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L 37 Nutrition

Maternal Nutrition

  • Concept: fetal origins of disease — inadequate nutrition during fetal development can predispose to health issues and chronic diseases later in life. The fetus can only receive nutrients from the mother (host).
  • Preconceptual guidance for women to support fertility and fetal growth:
    • BMI before pregnancy: too low → anovulation; obesity → hormonal imbalance, irregular cycles, lower conception rates, higher congenital anomalies, lower live birth rates.
    • Multivitamin–multimineral supplementation is typically recommended to avoid deficiencies that affect fertility and fetal growth (e.g., zinc, iron, vitamin D, folic acid).
    • Vitamin D deficiency can be related to insulin resistance and polycystic ovary syndrome (PCOS).
    • Adequate protein, choline, and long-chain polyunsaturated fatty acids are important.
  • Male infertility and nutrition:
    • Vitamin D deficiency can affect testosterone levels and sperm quality.
    • Calcium is needed for spermatogenesis, sperm motility, and activation.
    • Sperm count benefits from zinc, folic acid, and antioxidants; alcohol and tobacco hinder fertility.
    • Tobacco can cause DNA damage to sperm; alcohol (>5 drinks/week) can reduce sperm concentration and normal morphology.
    • Fertility improvements with: high fiber, low GI, lower animal protein, plant-based iron sources, multivitamins, and moderate physical activity.
  • During pregnancy: exposure to harmful substances in maternal diet can affect fetal development:
    • Alcohol: negative effects on fetal development; high intake in early pregnancy → poor placental growth and reduced taurine transport to fetus.
    • Fetal alcohol spectrum disorders (FASD) include fetal alcohol syndrome and alcohol-related neurodevelopmental disorder; FAS is the most severe form with high prenatal mortality, teratogenesis, and cognitive impairment; survivors may be irritable and hyperactive at birth.
    • Physical patterns of FASD abnormalities include short palpebral fissure length, thin upper lip, smooth philtrum, short nose, small head, low nasal bridge.
    • Alcohol can alter gene expression related to CNS development and organ morphogenesis; maternal alcohol use is linked to miscarriage, placental abruption, low birth weight, and cognitive issues; no safe threshold identified; recommendation: refrain from alcohol.
    • Caffeine crosses the placenta; high intake may increase risk of low birth weight, subfertility, and spontaneous abortion; <200 mg/day is not clearly linked to miscarriage, preterm birth, or birth defects (e.g., ~95 mg in an 8-oz cup of coffee).
    • Artificial sweeteners: FDA-deemed safe in moderation during pregnancy (saccharin, acesulfame-K, sucralose, aspartame, neotame, advantame, stevia, monk fruit).
    • Cigarette smoke exposure: increased risk of miscarriage, growth restriction, low birth weight, preterm delivery.
  • Physiological changes in pregnancy that support fetal development:
    • Blood volume increases (plasma volume and red blood cells), leading to lower hematocrit and hemoglobin in pregnancy.
    • Basal metabolic rate (BMR) increases; energy needs for fetal growth rise and depend on changes in activity and BMR.
    • Trimester energy requirements:
    • 1st trimester: about the same as nonpregnant women.
    • 2nd trimester: +340 kcal/day.
    • 3rd trimester: +452 kcal/day.
    • Cumulative fetal support energy for a term pregnancy ≈ 8.0 imes 10^{4} ext{ kcal}.
    • Glucose is the main energy source for the fetus; fetal glycogen stores are low, so the fetus relies on maternal glucose.
    • Fetal glucose use increases during pregnancy; maternal insulin sensitivity decreases, shunting more glucose to the fetus.
    • In the 3rd trimester, ~50–70% of daily fetal caloric needs come from glucose.
    • In preparation for later fetal energy needs, fat storage occurs in the 2nd trimester and fatty acids serve as maternal fuel in the 3rd trimester.
  • Placental glucose transport:
    • Glucose transporters on both sides of the placental membrane do NOT require insulin.
    • Maternal hyperglycemia can lead to excess glucose delivery to the fetus and macrosomia (large infant).
    • Gestational diabetes increases risks of preeclampsia and future diabetes.
  • Hormonal changes during pregnancy:
    • Insulin levels may decrease due to rapid fetal fuel consumption; counter-regulatory hormones (e.g., glucagon) rise, increasing lipolysis.
    • Estrogen and progesterone induce insulin resistance.
    • Placental lactogen stimulates lipolysis in adipose tissue.
  • Micronutrient deficiency concerns during pregnancy:
    • Folate (B9): required for cell division, erythropoiesis, fetal and placental growth. Deficiency linked to miscarriage, low birth weight, preterm birth, neural tube defects (NTDs) like spina bifida and anencephaly. Recommended: 400-800\,\mu g/day of folic acid preconceptually; folic acid (synthetic form) is more bioavailable than natural folate; enriched grains are important sources in the US.
    • Cobalamin (B12): required for generation of tetrahydrofolate and for growth/development. Vegans/vegetarians at risk; deficiency can impair cognitive/motor development and increase risk of NTDs.
    • Vitamin A: retinoids/carrotenoids cross the placenta and can be stored; increased maternal requirements to support rapid growth and development; deficiency risks include IUGR and higher neonatal/maternal mortality; high-dose retinoids are teratogenic; stop acne medications like isotretinoin during childbearing years; limit liver in the first trimester.
    • Iron: Recommended dietary allowance (RDA) nearly doubles during pregnancy; iron deficiency anemia is common (~42% worldwide); iron is needed for maternal and fetal hemoglobin.
    • Calcium: fetal skeletal mineralization increases in the third trimester; insufficient calcium raises risk of IUGR and preeclampsia; maternal hormonal factors strongly influence calcium metabolism.
    • Iodine: thyroid hormone (thyroxine) synthesis increases in pregnancy; iodine is part of thyroxine; thyroxine is needed for metabolism and fetal neural myelination; deficiency linked to miscarriage, congenital anomalies, stillbirth, poor fetal growth, and lower IQ; severe deficiency is uncommon in the US but worldwide; iodized salt helps prevent deficiency.
    • Zinc: required for growth and development; involved in metabolism of macronutrients; deficiency can lead to teratogenesis.
    • Magnesium: helps prevent teratogenesis and supports enzyme cofactors; deficiency may be linked to risk of sudden infant death syndrome (SIDS).
  • Food safety during pregnancy:
    • Listeria monocytogenes risk — pregnant women are ~10x more likely to be infected; can cause miscarriage, preterm birth, stillbirth, neonatal meningitis/sepsis, and flu-like maternal symptoms; sources include contaminated animal foods and raw produce; refrigerate and heat foods appropriately; avoid raw milk, smoked seafood, uncooked meats, soft cheeses, and deli meats; choose pasteurized products and heat-prepared meats.
    • Other pathogens (Brucella spp., Salmonella spp., Campylobacter jejuni) can cross the placenta and cause miscarriage, preterm birth, or stillbirth; prompt antibiotic treatment is essential.

