Measurements Urinary DHA was measured using a rapid and robust ultra high power liquid chromatography - electrospray tandem mass spectrometry (UPLC-MS/MS)), recently developed by our group. The 24-hour urinary DHA excretion (mg/24-hours) was measured and the urinary DHA-to-creatinine ratio (mg/mmol) in first morning urine samples was calculated. Urine and serum creatinine concentrations were measured with an isotope dilution mass spectrometry (IDMS) standardized laboratory method.