Nutrition; Fifth Edition; Chapter 10; Fat-Soluble Vitamins

List at least three characteristics of fat-soluble vitamins.

- Vitamins A, D, E, and K are found in the fat and lipid components of food. - Fat-soluble vitamins require bile for absorption and first travel in the lymphatic system (inside chylomicrons) before entering the blood stream. - Most fat-soluble vitamins are not readily excreted and are stored in the liver and adipose tissue.

Calcitriol

-1,25-dihydroxycholecalciferol, or vitamin D3

Identify sources of vitamin K.

...

The active form of vitamin D, _____, is an important regulator of blood calcium levels.

1,25-dihydroxyvitamin D3 [1,25(OH)2D3]

KEY CONCEPT 2

All types of foods contain vitamins. Provitamins are vitamin precursors that the body can convert to active vitamin form. Growing conditions, storage, processing, and cooking all affect the amounts of vitamins in food.

KEY CONCEPT 8

Because vitamin D's primary function is to regulate the level of calcium in the blood, which affects storage of calcium in bone, a deficiency of the nutrient affects the skeletal system. In children, a vitamin D deficiency leads to rickets; in adults, lack of the nutrient causes osteomalacia and contributes to osteoporosis. Vitamin D is toxic when consumed in excess, and large doses should be taken only under a Physician's supervision. Exposure to sun does not cause vitamin D toxicity.

What antioxidant is responsible for the yellow-orange color of cantaloupes?

Beta-carotene

_____ is a hormone secreted by the thyroid gland in response to elevated blood calcium. It stimulates calcium deposition in bone and calcium excretion by the kidneys, thus reducing blood calcium.

Calcitonin

Which of the following is true about the forms of vitamin A? a. Retinoids are found in plant foods b. Carotenoids are found in animal foods c. Carotenoids can be converted retinoids d. Retinoids are converted to carotenoids.

Carotenoids can be converted retinoids

From what precursor can vitamin D be synthesized?

Cholesterol

Menadione

Coumadin (warfarin), a medicinal form of vitamin K that can be toxic to infants; also known as vitamin K3

KEY CONCEPT 11

Deficiencies of vitamin E are rare in adults, occurring primarily in people with fat malabsorption syndrome. Preterm infants also run a high risk of vitamin E deficiency because they are delivered before the nutrient has a chance to move from the mother to the infant. Hemolysis is the hallmark of such a deficiency. Vitamin E is relatively nontoxic, although large doses interfere with blood clotting.

KEY CONCEPT 5

Deficiency of vitamin A results in progressive vision loss from temporary night blindness, to reversible blindness, and finally to permanent blindness. In addition, the lack of mucus secretions and reduced immune function make the person with vitamin A deficiency vulnerable to infections. Vitamin A toxicity can result from the use of supplements, even with dosages a few times higher than the RDA. The consequence of vitamin A toxicity during pregnancy are potentially devastating, and pregnant women should avoid both retinol-containing supplements and medications made from retinoids, such as Accutane and Retin-A.

KEY CONCEPT 13

Dietary recommendations for vitamin K intake are small. The Al for adult men is 120 micrograms, and for adult women is 90 micrograms. Vitamin K is found primarily in green vegetables and in some vegetable oils. Animal foods, in general, contain limited amounts of vitamin K.

The millions of cells that line and protect the external and internal surfaces of the body are _____. These form epithelial tissue such as skin and mucous membranes.

Epithelial cells

Vitamin C impairs the absorption of iron. a. True b. False

False

Which of the following is true about the absorption, transport, and storage of fat-soluble vitamins? a. They enter the bloodstream directly after absorption b. Fat in the digestive contents is not important for their absorption. c. They are not stored to any great extent. d. After absorption, they are transported in the bloodstream to body cells and/or stored in the liver and fatty tissue.

Fat in the digestive contents is not important for their absorption

When consumed in excess amounts, fat-soluble vitamins generally pose a greater risk of toxicity than water-soluble vitamins. In relationship to vitamin storage, explain why this is true.

Fat-soluble vitamins (A, D, E and K), unlike water-soluble vitamins that need regular replacement in the body, fat-soluble vitamins are stored in the liver and fatty tissues, and are eliminated much more slowly than water-soluble vitamins.

Although there is no evidence that carotenoids are essential nutrients in the technical sense, they do have important roles which contribute to our health and well-being. Identify the role(s) of carotenoids.

