title: Effects of maternal hydration status on the osmolality of maternal milk.
abstract: BACKGROUND
  It has been demonstrated that human milk osmolality (Mosm) is regulated within an established range, typically 290 to 300 mOsm/kg, and appears to be resistant to effects of maternal dehydration, as refl ected by high urinary osmolality (Uosm).
  
  
  OBJECTIVE
  To determine the degree of association between Mosm and Uosm at a common point in time, as well as the reproducibility of both measures over a one-week interval of sampling.
  
  
  METHODS
  Mosm and Uosm were measured with a Vogel Löser 450 osmometer on samples of the respective biological fluids collected concurrently in 31 lactating women, with infants aged between 30 and 340 days. In the first 15 women recruited, collections were repeated 7 days after the initial ones.
  
  
  RESULTS
  The median Mosm for the 46 samples collected was 308 mOsm/kg with a range from 288 to 448 mOsm/kg. The corresponding values for Uosm were 598 mOsm/kg with a range from 93 to 1,678 mOsm/kg. The Spearman rank-order correlation coeffi cient for within-individual association of Mosm and Uosm was r = 0.214 (p = 0.153). The median Mosm for the 15 repeat-subjects was 309 mOsm/kg on both occasions, with a within-individual Spearman coeffi cient of r = 0.326 (p = 0.118). By contrast, for the Uosm, the within-subject association was much stronger, with r = 0.699 (p = 0.002).
  
  
  CONCLUSIONS
  The osmometry technique proved to be a highly stable and reproducible measurement technique. Mosm and Uosm are not significantly associated at a point in time. Intra-subject Mosm varies more across time than intra-subject Uosm.
authors: Center for Studies of Sensory Impairment, Aging and Metabolism. Guatemala City.. clinicanutricion@gmail.com.
authors: María José
authors: MJ
authors: Soto-Méndez
authors: Alejandra
authors: A
authors: Maldonado
authors: Lauren
authors: L
authors: Burgunder
authors: Laura
authors: L
authors: Scieszka
authors: Ángel
authors: Á
authors: Gil
authors: Noel W
authors: NW
authors: Solomons
mesh_terms: D000293:Adolescent; D000328:Adult; D001834:Body Water / Q000502:physiology*; D003681:Dehydration / Q000378:metabolism; D005260:Female; D006801:Humans; D008875:Middle Aged; D008895:Milk, Human / Q000737:chemistry*; D009752:Nutritional Status; D009994:Osmolar Concentration; D014882:Water-Electrolyte Balance; D055815:Young Adult
keywords: Breastfeeding. Milk osmolality. Urine osmolality. Hydration status. Guatemala