Micronutrient Requirements During Pregnancy PDF

Chapter 5 – Part II Micronutrient Requirements during Pregnancy Thiamin and Pregnancy Requirement ↑ by ~30% ↑ Growth in maternal and fetal compartments (20%) Small ↑ in energy utilization (10%) RDA 14 – 50 years: 1.4 mg/d Nonpregnant Women RDA = 14-18 years: 1.0 mg/d 19-50 years: 1.1 mg/d needed for...

Chapter 5 – Part II Micronutrient Requirements during Pregnancy Thiamin and Pregnancy Requirement ↑ by ~30% ↑ Growth in maternal and fetal compartments (20%) Small ↑ in energy utilization (10%) RDA 14 – 50 years: 1.4 mg/d Nonpregnant Women RDA = 14-18 years: 1.0 mg/d 19-50 years: 1.1 mg/d needed for energy utilization: requirement goes up bc heavier (same as thiamin) Riboflavin and Pregnancy Additional riboflavin requirement 0.3 mg/d ↑ Growth in maternal & fetal compartments Small ↑ in energy utilization RDA 14 – 50 years: 1.4 mg/d Nonpregnant Women RDA = 14-50 years: 1.1 mg/day Niacin and Pregnancy No direct evidence to suggest a change in niacin requirement during pregnancy EAR: estimated that need ↑ by 3 mg/d of NEs (↑ energy utilization & growth) NE bc tryptophan —> niacin RDA 14 – 50 years: 18 mg NE/day Nonpregnant Women RDA = 14-50 years: 14 mg NE/day Vitamin B6 and Pregnancy Significant fetal uptake of vitamin B6 Maintenance of plasma [pyridoxal phosphate] at nonpregnant values requires ~2 mg/d supplemental B6 in the 1st trimester 4 – 10 mg/d in 3rd trimester Poorer vitamin status or normal physiological changes during pregnancy? hemodilution bc higher blood volume: higher than normal intake Vitamin B6 and Pregnancy Fetus & placenta accumulate ~25 mg of B6 = ~ 0.1 mg/day ↑Metabolic needs & weight of the mother And ~75% bioavailability of food B6  additional average pregnancy need: 0.25 mg Vitamin B6 and Pregnancy The ↑need is concentrated in the 2 nd half of gestation B6 is not stored in the body to any substantial extent unlikely that surplus in early gestation would satisfy the ↑need in later gestation Extra 0.6 mg/day of B6 to meet need in the 3rd trimester RDA (Pregnancy) 14 – 50 years: 1.9 mg/d RDA for Nonpregnant Women, 14 – 18 years = 1.2 mg/day 19 – 50 years = 1.3 mg/day Folate and Pregnancy Folate requirements ↑ substantially ↑ single-carbon transfer reactions Nucleotide synthesis (cell division): Uterine enlargement Placental development Expansion of maternal erythrocyte number Fetal growth Folate and Pregnancy ↑ [Folate] in cord blood vs maternal blood  Folate actively transferred to the fetus Inadequate folate intake: Maternal serum & erythrocyte [folate]s ↓ Megaloblastic marrow changes Megaloblastic anemia may develop if inadequate intake continues Folate and Pregnancy Primary indicator of adequacy: Erythrocyte folate maintenance (reflects tissue stores) 100 μg/d supplementation with a low-folate diet is insufficient To prevent deficient blood concentrations in 33% of women To prevent megaloblastic anemia in 5% of women Folate and Pregnancy Low dietary folate +100 μg supplemental folate (200 μg/day of DFEs): inadequate ⇒ EAR derived by adding This quantity in DFEs (200 μg/d) + EAR for non-pregnant women (320 μg/d) = 520 μg/d of DFEs (15 – 50 years) Folate EAR and RDA for Pregnancy EAR 14 – 50 years: 520 μg/day of DFE CV = 10% RDA (Pregnancy) 14 – 50 years: 600 μg/day of DFE RDA for