Lactation

  • Lactation increases macronutrient and micronutrient requirements.
  • Exclusive breastfeeding for the first 6 months is recommended, with continued breastfeeding as long as possible.
  • Benefits to the mother include decreased menstrual blood loss, reduced risk of certain cancers (hormonal) and postmenopausal osteoporosis, and easier return to pre-pregnancy weight.
  • Breast milk composition reflects maternal stores and diet; generally, no severe deficiency present unless maternal intake is very poor.
  • Early suckling and milk removal stimulate prolactin to promote milk production; sub-optimal nutrition can elevate prolactin but may deprive the mother of nutrients.
  • Macronutrient content in breast milk varies between and within mothers and is influenced by diet, duration of feeding, and time of day.
  • Energy cost of milk production:
    • ~100 mL milk production requires ≈ 85\,\text{kcal} expenditure.
    • Daily production in first 6 months ≈ 550-1200\,\text{mL/day}, equating to ≈ 467.5-1020\,\text{kcal/day} of energy.
  • Additional daily energy needs during lactation:
    • First 6 months: +330\,\text{kcal/day};
    • Second 6 months: +400\,\text{kcal/day}.
  • Weight changes:
    • Breastfeeding can lead to ≈1 lb/week weight loss while providing adequate milk; exclusive breastfeeding is associated with greater weight loss.
    • Avoid aggressive intentional weight loss until about 2 months after breastfeeding is established.

