171. Nitrate and VITAMIN C from fruits and vegetables: impact of intake variations on nitrate and nitrite excretions of humans.
Plant Foods Hum Nutr 1994 Jan;45(1):71-80
Bednar C, Kies C Texas Woman's University, Denton.
The objective of the study was to determine nitrate + nitrite excretions of human subjects fed variable amounts of nitrates and nitrites and VITAMIN C from fruits and vegetables. During four, randomly-arranged experimental periods of seven days each, the 12 apparently healthy, adult human subjects consumed laboratory controlled, constant, diets which were systematically varied in kinds of fruits and vegetable to provide the four following variations: 414 mg nitrate + nitrite and 23 mg VITAMIN C, 412 mg nitrate + nitrite and 177 mg VITAMIN C, 23 mg nitrate + nitrite and 39 mg VITAMIN C, and 21 mg nitrate + nitrite and 193 mg VITAMIN C per subject per day, respectively. Subjects made complete collections of urine and stools throughout the study. Regardless of type of experimental diet fed, no nitrates and nitrites were detected in the feces. Urinary excretion of nitrate + nitrite was significantly greater at the higher levels of nitrate + nitrite intake than at the lower intake levels. Increased intake of VITAMIN C at either level of nitrate + nitrite intake resulted in apparent decreased urinary excretions of nitrite + nitrate. Publication Types: Clinical trial Randomized controlled trial PMID: 8146105, UI: 94195709
172. Clinical trials using Ascorbic acid aerosol to aid smoking cessation.
Drug Alcohol Depend 1993 Oct;33(3):211-23
Levin ED, Behm F, Carnahan E, LeClair R, Shipley R, Rose JE Department of Psychiatry, Duke University Medical Center, Durham, NC.
Sensory aspects of cigarette smoke are important for providing smoking satisfaction. In previous studies, we have found that substitution of the sensory cues of smoking with a citric acid aerosol significantly reduces craving for cigarettes and enhances smoking reduction and cessation with people trying to quit smoking cigarettes. In the current study, we conducted two clinical smoking cessation trials using an Ascorbic acid aerosol as a sensory substitute. The cigarette substitute consisted of a cigarette-sized tube which delivered a fine aerosol of Ascorbic acid (approx. 1 mg/puff, up to a maximum of 300 mg/day). Study 1 examined the overall effectiveness of the Ascorbic acid smoking substitute device. One group of subjects which used the device and received clinical counseling was compared with another group which received only clinical counseling. The group using the device showed significantly greater abstinence rates at 3 weeks post-cessation. After the subjects stopped using the device, no difference in abstinence was detected. Study 2 was conducted to focus specifically on the role of tracheobronchial sensations in relieving craving for cigarettes. Two closely matched Ascorbic acid delivery systems were compared. One device delivered fine particles of Ascorbic acid that were targeted to reach the trachea, while the other delivered coarser particles of Ascorbic acid that were not expected to reach the trachea or lower airways. An initial enhancement in smoking reduction was found for subjects using the fine particle device relative to those using the coarse particle device. However, by the end of treatment (5 weeks) both groups showed similar degrees of smoking reduction. For those who were abstinent from smoking at the end of treatment, craving for cigarettes and negative mood were both significantly lower for those using the fine particle device. Also, hunger for food was significantly lower in the fine particle device group. These results suggest that Ascorbic acid delivered from a cigarette substitute may be effective in reducing smoking and promoting smoking abstinence. Publication Types: Clinical trial Randomized controlled trial PMID: 8261886, UI: 94085199
173. Changes in plasma antioxidant status during eccentric exercise and the effect of vitamin supplementation.
Free Radic Res Commun 1993;19(3):191-202
Maxwell SR, Jakeman P, Thomason H, Leguen C, Thorpe GH Department of Medicine, Birmingham University, UK.
