Vitamin recommended daily allowance

Of the water-soluble vitamins, intakes of nicotinic acid [59-67-6] on the order of 10 to 30 times the recommended daily allowance (RE)A) have been shown to cause flushing, headache, nausea, and moderate lowering of semm cholesterol with concurrent increases in semm glucose. Toxic levels of foHc acid [59-30-3] are ca 20 mg/d in infants, and probably approach 400 mg/d in adults. The body seems able to tolerate very large intakes of ascorbic acid [50-81-7] (vitamin C) without iH effect, but levels in excess of 9 g/d have been reported to cause increases in urinary oxaHc acid excretion. Urinary and blood uric acid also rise as a result of high intakes of ascorbic acid, and these factors may increase the tendency for formation of kidney or bladder stones. AH other water-soluble vitamins possess an even wider margin of safety and present no practical problem (82). 

The recommended daily allowance for vitamin E ranges from 10 international units (1 lU = 1 mg all-rac-prevent vitamin E deficiency in humans. High levels enhance immune responses in both animals and humans. Requirements for animals vary from 3 USP units /kg diet for hamsters to 70 lU /kg diet for cats (13). The complete metaboHsm of vitamin E in animals or humans is not known. The primary excreted breakdown products of a-tocopherol in the body are gluconurides of tocopheronic acid (27) (Eig. 6). These are derived from the primary metaboUte a-tocopheryl quinone (9) (see Eig. 2) (44,45). 

C03-0076. The U.S. Recommended Daily Allowances (RDAs) of several vitamins follow. In each case,... 

Coenzyme Q10 is an antioxidant essential for mitochondrial function. A dose of 1200 mg daily was associated with a slower decline in UPDRS scores than patients not receiving coenzyme Q10. Lower doses were no better than placebo, but the drug continues to be studied in doses up to 2400 mg daily. Many formulations contain vitamin E, and patients should not exceed recommended daily allowances of this vitamin, as bleeding times may be prolonged.42,43... 

Human adult needs for this vitamin (vitamins) are not established quantitatively. Most human studies have involved preventing or curing rickets in infants or children, and the recommended daily allowance of the Food and Nutrition Board is 400 units. Even among "normal" children, however, there is evidence of variation in vitamin D needs. According to Spies and Butt,38 "The activated milk does not exhibit sufficient potency in vitamin D for the prevention of rickets in cases in which a susceptibility exists" (italics added). They note that "susceptible" children may require 5,000 to 10,000 units daily. 

The figure comes from a series of reports issued by the Institute of Medicine over the past decade. The experts who authored these reports revisited the question of recommended daily allowances and other measures of nutrient adequacy, and made recommendations regarding macronutrients (proteins, carbohydrates, fats and oils) and for micronutrients (vitamins and minerals). The Institute has had a long history of developing recommended intake levels, but in the recent... 

Vitamin Active compound Sources Recommended daily allowances... 

Scurvy remains a problem today. The malady is still encountered not only in remote regions where nutritious food is scarce but, surprisingly, on U.S. college campuses. The only vegetables consumed by some students are those in tossed salads, and days go by without these young adults consuming fruit. A 1998 study of 230 students at Arizona State University revealed that 10% had serious vitamin C deficiencies, and 2 students had vitamin C levels so low that they probably had scurvy. Only half the students in the study consumed the recommended daily allowance of vitamin C. 

Although there is much controversy about the exact requirement, the adult Recommended Daily Allowance of vitamin C is 70 mg per day. Some scientists and physicians have suggested doses up to 1 to 3 grams per day in order to help resist the common cold. Deficiency of vitamin C results in swollen joints, abnormal development and maintenance of tissue structures, and eventually scurvy. 

Of the water-soluble vitamins, intakes of nicotinic acid on the order of 10 to 30 times the recommended daily allowance (RDA) have been shown to cause Hushing, headache, nausea, and moderate lowering ol serum... 

If vitamins and/or minerals are claimed they must be declared both quantitatively and as a percentage of the recommended daily allowance specified in the regulations. 

It is found in citrus fruits and brighdy coloured vegetables, such as peppers and broccoli. Many people take vitamin C supplements, which are readily available from supermarkets and pharmacies (Figure 15.14). Although vitamin C is destroyed by exposure to air and heat, the average person usually reaches the recommended daily allowance of 60 mg through food. 