In human nutrition, carotenoids, as antioxidants, serve to protect cells from the danger of free radicals that may be produced by the body during metabolism or by cigarette smoke, sunlight, radiation, pollutants, or even stress.

KEY CONCEPT 7

Intake recommendations for vitamin D are very small: only 5 micrograms per day for young adults. Needs from the diet increase with age as the ability of the skin to synthesize vitamin D declines. Few foods are naturally good sources of vitamin D, and so most of the dietary intake comes from fortified milk and other fortified foods.

An outdated system to measure vitamin activity, _____ does not consider differences in bioavailability.

International Units (IUs)

_____ is a medicinal form of vitamin K; it is also known as vitamin K3.

Menadione

Which two fat-soluble vitamins are most toxic? Least toxic?

Most toxic fat-soluble vitamins are A & D, the least toxic fat-soluble vitamins are E & K.

The inability of the eyes to adjust to dim light or to regain vision quickly after exposure to a flash of bright light is called _____.

Night Blindness

A protein that combines with retinal to form rhodopsin in rod cells is _____.

Opsin

Insufficient vitamin D during adulthood is associated with: a. Ricketts b. Osteomalacia c. Kidney stones d. Hypocalcemia

Osteomalacia

_____ is a hormone secreted by the parathyroid glands in response to low blood calcium. It stimulates calcium release from bone and calcium absorption by the intestines, while decreasing calcium excretion by the kidneys.

Parathyroid Hormone

The form of vitamin K that comes from plant sources is _____; it is also known as vitamin K1.

Phylloquinone

The acid form of vitamin A is _____.

Retinoic Acid

The alcohol form of vitamin A is _____.

Retinol

Light sensitive cells in the retina that react to dim light and transmit black-and-white images are _____.

Rods

George wants to increase his consumption of vitamin A for the possible cancer risk-reducing effects. Which of the following foods should he choose? a. Spinach b. Salmon c. Pears d. Potato

Spinach

Formative cells whose daughter cells may differentiate into other cell types are _____.

Stem Cells

KEY CONCEPT 10

The RDA for vitamin E is 15 milligrams if alpha-tocopherol for both men and women. Vitamin E is found in wheat germ, vegetable and seed oils, and products made from these oils, such as salad dressing and margarine. Processing foods can reduce their vitamin E content.

KEY CONCEPT 6

The best known function of vitamin D, in the active form of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3], is to help regulate blood calcium levels. 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] works with two other hormones, parathyroid hormone and calcitonin, to alter the amount of calcium in the bone, the amount excreted from the kidneys, and the amount absorbed from the intestine to keep blood levels in normal range. It is known that 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] has effects on other tissues, but these functions have not been well established.

_____ is the chemical name for vitamin E. There are four kinds (alpha, beta, gamma, and delta), but only alpha is active in the body.

Tocopherol

_____ and tocopherols are collectively known as vitamin E.

Tocotrienols

Although vitamins are not an energy source, how do they contribute to energy production?

Unlike carbohydrates, fats, and proteins, vitamins are not sources of energy. Instead, vitamins are involved in the body's metabolism, cell production, tissue repair, and other vital processes.

What vitamin deficiency is associated with night blindness?

Vitamin A

What are the main roles of vitamin A in the body?

Vitamin A is necessary for vision, reproduction, cell differentiation, immune function, and bone health.

KEY CONCEPT 3

Vitamin A occurs in three forms in the body: retinol, retinal, and retinoic acid. Each form of the vitamin has specific roles in the body. Most vitamin A is stored by the liver in the form of retinyl esters. Retinol-binding protein carries vitamin A in the bloodstream.

KEY CONCEPT 4

Vitamin A plays a crucial role in vision as part of the compound rhodopsin in the rod cells of the retina. When light hits the retina, rhodopsin separates, changes shape, and sends a nerve impulse to the brain. When vitamin A is inadequate, the lack of rhidopsin makes it difficult to see the dim light. Vitamin A also is involved in cell differentiation, growth and development, immune function, reproduction, and bone health.

Which fat-soluble vitamin is considered a hormone? Which organ does this hormone affect?

Vitamin D, it affect our bone growth and calcium levels in our blood

Which vitamin prevents free radical damage?

Vitamin E functions as an antioxidant, protecting cell membranes in all parts of the body from the damaging effects of oxidation.

Identify vitamin E's most prominent role.

Vitamin E has many biological functions, the antioxidant function being the most important and best known. Other functions include enzymatic activities, gene expression, and neurological function(s). The most important function of vitamin E has been suggested to be in cell signaling (and it may not have a significant role in antioxidant metabolism).

