Preconception Nutrition Flashcards
Define infertility.
absence of production of children
Define infecundity
biological inability to bear children after 1 year of unprotected intercourse
Define miscarriage
generally, the loss of a conceptus in the first 20 weeks
aka: spontaneous abortion
Define endocrine
system of the body
ductless glands that produce secretions that affect bodily functions (testes, thyroid, adrenal, ovaries)
Define subfertility
reduced level of fertility characterized by unusually long time to conception (over 12 months) or repeated early pregnancy losses
Who is considered subfertile?
women who experience multiple miscarriages
women who ovulate infrequently
men with sperm abnormalities
What is the purpose of the menstrual cycle?
prepare an ovum for fertilization and the uterus for implantation by building up a supply of blood and nutrients in the walls of the uterus
What glands secrete the hormones the cause menstrual cycles?
pituitary gland, ovaries, hypothalamus
What are the phases of the menstrual cycle?
follicular - first 14 days
luteal - the last 14 days
What is GnRH?
gonadotropin-releasing hormone
secreted by the hypothalamus
What is FSH?
follicule and sperm stimulating hormone
secreted by the pituitary gland
prompts the growth and maturation of 6-20 follicles
its presence stimulates the production of estrogen
together they further stimulate the growth and maturation of follicles
What is LH?
luteinizing hormone
secreted by the pituitary gland
cause cells within the follicles to secrete progesterone
stimulates secretion of E, P and T and growth of the CL
What is the cycle of hormones at the beginning of the follicular phase?
estrogen –> GnRH –> FSH –> LH
What do estrogen and progesterone do?
prompt the uterine wall to store glycogen and other nutrients, expand the growth of blood vessels and connective tissue
When do blood levels of FSH and LH peak?
just prior to ovulation
the surge in LH causes on ovum to release from a follicle
What is the corpus luteum?
formed from the cells left behind in the follicle after ovulation
secretes large amounts of progesterone and some estrogen
hormones inhibit the production of GnRH so FSH and LH aren’t secreted which means the ova don’t mature and aren’t released
stimulates further development of the endometrium
provides nutrients to the fetus until the placenta forms
What happens if the ovum isn’t fertilized?
production of hormones by the corpus luteum declines
blood levels of estrogen and progesterone fall
removes the inhibitory effect on GnRH release
so the cycle can start over and uterine wall sheds its outer layer
What are prostaglandins?
substances that cause the uterus to contract and release the stored blood and nutrients
derived from essential fatty acids
What happens if the ovum is fertilized?
generally will implant in the uterus lining in 8-10 days
hormones secreted by the fertilized egg signal the corpus luteum to increase in size and to continue to produce E and P to maintain nutrient and blood supply
CL ceases to function in the first few months when it is no longer needed for hormone production
What glands secrete hormones in the male reproductive system?
pituitary gland, hypothalamus, testes
What triggers the production of testosterone in males?
GnRH –> FSH and LH –> testosterone
What does testosterone do?
stimulates the maturation of sperm (70-80 days)
source is mostly the testes
Where are mature sperm stored?
epididymis (tissue on top of the testes)
What is semen formed from?
sperm mixed with secretions from the testes, seminal vesicle, prostate, and bulbourethral gland
What is estrogen?
controls release of GnRH, stimulates thickening of uterine wall
source: ovaries, testes, fat cells, CL, placenta
What is progesterone?
source: ovaries and placenta
stimulates uterine lining buildup
helps stimulate cell division of fertilized ova
inhibits action of testosterone
What are sources of disruption in fertility?
adverse nutritional exposures contraceptive use severe stress infection tubal damage and other structural problems chromosomal abnormalities
How do these conditions modify fertility?
affect hormones that regulate ovulation
affect the presence and length of the luteal phase
sperm production
tubular passageways
What is PID?
pelvic inflammatory disease
generally caused by an infection from an STD or IUD
infection of parts of the female reproductive system
can cause scarring and blockage of fallopian tubes
What is endometriosis?
