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Basic Nutrition – Lipids Digestion, Absorption & Metabolism

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

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Basic Nutrition – Lipids Digestion, Absorption & Metabolism

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  1. Basic Nutrition – LipidsDigestion, Absorption & Metabolism

  2. Outline – Dietary Lipids Digestion Transport Metabolism Recommendations - DRI

  3. Dietary 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

  4. What about lipid absorption? GLUT2 Fructose GLUT5 Fructose Glucose Galactose Fructose Glucose Galactose Disaccharidases Fructose Glucose Galactose Na+ K+ Glucose Galactose ATPase SGLT-1 Na+ K+ Na+ H2O H2O Na+ Brush border membrane Basolateral membrane

  5. 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

  6. 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

  7. Dietary Fat Classifications • Saturated Fats • Cis monounsaturated fatty acids • Cis polyunsaturated fatty acids • n-6 fatty acids • n-3 fatty acids • Trans fatty acids

  8. Fat 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

  9. Total Fat DRI Values ** Not Determinable

  10. Estimating 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.

  11. Estimated 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

  12. n-6 polyunsaturated fatty acids (linoleic acid) * Recommendations change for pregnant or lactating women

  13. n-3 polyunsaturated fatty acids (α-linolenic acid) * Recommendations change for pregnant or lactating women

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