Infancy, childhood and adolescence
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What is a good indicator of whether energy needs are being met?
When is the energy cost of growth an issue in infants?
Only during the 1st half of infancy
How is energy content of tissue deposition computed for infants?
- Computed from rates of protein and fat deposition (longitudinal studies)
- ~175 kcal/d for 0 – 3 months -> 20 kcal/d for 13 – 35 months
Why is there a single equation for EER for 0-2 years?
Lack of gender differences
Why is PAL not included in EER equation for infants?
Limited range of physical activity?
Why is growth velocity important in infants?
- Sensitive indicator of energy status
- Will detect growth faltering earlier than growth charts
What is weight velocity in infants affected by?
Acute episodes of dietary intake
What is length velocity in infants affected by?
Affected by chronic factors
How does energy expenditure/kg compare from infants to adults?
Energy expenditure/kg is 2x greater in infants than adults
What is the energy cost of growth?
- Energy content of newly synthesized tissue
- Estimated from cost of protein and fat deposition
Where do infants basal metabolism come from?
Primarily brain, liver, heart and kidney
Why does O2 consumption increase in infants?
- Increase during the transition to extrauterine life
- After birth, O2 consumption of these vital organis increases in proportion to increase in organ weight
- Brain contribution exceptionally high (70%) in newborn, and in 1st years of life (60-65%)
How does energy cost of growth vary throughout infancy?
- Decreases from 35% at 1 month to 3% at 12 months
- Remains low until pubertal growth spurt where it increases to 40%
What happens when a neonate is exposed to milk cold?
- Increase in non-shivering thermogenesis --> increase in metabolic rate
- Most important contribution by increase oxidation of A in brown adipose tissue
How does PA vary as a child grows?
Increasingly larger component of TEE as child grows
What is the purpose of energy requirements for adolescents?
Defined to maintain health, promote optimal growth and maturation, support a desirable level of PA
What is growth defined as?
Increase in stature and weight, changes in body composition and organ systems
What is adolescence defined as?
Developmental changes in reproductive organs, development of secondary gender characteristics, changes in cardiorespiratory and muscular systems (increase strength and endurance)
What is the bulk of the active metabolic tissue?
Why are there higher energy and nutrient requirement in boys during adolescence?
Marked gender differences in intensity and duration of growth spurt in FFM
What is the carbohydrate intake required during the first 6 months of life?
~60g CHO=37% of total food energy (amount in milk is assumed to be optimal)
How much milk is consumed in the first 6 months of life?
How much CHO is needed during 7-12 months?
median CHO intake from weaning foods =50g/day
How much milk is secreted at 7-12 months?
Why is solid food needed at 7-12 months?
- CHO from human milk=44g
- CHO from foods = 50g
- Total needed=94g
What is the impact of added sugar on micronutrient intakes in infants?
- Nutrient dilution effect by nonmilk extrinsic sugars
- High [sugar] intake (>24% of energy)--> most micronutrient intakes between 6-20% below average
Describe the rate of brain glucose consumption after age 1.
- Constant of increases modestly
- In the range reported for adults
- EAR and RDA for CHO based n information used for adults
- Same for both genders
What is the AI for fiber for each age group?
14g/1000kcal x median energy intake
Why are fiber recommendations a function of energy intake?
- Individuals consuming less than median energy intake need less fiber
- 1 year olds not meeting this energy consumption level will not require as much fiber and their intake should be scaled back accordingly
Why do infants not need fiber?
- No functional criteria for fiber status reflecting response to dietary intake
- Human milk is the optimal source of nourishment and it contains no fiber
Why are weight and lean body mass gains higher in formula-fed infants?
Formula is higher in protein than milk
Even though it is higher in protein, why is formula not as good?
Despite lower protein intakes, breast-fed intants have better imune function and behavioural development
How does protein intake change from 0-6 months to 7-12 months?
- Stays about the same 1.52g/kg/day
- May be a bit of an overestimate since growth slows down towards the end
What method is used to estimate protein requirements?
- Factorial method
- Relationship between protein intake and nitrogen balance were utilized to estimate protein requirements by the factorial method
What does the factorial method include?
- Estimates of maintenance requirement
- Measurement of rates of protein deposition
- Estimates of the efficiency of protein utilization for growth
What is the factor used in the factorial method?
1.72 the efficiency of protein utilization for growth
How much fat do infants need?
- 0-6 months: 31g/day
- 7-12 months: 30g/day
Does human milk contain the correct amount of fat?
For older infants, what is the fat AI based on?
Based on average intake of fat from human milk and complementary foods
How much fat do older infants get form complementary foods?
What is the n-6 PUFA requirement for 0-6 months based on?
- Amount of n-6 PUFAs in human milk
How much PUFAs do 7-12 month olds get from complementary foods?
What is the average energy intake from human milk and complementary foods for 7-12 month olds?
- Milk: 390kcal/day
What percentage of energy consumed is PUFAs in 7-12 month olds?
Why is n-3 more important than n-6 for infants?
Provide DHA which is important for the developing of the brain and retina
What is the AI for n-3 for 0-6 month olds?
- 1% of energy intake
How much water is needed for 0-6 month olds and where does this number come from?
- Because 0.78L of milk is consumed and milk s 87% water
- Round to 0.7L/day
How much water do 7-12 month olds need?
Need 0.8L/day- comes from milk (0.52L) and complementary foods (0.32)
What are water requirements in children based on?
- Normal hydration status can be achieved with a wide range of total water intakes
- AI for total water is based on median total water intake of children and adolescents
What is the sodium and chloride AI in infancy based on?
