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Advanced Nutrition
Lipids 3
MargiAnne Isaia, MD MPH
LIPIDS
LIPIDS
Essential Fatty Acids
18:2 n-6 and 18:3 n-3 are absolutely needed
(essential for development)
Functions of EFA –overview:
- Growth
- Maintenance of skin and hair
- Regulation of Cholesterol metabolism
- Maintenance of reproductive functions
- Membrane integrity
LIPIDS
FUNCTIONS of EFFAs
-Provide energy
PUFA more rapidly oxidized than SFA or MUFA
- Are incorporated into structural lipids
The major elements in the diet that determine the final distribution of LC
PUFA, in cell membrane phospholipids include:
- the relative proportion of n-3, n-6, n-9 FA families,
- the preformed long chain PUFA vs. their shorter chain precursors.
- Eicosanoids synthesis
- Regulate gene transcription through PPARs
- Membrane function & integrity
membrane fluidity, normal function of membrane–bound enzymes, activity of
receptors,
membrane permeability and transport properties
(brain, retina –V LC derivative of n-3 PUFA)
- Modulations of cell-cell interactions
PPARs = Peroxisome Proliferator Activated Receptor, nuclear hormon receptor, role on
the genetic regulation of FA oxidation and lipogenesis
LIPIDS
LIPIDS – ESSENTIAL FATTY ACIDS
Essential Fatty Acids (C 18:2 n-6 and C 18:3 n-3) provided by diet
(the body cannot synthesize them)
EFFAs deficiency results in:
-reduced growth rate, scaly dermatitis, hair loss, infertility, depressed
inflammatory response,
-kidney and liver abnormalities, decreased capillary resistance, increased
fragility of RBC, reduced contraction of myocardial tissue, poor wound healing.
LIPIDS
ESSENTIAL FATTY ACID STATUS
EFA adequate:
triene/tetraene =/ < 0.4
Eicosatrienoic Acid / Arachidonic Acid (C 20:3 n-9 / C20:4 n-6)
EFA deficiency:
triene/tetraene > 0.4
Eicosatrienoic Acid (C 20:3 n-9) biomarker of EFA status.
Amount of EFA required to keep ratio normal is 1-2% of total energy.
An EFA deficient diet for longer than 6 months is required to produce
deficiency in adults.
LIPIDS
EFA STATUS
Total intake of n-3 FA similar among vegans, LOV, omnivores (1-3g/d)
Intake of very long chain n-3 FA varies
- Vegans negligible
- LOV < 5 mg/d EPA and DHA; it varies depending on DHA eggs in the diet)
- Omnivores 100-150mg/d (it varies based on fatty fish consumption)
Intake of n-6 FA higher in vegans and LOV
n-6: n-3 ratio higher among vegans (14:1 -20:1)
LOV 10:1-16:1, omnivores 10:1
Ideal ratio 4:1
LIPIDS
EFA STATUS
EPA and DHA in body stores - lower in vegans
- Plasma levels
- RBC membrane composition (long term)
Lactating vegans and LOV had higher Linoleic Acid and a-Linolenic Acid,
but less EPA and DHA in the milk than omnivores
- Need to take measures to increase intakes
- Full term infants have stores of EFA
LIPIDS
ACHIVING OPTIMAL STATUS
2 methods
- maximize conversion of ALA to EPA and DHA
- provide a direct source of EPA and DHA
Maximize conversion:
- Factors affecting: genetics, age, overall health, diet
- Proper calories and protein intake
- Optimal status of vit B6, biotin, calcium, magnesium and zinc
- Lower SFA and trans FA (avoid processed food with trans FA)
- No alcohol intake
- Lower n-6 PUFA intake (total PUFA 7-10% energy)
(1.5-2.0% should come from n-3 FA, the rest from n-6 PUFA
to produce the ratio of 4:1)
Avoid cooking oils rich in n-6 PUFA : corn oil, soybean oil,
use instead MUFA: olive oil, canola oil.
- Increase ALA intake (1.1-2.2g /1000cal/d)
LIPIDS
ACHIEVING OPTIMAL STATUS
- Provide a direct source of long chain n-3FA
- fatty fish or fatty fish oil as a supplement
- LOV can include DHA enriched eggs
(eggs from chicken fed flax or micro algae) 60-150mg DHA/egg
- Plant source is micro algae (original source)
- direct from seaweeds may not be practical because of low concentration.
100 g seaweeds contains about 100mg
Low consumption in US, but higher in Japan.
Supplements available
EPA will come from retro-conversion of DHA to EPA
Conversion of ALA g
EPA 5-10% - for vegan population
DHA 2-5%
Rate of conversion depends on background diet
Recommended EPA + DHA intake: 500-800 mg/day
LIPIDS
REQUIREMENTS
Pregnancy: EFA required for maternal and fetal needs.
Fetal organs (liver, brain, retina) incorporate long chain PUFA
during last semester in utero.
Maternal EFA consumption : n-6 13 g/d;
n-3: 1.4g/d
Lactation
- 4-5% energy in human milk is 18:2 n-6, 18:3 n-3
- 1% energy as long chain PUFA
Efficiency of converting dietary EFA to milk LC EFA not known
requirements: n-6 13 g/d;
n-3 1.3g/d
LIPIDS
REQUIREMENTS
Infancy and childhood, adult :
n-6 : n-3
0-6 months:
6-12 mo:
4-5 years:
4-8 years:
9-13 years:
14+ years:
51+ years:
4.5 g/day: 0.5 g/d
5.4 g/day: 0.5 g/d
7.0 g/day: 0.7 g/d
10.0 g/day: 0.9 g/d
16.0 g/day: 1.2 g/d
17.0 g/day: 1.6 g/d
18.0 g/day: 1.4 g/d
LIPIDS
ESSENTIAL FA
Vegetarian diets – lower in total fat, saturated fat and cholesterol than non
vegetarians.
They provide comparable levels of EFA.
Vegetarian (vegan especially) diets
- relatively low in ALA company with LA
- little, if any EPA and DHA
Clinical studies
- tissue levels of very long chain n-3 FA are depressed in a
vegetarians (vegans)
-n-3 cardio-protective effects ALA, EPA, DHA less for ALA than for
EPA/DHA
Conversion of ALA g EPA < 5-10%
g DHA 2-5%
Total requirements for n-3FA may be higher for vegetarians
Vegetarians - make dietary changes to optimize n-3 FA status
LIPIDS
REFERENCES
1. Shils M et al, Modern Nutrition in Health and Disease, 10th Edition
2. www. Pubmed.org
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