Response of lingual ascorbic acid test and salivary ascorbate levels to changes in ascorbic acid intake.

This study sought to determine whether the lingual ascorbic acid test (LAAT) and measurement of salivary ascorbate reflect plasma and leukocyte ascorbate levels during controlled periods of ascorbic acid depletion and supplementation. Eleven healthy non-smoking men, aged 19-28 years, ate a diet that was repeated every seven days and was adequate in all nutrients except ascorbic acid (AA). This basal diet, which provided less than 5 mg of AA per day, was supplemented with 60 mg of AA per day for two weeks, 0 mg (placebo) per day for four weeks, 600 mg per day for three weeks, and 0 mg per day for four weeks. Oral examinations, the lingual ascorbic acid test, and measurement of salivary, plasma, and leukocyte ascorbate concentrations were conducted throughout the study. Ascorbic acid concentrations in plasma and leukocytes responded rapidly to changes in vitamin C intake. LAAT-derived ascorbate values were unrelated to ascorbic acid intake and plasma and leukocyte ascorbate concentrations. Salivary ascorbate levels approached the lower limits of detection of the assay and remained constant throughout the investigation. Oral hygiene was consistently excellent, and no severe mucosal or periodontal changes were observed. It was concluded that lingual ascorbic acid test values and salivary ascorbate levels are not related to changes in ascorbic acid intake and are not consistent with plasma or leukocyte ascorbate concentrations.