KEY CONCEPT 9

Vitamin E is really a set of compounds called tocopherols and tocotrienols. Alpha-totopherol is the only form of vitamin E that meets the vitamin E requirement. Vitamin E functions as an antioxidant, protecting cell membranes in all parts of the body from the damaging effects of oxidation. Vitamin E has been connected to reduction of risks for many degenerative diseases, such as heart disease and cancer.

What are the toxicity and deficiency symptoms of vitamin E?

Vitamin E is relatively non-toxic, large dose may counter-react with vitamin K's blood clotting mechanism, deficiency usually only occur in premature infants and in those unable to absorb fats that result in the breaking down of red blood cells.

Without this vitamin to promote blood clotting, a single cut would eventually lead to death by blood loss.

Vitamin K

KEY CONCEPT 14

Vitamin K deficiencies are extremely rare. Because it takes several weeks before the intestinal bacteria that produce vitamin K to begin to flourish in the intestine, newborns are routinely given injections of vitamin K at birth. Vitamin K toxicity is rare because the body excretes the nutrient more readily than the other fat-soluble vitamins.

How does a vitamin K deficiency lead to the inability to form a blood clot?

Vitamin K is necessary for the production of prothrombin, a protein that when activated is responsible for the formation of a solid blood clot.

KEY CONCEPT 12

Vitamin K was named for the danish word "koagulation" because the nutrient works to promote the formation of blood clots. Vitamin K is also involved in bone health.

Which fat soluble vitamins are most toxic if consumed in excess amounts over long periods of time? a. Vitamins D and K b. Vitamins A and E c. Vitamins A and D d. Vitamins D and K

Vitamins A and D

What are the major roles of vitamins in the body?

Vitamins are a group of substances that are essential for normal cell function, growth, and development.

KEY CONCEPT 1

Vitamins are organic substances needed in minuscule amounts for various roles in regulation of body processes. Two classes of vitamins have been classified: fat-soluble vitamins (A, D, E and K) and water-soluble vitamins (the B vitamins and vitamin C). Fat-soluble vitamins, which are stored in the liver and fatty tissues of the body, are generally excreted much more slowly than water-soluble vitamins. Because they are stored for long periods, fat-soluble vitamins generally pose a greater risk of toxicity than water-soluble vitamins when consumed in excess.

Osteoporosis

a bone disease characterized by a decrease in bone mineral density and the appearance of small holes in bones resulting from the loss of minerals

Rickets

a bone disease in children that results from vitamin D deficiency

Retinol-Binding Protein (RBP)

a carrier protein that binds to retinol and transports it in the bloodstream from the liver to destination cells

Bleaching Process

a complex light-stimulated reaction in which rod cells lose color as rhodopsin is split into Vitamin A (retinal) and opsin

Xerophthalmia

a condition caused by vitamin a deficiency that dries the cornea and mucus membranes of the eye

Osteomalacia

a disease in adults that results from vitamin D deficiency; it is marked by softening of the bones, leading to bending of the spine, bowing of the legs, and increased risk for fractures

Stem Cells

a formative cell whose daughter cells can differentiate into other cell types

Carotenoids

a group of yellow, orange, and red pigments in plants, including foods; many of these compounds are precursors of vitamin A

Carotenodermia

a harmless yellow-orange cast to the skin due to high levels of carotenoids in the bloodstream resulting from consumption of extremely large amounts of carotenoid-rich foods, such as carrot juice

Parathyroid Hormone

a hormone secreted by the parathyroid glands in response to low blood calcium; it stimulates calcium release from bone and calcium absorption by the intestines, while decreasing calcium excretion by the kidneys; it acts in conjunction with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] to raise blood calcium; also called parathormone

Calcitonin

a hormone secreted by the thyroid gland in response to elevated blood calcium; it stimulates calcium deposition in bone and calcium excretion by the kidneys; thus reducing blood calcium

Retina

a paper-thin tissue that lines the back of the eye and contains cells called rods and cones

Opsin

a protein that combines with retinal to form rhodopsin in rod cells

Glutathione

a tripeptide of glycine, cysteine, and glutamic acid that is involved in production of cells from oxidative damage

Retinol Activity Equivalents (REAs)

a unit of measurement of the vitamin A content of a food; one REA equals one microgram of retinol

