Reduced serum zinc concentration during pregnancy

Area of Science:

• Biochemistry
• Human Physiology
• Nutritional Science

Background:

• Serum zinc concentration is a key indicator of zinc status.
• Zinc is primarily bound to albumin and alpha 2-macroglobulin in serum.
• Pregnancy involves significant physiological adaptations, including changes in blood volume and protein concentrations.

Purpose of the Study:

• To investigate serum zinc concentrations and partitioning in pregnant versus nonpregnant women.
• To determine if lower serum zinc in pregnancy reflects inadequate zinc intake or a normal physiological adaptation.
• To assess the binding of zinc to serum albumin and alpha 2-macroglobulin during pregnancy.

Main Methods:

• Controlled diet study with 16 mg/day zinc intake.
• Measurement of serum zinc concentration in ten pregnant and five nonpregnant women.
• Analysis of serum zinc partitioning between albumin and alpha 2-macroglobulin.

Main Results:

• Pregnant women showed 19-27% lower total serum zinc concentrations compared to nonpregnant controls.
• This decrease was associated with lower serum albumin concentrations.
• Despite lower absolute amounts, the distribution of serum zinc (75% albumin-bound, 25% alpha 2-macroglobulin-bound) remained consistent between groups.

Conclusions:

• The decline in serum zinc concentration during pregnancy is a normal physiological adjustment.
• Lower serum zinc in pregnancy does not necessarily indicate inadequate zinc nutriture.
• Expanded maternal blood volume may contribute to a larger total circulating zinc pool despite lower serum concentration.