Carbohydrate • Protein • Lipids
2002 DRI for Carbohydrate • DRIs for carbohydrate based on brain glucose utilization • RDA for adults and children = 130 g/day • Median intake ~: • Men: 200-330 g/day • Women: 180-230 g/day
2002 DRI for Carbohydrate in Pregnancy • Fetal brain needs a minimum of 33 g/day • EAR for pregnancy (all ages) = 135 g/day • RDA for pregnancy (all ages) = 175 g/day • CV is 15% based on variations in brain glucose utilization • RDA = EAR plus twice CV CV: coefficient of variation (used when insufficient data to determine standard deviation) EAR: Estimated Average Requirement
2002 DRI for Fiber in Pregnancy • “There is no evidence to suggest the beneficial effects of fiber in reducing risk of CHD is different from non-pregnant adolescent girls and women.” • AI = 28 g/day (14 g/1,000 kcal x median kcal intake for group) • AI for non-pregnant women is 25 g/day
Effect of a low-glycemic-index diet during pregnancy on obstetric outcomes(Moses et al. AJCN 2006) • 62 women randomized to counseling to promote low GI (LGI) or moderate/high GI (HGI) • Outcomes for HGI diet: • Higher birthweight (3408 vs 3644) • Higher prevalence LGA (3% vs 33%) • Conclusion: “Because birth weight and ponderal index may predict chronic disease in later life, a low-GI diet may favorably influence long-term outcomes.”
Dietary fiber intake, dietary glycemic load, and the risk for gestational diabetes mellitusZhange et al. Diabetes Care, 2006 • Examined prepregnancy diet in the Nurses Health study (758 pregnancies in 13,110 women over 8 years), adjusted for age, parity, prepregnancy BMI, and other covariates • Results • Each 10-g/day increment in total fiber intake was associated with 26% (95% CI 9-49) reduction in risk of GDM • Each 5-g/day increment in cereal or fruit fiber was associated with a 23% (9-36) or 26% (5-42) reduction, respectively. • Dietary glycemic load was positively related to GDM risk. Multivariate relative risk for highest versus lowest quintiles was 1.61 (1.02-2.53) (P for trend 0.03).
The dietary glycemic index during pregnancy: influence on infant birth weight, fetal growth, and biomarkers of carbohydrate metabolismScholl et al, Am J Epi, 2004) • n=1082, very low income, mostly young, ethnic minorities in Camden NJ • women with a dietary glycemic index in the lowest quintile had approximately a twofold increased risk of bearing a growth-restricted infant compared to middle quintile (AOR = 1.75 (1.10, 2.77)
EAR for Protein in Pregnancy • EAR = 21 g/day above protein needs at prepregnancy weight • EAR Per kg • Increased amount on a per kg basis is 0.22 g/protein/kg/day • EAR for non-pregnant = 0.66 g protein/kg per day • EAR for pregnancy = 0.88 g/kg/day
RDA for Protein for Pregnancy • 1.1 g/kg/day or 25 g/day additional protein (EAR plus allowance for individual variation) • RDA for women aged 19-50 is 46 g/day • RDA is 71g protein per day Reference woman is 57 kg
RDA to Diet • RDAs calculated using high quality reference proteins like egg, meat, milk or fish • However, even with adjustments for lower quality proteins most women in the US who are meeting energy needs with reasonable food choices, will meet protein needs. • Range in US is 75 to 110 g per day for women.
Energy and Protein • If energy needs are not met by diet then protein will be used for energy • RDA calculations assume adequate energy intake
Protein Supplementation • In developing countries protein and energy supplements may improve pregnancy outcomes when women are undernourished • There is little evidence that protein supplementation affects outcome in developed countries
Adverse Effects of Protein Supplementation • Several human and animal studies of protein supplementation have found adverse effects including retarded fetal growth, increase in prematurity, and increased neonatal deaths.
Cochrane Collection: Energy and Protein Intake in Pregnancy (Kramer et al, 2004) • objectives: To assess the effects of advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction during pregnancy on energy and protein intakes, gestational weight gain, and the outcome of pregnancy
Cochrane Collection: High protein supplementation in pregnancy • Selection criteria: acceptably controlled trials of dietary advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction, during pregnancy.
Results: dietary advice to increase energy and protein intakes • 5 trials, 1134 women • Dietary advice increased intakes • No consistent benefit was observed for pregnancy outcomes
Results: Balanced Energy/Protein Supplementation • 13 trials, 4665 women • Modest increase in maternal weight gain and mean birth weight • Reduction risk for SGA • Reduced risk of stillbirth and neonatal death • No significant effects on preterm birth
Results: High Protein Supplementation • Two trials, 1076 women • Small, nonsignificant increase in maternal weight gain and nonsignificant reduction in birth weight • Increased risk of SGA • Nonsignificant increased risk of neonatal death
Results: Energy/protein restriction for overweight women • 3 trials, 384 women • Reduced maternal weight gain • Reduced mean birth weight • No effect on pregnancy induced hypertension or pre-eclampsia
Lipids • General lipid recommendations for pregnancy • Essential fatty acids & LCPUFA • Trans FA
Lipids: Maternal • Metabolism changes to: • meet increased maternal needs for energy and hormones precursors • to insure adequate fetal accretion • Serum cholesterol rises 25-40% • Triglycerides rise 200-400%
Lipids: Maternal Recommendations, 2002 DRI • 30% of kcals from fat is a reasonable goal in pregnancy. • There is no need to try to affect the physiological rise in blood lipids
Background: LCPUFA • Dietary sources of n-3 and n-6 fatty acids are essential. • Fetal ability to elongate and desaturate fatty acids is limited. • Conversion of LNA to DHA is highly variable among individual infants.
