin A

retinal

the aldehyde form of vitamin A

tissue saturation

the limited storage capacity of water-soluble vitamins in the tissues

bioavailability

the rate at and the extent to which a nutrient is absorbed and used

beriberi

the thiamin-deficiency disease; characterized by loss of sensation in the hands and feet, muscular weakness, advancing paralysis, and abnormal heart action

metastasize

to spread by transferring a disease-causing agent from the site of the disease to other parts of the body

Niacin can be synthesized in the body from the amino acid

tryptophan

Pernicious anemia is related to impaired absorption of

vitamin B-12.

Noodles, spaghetti, and bread are made from wheat flour that is enriched with all of the following nutrients except

vitamin B-6

As part of the body's antioxidant defenses, vitamin C participates in the recycling of

vitamin E.

A deficiency of vitamin A can lead to the disease called

xerophthalmia.

Drying of the cornea due to vitamin A deficiency is called

xerophthalmia.

malignant

(adj.) deadly, extremely harmful, evil; spiteful, malicious

nitrosamine

A carcinogen formed from nitrates and breakdown products of amino acids; can lead to stomach cancer.

coenzyme

A compound (e.g., water-soluble vitamin) that combines with an inactive enzyme to form a catalytically active form. In this manner, coenzymes aid in enzyme function.

anemia

A condition in which the blood is deficient in red blood cells, in hemoglobin, or in total volume.

international unit (IU)

A crude measure of vitamin activity, often based on the growth rate of animals in response to the vitamin. Today IUs have largely been replaced by more precise milligram or microgram measures.

megaloblast

A large, immature red blood cell that results from the inability of the cell to divide normally (megalo = large; blast = primitive or immature).

retina

A light-sensitive lining in the back of the eye. It contains retinal.

tumor

A mass of abnormal cells that develops when cancerous cells divide and grow uncontrollably.

prostate gland

A solid, chestnut-shaped organ surrounding the first part of the urinary tract in the male. The prostate gland secretes substances into the semen

Community-supported agriculture (CSA)

A system in which consumers pay farmers in advance for a share of their yield, usually in the form of weekly deliveries of produce.

How are the carotenoids related to vitamin A?

About 65% of the vitamin A in the typical North American diet comes from preformed vitamin A sources, whereas provitamin A (carotenoids) dominates in the diet among poor people in other parts of the world. The provitamin A carotenoids are mainly found in dark green and yellow-orange vegetables and some fruits. Carrots, spinach and other greens, winter squash, sweet potatoes, broccoli, mangoes, cantaloupe, peaches, and apricots are examples of such sources.

What group of people is at very high risk of deficiency of thiamin?

Adults with low incomes and older people may barely meet their needs for thiamin.

homocysteine

An amino acid that arises from the metabolism of methionine. Vitamin B-6, folate, vitamin B-12, and choline are required for its metabolism. Elevated levels are associated with an increased risk of cardiovascular disease.

vitamin

An essential organic (carbon-containing) compound needed in small amounts in the diet to help regulate and support chemical reactions and processes in the body.

megaloblastic (macrocytic) anemia

Anemia characterized by the presence of abnormally large red blood cells

Which of the following statements is true?

As we age, we need more vitamin D and fewer kilocalories

What body organs or tissues are most likely to show symptoms if there is a deficiency of B vitamins?

B vitamin-deficiency symptoms typically occur in the brain and nervous system, skin, and GI tract. Cells in these tissues are metabolically active, and those in the skin and GI tract are also constantly being replaced.

water-soluble vitamins

B vitamins and C Vitamins dissolve in water

What are some rich food sources of vitamin E?

Because vitamin E is only synthesized by plants, plant products (especially the oils) are the best sources. In the North American diet, nearly two-thirds of vitamin E is supplied by salad oils, margarines, spreads (low-fat margarine), and shortening. Breakfast cereals fortified with vitamin E are good sources, but other than wheat germ, few other grain products provide much vitamin E. Milling of grains removes the germ, which contains the oils (mostly PUFAs) and vitamin E. By removing the germ, the resulting grain product has less chance of spoiling (i.e., rancidity of the PUFAs) and thus a longer shelf life. Other good sources of vitamin E are nuts and seeds.

