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CHEM 181 (47)
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woc 8- supplementing with vitamins.docx

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Department
Chemistry
Course
CHEM 181
Professor
David Harpp
Semester
Winter

Description
pages 251258 SUPPLEMENTING WITH VITAMINSThere are several ways to investigate the potential role of supplements o Surveys can identify those people who take supplements and make correlations to their health statusA typical surveytype or observational study involved over 83000 healthy American physicians who filled out questionnaires about supplement intake and dietary habits 30 of the doctors regularly took vitamin supplements After 6 years 1000 had died from cardiovascular disease and there was no relationship between supplement intake and cardiovascular death It could be that physicians are more health conscious and got more antioxidants in their diets howeverSome studies have shown a negative supplement effect Analysis of data collected from some 70000 postmenopausal nurses showed that over an 18 year period those who consumed the most vitamin A from food or from supplements had the greatest risk of bone fractures On the other hand low vitamin E intake during pregnancy has been shown to increase the risk of childhood asthma and women who take vitamin supplements during pregnancy appear to have a reduced risk of giving birth to infants who develop brain tumors o Researchers can measure blood levels of specific antioxidants and relate the findings to disease patternsIn one case English researchers found that in about 20000 people those who had the highest levels of vitamin C in the blood lived the longest But was it is vitamin C itself or was vitamin C just a marker of increased fruit intakeLow levels of folic acid have been linked with breast cancer heart disease and with giving birth to babies with neural tube defects Still such studies do not show cause and effectIMPORTANT you can never be certain that the observations are not due to some other dietary factor that happens to parallel folic acid in its presence This is why intervention studies are most meaningful o They can carry out intervention studies in which results are evaluated after subjects take either the substance being tested or a placebo over an extended periodIntervention studies in the case of folic acid back up observational studies Supplementing the diet with 400 micrograms of folic acid daily significantly reduces the risk of neural tube defectsAs for the hypothesis that antioxidants such as vitamin E or C or the vitamin A precursor betacarotene should play a role in preventing heart disease it is pretty reasonable This is because cholesterol is more likely to damage coronary arteries when it is oxidized Therefore antioxidants should counter this effect But in practice this is not the case Researchers in Oxford England enrolled over 20000 adults with heart disease risk factors such as diabetes high blood pressure or high blood cholesterol in a major study Half received a daily supplement of 600 IU of vitamin E 250 milligrams of vitamin C and 20 milligrams of betacarotene while the others got a placebo
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