ASCORBIC ACID FUNCTION AND METABOLISM DURING COLDS

Investigations of the relationship between symptoms of the natural common cold and administration of supplementary vitamin C must record and take into account the following factors: 1. Definition of the cold syndrome in terms of incidence (number of colds per person in unit time, generally taken as duration of study); duration of syndrome (number of days during which a defined number of symptoms persist in individual patients); and severity of symptoms (recorded subjectively on a daily basis for individual symptoms on a graded scale of which the lowest value records absence of the symptom). Days of absence from work provide a general measure arising from cold disability.1 Integrated morbidity2 is defined as the product of incidence of colds, and severity of individual colds. The two values for incidence and integrated morbidity are not independent of one another. Integrated morbidity provides a general measure of intensity of the syndrome as opposed to the disability it produces. Total symptom intensity provides a similar measure to integrated morbidity. The Total Intensity Score is defined as the total severity of any symptoms of the cold syndrome present on each day of reporting, divided by the total number of days of reporting.3 Variation in symptom quality can be evaluated by measuring the degree of association between symptom pairs.4 If viral diagnostic tests, or antibody measurement, are not included in the investigation, a screening process is necessary to exclude upper respiratory allergic disease. Local respiratory symptoms of an allergic nature, those produced by mental stress in subjects prone to vasomotor rhinitis, and those arising from chronic infection of the nasal passages,5 are eliminated from the data on the cold syndrome by excluding syndromes that exceeded 21 days in duration.3 2. Measurement of plasma and leukocyte ascorbic acid concentrations in the subjects. Correlation of these measurements with the cold symptomatology enables the relationship between tissue ascorbic acid and the cold syndrome to be measured directly. Administration of exogenous supplementary vitamin C during the cold syndrome only allows indirect assumptions to be made about the relationship between the cold syndrome and the effect associated with vitamin C administration. 3. The preliminary decision as to whether supplementary vitamin C will be administered on a prophylactic or a therapeutic basis. If it is decided that a prophylactic investigation will be carried out, it is essential that the period of administration of supplementary vitamin C is sufficiently long to ensure that tissue concentrations of ascorbic acid have been elevated in the subjects when they are included in the trial. Factors such as sex, age, dietary intake of vitamin C, and initial ascorbic acid status of the tissues can all have profound effects on