What is the role of biotin in energy metabolism?

Biotin assists in the addition of carbon dioxide to other compounds, a reaction critical in synthesizing glucose and fatty acids, as well as breaking down certain amino acids.

What are the names of four carotenoids known to have antioxidant functions?

Carotenoids, which are precursors of vitamin A, have profound antioxidant properties. Because carotenoids can be turned into vitamin A, they are termed provitamin A. Beta-carotene, the orange-yellow pigment in carrots, is the only carotenoid that can be sufficiently absorbed and converted into retinol to play a significant role as a source of vitamin A and as a powerful antioxidant. The other two carotenoids that can be converted into vitamin A (though not very effectively) are alpha-carotene and beta-cryptoxanthin. Beta-carotene is split in half by cells in the body to form two molecules of retinal. Neither the conversion of the provitamin A carotenoids into vitamin A nor the absorption of carotenoids is an efficient process. Other carotenoids that may play a role in human health but are not vitamin A precursors include lycopene, zeaxanthin, and lutein.

Coenzyme Q (CoQ) is an organic compound that is required for the electron transport chain and has some antioxidant functions. This compound is synthesized within cells, and under most circumstances, the body synthesizes enough CoQ to meet its needs. Is CoQ a vitamin? Why or why not?

Coenzyme Q-10 (CoQ-10 or Ubiquinone) is a naturally occurring quinone that is found in most aerobic organisms from bacteria to mammals. Coenzyme Q10 is also known as Coenzyme Q, CoQ, CoQ10, Ubiquinone, Ubiquinone-Q10, Ubidecarenone, or Vitamin Q10. CoQ10 is essential for the health of virtually all human tissues and organs. Coenzyme Q10 is one of the most significant lipid antioxidants, which prevents the generation of free radicals and modifications of proteins, lipids, and DNA. In many disease conditions connected with increased generation and the action of reactive oxygen species (ROS), the concentration of coenzyme Q10 in the human body decreases and the deficiency of coenzyme Q10 leads to the dysfunction of the respiratory chain, which is due to the insufficient production of highly energetic compounds, which decrease the efficiency of cells.

What are the three distinct signs of a niacin deficiency?

Early symptoms include poor appetite, weight loss, and weakness. The distinct 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). Left untreated, death often results.

What are the possible results of vitamin E toxicity?

Excessive intake of vitamin E can interfere with vitamin K's role in the clotting mechanism, leading to hemorrhage. The risk of insufficient blood clotting is especially high if vitamin E is taken in conjunction with anticoagulant medications (e.g., Coumadin or heavy aspirin use). Always be cautious about using dietary supplements. In addition to the significant risk of drug interference and prolonged bleeding, vitamin E supplements can produce nausea, gastrointestinal distress, and diarrhea.

Explain why macrocytic (megaloblastic) anemia occurs.

Few mature red blood cells arrive in the bloodstream because the bone marrow of a folate-deficient person produces mostly immature megaloblast cells. When fewer mature red blood cells are present, the blood's capacity to carry oxygen decreases, causing a condition known as megaloblastic anemia (also called macrocytic or large-cell anemia).

What are the best sources of biotin?

Foods rich in protein, such as egg yolks, peanuts, and cheese, are good sources of biotin

25-hydroxyvitamin D3 (calcidiol or calcifediol)

Form found in blood. Sometimes shortened to 25(OH)D3

vitamin D2 (ergocalciferol)

Form found in nonanimal sources, such as in some mushrooms.

Why are fresh foods the best sources of vitamin C?

Fresh, ripe fruits and vegetables are loaded with vitamin C. Allowing them to "ripen" further in the grocery store or on your countertop at home will not increase vitamin C and actually can decrease it. The brighter the fruit or vegetable is, the higher it tends to be in vitamin C. Vitamin C is rapidly lost in processing and cooking as it is unstable in the presence of heat, iron, copper, or oxygen and is water soluble. Boiling fruits and vegetables for an extended time can destroy much of the vitamin C or cause it to leach out of the food

xerophthalmia

Hardening of the cornea and drying of the surface of the eye, which can result in blindness.

What is a megadose? Are there any negative consequences of consuming megadoses of vitamins? Are there any situations in which megadoses of vitamins are useful?

