• The incidence and course of common colds were followed in 89 medical students and nurses who volunteered in a study of the efficacy of naringin, a bioflavonoid extracted from grapefruit peel and used in remedies for colds. One group of 22 subjects received 333 mg. of naringin and 65 mg. of ascorbic acid three times daily for three months; a second group received naringin only, another ascorbic acid only, and the fourth a placebo. These substances were administered in capsules as nearly alike as possible. Symptoms of colds were systematically recorded, and the levels of ascorbic acid in the blood were determined periodically. The average level of ascorbic acid in 22 men who were to receive ascorbic acid by mouth was initially 0.96 mg. per 100 cc. of blood; after 12 weeks of taking only ascorbic acid the average for this group was 1.41 mg. per 100 cc. of blood. In all groups and at all stages, the blood ascorbic acid levels for males were significantly lower than those for females. There was no evidence that the naringin affected the ascorbic acid level of the blood, prevented colds, or cured them.
Franz WL, Sands GW, Heyl HL. BLOOD ASCORBIC ACID LEVEL IN BIOFLAVONOID AND ASCORBIC ACID THERAPY OF COMMON COLD. JAMA. 1956;162(13):1224–1226. doi:10.1001/jama.1956.02970300024009
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