Vitamin C metabolism and the common cold

Summary Male and female university students at the commencement of common cold symptoms were given a single dose of 500 mg of vitamin C. Plasma and leucocyte ascorbic acid concentrations were then measured for six hours. Symptom severity was recorded. The test was repeated twenty-three days after the last symptom had disappeared. The ascorbic acid blood response curve had then returned to normal. Significant and similar elevations of plasma ascorbic acid occurred in both sexes in the cold and post-cold tests. The leucocyte response was significantly reduced in the males but was unaffected in the females in the cold test. The regression coefficients between leucocyte and plasma values (P/L regressions) confirmed that ascorbic acid metabolism was less deranged in females than males during the cold test. Administration of ascorbic acid was associated with increases in blood ascorbic acid concentrations during the post-cold period but not during colds. A single dose of 1000 mg raised blood ascorbic acid concentrations in both sexes during their colds. The elevation was higher, and maintained for two hours longer in the females.In vitro incubation of leucocytes in ascorbic acid confirmed that their ascorbic acid load could be increased by approximately 100% while cold symptoms were present. A significant association between cold symptoms and the state of ascorbic acid metabolism was demonstrated by correlating the ratio of toxic to catarrhal symptoms with P/L regressions during colds. When catarrhal symptoms are severe, ascorbic acid passes from the leucocytes into the plasma, and thence into the inflamed respiratory membranes. When toxic symptoms are relatively more severe, ascorbic acid is retained in the cells. The beneficial effect of vitamin C on the common cold is associated with its influence on ascorbic acid metabolism. A sex-linked difference in ascorbic acid metabolism is manifested during the common cold which affects assessment of the effects of vitamin C on the common cold.     

The beneficial effect of Vitamin C on the common cold

Summary The occurrence of common cold symptoms was recorded daily for a period of nine months by children from two male and two female boarding schools. All the children in one male and one female school received tablets containing 200 mg Vitamin C, or placebo tablets, daily on a double blind basis. Children in the other two schools received 200 or 500 mg tablets of Vitamin C. Leucocyte ascorbic acid concentrations were significantly raised in those children receiving active tablets. Comparisons of incidence, duration, severity and total intensity of cold characteristics, and of cold frequencies, were made between the different treatment groups. Cold symptoms were grouped into those characteristic of Catarrhal (C-colds), and those of Toxic (T-colds), colds. Whole (W-colds) consisted of at least one C-symptom in combination with one or more T-symptoms. 200 mg of Vitamin C had a beneficial effect on severity and total intensity of C- and W-colds, but did not affect T-colds, in girls. 500 mg produced further slight beneficial effects. With 200 mg the cold categories in boys tended to show a deterioration, and the deterioration continued in the group receiving 500 mg. Analysis of cold frequency indicated that T-colds are commoner in girls. Their C-cold frequency diminished with the smaller dose, and their T-cold frequency was reduced by the larger dose of Vitamin C. In boys C-cold frequency diminished with 500 mg of Vitamin C daily. These data suggest that there is a sexual difference in the effects of Vitamin C on the characteristics of the common cold. Evaluation of the effects of Vitamin C on toxic and catarrhal symptoms in relation to administered doses is of more importance than examination of its prophylactic or therapeutic actions. 500 mg had some beneficial effect in girls: any beneficial effect of Vitamin C on the common cold in boys will probably be associated with administration of a higher daily dose.     

Ethanol metabolism in the vitamin C deficient guinea-pig

Vitamin C deficiency, although reducing microsomal aniline hydroxylase and NADPH oxidase activities and decreasing the amount of cytochrome P-450, had no effect on the rate in vivo of ethanol elimination. Ethanol given as a daily oral dose of 2.5g/kg for 14 days did not induce microsomal enzyme activities or increase the concentration of microsomal electron transport components. Drugs that are metabolized by the microsomal drug metabolizing system have increased plasma half lifes in scorbutic guinea-pigs, but no decrease in ethanol disappearance from the blood in the scorbutic animals used in the present study was noted. It is concluded that when ADH activity is normal, no further systems are required for ethanol metabolism.     

The role of the common cold in asthma

It has long been known that patients with viral respiratory infections develop temporary asthma-like symptoms or see a worsening of their existing asthmatic symptoms or develop full-blown asthma during the infection. It should not be surprising, in view of this observation, that these same viruses have been found to initiate the same inflammatory processes as seen and characterized in the asthmatic patient. This has clear implications for therapy of asthmatic patients.     

The effect of vitamin supplementation upon antipyrine metabolism in the elderly.

