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Omega-3 Fatty Acids : Naming, sources, intakes, metabolism and health benefits Philip Calder

Omega-3 Fatty Acids : Naming, sources, intakes, metabolism and health benefits Philip Calder Professor of Nutritional Immunology University of Southampton. This lecture will cover. Fatty acid structure, nomenclature, sources, and intakes

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Omega-3 Fatty Acids : Naming, sources, intakes, metabolism and health benefits Philip Calder

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  1. Omega-3 Fatty Acids : Naming, sources, intakes, metabolism and health benefits Philip Calder Professor of Nutritional Immunology University of Southampton

  2. This lecture will cover • Fatty acid structure, nomenclature, sources, and intakes • Metabolic relationship between a-linolenic acid and long chain omega-3 fatty acids • Omega-3 fatty acids and cardiovascular health • Omega-3 fatty acids and visual and brain development • Recommendations for omega-3 fatty acid intake

  3. Fats in the diet CH2.O.CO.R1 R2.CO.OCH CH2.O.POO.O.Base CH2.O.CO.R1 R2.CO.OCH CH2.O.CO.R3 Phospholipids Triglycerides Also sphingolipids cholesterol and cholesterol esters

  4. Fatty acid structure H3C COOH

  5. Fatty acid structure andnomenclature H3C COOH 18:0 Stearic acid 9 H3C COOH 18:1w-9 Oleic acid H3C COOH 18:2w-6 Linoleic acid 6 3 COOH 18:3w-3 a-Linolenic acid H3C Omega = w- = n- Mammals cannot insert double bonds in here

  6. Saturated Monounsaturated Polyunsaturated Sunflower oil Corn oil Soybean oil Olive oil Pig fat Beef fat Butter 0 20 40 60 80 100

  7. Latest fatty acid intake data for adults in UK (g/day) Males Females Total fat 87 (36% energy) 61 (35% energy) Saturated 33 23 Trans 3 2 Monounsaturated 29 20 Omega-6 PUFA 13 9 Omega-3 PUFA 2.3 1.7

  8. Omega-3 PUFAs COOH a-Linolenic acid (18:3w-3) H3C EPA (20:5w-3) COOH H3C COOH DPA (22:5w-3) H3C H3C DHA (22:6w-3) COOH

  9. These have different dietary sources and their intake differs markedly

  10. a-Linolenic acid (18:3w-3) • Found in green plant tissues • Found in some vegetable oils (e.g. soybean, rapeseed) • Found in some nuts (e.g. walnut) • Found in linseed (flaxseed) and linseed oil • Contributes 85 to 95% of w-3 PUFA intake in UK adults (ca. 2.1 g/day in males; 1.5 g/day in females)

  11. Long chain w-3 PUFAs (EPA, DPA, DHA) • - oily fish are the only rich source of preformed long chain w-3 PUFAs • adults in the UK consume on average 1/3 of a portion of oily fish per week (53 g/week) • fish consumers consume 1.3 portions of oily fish per week (about 195 g/week) • average long chain w-3 PUFA intake is < 0.2 g/day (200 mg/day) • long chain w-3 PUFAs are found in fish oils

  12. Long chain w-3 PUFA content of fish EPA DPA DHA Total (g/100 g food) g/portion Cod 0.08 0.01 0.16 0.30 Haddock 0.05 0.01 0.10 0.19 Herring 0.51 0.11 0.69 1.56 Mackerel 0.71 0.12 1.10 3.09 Salmon 0.55 0.14 0.86 1.55 Crab 0.47 0.08 0.45 0.85 Prawns 0.06 0.01 0.04 0.06

  13. a-linolenic acid is metabolically related to long chain w-3 PUFAs a-Linolenic acid (18:3w-3) Delta 6-desaturase 18:4w-3 Elongase 20:4w-3 Delta 5-desaturase EPA (20:5w-3) DHA (22:6w-3) DPA (22:5w-3)

  14. a-Linolenic acid This pathway does not work very well in humans EPA DHA

  15. Key points (so far) • w-6 and w-3 PUFAs are distinct fatty acid families • Most w-3 PUFA in the diet is in the form of a-linolenic acid • Long chain w-3 PUFAs are found in oily fish (fish oil capsules) • Average intake of long chain w-3 PUFAs is < 0.2 g/day • a-Linolenic acid is poorly converted to long chain w-3 PUFAs in humans