In addition to their use in correcting deficiency diseases, a few vitamins have also proved useful in treating several nondeficiency diseases. These medical applications require administration of megadoses, well above typical human needs for the vitamins. For example, megadoses of a form of niacin can be used as part of blood cholesterol-lowering treatment for certain individuals. Still, any claimed benefits from use of vitamin supplements, especially intakes in excess of the Upper Level (if set), should be viewed critically because unproved claims are common. Remember, whenever you take a supplement at high doses, you are taking it at a pharmacological dose—that of a drug. Expect side effects as you would from any drug.

Why does consumption of raw eggs lead to biotin deficiency?

In raw egg whites, biotin is bound to avidin, which inhibits absorption of the vitamin. Consuming many raw egg whites can eventually lead to biotin-deficiency disease.

The American Institute for Cancer Research Recommendations for Cancer Prevention include all of the following except

Increase consumption of red meats (e.g., beef, pork, and lamb)

A vitamin synthesized by bacteria in the intestine is

K

Describe three situations in which use of dietary supplements is necessary

MVM: • People who consume <1200 kilocalories per day (e.g., some women and older adults) • People with unbalanced or inadequate diets (e.g., in cases of food insecurity or children who are "picky" • People with malabsorptive diseases eaters) • People who take medications that interfere with nutrient absorption or metabolism Various B vitamins: • People who abuse alcohol Folic acid • Women of childbearing age (especially during pregnancy and breastfeeding) Vitamin B-12: • Older adults • Strict vegans Vitamin C: • People who smoke Vitamin D: • People with limited milk intake (due to allergies or lactose intolerance) • People with limited exposure to sunlight (e.g., all infants, many African-Americans, and some older adults) • Strict vegans Vitamin E: • People who follow diets low in fat (especially low in plant oils) Vitamin k: • Newborns (given by injection shortly after birth) Calcium: • Strict vegans • Older adults with bone loss Fluoride: • Some older infants and children (as directed by a dentist) Iron: • Women with excessive bleeding during menstruation • Women who are pregnant) • Strict vegans Zinc: • Strict vegans

What are some excellent sources of niacin?

Major sources of niacin are tuna, poultry, peanuts, fish, ready-to-eat cereals, beef, and asparagus. Coffee and tea also contribute some niacin to the diet. Niacin is heat stable; little is lost in cooking.

What types of foods are the best sources of riboflavin?

Major sources of riboflavin are ready-to-eat breakfast cereals, milk and milk products, enriched grains, meat, and eggs. Vegetables such as asparagus, broccoli, and various greens (e.g., spinach) are also good sources. Riboflavin is a relatively stable water-soluble vitamin; however, it is destroyed by light. Milk is sold in paper or opaque plastic containers rather than clear glass to protect the riboflavin. In the United States, many meet the riboflavin recommendation by consuming three servings of dairy products each day.

What are some excellent sources of thiamin?

Major sources of thiamin include pork products, whole grains (wheat germ), ready-to-eat breakfast cereals, enriched grains and flour, green beans, milk, orange juice, organ meats, peanuts, dried beans, and seeds

What are the primary sources of vitamin B-6?

Major sources of vitamin B-6 are animal products and fortified ready-to-eat breakfast cereals. Other sources are vegetables and fruits such as potatoes, spinach, bananas, and cantaloupes.

How does vitamin E work to prevent oxidative damage?

Many of the lipids within these membranes are polyunsaturated fatty acids (PUFA), which are particularly susceptible to oxidative attack by free radicals. The formation of free radicals may destabilize the cell membrane, which may ultimately alter the ability of the cell to function properly. Vitamin E can donate electrons or hydrogen to free radicals found in membranes, thereby making them more stable. The antioxidant function of vitamin E appears to be critical in cells continually exposed to high levels of oxygen, particularly red blood cells and the cells lining the lungs.

pellagra

Niacin deficiency

How is niacin involved in energy metabolism?

Niacin functions in the body as one of two related compounds: nicotinic acid and nicotinamide. The coenzyme forms of niacin function in many cellular metabolic pathways. When you are generating energy (ATP) by burning carbohydrate and fat, a niacin coenzyme, nicotinamide adenine dinucleotide (NAD) or nicotinamide adenine dinucleotide phosphate (NADP), is used. Anabolic pathways in the cell—those that make new compounds—also often use a niacin coenzyme. This is especially true for fatty-acid synthesis.