Twenty-four healthy students undertook one hour of box-stepping exercise. Prior to exercise eight had received no medication (Group A), eight received 400 mg of VITAMIN C daily for three weeks before and one week after exercise (Group C) and eight received 400 mg of vitamin E for the same period (Group E). Groups C and E had significantly higher levels of VITAMIN C (p < 0.01) and vitamin E (p < 0.01) respectively than group A at the commencement of exercise. Plasma total antioxidant capacity rose significantly during exercise in all group (A - p < 0.05; C - p < 0.001; E - p < 0.001). This rise was accounted for by increases in plasma uric acid in all groups. In addition there were significant increases in VITAMIN C in group C (p < 0.001) and vitamin E in group E (p < 0.05). There were no significant changes in plasma malondialdehyde following exercise in any group. It is concluded that plasma antioxidant capacity rises in response to one hour of eccentric exercise and that the contribution of individual antioxidants to this change can be influenced by vitamin supplementation. The possible mechanisms of the antioxidant changes during exercise and their implications are discussed. PMID: 8244088, UI: 94063573
174. Effects of Ascorbic acid and pyridoxine supplementation on oxalate metabolism in peritoneal dialysis patients.
Am J Kidney Dis 1992 Jul;20(1):42-9
Shah GM, Ross EA, Sabo A, Pichon M, Reynolds RD, Bhagavan H Department of Medicine, Veterans Affairs Medical Center, Long Beach, CA 90822.
We studied the effect of VITAMIN C and B6 supplementation on oxalate metabolism in seven patients receiving chronic peritoneal dialysis therapy. The study was divided into three phases, each lasting 4 weeks. Plasma oxalate, total Ascorbic acid, and pyridoxal-5'-phosphate (PLP) were measured at the end of each phase. Twenty-four-hour urinary excretion and dialysate removal rates of oxalate were also obtained. At the end of phase I (supplement-free period), plasma oxalate levels were markedly elevated at 47.6 +/- 7.1 mumol/L (437 +/- 66 micrograms/dL) (normal, 3.4 +/- 0.4 mumol/L [30.3 +/- 1.6 micrograms/dL]). Plasma total Ascorbic acid levels were 62 +/- 6 mumol/L (1.0 +/- 0.1 mg/dL) (normal, 45 to 57 mumol/L [0.8 to 1.0 mg/dL]), while plasma PLP levels were markedly reduced to 24 +/- 5 nmol/L (normal, 40 to 80 nmol/L). Daily supplements of 0.57 mmol (100 mg) Ascorbic acid orally (phase II) resulted in a 19% increase in the plasma oxalate levels to 57.8 +/- 6.1 mumol/L (520 +/- 55 micrograms/dL) (P less than 0.03), with a concomitant 60% increase in the plasma ascorbate levels (91 +/- 6 mumol/L [1.6 +/- 0.1 mg/dL], P less than 0.01). Plasma PLP values remained low. Finally, during phase III (0.57 mmol or 100 mg Ascorbic acid plus 59.6 mumol or 10 mg pyridoxine HCI orally daily), plasma oxalate levels declined by 17% to 47.9 +/- 5.2 mumol/L (431 +/- 47 micrograms/dL) (P greater than 0.05 v phase II). PMID: 1621677, UI: 92321109
175. Dietary antioxidants and carotid artery wall thickness. The ARIC Study. Atherosclerosis Risk in Communities Study.
Circulation 1995 Oct 15;92(8):2142-50
Kritchevsky SB, Shimakawa T, Tell GS, Dennis B, Carpenter M, Eckfeldt JH, Peacher-Ryan H, Heiss G
Department of Preventive Medicine, University of Tennessee, Memphis 38163, USA.
BACKGROUND: Evidence that dietary antioxidants may prevent atherosclerotic disease is growing. The relationship between the intake of dietary and supplemental vitamin C, alpha-tocopherol, and provitamin A carotenoids and average carotid artery wall thickness was studied in 6318 female and 4989 male participants 45 to 64 years old int he Atherosclerosis Risk in Communities Study. METHODS AND RESULTS: Intake was assessed by use of a 66-item semiquantitative food-frequency questionnaire. Carotid artery intima-media wall thickness was measured as an indicator of atherosclerosis at multiple sites with B-mode ultrasound. Among men and women > 55 years old who had not recently begun a special diet, there was a significant inverse relationship between vitamin C intake and average artery wall thickness adjusted for age, body mass index, fasting serum glucose, systolic and diastolic blood pressures, HDL and LDL cholesterol, total caloric intake, cigarette use, race, and education (test for linear trend across quintiles of intake, P = .019 for women and P = .035 for men). An inverse relationship was also seen between wall thickness and alpha-tocopherol intake but was significant only in women (test for linear trend, P = .033 for women and P = .13 for men). There was a significant inverse association between carotene intake and wall thickness in older men (test for linear trend, P = .015), but the association weakened after adjustment for potential confounders. No significant relationships were seen in participants < 55 years old. CONCLUSIONS: These data provide limited support for the hypothesis that dietary vitamin C and alpha-tocopherol may protect against atherosclerotic disease, especially in individuals > 55 years old.
