Nutrient Bioavailability during Reproduction Janet C. King, Ph.D. Director and Professor Western Human Nutrition Research Center University of California, Davis

Bioavailability Fraction of the ingested nutrient that is used for normal physiological functions or storage

Endogenous Factors Influencing Bioavailability Body ‘status’ of the nutrient, i.e. need –growth –pregnancy –lactation –previous intake of the nutrient Gut Function –Efficiency of digestion –Transit time –Presence of disease

Effect of Pregnancy and Lactation on the Bioavailability of: Calcium and Zinc Regulated by Gastrointestinal Tract Selenium Regulated by Kidney

Calcium and Zinc Needs for Pregnancy and Lactation PG + 6 Mo Lactation% Bone Calcium65 g 7% Zinc370 mg 80% PG + 24 Mo Lactation% Bone Calcium140 g14% Zinc640 mg 140%

Sources of Calcium or Zinc for Pregnancy and Lactation FETUS/MILK BONE ECF/PLASMA SMALL INTESTINE KIDNEY Absorption Endog.Secretion Accretion Resorption Reabsorption Filtration *Diet Intake *Net retention*Mobilization * Net retention

Calcium and Zinc Metabolism during Pregnancy and Lactation: Longitudinal Studies L. D. Ritchie, E. B. Fung, L.R. Woodhouse, C. Donangelo, R. Roehl, S.A.Abrams, B.Halloran, C. Cann, M. Van Loan, J.R. Turnlund, and J.C. King

Study Design Pre- PG 8-10 Wks Wks Wks 7-9 Wks 6 mo after menses Concep- tion Birth 2 wks Pregnancy Lactation DietXXXXXX AbsXXXXXX BloodXXXXXX UrineXXXXXX MilkX

Changes in Calcium and Zinc Intakes

Fractional Absorption of Calcium and Zinc

Changes in Urinary Excretion of Calcium and Zinc

Changes in Lumbar Spine Bone Mineral Content: QCT

Calcium Homeostasis: Late Pregnancy Adjustments FETUS BONE ECF/PLASMA SMALL INTESTINE KIDNEY Net Absorption: 380 mg/d Filtration: +80 mg/d Diet Intake: +300 mg Ca/d +300 mg/d

Zinc Homeostasis: Late Pregnancy Adjustments Fetus BONE ECF/PLASMA SMALL INTESTINE KIDNEY Net Absorption: 1.0 mg/d Filtration: mg/d Diet Intake: +3 mg Zn/d 0.7 mg/d

Calcium Homeostasis: Lactation Adjustments MILK BONE ECF/PLASMA SMALL INTESTINE KIDNEY Net Resorption Reabsorption Diet Intake: +65 mg Ca/d 215 mg/d 95 mg/d 120 mg/d

Zinc Homeostasis: Lactation Adjustments BONE ECF/PLASMA SMALL INTESTINE KIDNEY Net Absorption: 1.3 mg/d Net Resorption: 0.9 mg/d Filtration: 0.2 mg/d Diet Intake: +1 mg Zn/d 2.0 mg/d Milk

Conclusion The fraction of ingested calcium and zinc retained increases during pregnancy and lactation. –Adjustments for pregnancy differ from lactation. –Adjustments for calcium differ from zinc

Effect of Low Calcium Intakes on Calcium Metabolism during Pregnancy and Lactation Nine parous women from Rio de Janeiro Usual calcium intake: 440 mg/d Calcium intake increased by 75 mg/d in LP No supplemental calcium Studied at 10-12, wks gestation; 7-9 wks lactation

Effect of Maternal Status on Calcium Absorption

Effect of Maternal Status on Urinary Calcium Excretion

A Comparison of Selenium Bioavailability in Pregnant and Nonpregnant Women Christine A. Swanson, Donald C. Reamer, Claude Veillon, Janet C. King, and Orville A. Levander

Selenium Balance NP (n=6)EP (n=6)LP (n=4) Se Intake, µg/d Fecal Se, µg/d Urinary Se, µg/d Balance, µg/d

Recommended Multivitamin Mineral Supplement for Pregnancy* NutrientAmount Iron30 mg Zinc15 mg Copper 2 mg Calcium 250 mg Vitamin B 6 2 mg Folate 300 µg Vitamin C 50 mg Vitamin D 5 µg * IOM, 1990

Gaps in Knowledge Bioavailability of chemical forms of nutrients in supplements Interaction of nutrients provided in prenatal supplements Effect of food on the bioavailability of nutrients in prenatal supplements UL for nutrients during pregnancy and lactation