How is thiamin involved in energy metabolism?

One of its primary functions is to help release energy from carbohydrate. Its coenzyme form, thiamin pyrophosphate (TPP), participates in reactions in which carbon dioxide (CO2) is released. Such reactions are particularly important in the body's ATP-producing energy pathways, which involve the breakdown of carbohydrates and certain amino acids. Thiamin also functions in chemical reactions that make RNA, DNA, and neurotransmitters.

What is the role of vitamin B-6 in energy metabolism and other body functions?

One of the primary functions is as a coenzyme in over 100 chemical reactions that involve the metabolism of amino acids and protein. The B-6 coenzyme, PLP, participates in reactions that allow the synthesis of nonessential (dispensable) amino acids by helping split the nitrogen group (−NH2) from an amino acid and making it available to another amino acid. Vitamin B-6 also plays a role in the metabolism of the nonprotein amino acid homocysteine. Among the other important functions of vitamin B-6 are the synthesis of neurotransmitters such as serotonin and gamma aminobutyric acid (GABA); conversion of tryptophan to niacin; breakdown of stored glycogen to glucose; and synthesis of hemoglobin and white blood cells. Vitamin B-6 is also important for the synthesis of the heme portion of hemoglobin.

What is the role of pantothenic acid in energy metabolism?

Pantothenic acid is required for the synthesis of coenzyme A (CoA), a coenzyme in chemical reactions that allow the release of energy from carbohydrates, lipids, and protein. It also activates fatty acids so they can yield energy and is used in the initial steps of fatty-acid synthesis.

Why is it important for people who take Coumadin to monitor their dietary intake of vitamin K?

People who are prone to develop blood clots may take anticoagulants or "blood thinners." One example is Plavix (clopidogrel), which works by inhibiting the activity of platelets. Another commonly prescribed anticoagulant is Coumadin (warfarin). This medication inhibits vitamin K-dependent coagulation factors. When taking Coumadin or similar drugs, it is important to keep vitamin K intake consistent from day to day

Which of the following meals is most compatible with American Institute for Cancer Research guidelines for cancer prevention?

Poached salmon, steamed broccoli, and corn on the cob

Why do daily folate needs increase from 400 to 600 micrograms for pregnant women?

Pregnant women need extra folate (a total of 600 micrograms DFE) to accommodate the increased rates of cell division and DNA synthesis in their bodies and in the developing fetus. A healthy diet can supply this much. Still, prenatal care often includes a specially formulated multivitamin and mineral supplement enriched with folic acid to meet the higher RDA during pregnancy.

Why are preterm infants, smokers, and people with fat malabsorption particularly susceptible to oxidative damage to cell membranes?

Preterm infants tend to have low vitamin E stores because this vitamin is transferred from mother to baby during the late stages of pregnancy. Hence, the potential for oxidative damage, which could cause the cell membranes of red blood cells to break (hemolysis), is of particular concern for preterm infants. The rapid growth of preterm infants, coupled with the high oxygen needs of their immature lungs, greatly increases the stress on red blood cells. Special vitamin E-fortified formulas and supplements designed for preterm infants compensate for lack of vitamin E. Smokers are another group at high risk for vitamin E deficiency, as smoking readily destroys vitamin E in the lungs. One study showed that megadosing will not correct this vitamin E destruction by smokers. Others at risk of vitamin E deficiency include adults on very low-fat diets (< 15% total fat) or those with fat malabsorption.

R-proteinst

Proteins produced by the salivary glands that bind to free vitamin B-12 in the stomach and protect it from stomach acid.

What are some rich sources of pantothenic acid?

Rich sources of pantothenic acid are sunflower seeds, mushrooms, peanuts, and eggs. Other rich sources are meat, milk, and many vegetables.

What is the role of vitamin K in blood clotting?

Serves as cofactor in chemical reactions, enabling proteins to bind calcium Converts soluble fibrinogen into insoluble fibrin (the clot)

List three ways to incorporate more choline into the diet

Soybeans, egg yolks, beef, cauliflower, almonds, and peanuts are good sources. In addition to natural food sources, lecithin is often added to food products as an emulsifier during processing, so many other foods are sources of choline.

