ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—In a double-blinded randomized controlled trial, we investigated the long-term effect of vitamin C supplementation on blood pressure. A total of 439 Japanese subjects with atrophic gastritis initially participated in the trial using vitamin C and &bgr;-carotene to prevent gastric cancer. Before and on early termination of &bgr;-carotene supplementation, 134 subjects dropped out of this trial, whereas 120 and 124 subjects took the vitamin C supplement daily at either 50 mg or 500 mg, respectively, for 5 years. Before supplementation, neither systolic nor diastolic blood pressure was significantly related with the serum vitamin C concentration. This relationship was unchanged after adjustment for age, body mass index, and alcohol intake or after stratification by gender. After 5 years, systolic blood pressure significantly increased in groups, regardless of vitamin C dose, compared with baseline. Systolic blood pressure in the high-dose group (500 mg daily) increased from 125.4 to 131.7 mm Hg (5.88 mm Hg increase; 95% confidence interval [CI], 3.11 to 8.65). This value was similar with that of the low-dose group (5.73 mm Hg increase; 95% CI, 2.62 to 8.83) and of the dropout group (4.52 mm Hg increase; 95% CI, 1.26 to 7.77). There was no difference in change of diastolic blood pressure among the 3 groups. In conclusion, we observed no reduction in blood pressure with long-term moderate doses (500 mg/day) of vitamin C supplementation in a high-risk population for stomach cancer and stroke.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Experimental evidence suggests that acute parenteral administration of high-dose ascorbic acid has beneficial vascular effects in type 2 diabetes. We studied the hemodynamic effects of chronic oral supplementation in this condition. Thirty patients, 45 to 70 years of age, with type 2 diabetes, were randomly assigned in a double-blind manner to receive 500 mg ascorbic acid daily by mouth or placebo. Patients were studied at baseline and after 4 weeks of assigned treatment. The central aortic augmentation index (AgIx) and the time to wave reflection (Tr) were derived from radial artery pulse wave analysis data. AgIx and Tr were used as measures of systemic arterial stiffness and aortic stiffness, respectively. Ascorbic acid decreased brachial systolic blood pressure from 142.1±12.6 (SD) to 132.3±12.1 mm Hg (difference [95% CI] 9.9 [4.7, 15.0];P<0.01), brachial diastolic pressure from 83.9±4.8 to 79.5±6.0 mm Hg (4.4 [1.8, 7.0];P<0.01), and AgIx from 26.8±5.5% to 22.5±6.8% (4.3 [1.5, 7.1];P<0.01). Tr increased from 137.1±12.6 to 143.4±9.2 ms (−6.3 [−10.1, −2.5];P<0.01). Placebo had no hemodynamic effects, and this difference between treatments was significant (P<0.01 for blood pressure and Tr,P=0.03 for AgIx). We have therefore shown that after 1 month, oral ascorbic acid lowered arterial blood pressure and improved arterial stiffness in patients with type 2 diabetes. As strict control of blood pressure reduces cardiovascular risk in diabetes, ascorbic acid supplementation may potentially be a useful and inexpensive adjunctive therapy. Larger and longer studies now need to be performed.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID

摘要:

Abstract—Serum vitamin C has been inversely associated with blood pressure in several epidemiologic studies, but little is known about effect of other antioxidant vitamins. We examined the relation between serum vitamins A, C, and E, &agr;-carotene, and &bgr;-carotene levels and blood pressure among 15 317 men and women ≥20 years of age who participated in the Third National Health and Nutrition Examination Survey. Blood pressure was characterized as the average of 6 measurements obtained over 2 visits by trained observers and hypertension was defined as blood pressure ≥140/90 mm Hg and/or taking antihypertensive medications. In multivariate models, a 1 SD difference in vitamin A (16.2 &mgr;g/dL) and vitamin E (20.4 &mgr;g/dL) was associated with a 43% (OR, 1.43; 95% CI, 1.34 to 1.53) and 18% (OR, 1.18; 95% CI, 1.09 to 1.27) higher odds of hypertension, respectively. A 1 SD difference in &agr;-carotene (0.47 &mgr;g/dL) and &bgr;-carotene (496 &mgr;g/dL) was associated with a 16% (OR, 0.84; 95% CI, 0.76 to 0.94) and 11% (OR, 0.89; 95% CI, 0.82 to 0.97) lower odds of hypertension, respectively. In addition, serum vitamins A and E were positively and significantly associated with both systolic and diastolic blood pressure, whereas &agr;-carotene and &bgr;-carotene were inversely and significantly associated with systolic and vitamin C associated with diastolic blood pressure in multivariate linear regression analyses. These findings indicate that antioxidant vitamins may be important in the underlying cause and prevention of hypertension. Further studies in this important area are warranted.

ISSN:0194-911X    

出版商:OVID    

年代:2002

数据来源: OVID