Many vegetables and fruits, other than citrus, contain ascorbic acid. It was estimated that citrus fruits and tomatoes provided only 18% of the total vitamin C intake in the American diet during the decade of 1910. These two fruits supplied 41% of vitamin C in 1956-58 (6j. Today orange juice alone provides nearly 60% of the U.S. Recommended Daily Allowance (U.S. RDA) of vitamin C in the American diet (7). 

The lipophilic vitamin A is a cyclic polyene alcohol (Figure 29.4). The recommended daily allowance is 700 to 900 /u. g, increasing to 1300 /xg during lactation (1 /xg of vitamin A equals 12 /xg of p-carotcnc or 24 jig of other provitamin A carotenoids).26,71... 

Vitamin D regulates calcium and phosphorus absorption and deposition and serum alkaline phosphatase levels. The recommended daily allowance is 5 /xg, increasing to 10 to 15 /xg in older age.109 Vitamin D3 is synthesized under UVB irradiation in the skin where it is stored and released into the circulation in a complex with the vitamin D binding protein. In liver it is hydroxylated to 25(OH)-cholecalciferol, the hormonal precursor, followed by another hydroxylation step in the... 

Vitamin K is essential for the synthesis of coagulation factors II, VII, IX, X, and proteins C and S. About half of the daily requirement is synthesized by the gastrointestinal flora. Deficiency leads to an impairment in the coagulation cascade, clinically presenting as purpura, ecchymoses, and hemorrhage anywhere in the body.29 The recommended daily allowance is 90 fig for females and 120 fig for males.71... 

Perhaps the most controversial aspects of vitamins is whether we need to take them and, if so, at what dose Tables 16.5 and 16.6 show the recommended daily allowances (RDAs) for fat- and water-soluble vitamins, respectively. 

Vitamin A levels are frequently expressed in International Units (IU), although this unit is officially no longer accepted. One IU equals 0.344 pg of crystalline vitamin A acetate, or 0.300 pg vitamin A alcohol, or 0.600 pg P-carotene. The recommended daily allowance (RDA) of vitamin A of the National Research Council Food and Nutrition Board is 5000 IU for an adult. Other sources quote the human requirement at about 1 pg/day. Conditions of rapid growth, pregnancy, or lactation increase the need for vitamin A. 

A priori, the best means of determining vitamin C requirement would seem to be determination of the total body pool and its fractional rate of loss or catabolism. An appropriate intake would then be that to replace losses and maintain the body pool. Clinical signs of scurvy are seen when the total body pool of ascorbate is below 1.7 mmol (300 mg). The pool increases with intake, reaching a maximum of about 8.5 mmol (1,500 mg) in adults -114 /rmol (20 mg) per kg of body weight. The fractional turnover rate of ascorbate is 3% to 4% daily, suggesting a need for 45 to 60 mg per day for replacement. The basis for the 1989 U.S. Recommended Daily Allowance (RDA) of 60 mg (National Research Council, 1989) was the observed mean fractional turnover rate of 3.2% of a body pool of 20 mg per kg of body weight per day, with allowances for incomplete absorption of dietary ascorbate and individual variation. 

Although absolute vitamin deficiency (e.g., beriberi, pellagra, scurvy) may be relatively rare in developed coiuitries, malabsorption, poor nutritional habits, or other fectors may lead to such situations. In feet, many Americans may be vitamin deficient based on recommended daily allowance or recommended daily intake.The interested reader is referred to the U.S. Department of Agriculture fiaod and nutrition information center fiar recommended daily aUonrance and recommended daily intake (http //fiiic.nal.usda.gov/).These are also summarized in Table 17-1 as DRI ralues. 

NAD% the oxidized form of NADH, is a biological oxidizing agent capable of oxidizing alcohols to carbonyl compounds (it forms NADH in the process). NAD is synthesized from the vitamin niacin, which can be obtained from soybeans among other dietary sources. Breakfast cereals are fortified with niacin to help people consume their recommended daily allowance of this B vitamin. 

Nutrition is an important part of ready-to-eat cereal. To make cereal healthier, mai r nutrients are added. Unfortunately, nutrients degrade over time, making it necessary to add more than the declared amount to assure enough for the life of the cereal. Vitamin X is declared at a level of 20% of the Recommended Daily Allowance per sewing size (serving size = 30 g). The Recommended Daily Allowance is 6500 lU (1.7 x 10 lU = 1 g). It has been formd that the degradation of this nutrient is first-orderin the amount of nutrients. Accelerated... 

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