Are vitamin B-6 supplements safe?

Studies have shown that intakes of 2 to 6 grams of vitamin B-6 per day for 2 or more months can lead to irreversible nerve damage. Symptoms of vitamin B-6 toxicity include walking difficulties, and hand and foot tingling and numbness. Some nerve damage in individual sensory neurons is probably reversible, but damage to the ganglia (where many nerve fibers converge) appears to be permanent. With 500-milligram tablets of vitamin B-6 available in health-food stores, taking a toxic dose is easy

What are some rich food sources of vitamin D?

Sunlight is the best source of vitamin D. Fatty fish are considered the richest natural sources of vitamin D. Wild-caught salmon tops the list with around 600 to 1000 IU of vitamin D in a 3.5-ounce serving. Farmed salmon contains less at between 100 to 250 IU per 3.5-ounce serving. Tuna is a bit farther down the list with 6 ounces of canned light tuna providing about 300 IU. Eggs are another natural source with 1 large egg yolk delivering 41 IU. Although butter, liver, and a few brands of margarine contain some vitamin D, large servings must be eaten to obtain an appreciable amount of the vitamin; therefore, these foods are not considered significant sources.

What body organs or tissues are most likely to show symptoms if there is a deficiency of riboflavin?

Symptoms associated with riboflavin deficiency (ariboflavinosis) 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. Such symptoms develop after approximately 2 months on a riboflavin-poor diet. Riboflavin deficiency typically would occur jointly with deficiencies of niacin, thiamin, and vitamin B-6 because these nutrients often occur in the same foods.

What are the signs and symptoms of biotin deficiency?

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.

What are the coenzymes associated with each of the B vitamins involved in energy metabolism?

The B vitamins are thiamin, riboflavin, niacin, pantothenic acid, biotin, vitamin B-6, folate, and vitamin B-12. Choline is a related nutrient, but currently is not classified as a vitamin. Vitamin C is also a water-soluble vitamin.

What is the relationship between tryptophan and niacin?

The RDA for niacin is expressed as niacin equivalents (NE) to account for niacin received intact from the diet, as well as that synthesized from tryptophan: 60 milligrams of tryptophan in a diet yield about 1 milligram of niacin. Intakes of niacin by adults are about double the RDA, without considering the contribution from tryptophan. (Tables of food composition values also ignore tryptophan contribution.) Although pellagra was once common, today it is typically only seen associated with chronic alcoholism, in conjunction with poverty and malnutrition, and in those with rare disorders of tryptophan metabolism (for example, Hartnup disease).

How is riboflavin involved in energy metabolism?

The coenzyme forms of riboflavin, flavin dinucleotide (FAD) and flavin mononucleotide (FMN), participate in many energy-yielding metabolic pathways, such as the breakdown of fatty acids. Some metabolism of vitamins and minerals also requires riboflavin. Indirectly, riboflavin also has an antioxidant role in the body through its support of the enzyme glutathione peroxidase.

fetus

The developing human life form from 8 weeks after conception until birth.

How is vitamin D activated in the body?

The human production of vitamin D begins when the ultraviolet B (UVB) rays of the sun convert a cholesterol precursor of vitamin D (7-dehydrocholesterol) found in the skin into an inactive form of vitamin D (cholecalciferol). As illustrated in Figure 8-7, this compound must be activated to 25-hydroxyvitamin D3 (calcidiol) in the liver and to 1,25-dihydroxyvitamin D3 (calcitriol) in the kidney before it can function as the vitamin D hormone.

What happens during the refining of grains that causes a decrease in nutrient density?

The production of refined grains, such as white flour from wheat, leads to the loss of B vitamins as well as other vitamins and minerals. In milling grains to make refined products, seeds are crushed and the germ, bran, and husk layers are discarded, leaving just the starch-containing endosperm in the refined grains. This starch is used to make white flour, bread, and cereal products. Unfortunately, many nutrients are lost along with the discarded germ, bran, and husk materials.

What are some rich food sources of carotenoids?

