Wardlaw's Perspectives in Nutrition Ch. 12

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41 Terms

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Define Vitamins and list general characteristics

Vitamins are essential, organic substances needed in small amounts in the diet. They can not be synthesized in the body at all or only in insufficient quantities. Health declines when the substance is not consumed. deficiency can be alleviated by increased intakes if not advanced.

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Fat Soluble Vitamins

A, D, E, K

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Water Soluble Vitamins

B vitamins and C.

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Vitamin Absorption rates

Fat Soluble Vitamins: 40-90%; Water Soluble vitamins: 90-100%. If malabsorption occurs due to GI tract issues more of the vitamin must be consumed.

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Fat Soluble Vitamin Transport

Once absorbed, packaged for transport through the lymphatic system, mainly by way of chylomicrons and other lipoproteins. Once it gets to the liver any remnant fat sol vitamins are repackaged with new proteins for transport in the blood or stored in the adipose tissue or liver.

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Water Soluble Vitamin Transport

delivered directly to the blood stream and distributed throughout the body.

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Dietary Sources of Vitamin A retinoids

Liver, fish oils, fortified dairy products including margarine, and eggs

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Vitamin A retinoids

Active form of Vitamin A. Retinal, retinol and retinoic acid can interconvert.

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Vitamin A Carotenoids

Not Active. Provitamins that can be converted to Vitamin A when the body knows you need it. Stored in subcutaneous fat.

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Dietary Sources of Vitamin A Carotenoids

dark green, and yellow orange fruits and vegetables such as carrots, spinach, winter squash, sweet potatoes, broccoli, mangoes, cantaloupe, peaches and apricots.

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Most active form of carotenoids

Betacarotene. In supplements, most should be in carotenoid form.

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Functions of Retinoid Vitamin A

Growth and Development: embryonic development, epithelial cells, mucous forming cells, eyes, limbs, cardio and nervous systems; Cell differentiation: triggers interaction between DNA and mRNA to get code for protein; Vision: in retina to turn visual light into nerve signals. Immune functions: healthy epithelial to block and protect from bacteria.

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Functions of Carotenoid Vitamin A

Betacarotene is an antioxidant. In the provitamin A form it has an extra electron to donate to free radicals to stop them from scavenging. Can decrease risk of some cancers, cardiovascular disease, and eye disease like macular degeneration.

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Vit A absorption, transport, storage, excretion

Packaged with chylomicrons and transported via the lymphatic system. 90% stored in the liver. Transported after the liver. Retinoids are bound to retinol binding protein, caratenoids are carried by VLDL and go to fat cells with VLDL. Excreted in small amounts in urine.

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Retina

a form of vitamin A. Transretinol is a good trans. Need the cis to go straight to a trans form so can send message to the brain about what you see. Without retinol night blindness can set in. Retina needs to be regenerated in early stages of deficiency. If not corrected cornea can dry out.

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Rhodopsin

Visual pigment. Concentrations increase and decrease to allow for dark and light conditions. If Vitamin A pools become depleted the process of dark adaptation in impaired making it difficult to see in dim light, known as night blindness.

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Vitamin A deficiency disease

Rare in North America but major problem in developing countries. Night Blindness, Xerophthalmia: irreversible blindness due to drying of cornea, Follicular hyperkeratosis: keratin accumulates around follicule. dry skin

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Vitamin A toxicity

Hypervitaminosis A: Acute: 1 large dose or large doses over several days. GI tract upset, headache, blurred vision, poor muscle coordination. Chronic: joint pain, loss of appetite, skin disorders, headache, reduced bone mineral, liver damage, double vision, hemorrhage, coma. Teratogenic: can cause birth defects or spontaneous abortion.

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Synthetic Vitamin A used in dermatology

all-trans-reinoic acid; topical tretinoin A or Retin A. and 13-cis-retinoic; oral isotretinoin or Accutane.

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Food sources of Vitamin D

Fatty fish, cod liver oil, fortified milk, and some fortified breakfast cereals, egg beaters

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Vitamin D formation in the skin

from cholesterol. Sunlight changes 7-dehydrocholesterol to cholecalciferol. It travels to liver and then kidneys where converted to bioactive form - calcitriol. Liver or kidney disease can affect ability to activate it.

