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

Calcium 65 g 7%

Zinc 370 mg 80%

PG + 24 Mo Lactation % Bone

Calcium 140 g 14%

Zinc 640 mg 140%

Sources of Calcium or Zinc for Pregnancy and Lactation

FETUS/MILK

BONE

ECF/PLASMA

SMALLINTESTINE

KIDNEY

Absorption

Endog.Secretion

Accretion

Resorption

ReabsorptionFiltration

*Diet Intake

*Net retention *Mobilization

* Netretention

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

8-10Wks

24-26 Wks

34-36Wks

7-9Wks

6 moaftermenses

Concep-tion

Birth 2 wks

Pregnancy Lactation

Diet X X X X X X

Abs X X X X X X

Blood X X X X X X

Urine X X X X X X

Milk X

Changes in Calcium and Zinc Intakes

0.0%

10.0%

20.0%

30.0%

Per

cen

t of

Pre

-Pre

gnan

cy I

nta

ke

2T 3T LC

Zinc

Calcium

*

*

* = p<0.05

Fractional Absorption of Calcium and Zinc

0.0%

20.0%

40.0%

60.0%

80.0%

Per

cen

t of

Pre

-Pre

gnan

cy

2T 3T LC

Zinc

Calcium

*

*

*=p<0.001

o

o=p<0.05

Changes in Urinary Excretion of Calcium and Zinc

(75)%

(50)%

(25)%

0%

25%

50%

75%

100%

Per

cen

t of

Pre

-pre

gnan

t V

alu

e

2T 3T LC

Zinc

Calcium

b

a

b,c

Ca: p<0.001

b

a,b a,b

Zn: p<0.01

Changes in Lumbar Spine Bone Mineral Content: QCT

(10)%

(7)%

(5)%

(2)%

0%

2%

Ch

ange

fro

m P

rep

regn

ancy

PrePg-Birth Birth-LC PrePg-Post Menses

*

* = P<0.001

Calcium Homeostasis: Late Pregnancy Adjustments

FETUS

BONE

ECF/PLASMA

SMALLINTESTINE

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

SMALLINTESTINE

KIDNEY

Net Absorption: 1.0 mg/d

Filtration:+ 0.3 mg/d

Diet Intake: +3 mg Zn/d

0.7 mg/d

Calcium Homeostasis: Lactation Adjustments

MILK

BONE

ECF/PLASMA

SMALLINTESTINE

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

SMALLINTESTINE

KIDNEY

Net Absorption: 1.3 mg/d

Net Resorption:0.9 mg/dFiltration:

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, 34-36 wks gestation; 7-9 wks lactation

Effect of Maternal Status on Calcium Absorption

0

10

20

30

40

50

60

70

80

90

100

10-12 wks gestation 34-36 wks gestation 7-8 wks lactation

Tru

e A

bs

orp

tio

n, %

U.S. Women

Rio Women

Effect of Maternal Status on Urinary Calcium Excretion

0

50

100

150

200

250

300

10-12 wks gestation 34-36 wks gestation 7-8 wks lactation

Uri

na

ry C

alc

ium

, m

g/d

U.S. Women

Rio Women

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 150 154 158

Fecal Se, µg/d 28 33 28

Urinary Se, µg/d 111 100 96

Balance, µg/d 11 21 34

Recommended Multivitamin Mineral Supplement for

Pregnancy*Nutrient Amount

Iron 30 mg

Zinc 15 mg

Copper 2 mg

Calcium 250 mg

Vitamin B6 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