The provitamin A carotenoids are mainly found in dark green and yellow-orange vegetables and some fruits. Carrots, spinach and other greens, winter squash, sweet potatoes, broccoli, mangoes, cantaloupe, peaches, and apricots are examples of such sources.Beta-carotene accounts for some of the orange color of carrots. Green vegetables also contain provitamin A. The yellow-orange beta-carotene is masked by dark-green chlorophyll pigments. Green, leafy vegetables, such as spinach and kale, have high concentrations of lutein and zeaxanthin. Tomato products contain significant amounts of lycopene. Cooking food improves the bioavailability of carotenoids. In raw fruits and vegetables, carotenoids are bound to proteins. Cooking disrupts this protein bond and frees the carotenoid for better absorption.

What body organs or tissues are most likely to show symptoms if there is a deficiency of thiamin?

The thiamin-deficiency disease is called beriberi, a word that means "I can't, I can't" in the Sri Lankan language of Sinhalese. This disease was described long before thiamin was discovered to be a vitamin in 1910. The symptoms include 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.

Is it necessary to take dietary supplements of vitamin-like compounds, such as carnitine and taurine? Why or why not?

These vitamin-like compounds can be synthesized by cells using common building blocks, such as amino acids and glucose. Our diets are also a source. In disease states or periods of active growth, the synthesis of vitamin-like compounds may not meet needs, so dietary intake can be crucial. The needs for vitamin-like compounds in certain groups of individuals, such as for preterm infants, are being investigated. Although promoted and sold by health-food stores, these vitamin-like compounds need not be included in the diet of the average healthy adult.

Why are B vitamins lost when foods are cooked in water?

They dissolve in water, so large amounts of these vitamins can be lost during food processing and preparation. Vitamin content is best preserved by light cooking methods, such as stir-frying, steaming, and microwaving. About 10% to 25% of these vitamins are lost from food during food processing and preparation because they dissolve in water. Light cooking methods, such as stir-frying, steaming, and microwaving, best preserve vitamin content

What is added during the "enrichment" of grain products, and why is it important?

To counteract these losses, in the United States, bread and cereal products made from milled grains are enriched with four B vitamins (thiamin, riboflavin, niacin, and folic acid) and with the mineral iron.

Explain the role of specific factors required for vitamin B-12 absorption.

To illustrate the multistep process by which vitamin B-12 is absorbed, we will trace the path of a meal containing vitamin B-12 through the digestive tract: 1. In food, much of the vitamin B-12 is bound to protein and therefore cannot be absorbed. 2. When food enters the mouth, R-proteins are secreted by the salivary glands. 3. The bolus of food, including the R-proteins, travels down the esophagus to the stomach. 4. Acid and enzymes present in the stomach release vitamin B-12 from food proteins, and the free vitamin B-12 then binds to R-protein. 5. While food is in the stomach, the stomach cells release a proteinlike compound called the intrinsic factor. 6. When the chyme reaches the duodenum, pancreatic enzymes release vitamin B-12 from R-proteins. 7. The free vitamin B-12 then combines with intrinsic factor. 8. The vitamin B-12-intrinsic factor complex travels the length of the small intestine to the ileum, where vitamin B-12 is finally absorbed.

Can vitamin D be toxic?

Too much vitamin D taken regularly can create serious health consequences in infants and children. Due to the role of vitamin D in calcium absorption, excretion, and release of calcium from bone, supplementation with high doses of vitamin D can cause calcium levels in the blood to increase above the normal range. The UL is based on the risk of overabsorption of calcium and eventual calcium deposits in the kidneys and other organs. Calcium deposits in organs can cause metabolic disturbances and cell death. Toxicity symptoms also include weakness, loss of appetite, diarrhea, vomiting, mental confusion, and increased urine output. Please note that vitamin D toxicity does not result from excessive exposure to the sun because the body regulates the amount made in the skin (i.e., as exposure to sunlight increases, vitamin D synthesis decreases). Unlike with supplements, you can never receive a toxic dose.

Identify two population groups that are at risk for vitamin B-12 deficiency. Explain why these people are at risk.