common cause of reduced fertility
presence of endometrial tissue in abnormal locations
How does nutrient intake and body fat primarily affect fertility?
altering the environment in which eggs and sperm develop
modifying levels of hormones
How does chronic undernutrition impact fertility?
reduces it only by a small amount
primary effect is small, frail babies
can greatly affect neonatal outcomes though
How does acute undernutrition impact fertility?
clearly decreases fertility - dramatic decline
ex) famine or eating disorder
seems to modify hormonal signals and impair sperm maturation
fertility is usually restored as soon as the problem is corrected
How does excess body fat impact fertility?
increased levels of oxidative stress
changes availability of estrogen, androgens and leptin which interferes with reproductive processes
What are androgens?
types of steroid hormones produced from cholesterol
What is leptin?
protein secreted by fat cells
decreases appetite, increases energy expenditure, stimulates gonadotropin secretion
influenced by body fat level
How does being obese impact hormone levels in women?
increases estrogen, androgens, and leptin
favors the development of irregular cycles, ovulatory failure, amenorrhea, and anovulatory cycles
makes infertility treatments less effective
How does being obese impact hormone levels in men?
associated with lower testosterone and increased estrogen and leptin which reduces sperm production in some men and causes above average rates of ED
What is an anovulatory cycle?
menstrual cycle where ovulation doesn’t occur
How does being underweight impact women?
decreases estrogen, LH and FSH
consequences: amenorrhea, anovulatory cycles, short or absent luteal phases
* weight loss that exceeds 10-15% of usual weight in normal-weight women or BMI less than 20
How does being underweight impact men?
lowered libido, reduced sperm production
How can exercise impact fertility?
young female athletes can experience delayed puberty and lack menstrual cycles
very high levels of activity can interrupt previously normal cycles
results from hormonal and metabolic changes - primarily from caloric deficit, not intense exercise
reduced levels of estrogen, low body fat, decreased bone density
How can oxidative stress impact fertility?
reactive oxygen molecules
attack PUFAs in sperm - reduce motility, ability to fuse, enter cell and damage DNA
harm egg and follicle development, interfere with CL function and implantation
How can antioxidants impact fertility?
lower oxidative stress which occurs when free radicals exceed antioxidant defenses
prevent or reverse the effects of oxidative stress
Which nutrients have beneficial antioxidants?
vitamin E, vitamin C, beta-carotene, selenium
How does zinc status impact fertility in men?
reduces oxidative stress
has a role in sperm maturation, testosterone synthesis
lower zinc status has been related to poorer sperm quality and concentration and abnormal shape
How do plant foods impact fertility?
plant-based, low-fat diets are more likely to have irregular menstrual cycles regardless of body weight
diets with less than 20% fat appear to lengthen cycles
regular intake of soy foods appear to reduce sperm count
How does multivitamin use impact fertility?
associated with lower risk of ovulatory infertility
likely from the folic acid intake
folate intake in males can impact presence of chromosomal abnormal sperm
How is iron status related to fertility?
infertility due to lack of ovulation is related to iron intake
iron deficiency prior to pregnancy increases the risk of iron deficiency anemia and babies born with low iron stores and preterm delivery
easier to build up stores before pregnancy
How does caffeine impact fertility?
conflicting research
overall effects are likely weak
appears to prolong time to conception
27% reduction at 300mg, 50% reduction at 500mg
How does alcohol impact fertility?
may decrease estrogen and testosterone and disrupt cycles and testicular functions
research isn’t fully conclusive
1-5 drinks/week = 39% reduction
more than 10/week = 66% reduction
How does heavy-metal exposure impact fertility?
lead - decreased sperm production, motility, abnormal shape from lowered testosterone levels
mercury - decreased sperm and abnormal semen
other metals also impact male fertility
How do oral contraceptives impact nutrition status?