Infancy (birth to 1 year)

  • Infancy is marked by rapid growth and development; energy and protein needs are high relative to body size.
  • Growth patterns:
    • Infants typically triple birth weight by 1 year.
    • Length increases by about 50% in the first year.
    • Weight loss ~7% immediately after birth due to fluid loss, usually regained by day 10.
  • Energy requirements in infancy:
    • Approx. 90-120\,\text{kcal/kg/day} (much higher per kg than adults).
    • High resting metabolic rate and rapid growth drive energy needs; absorption is relatively inefficient.
  • Breast milk as optimal nutrition:
    • Carbohydrates provide 30–60% of energy; main carbohydrate is lactose, comprising about 40% of milk calories.
    • Lactose intolerance can occur in premature infants due to immature lactase activity (about 50% of normal activity at 30–40 weeks gestation).
    • Human milk oligosaccharides (HMOs) are indigestible but act as prebiotics; promote growth of beneficial gut bacteria and protect against infections by mimicking glycan receptors.
    • Predominant gut microbiota in breastfed infants is Bifidobacterium infantis, which degrades complex sugars and feeds beneficial bacteria.
  • Fat in breast milk:
    • Provides essential fatty acids: arachidonic acid (omega-6) and docosahexaenoic acid (DHA, omega-3).
    • DHA content varies with maternal diet; DHA is important for neural tissues and photoreceptors.
  • Protein in breast milk:
    • Supports growth and lean body mass; some amino acids are conditionally essential in infancy (histidine; tyrosine; cystine; taurine for premature infants).
    • Protein content in breast milk is sufficient for the first 6 months; after 6 months, supplementation with high-quality protein is often needed.
    • Two classes of protein in milk: whey and casein. In human milk, whey:casein ≈ 60:40 (in cow's milk it’s roughly 20:80).
    • Whey, rich in lactalbumins, supports gut health and forms easier-to-digest milk curds; casein forms firmer curds.
  • Micronutrients and supplementation in infancy:
    • Vitamin D: supplementation commonly required — typical dose ≈ 400\,\text{IU/day} (as drops).
    • Iron: human milk is relatively low in iron; though prenatal iron stores exist, iron supplementation may be started around 6–9 months.
  • Water balance and renal considerations in infancy:
    • Infants are at risk for water imbalance due to immature kidneys and higher extracellular water proportion.
    • Typical water requirement ≈ 0.7\text{ L/day} up to 6 months, usually met by breast milk or formula.
    • Renal solute load is the amount of waste to be excreted; breast milk has the lowest renal load compared with whole cow’s milk which has the highest.
    • Hypernatremic dehydration can cause neurological issues; hyponatremia from water intoxication can cause GI distress and seizures.
  • Vitamin K:
    • Administered via intramuscular injection after birth (phylloquinone) to prevent VK deficiency bleeding; newborns have low vitamin K.
    • Synthetic vitamin K (menadione) is not given due to jaundice risk.
  • Immune protection in breast milk:
    • Oligosaccharides promote beneficial bacteria.
    • Bifidus factor promotes growth of beneficial bacteria.
    • Secretory immunoglobulin A (IgA) provided in breast milk helps protect against enterobacteria; not produced by the infant in the early weeks.
    • Lactoferrin binds iron to limit bacterial growth; lysozyme damages bacterial membranes to cause lysis.
  • Formula feeding:
    • Formula is based on non-fat cow’s milk or soy, heat-treated and supplemented with fats, vitamins, and minerals to resemble human milk.
    • FDA regulations (1985) establish infant formula composition; formulas do not replicate immunological properties, digestibility, or trophic effects of human milk.
    • Cow’s milk is not recommended as the sole infant beverage before 12 months; it has poorly digested fat, lower vitamins C and E, iron, and linoleic acid.
    • Soy-based formula used for lactose intolerance or vegetarian family preferences; phytoestrogens/isoflavones may have uncertain effects on fetal development.
  • Solid foods and introduction:
    • Extrusion reflex prevents solid food intake before approx. 4–5 months.
    • Solid foods typically begin at 4–6 months after birth when oral and motor skills have developed.