Vegan diets supply little vitamin B-12 unless they include vitamin B-12-enriched food (e.g., soy milk) or supplements. Infants breastfed by vegetarian mothers are at risk for vitamin B-12 deficiency accompanied by anemia and long-term nervous system problems, such as diminished brain growth, degeneration of the spinal cord, and poor intellectual development. The problems may have their origins during pregnancy if the mother is deficient in vitamin B-12. Certainly, achieving an adequate vitamin B-12 intake is a key diet-planning goal for vegans.Pernicious anemia, which affects about 2% of older adults, is the most common cause of vitamin B-12 malabsorption. Other causes are age-related atrophy of the acid-producing cells of the stomach and bacterial overgrowth in the small intestine. When acid production is low, bacteria normally present in the large intestine may colonize the small intestine and compete with our intestinal cells for vitamin B-12 absorption. Certain medications also impair vitamin B-12 absorption

Which of the following is an example of a fat-soluble vitamin?

Vitamin A

night blindness

Vitamin A deficiency that results in loss of the ability to see under low-light conditions.

How does vitamin C function as an antioxidant and regenerate vitamin E?

Vitamin C also has a more general function as an antioxidant because it can readily accept and donate electrons. These antioxidant properties have been postulated to reduce the formation of cancer-causing nitrosamines in the stomach. Vitamin C also aids in the reactivation of vitamin E after it has donated an electron to a free radical. Population studies suggest that the antioxidant properties of vitamin C may be effective in the prevention of certain cancers (esophagus, mouth, and stomach) and cataracts. The extent to which vitamin C functions in the reduction of diseases is debatable based on the scientific studies to this point.

rickets

Vitamin D deficiency in children

Why is vitamin D sometimes not considered an "essential" nutrient?

Vitamin D is a fat-soluble vitamin with two unique qualities. First, vitamin D is the only nutrient that is also a hormone. Second, vitamin D is the only nutrient that can be produced in the skin upon exposure to ultraviolet light.

How does vitamin D work to maintain blood calcium levels?

Vitamin D regulates blood calcium in three ways: 1) it influences the absorption of calcium and phosphorus from the small intestine; 2) in combination with PTH and calcitonin, it regulates calcium excretion via the kidney; and 3) it affects the deposition or withdrawal of minerals from the bones

fat-soluble vitamins

Vitamins A, D, E, and K are soluble in fat; fat is required for their transport

Identify three potential risks from use of dietary supplements.

While there may be moderate benefits of consuming dietary supplements, uninformed use of supplements can be risky. Indeed, most cases of nutrient toxicity are a result of supplement use. High doses of one nutrient can affect absorption or metabolism of other nutrients. For example, excessive zinc intake can inhibit copper absorption, and large amounts of folate can mask signs and symptoms of a vitamin B-12 deficiency. In addition, some supplements can interfere with medications. For instance, high intakes of vitamin K or vitamin E alter the action of anticlotting medications, vitamin B-6 can offset the action of L-dopa (used in treating Parkinson's disease), and large doses of vitamin C might interfere with certain cancer therapy regimens.

Which two nutrient deficiencies could be responsible for macrocytic anemia?

Without vitamin B-12, reactions that require certain active forms of folate do not take place in the cell. Thus, a deficiency of vitamin B-12 can result in symptoms of a folate deficiency, including elevated homocysteine levels and macrocytic anemia

How do the signs of vitamin C deficiency relate to the many roles of the vitamin discussed in this chapter?

Without vitamin C, the skin and blood vessels weaken and wounds will not heal. The symptoms of scurvy, which include bleeding gums, tooth loss, bruising, and scaly skin, illustrate the important function of vitamin C in the formation of connective tissue.

retinoids

a class of chemical compounds derived from vitamin A that are used in skin care and treatment because of their effect on epithelial cell growth; one source is animal foods.

spina bifida

a congenital defect that occurs during early pregnancy when the spinal canal fails to close completely around the spinal cord to protect it

The first step in ensuring an adequate intake of vitamins is

a diet that matches MyPlate's Daily Food Plan

scurvy

a disease caused by lack of vitamin C

cheilosis

a disorder of the lips characterized by crack-like sores at the corners of the mouth

intrinsic factor

a gastric secretion that combines with vitamin B12 so that the vitamin can be absorbed

dementia

a slowly progressive decline in mental abilities, including memory, thinking, and judgment, that is often accompanied by personality changes

Vitamin E functions as

an antioxidant