Sources of Vitamin

The major dietary sources for preformed vitamin A are vertebrate animal products that are rich in vitamin A esters (liver, kidney, oil, dairy products, and eggs). Liver and oil, particularly from fish, are the major dietary sources of preformed vitamin A. Levels in milk and eggs depend on dietary retinoid and carotenoid intake. Freshwater fish are a source of vitamin A2 (3,4-dehydroretinol), which shows reduced vitamin A activity. Levels of retinal in food are very low, whereas retinoic acid has not been found. 

Plants are the major source for dietary provitamin A. As mammals and humans cannot synthesize carotenoids, dietary provitamin A is obtained from plant sources that contain carotenoids having 2,6,6-trimethyl-l-cyclohexen-l-yl rings, such as P-carotene. More than 600 carotenoids have been identified in plants and algae, which together biosynthesize about 0.1 billion tons of carotenoids each year. However, only about ten carotenoids, including P-carotene, are nutritionally significant members of the provitamin A class that can be oxidatively metabolized to retinal in mammals and humans by such organs as the intestine, liver, and kidney and then reduced to retinol. 

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The sohd product and its aqueous solutions are mildly acidic and irritate the skin, eyes, and mucous membranes. The soHd material when moist generates the pungent, irritating odor of sulfur dioxide. Food-grade sodium metabisulfite is permitted ia those foods that are not recognized as sources of vitamin B, with which sulfur dioxide reacts (316) (see Vitamins,THIAMINE). 

Rich sources of vitamin A include dairy products such as milk cheese, butter, and ice cream. Eggs as well as internal organs such as the Hver, kidney, and heart also represent good sources. In addition, fish such as herring, sardines, and tuna, and in particular the Hver oil from certain marine organisms, are excellent sources. Because the vitamin A in these food products is derived from dietary carotenoids, vitamin A content can vary considerably. Variation of vitamin A content in food can also result from food processing and in particular, oxidation processes (8). 

Vitamin D [1406-12-2] is a material that is formed ia the skin of animals upon kradiation by sunlight and serves as a precursor for metaboUtes that control the animal s calcium homeostasis and act ki other hormonal functions. A deficiency of vitamin D can cause rickets, as weU as other disease states. This tendency can be a problem wherever animals, including humans, especially kifants and children, receive an kiadequate amount of sunshine. The latter phenomenon became prevalent with the advent of the kidustrial revolution, and efforts to cute rickets resulted ki the development of commercial sources of vitamin D for supplementation of the diet of Hvestock, pets, and humans. 

Vitamin D is available ia a variety of forms. Cod Hver oil and percomorph Hver oil historically were good sources of vitamin D. Recent cost iacreases of these materials have caused a decline ia their market position. Cod Hver oil sold for 0.40—0.45/L ia 1970 and as high as 1.45/L ia 1979 and 3.43/L ia 1996. The prices of the cod Hver oils and of vitamin D2 and vitamin D from 1955 to 1995 are shown ia Table 12. 

Vitamin K is typically found ia green, leafy vegetables such as cabbage, broccoH, and spiaach at levels of 95—200 p.g/100 g of fresh vegetables. Cauhflowet at a level of 136 p.g/100 g also represents an excellent source of dietary vitamin K. Additionally, animal sources such as fiver and eggs provide good sources of vitamin K (11). 

An alkene, sometimes caJled an olefin, is a hydrocarbon that contains a carbon-carbon double bond. Alkenes occur abundantly in nature. Ethylene, for instance, is a plant hormone that induces ripening in fruit, and o-pinene is the major component of turpentine. Life itself would be impossible without such alkenes as /3-carotene, a compound that contains 11 double bonds. An orange pigment responsible for the color of carrots, /3-carotene is a valuable dietary source of vitamin A and is thought to offer some protection against certain types of cancer. 

Carotene, a yellow food-coloring agent and dietary source of vitamin A, can be prepared by a double Wittig reaction between 2 equivalents of jS-ionvlideneacetaldehyde and a diylide. Show the structure of the /0-carotene product. 

Terpenoids are classified according to the number of five-carbon multiples they contain. Monoterpenoids contain 10 carbons and are derived from two isopentenyl diphosphates, sesquiterpenoids contain 15 carbons and are derived from three isopentenyl diphosphates, diterpenoids contain 20 carbons and are derived from four isopentenyl diphosphates, and so on, up to triterpenoids (C30) and tetraterpenoids (C40). Monoterpenoids and sesquiterpenoids are found primarily in plants, bacteria, and fungi, but the higher terpenoids occur in both plants and animals. The triterpenoid lanosterol, for example, is the precursor from which steroid hormones are made, and the tetraterpenoid /3-carotene is a dietary source of vitamin A (Figure 27.6). 

Plants contain to some extent less bioavailable forms of vitamin B6, e.g., glycosylates, or biologically inactive metabolites, e.g., e-pyridoxin-lysin-complexes. In addition, the release of vitamin B6 from foods rich in fiber is assumed to be delayed. The bioavailability of vitamin B6 from animal-derived foods is therefore overall higher than from plant-derived foods. Good dietary sources of vitamin B6 include chicken, fish, pork, beans, and pulses [1]. 

Vitamin Bg is also found in a wide variety of food sources, It may be impossible to ask the patient to avoid these food sources entirely, but your patient may need to limit or decrease such intake to enhance or maintain the drug s effectiveness. Use the list below to teach your patient about possible food sources of vitamin Bg. 

