Hair zinc concentrations not subject to seasonal variation in adults in New Zealand

The analysis of recently grown hair for zinc provides a biomarker of recent zinc status. Seasonal variation of zinc in hair has been demonstrated in children. The aim of this study was to investigate whether on a month-by-month basis there is a seasonal variation in hair zinc concentration in an apparently well-nourished adult population in New Zealand. It was hypothesized that increased hours of daylight would be associated with an increase in zinc concentration in hair. Thirty-four subjects (20 F, 14 M) aged 18–54 yr had occipital hair sampled at monthly intervals between June and December. Food variety was assessed by questionnaire. After thorough washing of the hair followed by nitric acid digestion, zinc was determined by flame atomic absorption spectrometry (FAAS) with special attention to the inclusion of blanks, internal and international standards, and reduction of contamination in each sample run. Analyses between two laboratories confirmed that two FAAS instruments were giving the same reading. No seasonal variation in hair zinc concentration was found. Reported dietary variety, ethnicity, gender, and hair color were unrelated to hair zinc concentrations in this population. This study adds to evidence that will help define the role of hair zinc in determining recent zinc status.