  16. Omega-3 PUFAs and human health

  17. From a survey of distribution of diseases in Greenland Eskimos Disease Expected Actual Myocardial infarction 40 3 Psoriasis 40 2 Bronchial asthma 25 1 Diabetes 9 1 Multiple sclerosis 2 0 Kromann & Green (1980) Acta Med. Scand. 208, 410-406

  18. Many studies report an inverse correlation between fish consumption or w-3 PUFA status and CHD Kromhout et al. 1985 Fish  CVD mortality Shekelle et al. 1985 Fish  CVD mortality Norelle et al. 1986 Fish  CVD mortality Dolecek et al. 1992 Dietary w-3 PUFA  CVD mortality Feskens et al. 1993 Fish  CVD mortality Siscovik et al. 1995 Fish  CVD mortality Kromhout et al. 1995 Fish  CVD mortality Daviglus et al. 1997 Fish  CVD mortality Albert et al. 1998 Fish  sudden cardiac death Pedersen et al. 2000 Adipose tissue w-3 PUFA  MI mortality Albert et al. 2002 Whole blood w-3 PUFA  sudden death Hu et al. 2002 Fish and w-3 PUFA intake  CHD mortality Hu et al. 2002 Fish and w-3 PUFA intake  non-fatal MI Tavani et al. 2001 Fish and w-3 PUFA intake  non-fatal MI Gualler et al. 2003 Adipose tissue DHA  first MI Lemaitre et al. 2003 Plasma EPA and DHA  CHD mortality

  19. Prospective: Long chain w-3 PUFA status and sudden death Adjusted for age & smoking Also adjusted for BMI, diabetes, hypertension, hypercholesterolemia, alcohol, exercise & family history of MI 1 0.8 0.6 0.4 0.2 0 Relative risk of sudden death 1 2 3 4 Quartile of blood w-3 PUFAs Albert et al. (2002) New Engl J Med 346, 1113-1118

  20. Risk factors for atherosclerosis LDL-cholesterol Triglycerides Elevated blood lipids Hypertension Endothelial dysfunction Inflammation

  21. Meta-analysis of trials of fish oil and blood pressure Geleijnse et al. (2002) J. Hypertens. 20, 1493-1499 36 controlled trials reviewed incl. 22 double blind Fish oil: - decreased systolic BP by 2.1 mm Hg (95% CI 1.0, 3.2; P < 0.01) - decreased diastolic BP by 1.6 mm Hg (95% CI 1.0, 2.2; P < 0.01) Effects greater in older subjects Effects greater in hypertensive subjects Conclusion “increased intake of fish oil may lower BP, especially in older and hypertensive subjects”

  22. 10 0 -10 -20 -30 TAG < 2 mM TAG > 2 mM Relationship between dietary long chain w-3 PUFAs and blood TAG concentrations • Review of 72 placebo-controlled human trials • All > 2 weeksduration • Harris (1996) Lipids 31, 243-252 Placebo Fish oil Difference % Change

  23. Endothelium dependent coronary vasodilatation in patients with CHD before and after fish oil (4 months) 300 200 100 0 CHD patients after fish oil Controls CHD patients before fish oil Increase in coronary blood flow (%) Acetylcholine

  24. 1000 800 600 400 200 0 Placebo FO Fish oil and an inflammatory marker (sVCAM-1) • Healthy subjects aged > 55 y • Supplemented diet with a moderate amount of fish oil (= 1.2 g EPA+DHA/day) for 12 weeks • Plasma soluble VCAM-1 concentrations measured Pre Post * sVCAM-1 (ng/ml) Miles et al. (2001) Clinical Science 100, 91-100

  25. Risk factors for atherosclerosis Elevated blood TAG Hypertension Endothelial dysfunction Inflammation N-3 PUFA

  26. 100 95 90 85 0 200 400 600 800 Secondary prevention: DART • 1015 men aged < 70 y who had had a MI • Advised to eat oily fish or take fish oil capsules vs. no advice • Cardiovascular events and mortality followed for 2 years • Relative risk death 0.77 • Relative risk IHDdeath 0.84 Oily fish No advice % Surviviors Time (days) Burr et al. (1989) Lancet ii, 757-761

