nutrient bioavailability during reproduction janet c. king, ph.d. director and professor western...
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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