| May 9, 2000 |
National Academy of Sciences References
131. Int J Vitam Nutr Res 1994;64(3):212-9The clinical effects of VITAMIN C supplementation in elderly hospitalised patients with acute respiratory infections.Hunt C, Chakravorty NK, Annan G, Habibzadeh N, Schorah CJ Food & Nutrition Department, Huddersfield University.
A randomised double-blind trial involving VITAMIN C/placebo supplementation was conducted on 57 elderly patients admitted to hospital with acute respiratory infections (bronchitis and bronchopneumonia). Patients were assessed clinically and biochemically on admission and again at 2 and 4 weeks after admission having received either 200 mg VITAMIN C per day, or placebo. This relatively modest oral dose led to a significant increase in plasma and white cell VITAMIN C concentration even in the presence of acute respiratory infection. Using a clinical scoring system based on major symptoms of the respiratory condition, patients supplemented with the vitamin fared significantly better than those on placebo. This was particularly the case for those commencing the trial most severely ill, many of whom had very low plasma and white cell VITAMIN C concentrations on admission. Various mechanisms by which VITAMIN C could assist this type of patient are discussed. Publication Types: Clinical trial Randomized controlled trial
132. Am J Clin Nutr 1994 Nov;60(5):735-8Megadose of VITAMIN C delays insulin response to a glucose challenge in normoglycemic adults.Johnston CS, Yen MF Department of Family Resources and Human Development, Arizona State University, Tempe 85287-2502.
The effect of a megadose of Ascorbic acid (AA) on glucose and insulin responses after an oral-glucose-tolerance test (OGTT) is unknown. With a double-blind, placebo-controlled design, nine normoglycemic subjects (22 +/- 1 y, mean +/- SEM) consumed AA (2 g/d) or placebo for 2 wk after a 2-wk washout period with placebo, and an OGTT was performed after an overnight fast. This 4-wk protocol was repeated in a crossover fashion. Plasma glucose was significantly elevated 1-h postprandial in VITAMIN C-saturated subjects vs those taking a placebo. The plasma insulin response curve was shifted rightward in VITAMIN C-saturated subjects relative to baseline: plasma insulin was significantly depressed at 0.5 h postprandial but significantly elevated at 2 h postprandial. These data indicate that elevated plasma AA delays the insulin response to a glucose challenge in normoglycemic adults, thereby prolonging the postprandial hyperglycemia. These effects might be partially explained by the competitive inhibition of glucose transfer into pancreatic beta cells by high concentrations of circulating AA.
133. Plant Foods Hum Nutr 1994 Jan;45(1):71-80Nitrate and VITAMIN C from fruits and vegetables: impact of intake variations on nitrate and nitrite excretions of humans.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.
134. Drug Alcohol Depend 1993 Oct;33(3):211-23Clinical trials using Ascorbic acid aerosol to aid smoking cessation.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.
135. Free Radic Res Commun 1993;19(3):191-202Changes in plasma antioxidant status during eccentric exercise and the effect of vitamin supplementation.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.
136. Am J Kidney Dis 1992 Jul;20(1):42-9Effects of Ascorbic acid and pyridoxine supplementation on oxalate metabolism in peritoneal dialysis patients.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).
137. Ann N Y Acad Sci 1987;498:186-99Interaction of ascorbate and alpha-tocopherol.Niki E
Vitamins C and E function as water-soluble and lipid-soluble chain-breakingantioxidants, respectively, and protect lipids, proteins, and membranes fromoxidative damage. Vitamin C scavenges oxygen radicals in the aqueous phase,whereas vitamin E scavenges oxygen radicals within the membranes. Vitamin Cregenerates vitamin E by reducing vitamin E radicals formed when vitamin Escavenges the oxygen radicals. This interaction between vitamin C and vitamin Eradicals can take place not only in homogeneous solutions but also in liposomalmembrane systems where vitamins C and E reside separately outside and within the membranes respectively, and vitamin C can act as a synergist.
138. Can J Physiol Pharmacol 1993 Sep;71(9):725-31Partners in defense, vitamin E and vitamin C.Chan ACDepartment of Biochemistry, Faculty of Medicine, University of Ottawa, ON,Canada.