Nonpregnant Women 14 – 50 years: 400 μg/d DFEs Folate and Pregnancy To ↓risk of NTD for women capable of becoming pregnant: 400 μg/d folic acid from fortified foods, supplements, or both + consuming food folate from a varied diet Vitamin B12 and Pregnancy Absorption of B12 may ↑ during pregnancy – ↑number of intrinsic factor-B12 receptors Serum total [B12]s ↓ in 1st trimester More than could be accounted for by hemodilution Month 6: ↓ to ~ ½ nonpregnancy concentrations Some due to hemodilution Vitamin B12 and Pregnancy Only newly absorbed B12 is readily transported across the placenta Maternal liver stores: less important source of the vitamin for the fetus Vitamin B12 and Pregnancy Fetal deposition: 0.1 – 0.2 μg/d Maternal absorption becomes more efficient  EAR ↑ by 0.2 μg/d RDA (Pregnancy) 14 – 50 years: 2.6 μg/d RDA for Nonpregnant Women 14 – 50 years = 2.4 µg/d Biotin and Pregnancy Recent studies conflict: low plasma [biotin] ?? ↑ Biotin metabolite (3-hydroxyisovaleric acid) in > ½ healthy pregnant women by 3rd trimester ↓ Urinary excretion of biotin in ~ 50% of women Normal changes or indicative of low biotin intake vs need? AI for Pregnancy 14 – 50 years = 30 μg/d of biotin AI for male and female adults 14 -18 years = 25 µg/day > 19 years = 30 µg/day Choline and Pregnancy ↑↑↑ Choline delivered to fetus through placenta  Depletes maternal stores of choline Important during embryogenesis and perinatal development Rats: extra dietary choline  ↑ Spatial memory AI for Pregnancy 14 – 50 years: 450 mg/d AI for Women 14 – 18 years: 400 mg/d > 19 years: 425 mg/d DNA methylation Phosphatidylcholine S-adenosylmethionine (SAM) Methionine B12 5-Me-TH4Folate Homocysteine CHOLINE Phosphatdylethanolamine (PtdEtn) Methionine synthase S-adenosylhomocysteine (SAH) seafood, whole grains Betaine B6 Cystathionine B6 Cystathionase Cysteine Pantothenic Acid and Pregnancy No information showing that usual intakes are inadequate for pregnancy Rounding up from average intake:14 – 50 years: 6 mg/d AI for Women 14 – 50 years: 5 mg/d Vitamin C and Pregnancy Maternal plasma [vitamin C] ↓ with pregnancy progression Hemodilution Active transfer to the fetus  Additional vitamin C needed Vitamin C and Pregnancy No precise data on maternal vitamin C transfer to fetus 7 mg/d of vitamin C prevent young infants from developing scurvy  EAR for pregnancy estimated to ↑10 mg/d Vitamin C RDA for Pregnancy 14 – 18 years 80 mg/d of vitamin C 19 – 30 years 85 mg/d of vitamin C 31 – 50 years 85 mg/d of vitamin C RDA for Nonpregnant Women 14 – 18 years: 65 mg/day > 19 years: 75 mg/day Vitamin C and Pregnancy Subpopulations of pregnant women may have ↑requirements Street drugs & cigarettes Heavy alcohol use Regular aspirin use >20 cigarettes/d  require 2x vitamin C Vitamin A and Pregnancy EAR based on Accumulation in fetal liver Assumption that liver contains ~1/2 body's vitamin A when liver stores are low (newborns) Efficiency of maternal vitamin A absorption = 70% Accumulates mostly in last 90 d Requirement ↑by ~ 50 μg/d during last trimester Vitamin A and Pregnancy EAR: 50 μg/day + EAR for nonpregnant adolescent girls and women Vitamin A for Pregnancy EAR 14 – 18 years 19 – 50 years 530 μg RAE/d 550 μg RAE/d RDA 14 – 18 years 19 – 50 years 750 μg RAE/d 770 μg RAE/d Nonpregnant Women RDA = 700 RAE/day Vitamin D and Pregnancy higher amounts might be necessary especially when inadequate sunshine exposure like Canada Small quantities of 25(OH)D transferred to fetus Do not affect overall Vit. D status of pregnant women ↓Serum 25(OH)D levels as pregnancy progresses without vitamin D supplementation bioactive form in kidneys that plays role in calcium metabolism Prenatal supplements with 400–600 IU may be insufficient 1000–4000 IU → ↓ preeclampsia, ↑ neonatal and child bone calcium, ↓ tooth enamel defects in children RDA for Pregnant & Nonpregnant Women 14-50 y; 600 IU (15 mcg)/d Vitamin E and Pregnancy maternal supplementation doesn’t seem to help the prematurity Deficiency can occur in premature newborns  hemolytic anemia No reports of deficiency during pregnancy No evidence that maternal supplementation would prevent deficiency symptoms in premature offspring RDA for Pregnancy and Nonpregnant Women 14 – 50 years: 15 mg/day of α-tocopherol AI for Vitamin K AI for Pregnancy and Nonpregnant Women 14 – 18 years: 75 μg/day > 19 years: 90 μg/day Calcium in Pregnancy ~ 25 – 30 g of Ca transferred to the fetus Majority during the 3rd trimester Major physiological adaptation: ↑Efficiency in intestinal absorption Calcium in Pregnancy Blood [1,25(OH)2D] ↑ during pregnancy Role is unclear Dietary Ca intake: no changes in maternal bone mass during pregnancy Calcium Requirement for Pregnancy RDA for Pregnancy 14 – 18 years 1,300 mg/day 19 – 30 years 1,000 mg/day 31 – 50 years 1,000 mg/day Nonpregnant Women RDA 14 – 18 years = 1,300 mg/d 19 – 50 years = 1,000 mg/d Phosphorus RDA for Pregnancy 14 – 18 years mg/d 19 – 30 years 1,250 31 – 50 years 700 mg/d 700 mg/d Nonpregnant Women RDA 14 – 18 years = 1,250 mg/d 19 – 50 years = 700 mg/d Magnesium during Pregnancy Serum [Mg] ↓ during pregnancy Thought to be due to hemodilution Parallels the decrease seen in serum protein Magnesium RDA for Pregnancy 14 through 18 years 400 mg/day 19 through 30 years 350 mg/day 31 through 50 years 360 mg/day Nonpregnant Women RDA = 14-18 years 360 mg/day 19-30 years 310 mg/day 31-50 years 320 mg/day Iron: Factorial Modeling Used to Determine EAR The components of Fe requirement used as factors include Basal iron losses Menstrual losses Fetal requirements in pregnancy Growth: expansion of blood volume, and/or ↑ tissue and storage iron Iron Requirements During Pregnancy Requirement for absorbed Fe = Basal losses + Fe deposited in fetus & related tissues + Fe in expansion of Hb mass. Total usage of Fe throughout pregnancy = 250 mg (basal losses) + 320 mg (fetal & placental deposition) + 500 mg (↑ Hb mass) = 1,070 mg. Iron Requirements During Pregnancy Absorbed Req’t (mg/d) Absorption (%) Req’t (mg/d) 1st trimester 1.2 18 6.4 2nd trimester 4.7 25 18.8 3rd trimester 5.6 25 22.4 Stage of Gestation Iron Requirements During Pregnancy Severe anemia (Hb < 40g/L) Associated with perinatal maternal mortality Moderate anemia (Hb < 80 g/L) Associated with a 2X risk of maternal death Iron Requirements During Pregnancy Large epidemiological studies: Maternal anemia associated with premature delivery, LBW, ↑ perinatal infant mortality High [Hb] at the time of delivery Associated with adverse pregnancy outcomes (e.g. SGA) Iron Requirements During Pregnancy Habitual Canadian diet cannot