Nutrition During Pregnancy and Lactation Exploring New Evidence: Proceedings of a Workshop (2020) / Chapter Skim
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2 Macronutrient Requirements
2 Macronutrient Requirements
Pages 7-24
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Highlights from the session presentations are presented in Box 2-1. DIETARY FAT, FATTY ACIDS, AND THE SPECIFIC HEALTH EFFECTS OF OMEGA-3 FATTY ACIDS IN PREGNANCY AND LACTATION Maria Makrides, theme leader for SAHMRI Women and Kids at South Australian Health and Medical Research Institute, opened her remarks by explaining that although the omega-3 long-chain polyunsaturated fatty acids (LCPUFAs)
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. • Energy requirements during pregnancy vary by a woman's prepregnancy weight status, physical activity level, and stage of pregnancy (Redman)
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She also mentioned that this finding was consistent with recent systematic reviews. Risk of Allergy and Asthma in Children Makrides described a theory that posits that higher omega-3 fatty acid intake can decrease the conversion of the omega-6 fatty acid arachidonic acid to prostaglandin E2 (a pro-inflammatory compound)
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For instance, the DOMInO Study assessed children at high hereditary risk and provided a lower dose of EPA as compared to COPSAC. Size and Childhood Growth To explore the relationship between omega-3 fatty acid intake and size and childhood growth, Makrides again compared results from the DOMInO Study and COPSAC.
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Women who had a baseline omega-3 fatty acid status of less than or equal to 4.1 percent of total fatty acids and were supplemented experienced a 77 percent reduction in early preterm birth. Supplementing women who had a higher baseline omega-3 fatty acid status, however, may increase risk for early preterm birth.
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Trans fatty acid intake in Australia and concentrations in the blood are both very low, remarked Makrides. She offered that her group has investigated the possibility that arachidonic acid and linoleic acid, both omega-6 fatty acids, compete with omega-3 fatty acids, but neither fatty acid was related to the preterm birth outcomes.
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PROTEIN AND AMINO ACID REQUIREMENTS IN PREGNANCY AND LACTATION: NEW EVIDENCE CHALLENGES CURRENT RECOMMENDATIONS To provide context for his remarks, Rajavel Elango, associate professor in the Department of Pediatrics in the School of Population and Public Health at The University of British Columbia, explained that protein is needed throughout the life span for maintenance and during developmental stages for growth. Protein requirements have been defined as the lowest level of dietary protein intake that will balance the losses of n itrogen from the body, and thus maintain the body protein mass, in persons at energy balance with modest levels of physical activity, plus, in children or in pregnant or lactating women, the needs associated with the deposition of tissues or secretion of milk at rates consistent with good health.
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New Estimates of Protein Needs A new methodology, called indicator amino acid oxidation, was developed to overcome the limitations assessing protein needs using nitrogen balance studies. The concept -- which Elango attributed to Paul Pencharz, Ronald Ball, and colleagues -- uses stable isotopes to trace the utilization of a labeled amino acid by the body.
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Data from the Danish National Birth Cohort indicate a possible U-shaped relationship between protein intake and low birth weight; women whose total energy intake from protein was less than 10 percent, or more than 20 percent, were at increased risk for having a low birth weight infant, noted Elango. A trial conducted in Gambia reported that women given a supplement of 1,017 kcal/day and 22 g/day of protein reported a 39–42 percent reduction in low birth weight infants (Ceesay et al., 1997)
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Elango characterized the ketogenic diet as being perfectly normal for the clinical management of seizures during pregnancy. However, he noted that under normal circumstances glucose and amino acids are the primary sources of fuel for a fetus, and said, "You cannot switch it out and consider ketones to be a source for the fetus in the long run." Elango indicated that the safety of the ketogenic diet for healthy pregnant women is unknown, and caution needs to be exercised.
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The carbohydrate EAR for pregnant women of 135 g/day accounts g for both maternal and fetal brain glucose utilization. The carbohydrate EAR of 160 g/day for lactating women was estimated based on maternal brain glucose utilization and on breast milk lactose composition.
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for fiber based on epidemiological evidence that fiber intake reduces risk of coronary heart disease and some cancers and plays a role in weight management. Remarking that none of the outcomes used to derive the AI values were specific to pregnancy, Redman noted the total fiber AI for pregnancy was established at 28 g/day (14 g/1,000 kcals total energy intake)
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Evidence Relating Carbohydrate Intake to Pregnancy Outcomes Relationships between carbohydrate intake and pregnancy outcomes can be difficult to discern owing to differences in the proportion and quality of carbohydrates tested, stated Redman. One study reported that pregnant women who consume a low carbohydrate dietary pattern are at increased risk for gestational diabetes (Bao et al., 2014)
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Women in their first trimester have no additional energy requirements. Additional energy expenditure and energy deposition are accounted for in the EER equations for the second and third trimesters, resulting in an increase of 340 and 452 additional kcals/day, respectively (see Box 2-2)
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p s Elango confirmed its importance and said, "I do not think pregnant women who are already well nourished who started off in a fairly nourished state need additional protein beyond their normal consumption patterns." Build ing on this concept, Erica Gunderson of the Kaiser Permanente Northern California Division of Research wondered if Elango had related the protein requirements to lean body mass, given how it affects metabolic state. He replied that his group has not explored this yet, and that they primarily study healthy pregnant women and adults who have normal body composition.
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A question about placental needs over the course of pregnancy revealed differences in the methodologies for assessing carbohydrate and protein requirements. Redman reminded the audience that the current DRIs for carbohydrate needs were derived using brain glucose utilization estimates; she was unaware of any stable isotope studies that had been conducted in pregnant women to assess whole body oxidation of carbohydrates.
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Focusing on vegetarian and vegan pregnant women, an unidentified audience member asked if there are specific foods that should be consumed to meet the changing needs for specific amino acids. Elango cautioned that more work needs to be done before such recommendations could be made.
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