In addition to the enzymic mechanism of free-radical removal, essentialnutrients that can scavenge free radicals, such as vitamins E and C, constitutea strong line of defense in retarding free radical induced cellular damage.Distinct pathways for the repair of oxidized vitamin E in human cells have beenrecently identified. Within 0.5 min after the addition of arachidonic acid to ahuman platelet homogenate, over half of the platelet vitamin E and addedarachidonate were metabolized by platelet cyclooxygenase and lipoxygenasepathways. After adding nordihydroguaiaretic acid, a lipoxygenase inhibitor and astrong reductant, over 60% of the oxidized vitamin E was regenerated. To testother physiological, water-soluble reductants that may help regenerate vitaminE, eicosatetraynoic acid, a lipoxygenase inhibitor that is not an antioxidant,was used. In this system, both ascorbate and glutathione provided significant vitamin E regeneration. Kinetic analysis and studies of vitamin E regeneration in a protein-denaturing system revealed that ascorbate regenerates vitamin E by a nonenzymic mechanism, whereas glutathione regenerates vitamin E enzymatically. These studies suggest that significant interaction occurs between water- and lipid-soluble molecules at the membrane-cytosol interface and that vitamin C may function in vivo to repair the membrane-bound oxidized vitamin E.
139. Ann Allergy 1994 Aug;73(2):89-96; quiz 96-100Asthma and vitamin C.Bielory L, Gandhi RDivision of Allergy and Immunology, UMD-New Jersey Medical School, Newark.
OBJECTIVE. To define what role vitamin C may or may not play in the treatment ofasthma. DATA SOURCES. A comprehensive literature search of relevantEnglish-language papers identified through a Medline search and frombibliographies of the identified papers. STUDY SELECTION. We identified papersand studies pertaining to vitamin C in asthma and allergy and analyzed thesestudies according to their design, inclusion and exclusion criteria, populationstudied, variables or factors tested, method of intervention or treatment withvitamin C, and results and conclusions. We reviewed our data and divided itbased on significant or insignificant roles of vitamin C in asthma and allergy.RESULTS. From our review, we found a number of studies that support the use ofvitamin C in asthma and allergy. Significant results include positive effects onpulmonary function tests, bronchoprovocation challenges with methacholine orhistamine or allergens, improvement in white blood cell function and motility,and a decrease in respiratory infections. Our review also revealed severalstudies that did not support a beneficial role in vitamin C in asthma andallergy. These studies did not report improvements in pulmonary function testsor bronchoprovocation challenges. No benefit was noted in these studies whentesting cutaneous reactivity or specific immunologic factors and levels.CONCLUSIONS. Clearly from our review, the role of vitamin C in asthma andallergy is not well defined. The majority of the studies were short term andassessed immediate effects of vitamin C supplementation. Long termsupplementation with vitamin C or delayed effects need to be studied. Although,the current literature does not support a definite indication for the use ofvitamin C in asthma and allergy, the promising and positive studies revivecuriosity and interest. With a large portion of health care dollars being spenton alternative medicine and vitamin C in particular, further studies are neededto define its role.
140. Int J Vitam Nutr Res 1994;64(3):212-9The clinical effects of vitamin C supplementation in elderly hospitalized patients with acute respiratory infections.Hunt C, Chakravorty NK, Annan G, Habibzadeh N, Schorah CJFood & Nutrition Department, Huddersfield University.
A randomised double-blind trial involving vitamin C/placebo supplementation wasconducted on 57 elderly patients admitted to hospital with acute respiratoryinfections (bronchitis and bronchopneumonia). Patients were assessed clinicallyand biochemically on admission and again at 2 and 4 weeks after admission havingreceived either 200 mg vitamin C per day, or placebo. This relatively modestoral dose led to a significant increase in plasma and white cell vitamin Cconcentration even in the presence of acute respiratory infection. Using aclinical scoring system based on major symptoms of the respiratory condition,patients supplemented with the vitamin fared significantly better than those onplacebo. This was particularly the case for those commencing the trial mostseverely ill, many of whom had very low plasma and white cell vitamin Cconcentrations on admission. Various mechanisms by which vitamin C could assistthis type of patient are discussed.