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SU NSD 225 - Vitamins A,D

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1NSD 225 1st Edition Lecture 1Fat Soluble Vitamins A,D,E,K "Vitamin supplements unnecessary" USA Surgeon General What are vitamins?- Vitamins are essential (however you can make some in the body)- Needed in small amounts for normal function, growth, maintenance.- They are organic (contain carbon)- Fat soluble vitamins dissolve in fat and not very much in water.- Most scientists state that all vitamins have b een discovered- Except for vitamin K, the fat soluble vitamins are stored not excreted from the body- Since fat soluble vitamins are stored, too much can cause toxicity. VITAMIN A( Retinol) and carotenoidsa. There are many chemical forms of each vitamin. There are 2 SOURCES of this vitamin: the active pre formed vitamin A found only in animal sources and the inactive provitamin (carotene especially betacarotene) found in plants. The carotenes are converted to vit A during absorption in the intestinal wall. b. This vit can be destroyed by oxidation when exposed to air at warm temperatures or when exposed to ultraviolet light. Vit A can, therefore be destroyed if the fat or oil becomes rancid (tastes and smells terrible). Since this vitamin is FAT soluble, little is lost in cooking water.Functions a. Growth all vitamins are needed for growth. b. Maintenance of visual purple in the eye (responsible for dim light vision). If vit A is low, vision in dim light is not good called night blindness. c. Necessary for normal reproduction d. Maintenance of epithelial cells in the linings of all openings into the body. If you are low in vit A, these tissues dry up leading to infections.e. Anti-cancer effect of carotenes is controversial.Absorption, metabolism and storage. a. Absorption of vit A is decreased by any malabsorption disease, liver disease, diarrhea, mineral oil. Only about one sixth of the carotene in food can be utilized as vit A in the body. Most (95%) of vit A is stored in liver (rest in fat, lungs and kidneys) but carotene is not stored in the liver. An adult probably has enough vit A stored in liver for one year.b. Carotenes and vit A absorption is reduced when diets contain little fat. c. Deficiencies of protein, vit E, iron, and zinc also reduce vit A utilization a. Recommended Dietary Allowances are given in RE (retinol equivalents to include vit A and carotene) while the labeling US RDA uses IU (International Units). b. RDA for males 19 and older is 1000 RE (5000 IU); for females the RDA is 800 RE (4000 IU). During pregnancy and lactation, the RDA is increased.Deficiencies a. Growth ceases when reserves of vit A are depleted in liver2b. Slower dark adaptation and eventual night blindness. c. Xerophthalmia drying of conjunctiva, spreads to cornea and blindness results. In other countries, many children become blind because of vit A deficiency when a years supply of vit A only costsa few cents. Food sources are usually available but people are nutritionally uneducated. Deficiency in USA is rare. Toxicity a. High intakes of vit A can be toxic causing headaches, hair falling out, bone and joint pains, bone decalcification, birth defects, skin lesions, liver damage or even death (50,000 IU or greater taken over a month for adults and 20,000 for infants and children can lead to chronic toxicity). b. Carotene overdosing does not cause toxic reactions only yellow skin. Food sources a. Animal sources liver, cheese, egg yolk, whole milk or skim milk with A added. b. Plant sources spinach, carrots, broccoli, peas, apricots, yellow fruit. VITAMIN D Introductiona. Vitamin D is unusual because it is a steroid, it is converted to a hormonal form, and it is not a dietary requirement when you are exposed to sufficient amounts of ultraviolet light from the sun.b. There are at least 20 different forms of the vitamin.c. Major forms are vit D3 formed by UV light acting on skin and vit D2 made by UV acting on plant ergosterol.Functionsa. helps calcify bone. Regulates the intestinal absorption of calcium (Ca) and phosphorus (P).b. regulates the renal excretion of Ca and Pc. regulates the mobilization of Ca and P from the bone.Deficiencya. In children called rickets, defective bone formation caused by inadequate deposition of Ca and P in bone and bones bow out or in, get abnormal swellings on ribs, soft spot of skull does not close properly, eruption of teeth delayed,& poor growth.b. Osteomalacia (adult rickets) prevalent in women depleted of calcium by numerous pregnancies, prolonged nursing, low calcium diets, and long periods out of the sun.Requirementsa. RDA for infants (over 6 months), children, adolescents, men and women up to age 24, pregnant and breast-feeding women is 10 micrograms or 400 IU. The NAS-RDA is given in micrograms. b. The RDA for age 25 on (unless pregnant or lactating) 200 IU (5 ug) since requirements can be satisfied by exposure to sunlight (lots of luck in Syracuse). It is difficult for UV light to penetrate glass, smog, clothes.Sources of vit Da. Most natural foods are poor and unreliable sources of preformed vit D. Major food sources are animal: liver, eggs, salmon, butter and fish-liver oils b. Cod liver oil is a good source but should be considered a supplement since it contains so much ofthe vitamin.c. Milk is fortified with 400 IU of vit D per quart.d. Infants should have vit D supplements.3Toxicitya. Hypervitaminosis D (excess intake of vit D) provides no benefits and can be harmful. Toxic symptoms occur NOT from food but too many supplements since D is stored in liver.b. Excess causes nausea, headaches, excessive urination, weakness, fatigue, anemia, kidney damage, calcium deposits in soft tissue, injury to artery walls, high blood pressure, elevated blood cholesterol, depression.c. Vit D is the most toxic fat soluble vitamin. Consumption of as little as 45 ug (1800 IU) per day has been associated with signs of hypervitaminosis D in young children. Since the toxic level of vit D mayin some cases be only 5 times the RDA, and sunlight stimulated production of the vitamin is active throughout the warm months, dietary supplements may be detrimental for the normal child or adult who drinks at least 2 glasses of vit D-fortified milk per


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