176. Randomised controlled trial of vitamin E in patients with coronary disease: Cambridge Heart Antioxidant Study.
Lancet 1996 Mar 23;347(9004):781-6
Stephens NG, Parsons A, Schofield PM, Kelly F, Cheeseman K, Mitchinson MJ
Department of Medicine, Cambridge University.
BACKGROUND: Vitamin E (alpha-tocopherol) is thought to have a role in prevention of atherosclerosis, through inhibition of oxidation of low-density lipoprotein. Some epidemiological studies have shown an association between high dietary intake or high serum concentrations of alpha-tocopherol and lower rates of ischaemic heart disease. We tested the hypothesis that treatment with a high dose of alpha-tocopherol would reduce subsequent risk of myocardial infarction (MI) and cardiovascular death in patients with established ischaemic heart disease. METHODS: In this double-blind, placebo-controlled study with stratified randomisation, 2002 patients with angiographically proven coronary atherosclerosis were enrolled and followed up for a median of 510 days (range 3-981). 1035 patients were assigned alpha-tocopherol (capsules containing 800 IU daily for first 546 patients; 400 IU daily for remainder); 967 received identical placebo capsules. The primary endpoints were a combination of cardiovascular death and non-fatal MI as well as non-fatal MI alone. FINDINGS: Plasma alpha-tocopherol concentrations (measured in subsets of patients) rose in the actively treated group (from baseline mean 34.2 micromol/L to 51.1 micromol/L with 400 IU daily and 64.5 micromol/L with 800 IU daily) but did not change in the placebo group. Alpha-tocopherol treatment significantly reduced the risk of the primary trial endpoint of cardiovascular death and non-fatal MI (41 vs 64 events; relative risk 0.53 [95% Cl 0.34-0.83; p=0.005). The beneficial effects on this composite endpoint were due to a significant reduction in the risk of non-fatal MI (14 vs 41; 0.23 [0.11-0.47]; p=0.005); however, there was a non-significant excess of cardiovascular deaths in the alpha-tocopherol group (27 vs 23; 1.18 [0.62-2.27]; p=0.61). All-cause mortality was 36 of 1035 alpha-tocopherol-treated patients and 27 of 967 placebo recipients. INTERPRETATION: We conclude that in patients with angiographically proven symptomatic coronary atherosclerosis, alpha-tocopherol treatment substantially reduces the rate of non-fatal MI, with beneficial effects apparent after 1 year of treatment. The effect of alpha-tocopherol treatment on cardiovascular deaths requires further study.
177. Vitamins E plus C and interacting conutrients required for optimal health. A critical and constructive review of epidemiology and supplementation data regarding cardiovascular disease and cancer.
Department of Biochemistry and Molecular Biology, University of Berne, Switzerland.
Antioxidants are crucial components of fruit/vegetable rich diets preventing cardiovascular disease (CVD) and cancer: plasma vitamins C, E, carotenoids from diet correlate prevalence of CVD and cancer inversely, low levels predict an increased risk of individuals which is potentiated by combined inadequacy (e.g., vitamins C + E, C + carotene, A + carotene); self-prescribed rectification of vitamins C and E at adequacy of other micronutrients reduce forthcoming CVD, of vitamins A, C, E, carotene and conutrients also cancer; randomized exclusive supplementation of beta-carotene +/- vitamin A or E lack benefits except prostate cancer reduction by vitamin E, and overall cancer reduction by selenium; randomized intervention with synchronous rectification of vitamins A + C + E + B + minerals reduces CVD and counteracts precancerous lesions; high vitamin E supplements reveal potentials in secondary CVD prevention. Plasma values desirable for primary prevention: > or = 30 mumol/l lipid-standardized vitamin E (alpha-tocopherol/cholesterol > or = 5.0 mumol/mmol); > or = 50 mumol/l vitamin C aiming at vitamin C/vitamin E ratio > 1.3-1.5; > or = 0.4 mumol/l beta- (> or = 0.5 mumol/l alpha+ beta-) carotene. CONCLUSIONS: In CVD vitamin E acts as first risk discriminator, vitamin C as second one; optimal health requires synchronously optimized vitamins C + E, A, carotenoids and vegetable conutrients.