basic nutrition – lipids digestion, absorption & metabolism
DESCRIPTION
Basic Nutrition – Lipids Digestion, Absorption & Metabolism. Outline – Dietary Lipids. Digestion Transport Metabolism Recommendations - DRI. Dietary Lipids. Research focus on optimal fatty acid composition of the diet Importance of docosahexanoic acid and arachidonic acid - PowerPoint PPT PresentationTRANSCRIPT
Basic Nutrition – LipidsDigestion, Absorption &
Metabolism
Outline – Dietary LipidsOutline – Dietary Lipids
1.Digestion2.Transport3.Metabolism4.Recommendations - DRI
Dietary LipidsDietary Lipids
• Research focus on optimal fatty acid composition of the diet
• Importance of docosahexanoic acid and arachidonic acid
• Adults encouraged to limit saturated, trans fats, and be wary of energy density
• Triglyceride is prominent form in diet• Dietary lipids must ‘shift’ from aqueous
to non-aqueous environment• Digestion and absorption includes
emulsification, hydrolysis, micellization and uptake by the enterocyte
What about lipid absorption?What about lipid absorption?
Brush bordermembrane
Basolateralmembrane
Fructose GlucoseGalactose
GlucoseGalactose
Na+
Na+
Na+
K+
Fructose
SGLT-1
GLUT5
Na+
K+ ATPase
GLUT2
Disaccharidases
Fructose GlucoseGalactose
Fructose GlucoseGalactose
H2O H2O
Two mechanisms – passive diffusion and carrier-
mediated uptake
Two mechanisms – passive diffusion and carrier-
mediated uptake• Uptake studies demonstrated
saturable process• Putative fatty acid transport proteins
– Plasma membrane fatty acid binding protein
– Megalin– CD35– Caveolin– Family of fatty acid transporters
• Carriers likely most important when lipid concentration low
EAR - Meets the requirement of half the healthy individuals in life stage group
RDA - Meets the requirement of 97-98% of the healthy individuals in life stage group (RDA = EAR + 2 × SDrequirement)
AI - Experimentally determined approximations for healthy individuals in life stage group (used when no RDA set)
UL - Highest average daily nutrient intake level that is likely to pose no risk of adverse health effects
Dietary Fat ClassificationsDietary Fat Classifications
• Saturated Fats• Cis monounsaturated fatty
acids• Cis polyunsaturated fatty acids
– n-6 fatty acids– n-3 fatty acids
• Trans fatty acids
Fat DRIsFat DRIs
• Major fuel source for body
• Necessary for absorption of fat soluble vitamins
• Insufficient data to set RDA, AI, or UL for total fat
• Likewise, no RDA for saturated fat, n-9 cis monounsaturated fatty acids, trans fats
• AMDR is in place for total dietary fat intake
Total Fat DRI ValuesTotal Fat DRI Values
Function Age MalesRDA/AI g/d
FemalesRDA/AI g/d
AMDR(% total energy)
Energy source, allow for absorption of fat soluble vitamins
19-30 ND** ND 25-35
31-50 ND ND 25-35
50-70 ND ND 25-35
>70 ND ND 25-35
** Not Determinable
Estimating Fat RequirementsEstimating Fat Requirements
• Lack of clinical endpoints do not allow for setting EAR for total fat
• Saturated fatty acids can be synthesized as needed, no role in disease prevention
• Monounsaturated fatty acids have many functions, but can be synthesized
• n-6 Polyunsaturated fatty acids generally consumed well above deficiency level. AI evidence from total parenteral nutrition studies.
Estimated AMDRsEstimated AMDRs
• Set based on coronary heart disease (CHD) risk and obesity
• Linoleic acid– AI, lower limit of AMDR set at 5% of
energy– Lack of evidence above 10% of energy
(upper AMDR)• α-linolenic acid
– AI is 0.6% of energy– Upper AMDR is 1.2% of energy
n-6 polyunsaturated fatty acids (linoleic acid)
n-6 polyunsaturated fatty acids (linoleic acid)
Function Age MalesRDA/AI g/d
Females*RDA/AI g/d
AMDR(% total energy)
Component of cell membranes, skin health
19-30 17 12 5-10
31-50 17 12 5-10
50-70 14 11 5-10
>70 14 11 5-10
* Recommendations change for pregnant or lactating women
n-3 polyunsaturated fatty acids (α-linolenic acid)
n-3 polyunsaturated fatty acids (α-linolenic acid)
Function Age MalesRDA/AI g/d
Females*RDA/AI g/d
AMDR(% total energy)
Neurological development and growth
19-30
1.6 1.1 0.6-1.2
31-50
1.6 1.1 0.6-1.2
50-70
1.6 1.1 0.6-1.2
>70 1.6 1.1 0.6-1.2
* Recommendations change for pregnant or lactating women