Childhood and Adolescence

  • Growth and nutritional needs: large increases in height and weight; higher energy and protein needs relative to body size.
  • Children (1–10 years): focus on iron and calcium; expose to different tastes and textures; regular meals and snacks.
  • Adolescents (11–18 years): risk for deficiencies in vitamin A, thiamine (B1), folate (B9), calcium, iron, zinc; concerns about overall diet quality (fat, sodium, sugar overconsumption) and obesity risk; high energy needs can accompany overeating if not balanced.
  • Weight and bone health:
    • Adolescence accounts for about 45% of skeletal mass formed; calcium intake during adolescence is critical for attaining optimal bone mineral density later in adulthood.
    • Iron is especially important for girls due to menstruation-related losses; zinc is important for growth and sexual maturation.
  • Eating disorders risk:
    • 10–20% of teens engage in disordered eating behaviors (binge-purge, compensatory exercise, laxative/diuretic use, binge eating).
    • Can lead to anorexia nervosa or bulimia nervosa with complications in growth and bone health.
  • Growth monitoring:
    • Growth curves and age-based percentiles for weight, height/length, and BMI are used to track development.

Adulthood

  • Key concerns: obesity risk with overconsumption, particularly in the United States.
  • Young adults: emphasis on health maintenance, disease prevention, and diet quality.
    • Plant-based foods should be a major dietary component to increase fiber and limit saturated/trans fats.
    • Focus on nutrient-dense foods and functional foods with benefits beyond basic nutrients.
    • Health disparities arise from unequal access to affordable foods, healthcare, and resources, affecting diet quality and chronic disease risk.
  • Age-related physiological changes (gradual with age):
    • Increase in body fat; decrease in muscle mass (sarcopenia) and total body water; reduced bone density.
    • Decreases in gastric acid secretion, GI motility, and lactase activity; decreased taste and smell sensitivity.
    • Decreased hepatic blood flow and drug-metabolizing enzyme activity; diminished T-cell function; brain atrophy; reduced glomerular filtration rate (GFR).
  • Elderly nutrition concerns (often undernutrition):
    • Appetite may decrease due to dysgeusia (taste changes) and hyposmia (smell loss).
    • Physical limitations, oral health issues (edentulism), social isolation, medications with side effects, and other health problems can reduce intake.
    • Sarcopenia: loss of muscle mass/strength leading to functional impairment; reduced protein reserves during stress.
    • Common deficiencies: protein, calcium, vitamin D, cobalamin (B12), and pyridoxine (B6).
    • B12 concerns due to potential reductions in stomach acid and intrinsic factor, which help B12 absorption.
    • Lean mass declines with age; fat mass increases, affecting resting metabolic rate and energy needs.
    • Vitamin D requirements increase from 400 to 600 IU/day after age 70.
    • Decreased GFR in aging reduces production of active vitamin D, contributing to risk of deficiency.

Study Questions (from the transcript)

  • Question 1: Which statement concerning nutrition during infancy is INCORRECT?
    • a. On a per kilogram basis, energy requirement is the highest during infancy.
    • b. Human milk oligosaccharides provide prebiotic effects.
    • c. Infants may show some weight loss in the first week after birth.
    • d. Infants are vulnerable to water imbalance.
    • e. Vitamin B6 is required in order to prevent the risk of bleeding.
    • Answer: E
    • Explanation: Vitamin K, not B6, is the vitamin given to prevent VK deficiency bleeding in newborns.
  • Question 2: According to current recommendations, how many additional calories per day are adequate during the second and third trimesters of pregnancy, respectively?
    • a. 0 and 305
    • b. 110 and 200
    • c. 340 and 452
    • d. 564 and 850
    • e. 740 and 1000
    • Answer: C
  • Question 3: A 24-year-old woman in her third trimester wonders about breastfeeding; DHA in breast milk is which type of nutrient?
    • a. amino acid
    • b. monounsaturated fatty acid
    • c. omega-3 fatty acid
    • d. omega-6 fatty acid
    • e. saturated fatty acid
    • Answer: C
  • Question 4: Which physiological body composition component INCREASES with age in later adulthood?
    • a. Bone density
    • b. Fat
    • c. Muscle
    • d. Water
    • e. None of the above increase
    • Answer: B