Fetal Implications • Human brain is lipid based; ~ 60% of dry weight • 30% of fetal CNS tissue is LCPUFA with n-3 to n-6 ratio of 2:1 • Fetal brain development starts early & experiences “growth spurt” during last trimester and 1st 6 months of life • In 3rd trimester, storage of LCPUFA in fetal adipose tissue if adequate maternal sources • Adequacy of LCPUFA associated with CNS and retinal function.
Background: Placental Transfer • The fetus is totally dependent on maternal intake and placental transfer. • The placenta selectively transports LCPUFA • Concentrations of DHA and ARA are 300 to 400 fold higher in fetal vs maternal plasma phospholipids
Maternal LCPUFA status maters to the Infant • Women with higher plasma ARA and DHA during pregnancy have infants with higher ARA and DHA • Higher n-6 and n-3 status at birth results in higher ARA and DHA for several weeks.
Dunstan et al. Pediatr Res, 2007. Fish oil supplementation in pregnancy on breastmilk FA composition over the course of lactation • RCT, n=98, Fish oil (s.2.g DHA, 1.1 g EPA) vs olive oil from 20 wk to term • Breastmilk had higher DHA & EPA at 3 d and 6 weeks • Infants had higher DHA/EPA at 1 yr • Positive correlations between breastmilk DHA/EPA and infant developmental scores
Maternal LCPUFA Status matters to the Pregnancy • Eicosanoids derived from LCPUFA (prostaglandins, thromboxanes, prostacylcins, leukotrienes) play vital roles in pregnancy • The ideal ratio of n-3 to n-6 remains unknown • Dietary sources of EFA - both n-3 and n-6 are important
PIH and n-3 Fatty Acids • Possible biological pathway: • Vasoconstriction and epithelial damage of PIH is associated with imbalance of TXA2 (vasoconstrictor) and PGI2 (vasodilator) • If increased dietary intake of n-3: • EPA competes with Arachadonic Acid for enzymes so may have lower production of TXA2 and higher production of PGI3 (vasodilator)
PIH and n-3 Fatty Acids • Epidemiological Studies: • several studies have found that women with PIH have lower levels of n-3 • lower incidence of PIH in fish eating populations • RCT • “Compelling evidence for a beneficial effect of n-3 fatty acids on preeclampsia from recent prospective, double-blind studies is lacking (Jensen, Am J Clin Nutr, 2006)
N-3 and Prolonged Gestation • Faroe Islands: • high birthweights • longer gestations • diet high in marine oils • Theory: n-3 interference with uterine prostaglandin production
N-3 and Prolonged Gestation • Supplementation study: • increased gestational length by 4 days • prolonged bleeding times & increased blood loss at delivery
N-3 and Maternal Depression (Jensen, AJCN, 2006) • “Recent observational trials and open-label trials of n-3 FA supplementation appears promising.” • “At present, however, there is a paucity of data from controlled studies supporting the efficacy of n-3 FA in the prevention or treatment of depression during pregnancy or the postpartum period.”
N-3 intake and Depression by Country (Hibbeln, AJCN, 2006) • In model with 20 countries, correlation between postpartum depression rates and energy from n-3 FA was r=-0.78, p<0.001)
Infant visual function/neural development (Jensen, 2006) • Observational studies find both positive associations and no association. • Small intervention studies: possible associations with attention & distractibility and visual functioning.
Essential Fatty Acids in Mothers and Their Neonates(Hornstra, AJCN, 2000) • Maternal essential fatty acid status declines during pregnancy (absolute plasma levels in-crease, but non-essential increase more). • Pregnancy may cause maternal DHA depletion/mobilization from maternal stores. (Implications for close pregnancy spacing)
Essential PUFA status of newborns is restricted by that of the mother and may not be optimal. • Maternal PUFA supplementation affects neonatal PUFA status. • Maternal linoleate intake during pregnancy is negatively related to neonatal head circumference. • In preterm infants positive relationship between DHA in umbilical artery and birth weight. Length, and OFC.
Hornstra - Implications • Humans evolved with limited ability to elongate and desaturate EFA? • Limitations require special consideration during increased requirements of fetal development, lactation, and neonatal development.
Hibbeln et al. Maternal seafood consumption in pregnancy & neurodevelopmental outcomes in childhood. Lancet 2007 • Maternal seafood consumption of less than 340 g per week in pregnancy did not protect children from adverse outcomes; rather, we recorded beneficial effects on child development with maternal seafood intakes of more than 340 g per week, suggesting that advice to limit seafood consumption could actually be detrimental. These results show that risks from the loss of nutrients were greater than the risks of harm from exposure to trace contaminants in 340 g seafood eaten weekly.