1 Antipyrine plasma half-life and clearance rates were studied in 19 elderly patients shortly after admission to a geriatric ward and again 2 weeks after a course of dietary supplementation with Vitamins A, B complex, C and D. 2 Antipyrine half-life fell and clearance increased in the nine who had sub-clinical evidence of ascorbic acid deficiency. No correlation was found with other indices of nutritional status. 3 Vitamin supplementation in elderly people with no demonstrable deficiencies did not alter the metabolism of antipyrine.     

Influence of vitamin C on the absorption and first pass metabolism of propranolol

The effect of ascorbic acid on the availability of propranolol has been examined. After oral administration of propranolol 80 mg with or without ascorbic acid pretreatment (2 g), the plasma concentrations and urinary excretion of propranolol and its metabolites, 4-hydroxy-propranolol and propranolol-conjugated, were determined by HPLC. Compared to controls, vitamin C decreased the maximum concentration of propranolol from 463 to 334 nmol·l^–1, and the area under the propranolol concentration-time curve (from 0 to 24 hours) from 3,13 to 1,96 mol·l^–1·h. The time to reach maximum propranolol concentration was increased from 1,9 to 2,7. The total amount of drug recovered in urine has also significantly diminished (from 12,6 to 4,29 mg). No change in elimination rate was observed, indicating that ascorbic acid had affected both the absorption process and the first pass metabolism. The heart-rate decreased less when propranolol was administered with ascorbic acid in comparison to control subjects, although this interaction has little biological importance.     

The influence of antiepileptic drugs on vitamin B6 metabolism.

Vitamin B6 nutriture was measured by means of determination of activity of EGOT in 30 and of serum pyridoxal phosphate in 27 epileptic children under antiepileptic treatment with various antiepileptic drugs and with hydantoin and succinimide alone, 25 healthy infants and children were controls. Under the treatment with antiepileptic drugs, especially with hydantoin and succinimide a depression of the activity of EGOT and the level of pyridoxal-phosphate in serum followed. As an induction of vitamin B6 dependnet enzyme activity can be excluded a possible explanation for the disturbance in vitamin B6 metabolism could be the inhibition of activity of pyridoxalkinase. We consider the administration of vitamin B6 in addition to hydantoin and succinimide as appropriate.     

Changes in vitamin C and vitamin E during oxidative stress in myocardial reperfusion

Injury to the myocardial tissue due to ischemia and reperfusion occurs because of imbalance between the formation of oxidants and available antioxidants in the heart. Levels of vitamin C (ascorbic acid) and vitamin E (alpha--tocopherol) were evaluated in 52 patients of acute myocardial infarction (AMI) treated by streptokinase. They were further divided into reperfused group (39 patients) and non-reperfused group (13 patients). Twenty normal healthy subjects served as controls. Vitamin C and vitamin E were estimated in study group before and after thrombolytic therapy and in controls. Vitamin C levels were low in AMI cases as compared to controls (8.74 +/- 1.87 and 10.63 +/- 3.26 mg/L, respectively, P < 0.001). Trend of fall in vitamin C levels in the two study groups was not statistically significant. Vitamin E levels declined from 12.19 +/- 6.71 to 9.96 +/- 6.50 mg/L by 4 hours which was significant (P < 0.01) in the reperfused group, but the change in non-reperfused group (9.28 +/- 6.37 to 9.35 +/- 6.07 mg/dL by 4 hours) was non-significant. This is because of increased consumption of this antioxidant in suppressing the oxidative stress which occurs with reperfusion. Vitamin E can be proposed as a valid marker for reperfusion.     

The effect of cadmium on vitamin A metabolism

It has been reported that a number of toxic agents impair normal vitamin A (VA) metabolism (A. D. Bruin, 1976, In Biochemical Toxicology of Environmental Agents, pp. 937–980. Elsevier, Amsterdam). A study was conducted to explore the effect of cadmium chloride (CdCl₂) on VA metabolism. Female rats of the Wistar strain were given drinking water containing 50 ppm of cadmium (Cd) for 237 days. Cadmium ingestion did not affect the food intake and body weight, but a significant decrease in serum VA was observed, concurrently with an increase in liver VA. In studying ingestion of tritiated VA alcohol (all trans-[15-³H]retinol), it was found that the absorption of VA alcohol from the intestine, the release of newly absorbed VA from the liver to serum, and the conversion of VA to water-soluble metabolites in the liver were not influenced by Cd. These findings suggest that Cd interfered with the release of VA, especially stored VA, to serum.