  27. Secondary prevention: GISSI Study • 2836 men who had had a MI within the last 3 months assigned to fish oil (0.85 g LC w-3 PUFA/day) vs. placebo • Follow up for two years • 356 deaths and non-fatal CV events in fish oil group vs. 414 in placebo group Relative risk in fish oil group All fatal events 0.80 CV death 0.70 Coronary death 0.65 Sudden death 0.55 GISSI Prevenzione Investigators (1999) Lancet 354, 447-455

  28. There are also non-cardiovascular actions of long chain w-3 PUFAs

  29. DHA concentration in different human tissues 20.0 17.5 15.0 12.5 % Total fatty acids 10.0 7.5 5.0 2.5 0.0 Adipose Erythrocyte Placenta Liver Testis Brain Retina

  30. DHA status and infant mental development (1 year of age) 140 120 100 80 60 Bayley Mental Development Index 3 6 9 12 Infant red cell DHA (%) Gibson et al. (1997) Eur. J. Clin. Nutr. 51, 578-584

  31. Helland et al. (2003) Pediatrics 111, 39-44 “Maternal supplementation with very long chain n-3 fatty acids during pregnancy and lactation augments childrens IQ at 4 years of age” Placebo vs. 2.4 g long chain w-3 PUFAs/day (50:50 EPA & DHA) from week 18 of pregnancy until 3 months post partum Kaufman Assessment Battery for Children performed at 4 years of age - a measure of intelligence and achievement designed for children aged 2.5 to 12.5 years At 4 years of age: Children of mothers in control group = 102.3 (11.3) Children of mothers in fish oil group = 106.4 (7.4)

  32. Omega-3s in children with ADHD 0.25 0.2 0.15 0.1 0.05 0 EPA in plasma phospholipids Control Few ADHD Many ADHD Burgess et al. (2000) Am. J. Clin. Nutr. 71, 327S-330S

  33. The Durham Trial A randomised controlled trial of fish oil supplementation (vs. placebo) in children (5 – 12 years old) with developmental co-ordination disorder (n = 117) Placebo vs. 550 mg EPA + 175 mg DHA/day for 3 months Then all onto EPA + DHA for a further 3 months Richardson & Montgomery (2005) Pediatrics 115, 1360-1366

  34. Omega 3 Placebo Placebo then Omega-3 105 100 95 90 120 110 100 90 Baseline 3 mo 6 mo Baseline 3 mo 6 mo Reading age Spelling age

  35. Hyperactivity Omega 3 Placebo Placebo then Omega-3 63 61 59 57 55 Baseline 3 mo 6 mo

  36. Long chain w-3 PUFAs are important in: - membrane structure - brain and visual development - maintenance of cognitive and neurological function (during development & with aging) - regulation of - blood pressure - platelet function, thrombosis, fibrinolysis - blood lipid concentrations - vascular function - cardiac rhythmn - inflammation - immune response - bone health - insulin sensitivity

  37. Long chain w-3 PUFAs promote - optimal brain growth - optimal visual and neural function

  38. Long chain w-3 PUFAs are (or may be) protective against - hypertension - hypertriglyceridemia - thrombosis - vascular dysfunction - cardiac arrhythmias - cardiovascular disease - inflammatory conditions - allergic conditions - immune dysfunction - insulin resistance - psychiatric and neurological diseases of children and adults - neurodegenerative diseases of ageing - bone loss - some cancers

  39. Summary: Long chain w-3 PUFAs • Long chain w-3 PUFAs have a number of physiological effects • Through their physiological effects they alter risk of a wide range of human diseases • Lowered disease risk occurs through plausible biological mechanisms • There are newly emerging mechanisms of action of long chain w-3 PUFAs in some conditions • Long chain w-3 PUFAs exert health benefits right through the life cycle (womb to tomb!) -

  40. Long chain w-3 PUFAs Current intakes vs. Recommendations (g/day) Current av. UK intake < 0.2 ISSFAL 1999 0.65 BNF 1999 1.0-1.4 AHA 2003* 1.0 AHA 2003** 2 to 4 SACN/COT 2004 0.45 (minimum) *For patients with CHD **For patients with hypertriglyceridaemia

  41. What about a-linolenic acid?

  42. Consensus statement Sanderson et al. (2002) Brit. J. Nutr. 88, 573-579 “The studies …. suggested little, if any, benefit of a-linolenic acid, relative to linoleic acid, on risk factors for cardiovascular disease ….”

  43. However, a-linolenic acid may exert health benefits through conversion to longer chain derivatives But, this may require high intakes of a-linolenic acid

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