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Factors affecting Vit D synthesis

Age: kidneys don't function as well; Darker skin: blocks light; smog, clouds, tall buildings, sublock: blocking UV rays. Geographic location, time of day, the season.

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Is Vitamin D a vitamin

It is a conditional vitamin or prohormone. As a hormone it is made one place and goes where needed in the body. Goes to the intestine to help absorb calcium.

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Vitamin D absorption, transport, storage and excretion

Absorbed via micelles and transported chylomicrons in the lymph system. Bound to protein in the blood. Synthesis of the active form is regulated by parathyroid hormone and kidneys. Stored in adipose tissue. Excreted in bile and small amount in urine.

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Functions of Vitamin D

Calcitrol is the active form. Calcium and Phosphorous homeostasis. Aids in increasing absorption of Ca and P. When blood calcium levels too low kidneys active D to help intestines absorb. Aids in releasing calcium and P from bone when levels in blood to low. cell cycle regulation

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Additional functions of Vitamin D

Bone health, regulates immune function and secretion of several hormones, may reduce risk of certain types of infections and autoimmune diseases like multiple sclerosis, and protect from diabetes, hypertension, dementia, and certain cancers.

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Vitamin D deficiency diseases

Children: Rickets, bones weaken and bow,usually due to lack in diet. Adults: Osteomalacia, soft bones. Most likely from kidney or liver disease or intestinal impairments.

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Vitamin D toxicity

Does not occur from sunlight or dietary sources. Can occur with supplementation. Upper limit 4000IU. can cause over absorption of calcium.

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Vitamin E

8 compounds. 4 tocopherols, 4 tocotrienols. Most active tocopherol is alpha. It is one of the most powerful antioxidants because it sits in the cell membrane and can protect the integrity of the cell.

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Dietary sources of Vitamin E

Plant oils like canola, safflower, sunflower; wheat germ, avocado, almonds peanuts, and sunflower seeds.

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Vitamin E Absorption, Transport, Storage and Excretion

Absorption depends on amount consumed. Occurs by passive diffusion into micelles and then chylomicrons. Liver repackages with lipoproteins for transport. 90 % stored in adipose tissue. Excretion: bile, urine, skin

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Vitamin E functions

Antioxidant: stops lipid peroxidation, or chain reaction, caused by free radicals by donating extra electron. Vitamin C can give it a new one to regenerate it.

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Antioxidant compounds that work with Vitamin E

Glutathione peroxidase: enzyme dependent onSelenium. Superoxidase dismutase: enzyme dependent on copper, zinc and maganese. Catalse: enzyme heme iron dependent.

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Vitamin E deficiency diseases

Fairly rare. Hemolytic anemia. Preterm infants and smokers most susceptible, immune function impairment and neurological changes.

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Vitamin E toxicity

Can interfere with Vitamin K and cause hemorrhaging. Don't take before surgery. Upper limit: 1000mg from natural sources, 1100IU from synthetic.

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Forms of Vitamin K

Menaquinones: synthesized by bacteria in colon, found in fish oils and meats. Phylloquinones: from plants. Most biologically active form. green leafy vegies,

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Food sources of vitamin K

Most biologically active are plant forms. K is for kale. Dark green leafy vegetables, broccoli, peas and green beans.

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Vitamin K Absorption, Transport, Storage and Excretion

Absorbed in the small intestines via chylomicrons in lymphatic system. Transported via lipoproteins. Stored in the liver or in cells throughout the body. Excreted primarily in bile; small amount in urine.

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Vitamin K functions

K as in Clot. Synthesis of clotting factors both intrinsically and extrinsically by imparting calcium binding to proteins and in conversion of prethrombin to prothrombin, an active clotting factor; bone metabolism; k dependent Gla proteins are synthesized in bone.

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Vitamin K Deficiency and toxicity

Deficiency is rare. Newborns haven't had time to synthesize, long term antibiotic use that damages good bugs, or fat malabsorption diseases. NO Upper Limit. Excessive A can interfere intestinal absorption, Vitamin E can decrease clotting factors.

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Fat mal-absorption diseases

Chron's disease. Cystic Fibrosis.