Vitamin excess

While the human body can remove an excess of any water-soluble vitamin, excesses of fat-soluble vitamins are more serious. Early arctic explorers discovered that the Inuit regarded seal liver and polar bear liver as taboo and must not be eaten. Those explorers who ignored this advice risked retinol poisoning as the livers of both these species are rich in retinol (vitamin A) that can not be excreted. The effects of retinol poisoning are extremely unpleasant. It is for this reason that fortification with fat-soluble vitamins is not likely to be undertaken. 

Micronutrients (vitamins and minerals) are also listed on food packaging. The vitamins we require are compounds that are necessary for metahohc processes either our bodies cannot synthesize them, or they cannot synthesize them in amounts sufficient for our needs. As a result, we must obtain vitamins from dietary sources. DVs are listed for the fat-soluble vitamins—vitamins A, D, and E (Section 8.7)—but care must be taken to avoid overdoses of these vitamins. Excesses can be toxic when lai e amounts of fat-soluble vitamins accumulate in adipose tissue. Excess vitamin A is especially toxic. With water-soluble vitamins, turnover is frequent enough that the danger of excess is not normally a problem. 

Although there is an increase in the rate of metabolism and excretion of retinol as the concentration in the liver rises above 70 imol/kg, there is only a limited capacity to metabolize the vitamin. Excessively high intakes led to accumulation in the liver and other tissues, beyond the capacity of normal binding proteins, so that free, unbound, vitamin A is present, leading to tissue damage. 

Biotin was discovered as a growth factor of yeast. Experiments with animals also produced deficiency symptoms (dermatitis, loss of hair) when avidin was administered. Avidin is a protein isolated from raw egg white that firmly binds biotin, and thus inactivates the vitamin. Excessive consumption of raw egg white apparently may cause biotin deficiency even in man. 

The synthesis of vitamin Dj from a sensitive dienone was another etu-ly success of phosphorus ylide synthesis (H.H. Inhoffen, 1958 A). This Wittig reaction could be carried out without any isomerization of the diene. An excess of the ylide was needed presumably because the alkoxides formed from the hydroxy group in the educt removed some of the ylide. 

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). 

Phosphorus Disorders. Phosphoms nutrient deficiency can lead to rickets, osteomalacia, and osteoporosis, whereas an excess can produce hypocalcemia. Faulty utilisation of phosphoms results in rickets, osteomalacia, osteoporosis, and Paget s disease, and renal or vitamin D-resistant rickets. 

S-Methyl-L-methionine chloride (Vitamin U) [1115-84-0] M 199.5, [a]p +33 (0.2M pK[ 1.9, pKj 7.9. Likely impurities are methionine, methionine sulfoxide and methionine sulfone. from water by adding a large excess of EtOH. Stored in a cool, dry place, protected from light. 

A chiral nonracemic cyclic allyl iodide was shown to react with excess chromium(II) chloride and (4-methoxyphenylmethoxy)acetaldehyde to yield a single diastereomer, which was converted to la,25-dihydroxy vitamin D332. 

Patients receiving oral anticoagulants need to avoid eating excessive amounts ot food containing vitamin K. Otherwise, the anticoagulant will not be effective. Be sure your patient knows what foods contain vitamin K. Include the following list in your teaching plan ... 

Globally, undernutrition is widespread, leading to impaired growth, defective immune systems, and reduced work capacity. By contrast, in developed countries, there is often excessive food consumption (especially of fat), leading to obesity and to the development of cardiovascular disease and some forms of cancer. Deficiencies of vitamin A, iron, and iodine pose major health concerns in many countries, and deficiencies of other vitamins and minerals are a major cause of iU health. In developed countries, nutrient deficiency is rare, though there are vulnerable sections of the population at risk. Intakes of minerals and vitamins that are adequate to prevent deficiency may be inadequate to promote optimum health and longevity. 

There is only a limited capacity to metabolize vitamin A, and excessive intakes lead to accumulation beyond the capacity of binding proteins, so that unbound vitamin A causes tissue damage. Symptoms of toxicity affect the central nervous system (headache, nausea. 

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