- 0-6 months: based on mean intake of milk-fed infants
- 7-12 months: based on human milk and complementary foods
Why are AI requirements of sodium and chloride for 1-18 years similar to adults?
Maturation of kidneys is similar im normal children by 12 months of age
How is AI of sodium determined for children?
- Extrapolated down from the adult AI of 1.5g/day
- Using the average of median energy intake levels of the age groups for adults and for children
What is the AI for potassium based on for 0-6 months?
- Based on average amount of potassium in human milk
- Mean intake: 0.39g/day (round to 0.4g/day)
What is the AI for potassium for 7-12 months?
What are some conditions resulting from potassium deficiency in children and adolescents?
- Increased blood pressure, bone demineralization, kidney stones
- Result from inadequate intake over an extended period of time, including childhood
How are potassium intakes for children calculated?
- Extrapolated from adult intakes
- Adjusted based on energy intake
Why is potassium AI not adjusted based on weight?
- Adjusted based on energy intake
- Concern that adjustment based on weight might lead to a relatively low and potentially inadequate intake of potassium
- A greater intake of dietary K would be appropriate to mitigate adverse effects of Na
How is the AI for Chloride set?
- Set at a level equivalent on a molar basis to that of Na
- Almost all dietary Cl comes with the Na added during processing or consumption of foods
What is AI of vitamins and minerals for 0-6 months based on?
- Mean intake data from infants fed human milk exclusively
- Ad the [vitamin and mineral] of milk produced by well-nourished mothers
How is the AI for vitamins and minerals for 7-12 months determined?
Extrapolated from estimates of nutrient intake from human milk PLUS nutrients provided by usual intakes of complementary weaning foods
How are maintenance needs for vitamins and minerals extrapolated from adults to infants and children?
- Maintenance needs for vitamins and minerals expressed with respect to body weight (kgbody weight)^0.75
- Set to power of 0.75 to adjust for mertabolic differences related to body weight
How is the variability in requirements due to growth rate accounted for?
A 10% CV for the requirement is assumed unless data are available to support another value
How are AIs for vitamin K set?
Set on the basis of the highest median intake for each age group
Why is there a significant increase in AI for vitamin K from infancy to early childhood?
Most likely due to the method used to set the AI for older infants and the increased portion of the diet containing vitamin K-rich fruits and vegetables as the diet becomes more diversified
Why are newborn infants at risk for vitamin K deficiency?
Vitamin K is poorly transported across the placenta
What can happen as a result of low [plasma clotting factors] at birth?
- Increased risk of bleeding during the first weeks of life
- Hemorrhagic disease of the newborn
What is late HDNB?
- Between 3-8 weeks
- Usually associated with breast-feeding
How can HDNB be prevented?
- Can be effectively prevented by administration of vitamin K
- Infants born in North America routinely receive 0.5-1mg of phylloquinone i.m.
- OR 2mg orally within 6 h of birth (less effective)
How is AI for vitamin K determined?
Reflects a calculated mean vitamin K intake of infants principally fed human milk and provided vitamin K prophylaxis
How is older infant vitamin K AI obtained?
By extrapolating up from young infants
What is clinically significant vitamin K deficiency?
- Extremely rare in the general population
- Limited to individuals with malabsorption syndromes or those treated with drugs known to interfere with vitamin K metabolism
What is the net Ca accretion and RDA for 1-3 years of age?
- Using an estimate of 20% net Ca retention
- RDA is set for Ca at 700mg/day
What is the RDA for Calcium for males and females aged 4-8 years?
- Ca accretion=200mg/day
- Require a Ca intake of 800 to 900 mg
- RDA for calcium is 1000mg/day
What are the 3 major lines of evidence for Ca needs for the 9-18 age group?
- The factorial approach
- Ca retention to meet peak bone mineral accretion
- Clinical trials: bone mineral content measured in response to variable Ca intake
What is the RDA for Ca for boys ages 9-18?
1300mg/day: slightly above the 75th percentile of Ca intake
What is the RDA for Ca for girls ages 9-18?
- Slightly below the 90th percentile of Ca intake
Why are calcium supplements needed in adolescents?
- Current levels of Ca intake among adolescents not adequate to support development of optimal bone mass
- Supplements may be necessary
How is the AI for Fe determined for 0-6 month olds?
- Reflects mean Fe intake of infants principally fed human milk
- Assumed that the Fe provided by human milk si adequate to meet the Fe needs of infants exclusively fed human milk from 0-6 months
What are the major components of Fe need for older infants?
- Obligatory: fecal, urinary, and dermal losses (basal losses)
- Increased hemoglobin mass (increased blood volume and increase in [hemoglobin])
- Increase in tissue (non-storage) Fe
- Increase in storage Fe
What bioavailability is used to set Fe for 7-12 month olds and why?
Use 10% bioavailability because they mostly eat cereals and fruits and not many eat meat or meat mixutres
What bioavailability is used to sed Fe EAR for 1-8 years?
Use 18% bioavailability
What are the major components of Fe needs for children 9-18?
- Basal Fe losses
- Increase in hemoglobin mass
- Increase in tissue (non-storage Fe)
- Menstrual Fe losses in adolescent girls
- No provision for the development of Fe stores after early childhood
What is the EAR for iodine for children 1-8 years?
What is the AI for fluoride?
- Recommended for all ages >6 months
- Protection against dental carries
What is enamel fluorosis?
- Caused by Fe ingestion during the pre-eruptive development of the teeth
- After enamel has completed its pre-eruptive maturation--> no longer susceptible (by 8 years of age)
- Milder forms of fluorosis: white opaque patches, often most apparent on the edges of teeth (snow capping)
- Preeruptive maturation of the crowns of the anterior permanent teeth
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