In animals, the major function of carotenoids is as a precursor to the formation of vitamin A. Carotenoids with provitamin A activity are essential components of the human diet, and there is considerable evidence that they are absorbed through the diet and often metabohzed into other compounds. Beyond their important role as a source of vitamin A for humans, dietary carotenoids, including those that are not provitamin A carotenoids, have been implicated as protecting against certain forms of cancer and cardiovascular disease. ... 

Vitamin D is often combined in varying amounts with calcium salts. A multiple vitamin is another good source of vitamin D. Most multivitamins contain 400 IU per tablet. Vitamin D is also available as a single entity. Doses above 2000 IU/day should be avoided owing to the risk of hypercalciuria and hypercalcemia. Ergocalciferol (vitamin D2) and... 

Determine average calcium intake from diet (see Table 53-5) and supplements (see Table 53-6). Compare with age-adjusted recommendations (see Table 53—4). Evaluate the patient s sources of vitamin D. 

Elderberries are considered excellent sources of vitamins A and C. The high potassium phosphate content in the flowers may be part of what helps elder calm the nerves. The potassium sulfate present in the flowers, leaves and bark may be a factor in why elder helps relieve excess mucus. 

Mango fruit is a rich source of vitamin C and carotenoids, some of which function as provitamin A (Siddappa and Bhatia 1954 Thomas 1975, Yahia and others... 

Fresh peppers are excellent sources of vitamins A and C, as well as neutral and acidic phenolic compounds (Howard and others 2000). Levels of these can vary by genotype and maturity and are influenced by growing conditions and processing (Mejia and others 1988 Howard and others 1994 Lee and others 1995 Daood and others 1996 Simmone and others 1997 Osuna-Garcia and others 1998 Markus and others 1999 Howard and others 2000). Peppers have been reported to be rich in the provitamin A carotenoids (3-carotene, a-carotene, and (3-cryptoxanthin (Minguez-Mosquera and Hornero-Mendez 1994 Markus and others 1999), as well as xanthophylls (Davies and others 1970 Markus and others 1999). Bell peppers have been shown to exert low antioxidant activity (Al-Saikhan and others 1995 Cao and others 1996 Vinson and others 1998) or may even act as pro-oxidants (Gazzani and others 1998). 

Vitamin A deficiency affects more than 100 million children around the world (Miller and others 2002) and thus remains an important public health problem in many countries. Vitamin A is essential for vision, reproduction, growth, immune function, and general health of humans (van Lieshout and others 2001). The major sources of vitamin A in the human diet are retinyl esters (preformed vitamin A) found in foods of animal origin and provitamin A carotenoids from fruits and vegetables. Unfortunately, foods containing preformed vitamin A (meat, milk, eggs, etc.) are frequently too expensive for some economically deprived developing countries, and therefore dietary carotenoids are the main source of vitamin A in these countries. 

Rankins J, Sathe SK and Spicer MT. 2008. Solar drying of mangoes preservation of an important source of vitamin A in French-speaking West Africa. J Am Diet Assoc 108 986-990. 

Dietary /1-carotene, a nutritionally important source of vitamin A, exhibits a protective effect against cancer risk31,32. The deuteriated compound, 10,10, 19,19,19,19, 19, 19 -2H8-/S-carotene, 32, has been obtained33 by double condensation of the C-15 Wittig salt 33 with the symmetrical C10 dial 2,7-dimethyl-2,4,6-octatrienedial, 34 (equation 13) for the study of /J-carotene metabolism in humans. 

In turkeys, natural diets with as much as 800 mg Cu/kg ration have no adverse effects on growth or survival. But purified diets are toxic to turkeys in three weeks, and purified diets that contain as little as 50 mg Cu/kg ration produce adverse effects (Waibel et al. 1964). Turkeys fed purified diets with supplemented copper show a dose-dependent increase in mortality and decrease in growth these effects are attributed to a copper-accelerated dietary deterioration (Supplee 1964). Turkey growth and survival are acceptable when fed purified diets supplemented with as much as 800 mg Cu/kg ration provided that effective levels of added antioxidant (0.02% ethoxyquin) and stabilized sources of Vitamins A and D are present (Supplee 1964). 

The active vitamins are produced by conversion of provitamins by ultraviolet light. Ergosterol, a yeast sterol, is converted to its active form, ergocalciferol (vitamin D2), and 7-dehydrocholesterol, which is found in many natural foods and is also synthesized in man, is converted to cholecalciferol (vitamin D3). Fish liver oils are virtually the only source of vitamin D3 in nature. The most active form of vitamin D3 is 1,25-dihydroxycholecalciferol and this is produced by the hydroxylation of cholecalciferol at position 25 in the liver and then at position 1 in the kidney. 

The RDI/RDA for vitamin A for adult males is 900 micrograms/day (0.9 mg/day) and for adult females 700 micrograms/day (0.7 mg/day). Children require significantly less and lactating women significantly more. There are a number of excellent sources of vitamin A fish, dairy products, liver, leafy vegetables, and dark-colored fruits. 

The RDl for vitamin D is 5 micrograms/day for men and women, adults and children, a value independent of state of pregnancy or lactation. Middle-aged adults, ages 50-70 years old, require 10 micrograms/day and for those over 70 years old the valne goes np to 15 micrograms/day. Fish oils, the flesh of fatty fish, and fortified milk and cereals are excellent sources of vitamin D. Of course, vitamin D is also present in most multivitamin piUs. 

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