Zinc nutrition in healthy subjects and patients with taste impairment from the view point of zinc ingestion, serum zinc concentration and angiotensin converting enzyme activity

Objective To estimate the zinc nutrition in healthy subjects and patients with taste impairment. Dietary zinc intake, zinc concentration in the serum and the ratio of apo/holo-activities of angiotensin converting enzyme (ACE), a zinc dependent enzyme in the serum (ACE ratio) were used as indices. Subjects Healthy paramedical volunteers from a local hospital and patients with taste impairment seen in the Department of Otolaryngology, Tokushima University Hospital. Measurements Dietary zinc intake was estimated with the food frequency questionnaire (FFQ). Zinc concentration in the serum was measured by means of atomic absorption spectrometry. The ACE activity in the serum was measured spectrophotometrically as the activity of holo-ACE, which contains zinc and shows full ACE activity. The activity of apo-ACE, which dose not contain zinc, was determined as the increase of its activity over that of the initial holo-ACE activity after the addition of zinc to the serum in vitro. ACE ratio was used as a more sensitive indicator of zinc nutrition than measuring zinc concentration in the serum. Results There were no differences in dietary intake of zinc after adjusting for energy and zinc concentration in the serum between patients and age-adjusted healthy subjects. The ACE ratio in patients with taste impairment was significantly higher than that in age-adjusted healthy subjects (P < 0.05). Conclusion Our date demonstrate that zinc deficiency is a predominant factor underlying taste impairment and we hypothesize that patients with taste impairment may have malabsorption of dietary zinc.