Which of the following organs is responsible for the synthesis of vitamin D? a. skin b. liver c. kidneys d. all of the above

all of the above

International Units (IUs)

an outdated system of measuring vitamin activity; this measurement does not consider differences in bioavailability

Teratogen

any substance that causes birth defects

Osteoblasts

bone cells that promote bone deposition and growth

Osteoclasts

bone cells that promote bone resorption and calcium mobilization

Provitamin A

carotenoid precursors of vitamin A in foods of plant origin, primarily deeply colored fruits and vegetables

Epithelial Tissues

closely packed layers of epithelial cells that cover the body and line its cavities

Iodopsin

color-sensitive pigment molecules in cone cells that consist of otospin-like proteins combined with retinal

Retinoids

compounds in foods that have chemical structures similar to vitamin A; retinoids include the active forms of vitamin A (retinol, retinal, and retinoic acid) and the main storage forms of retinol (retinyl esters)

Hyperkeratosis

excessive accumulation of the protein keratin that produces rough and bumpy skin, most commonly affecting the palms and soles, as well as flexure areas (elbows, knees, wrists, ankles)

Which of the following is NOT a good source of vitamin K? a. exposure to sunlight b. spinach c. soybean oil d. intestinal bacteria

exposure to sunlight

Menaquinones

forms of vitamin K that comes from animal sources; also produced by intestinal bacteria; also known as vitamin K2

Rhodopsin

found in rod cells, a light-sensitive pigment molecule that consists of a protein called opsin combined with retinal

Tocotrienols

four comppounds (alpha, beta, gamma, delta) chemically related to tocopherols; the tocotrienols and tocopherols are collectively known as vitamin E

Provitamins

inactive forms of vitamins that the body can convert into active usable forms; also referred to as vitamin precursors

Vitamin K deficiencies are rare because: a. absorption of vitamin K from dietary sources is close of 100%. b. most foods contain some vitamin K. c. intestinal bacteria produce vitamin K. d. the majority of people take vitamin K supplements.

intestinal bacteria produce vitamin K

Cell Differentiation

is the process by which an immature cell develops into a specific type of mature cell

Cones

light-sensitive cells in the retina that are sensitive to bright light and translate it into color images

Rods

light-sensitive cells in the retina that react to dim light and transmit black-and-white images

Goblet Cells

one of the many types of specialized cells that produce and secrete mucus; these cells are found in the stomach, intestines, and portions of the respiratory tract

Antirachitic

pertaining to activities of an agent used to treat rickets

Lipid Peroxidation

production of unstable, highly-reactive lipid molecules that contain excess amounts of oxygen

Vitamin Precursors

provitamins

Preformed Vitamin A

retinyl esters, the main storage form of vitamin A; about 90% of dietary retinol is in the form of esters, mostly found in foods from animal sources

Retinoic Acid

the acid form of vitamin A; one of the retinoids; formed from the retinal but not interconvertible; helps growth, cell differentiation, and the immune system; does not have a role in vision or reproduction

1,25-dihydroxyvitamin D3 [1,25(OH)2D3]

the active form of vitamin D; it is an important regulator of blood calcium levels

Retinol

the alcohol form of vitamin A; one of the retinoids; thought to be the main physiologically active form of vitamin A; interconvertible with retinal

Retinal

the aldehyde form of vitamin A; one of the retinoids; the active form of vitamin A in the photoreceptors of the retina; interconvertible with retinol

Hemolysis

the breakdown of red blood cells that usually occurs at the end of the red blood cell's normal life span; this process releases hemoglobin

Tocopherol

the chemical name for vitamin E; there are four tocopherols (alpha, beta, gamma, delta), but only alpha tocopherol is active in the body

Phylloquinine

the form of vitamin K that comes from plant sources; also known as vitamin K1

Night Blindness

the inability of the eyes to adjust to dim light or to regain vision quickly after exposure to a flash of bright light

Retinyl Esters

the main storage form of vitamin A; one of the retinoids; retinyl esters are retinol combined with fatty acids, usually palmitic acid; also known as preformed vitamin A

Epithelial Cells

the millions of cells that line and protect the external and internal surfaces of the body; epithelial cells from epithelial tissue such as skin and mucus membranes

Dark Adaptation

the process that increases the rhodopsin concentration in the eyes, allowing them to detect images in the dark better

Cornea

the transparent outer surface of the eye

Drying of the cornea due to vitamin A deficiency is called a. apnea b. dysphagia c. xerophthalmia d. cachexia

xerophthalmia