Lecture 7 - Nutrition

• Nutrition


  Some people need the same nutrients, they just require them in different amounts at different times
• Nutrition in stages


  • Prior to pregnancy
  • During pregnancy
  • After pregnancy
  • Mother
  • Child (lactation)
  • Infancy
  • Childhood
  • Adulthood
  • Elderly/aging
• At no stage of life is nutrition more crucial than during pregnancy and infancy
• From conception through the end of the first year of life, adequate nutrition is essential for tissue formation, neurologic development and bone growth
• The ability to reach peak physical and intellectual potential in adult life is in part determined by the nutrition received during pregnancy and the first year of life
• Nutrition prior to pregnancy focuses on

  • Women
• Nutrition prior to pregnancy

  • Full nutrient stores prior to pregnancy
  • Essential to conception and healthy infant development
  • Developmental changes occur during early weeks of pregnancy
  • Even before the pregnancy is evident
  • Body provides the environment for growth and development of the child
• Habits that influence fertility and contribute to healthy pregnancy

  • Achieve and maintain a healthy body weight
  • Choose an adequate and balanced diet
  • Be physically active
  • Receive regular medical care
  • Avoid harmful influences (e.g., alcohol, cigarettes, drugs, environmental contaminants etc)
• Healthy body weight


  Preconception weight influences maternal health, strongly correlated to fetal growth and health, and affects infant health
• Appropriate weight prior to pregnancy benefits pregnancy outcome
• Underweight (undernourished) women


  • Low-birth weight babies
  • Preterm births
  • Increased risk of disabilities, impaired development and mortality
• Overweight or obese women

  • Maternal complications (hypertension, gestational diabetes, post partum-infection)
  • Complications of delivery (premature birth)
  • Infants born to obese women are more likely to be large for gestational age
  • Infant complications (neural tube defects, heart defects and other abnormalities)
• Goal: strive for healthy pre-pregnancy weight to minimize risks to mother and infant
• Decrease weight before not during pregnancy as dieting during pregnancy can harm the health of both mother and fetus by depriving them of critical nutrients
• Adequate and balanced diet


  Need to start pregnancy on an "even keel", nutrition is for mother and baby, malnutrition (undernutrition, overweight/obesity) reduces fertility and it will affect mother and baby
• Physical activity


  Benefit to everyone, need to be or become physically active before pregnancy, dietary requirements should reflect amount of physical activity
• Healthy support tissues


  • Healthy development of the placenta depends on adequate pre-pregnancy nutrition
  • Uterus: the muscular organ within which the infant develops before birth
  • Placenta: an organ that develops inside the uterus early in pregnancy and it is the supply depot and waste removal system for the fetus; the fetus receives nutrients and oxygen across the placenta; the mother's blood picks up carbon dioxide and other waste materials to be excreted via her lungs and kidneys
  • Umbilical cord: the ropelike structure through which the fetus's veins and arteries reach the placenta; the route of nourishment and oxygen into the fetus and the route of waste disposal from the fetus
  • Amniotic sac: the "bag of waters" in the uterus in which the fetus floats
• The events of pregnancy

  1. Fertilization and cell division

  2. Implantation (during the first week)

  3. The first 6 weeks

  4. Last 7 months: growth period (fetal period)
• Fertilized ovum (zygote) is a single cell that divides rapidly to become a blastocyst
• Blastocyst embeds itself in uterine wall, placental development begins
• At 8 weeks the fetus has complete nervous and digestive systems, well-defined fingers and toes, and beginnings of facial features
• Birth weight averages 6.8-7.9 pounds
• Each organ and tissue develops in its own pattern and timing, development of each takes place only at specific time (critical period), required nutrients and environmental conditions necessary during this period, malnutrition impairs organ development and effects are irreversible
• Growth and development


  • Placental
  • Embryogenesis and fetal development (Zygote (0-2 weeks), Embryo (2-8 weeks), Fetus (8 weeks-term))
• The embryo is most susceptible to teratogens (alcohol, drugs, x-rays, and nutrient deficiencies) during the critical period of 2-8 weeks
• Placental development


  • Begins after zygote implants, 4th week begin to see signs of placental formation, until then embryo depends on uterine cells for nutrients, 3 important structures (Amniotic sac, Umbilical cord, Placenta)
• Placenta


  • Formed from both embryonic (blastocyst) and maternal (uterus) tissue, fetal and maternal blood vessels are intertwined but don't mix, O2 and CO2 exchange between mother and fetus, waste products removal, nutrients supply for fetus, metabolically active organ that requires nutrients and produces hormones e.g., estrogen
• During the embryonic stage, the most critical periods are complete by the end of the first trimester, and the fetus is especially susceptible to nutrient defiencies, toxicities and teratogens during this time
• Nutrition is important before and throughout pregnancy to support fetal development without depleting the mothers reserves
• Folate


  Required for protein metabolism and DNA synthesis, RDA is 400 ug/day prior to pregnancy and 600 ug/day if pregnant, synthetic form (folic acid) is more bioavailable, adequate folate is especially critical during the first 48 days after conception for neural tube formation and closure
• Folate deficiency is associated with neural tube defects (NTD) such as spina bifida
• The Dutch Famine cohort showed that offspring of mothers who experienced severe undernutrition during the first trimester had 2X higher CVD risk, increased risk of metabolic disorders and cancers, 40-50 years later
• Epigenetics


  Pattern of gene expression regulated by modifications to DNA (e.g., methylation and histone acetylation), external factors or environmental factors can switch genes on and off, nutrients can impact epigenetic regulation
• Fetal programming - fetal genes can be turned on or off with maternal nutrients
• Nutrient needs increase during pregnancy

  • Large increases for protein, iron, iodine, zinc, folate, and B6
  • Medium increases for carbohydrates, thiamin, riboflavin and niacin
  • Small increases for water, energy, vitamin C, B12 and vitamin A
  • No changes for calcium
• Energy


  During the first trimester, a woman should actually consume approx. the same number of calories daily as during her non-pregnant days, increase in energy in second and third trimester (extra 340 kcal during the second and extra 450 kcal during the third trimester) to meet maternal needs and support fetal growth and development, improve nutrient density
• Carbohydrate


  Pregnant women are advised to aim for a carbohydrate intake of at least 175 g per day, glucose is the primary metabolic fuel of the developing fetus, majority of carbohydrate intake should come from whole foods, such as whole-grain breads and cereals, brown rice, fruits, vegetable, and legumes
• Protein


  Needs are increase a lot (25 grams per day higher than for non pregnant women) to build muscle, organs, skin, etc. of growing fetus, good sources include dairy products, meats, fish, poultry, eggs, and soy products, as well as legumes, nuts, and seeds
• Lipid


  Do not increase saturated fat intake, increase essential fatty acids (omega-3 and omega-6 fatty acids) which are important to the growth and development of fetus (especially for the fetal brain and eye development), oily fish consumption (e.g., sardines) during pregnancy will provide rich source of omega-3 fatty acids
• Pregnancy women who eat fish should be aware of the potential for mercury contamination, as even a limited intake of mercury during pregnancy can impair a fetus' developing nervous system