increase blood triglycerides and total cholesterol
slightly increases HDL
decrease blood levels of B12 and B6
increase blood levels of copper
How do contraceptive injections impact nutrition status?
weight gain
decreased bone density
decreased HDL
increased LDL and insulin
How do contraceptive implants impact nutrition status?
weight gan
How do contraceptive patches impact nutrition status?
increase cholesterol and triglycerides
slight increases in HDL
Why is it important to have optimal nutrition before conception?
first month of pregnancy is crucial to forming the basic structure of organs and establishing a blueprint for growth and development
many women don’t know they are pregnant at this point
Which nutritional exposures can adversely impact the fetus and embryo?
underweight and obesity insufficient folate excess vitamin A high levels of lead in the blood iodine deficiency iron deficiency alcohol intake poorly controlled diabetes
What does inadequate folate status increase the risk for?
neural tube defects - develop within 21 days
How do recommended dietary intakes differ from women who want to become pregnant?
consume folate
limit vitamin A in the retinol form
omit alcohol
What is the life course approach?
that there are fetal/developmental origins of adult health and disease
aka: thrifty phenotype hypothesis, Barker hypothesis, fetal programming hypothesis
What are some challenges of nutrition research?
study design, research subjects, generalizability and sample size, complexities of diets and lifestyles, ethics of research in vulnerable populations, issues with survey tools, expensive
What are some types and challenges of survey tools for nutrition research?
types - recall, diary, frequency questionnaire
issues - measurement error, recall bias, changing habits, literacy, survey fatigue, cultural inadequacies, telling the researcher what they want to hear
What is the difference between a systematic review and meta-analysis?
systematic review looks at studies individually and there can be author influence based on which studies they choose to summarize while a meta-analysis compiles all the research findings and comes up with one number regarding the relationship
What is the female HPG axis?
hypothalamus, pituitary, gonadal
negative feedback loop
hypothalamus –> LHRH –> pituitary –> LH and FSH –> ovaries –> progesterone and estrogen –> hypothalamus
What is the hierarchy of study designs?
randomized control trial
cohort study
case control
case series
Which things do you want to consider when you look at a journal article?
validity, results, relevance
Why is preconception nutrition important?
prevent complications and optimize fetal growth
women often don’t realize they are pregnant during the critical period of development
What percent of couples are infertile and what percent will conceive within 3 years without tech?
15%
40% of those diagnosed as “infertile”
What are the chances of a healthy couple conceiving within a given cycle?
23-30%
What is the female athlete triad?
eating disorder, osteoporosis, amenorrhea
What is the folate recommendation prior to conception and during pregnancy?
400 mcg prior
600 mcg pregnancy
associated with 70-90% reduction in NTD
What forms is iron found in in the body?
myoglobin (muscle), hemoglobin (blood), ferritin (storage form)
What is the iron deficiency spectrum?
normal –> depleted –> deficient –> anemia
What is the difference between genetics and epigenetics?
genetics is the study of DNA sequence and epigenetic is the study of how the DNA is packaged which determines how it is translated/degree of expression
What are the steps of DNA sequencing?
transcription
translation - reads mRNA to make amino acids
What is DNA methylation?
if a gene is methylated it won’t be expressed/can’t be transcribed
like an on/off switch
What is histone modification?
alters the degree that a gene is expressed
like a dial
What is chromatin remodeling?
twisting of DNA - tightness can impact gene expression
Why is epigenetics important?
gene expression is leads to protein synthesis
can effect ability to develop new cells, fight off infections or disease, metabolism of certain nutrients, physical phenotype
programs the fetus to prepare for the world it will enter (stress, food availability, diet preference)
offers a faster way to evolve
can carry through generations
What changes epigenetics?
environmental factors - diet, smoking, drugs, alcohol, physical activity, stress, toxins, weather, pathogens
impacts the signaling pathway
histone modification, chromatin remodeling, DNA methylation
changes the phenotype - physical shape, disease susceptibility, stress response, behavior, longevity