meet Fe RDA Recommend Fe supplements Supplementation: assumption of inadequate prepregnant Fe stores. Normal Fe stores  supplement is unnecessary (storage Fe can be used) Iron Supplementation During Pregnancy 3 Longitudinal European studies: Women in developed countries: high incidence of anemia ~1/2 – 1/3 of pregnancies among women who do not supplement Studies consistently show a high incidence of Fe-deficiency anemia among pregnant & non-pregnant women. Iron RDA for Pregnancy 14 – 18 years 27 mg/d 19 – 30 years 27 mg/d 31 – 50 years 27 mg/d Nonpregnant Women RDA = 14-18 years 15 mg/day 19-30 years 18 mg/day 31-50 years 18 mg/day Potassium AI in Pregnancy Very small potassium accretion during pregnancy No data to suggest a different requirement for potassium during pregnancy Highest median intake among pregnant women is used to set AI  Al = 2.9 g/d (19-50 y); 2.6 g/d (14-18 y) Nonpregnant Women RDA = 14-18 years 2.3 mg/day 19-30 years 2.6 g/day 31-50 years 2.6 g/day Sodium in Pregnancy Pregnancy requires an extra 2.1-2.3 g Na to Maintain the ↑ in plasma volume Provide for the products of conception This accumulation occurs over 9 months Additional Na needed (0.07 g/day [3 mmol/day]) So minimal  Na requirements during pregnancy do not differ from that of nonpregnant women.  Al = 1.5 g/d Zinc in Pregnancy Mean daily zinc accumulation in maternal and embryonic/fetal tissues during the four quarters of pregnancy = 0.08, 0.24, 0.53, and 0.73 mg Average fractional absorption of Zn is 27% EAR = based on the additional Zn requirement during the fourth quarter = 0.73/0.27 = 2.7 mg/day of zinc Plus EAR for nonpregnant women (6.8 mg/day) Zinc RDA for Pregnancy EAR 14-18 years 10.0 mg/day 19-30 years 9.5 mg/day 31-50 years 9.5 mg/day CV of 10 percent RDA 14-18 years 12 mg/day 19-30 years 11 mg/day Nonpregnant 31-50 years 11 mg/day Women RDA 14 – 18 years = 9 mg/d 19 – 50 years = 8 mg/d Iodine RDA for Pregnancy EAR >14 years 160 μg/day CV of 20 percent RDA >14 years 220 μg/day Nonpregnant Women RDA = 150 μg/day Iodine Iodine deficiency during pregnancy - miscarriage, stillbirth, and birth defects Fetal iodine deficiency caused by iodine deficiency in the mother Severe iodine deficiency during pregnancy - congenital hypothyroidism (cretinism) Selenium RDA for Pregnancy EAR for Pregnancy >14 years 49 μg/day RDA for Pregnancy >14 years 60 μg/day Nonpregnant Women RDA = 55 μg/day Copper RDA for Pregnancy bc of fetal deposition —> higher bioavailability of copper RDA 14-50 years 1,000 μg/day Nonpregnant Women RDA = 900 μg/day Manganese AI for Pregnancy goes up bc additional maternal weight Al 14-18 years 2 mg/day 19-30 years 2 mg/day 31-50 years 2 mg/day Nonpregnant Women AI = 1.8 mg/day Chromium AI For Pregnancy Al 14-18 years 29 μg/day 19-30 years 30 μg/day 31-50 years 30 μg/day additional maternal weight Nonpregnant Women AI = 25 μg/day Molybdenum RDA for Pregnancy additional maternal weight EAR >14 years 40 μg/day RDA >14 years 50 μg/day Nonpregnant Women RDA = 45 μg/day Fluoride Relationships between caries and water fluoride concentrations and fluoride intake, the Al for fluoride from all sources = 0.05 mg/kg/day Recommended for all ages > 6 months = high level of protection against dental caries Nonpregnant women 14-50 years = 3 mg/day Pregnancy AI = 3 mg/day