Misuse of hair analysis for nutritional assessment.

The analysis of hair for nutritional assessment has a number of potential pitfalls, which include: (1) contamination by sweat, (2) environmental contamination, (3) influence of previous beauty treatments, (4) critical dependence upon location of the hair sample, (5) paradoxic values depending upon the rate of hair growth, and (6) lack of clear definition of a normal range. The results of measuring metal concentrations in hair even under ideal circumstances may not correlate with those obtained in blood and urine. Long-term exposure to heavy metals, including lead, cadmium, arsenic, and mercury, can be readily identified by hair analysis. Little if any value is derived from a random examination of hair as the sole procedure for nutritional assessment. Nutritional recommendations should not be based on the results of hair analysis alone.