Considering whether improved knowledge of how we digest fat can help reduce its impact on health Professor Pete Wilde

Transcription

1 Considering whether improved knowledge of how we digest fat can help reduce its impact on health Professor Pete Wilde Institute of Food Research, Norwich, UK

2 Evolution of the modern diet Structurally rich Difficult to extract Slow to digest Prolonged release Satiety We have not evolved to modern diet Structurally poor Easy to extract Rapidly digested Rapid absorption GI, Satiety, Cholesterol

3 Obesity prevalence The Obesity Lifetime Bomb? Men Women Adult obesity prevalence by age and sex Health Survey for England Cost UK PLC > 10bn Age We have evolved to take on extra energy to store, for lean times Small surplus intake leads to long term weight gain. Psychological, physiological and sociological pressures to overconsume to maintain sufficient energy stores. Processed foods often do not prolong satiety. Intelligent design of everyday, commonly consumed foods with improved appetite control

4 Fat Digestion & Appetite Partial fat digestion in stomach Fats mainly digested and adsorbed in duodenum (sensing of fat slows emptying from stomach and enhances fullness ) Slow fat digestion, fats continue further down small intestine Sensing of fat more intense, feedback slows digestion & triggers appetite supressing hormones

5 Why Target Fats? Fats are essential nutrients, but have the highest calorific value Modulating digestion could have health benefits Reduced blood lipids and cholesterol Reduced Cardiovascular disease (CVD) risk Reduced appetite Reduce weight gain, obesity and related conditions (type 2 diabetes etc)

6 Mixed Messages

7 What the Scientists say GA Bray, BM Popkin - The American Journal of Clinical Nutrition 1999, 70: Increased dietary fat intake showed small increases on BMI and body fat. De Souza et al. British Medical Journal 2015;351:h3978 Saturated fat and trans fats increase Coronary Heart Disease risk, but saturated fats did not increase all cause mortality. Industrial trans fats appeared to induce higher risk than animal trans fats. Schwab, et al. Food & Nutrition Research 2014, 58: Replacing some saturated fat with unsaturated fats reduced circulating cholesterol, and decreased risk of cardiovascular disease, especially in men. Bhavsar, N et al. Current Opinion in Clinical Nutrition and Metabolic Care, 2016, 19; Not all saturated fats have the same effects. Medium Chain saturated fats appear to behave differently as they are metabolised for energy rather than stored. There is some evidence that they may also act synergistically with omega-3 to reduce CVD risk.

8 What the Scientists say GA Bray, BM Popkin - The American Journal of Clinical Nutrition 1999, 70: Increased dietary fat intake showed small increases on BMI and body fat. Even the scientific evidence is mixed, possibly because - not all studies are designed the same way De Souza et al. British Medical Journal 2015;351:h3978 Saturated - different fat and trans saturated fats increase or unsaturated Coronary fats Heart have Disease different risk, effects but saturated fats did not increase all cause mortality. Industrial trans fats appeared to induce higher risk than animal trans fats. Original advice on reducing dietary fats did not have benefit of recent Schwab, evidence. et al. Food & Nutrition Research 2014, 58: Replacing some saturated fat with unsaturated fats reduced circulating cholesterol, and decreased risk of cardiovascular disease, especially in men. Current advice is for a varied, balanced, nutritious diet, Bhavsar, N - et limiting al. Current energy Opinion intake Clinical and to Nutrition and Metabolic Care, 2016, 19; Not all saturated fats have the same effects. Medium Chain saturated fats appear to - limit the intake of saturated fat, particularly from behave differently as they are metabolised for energy rather than stored. There is some animal sources, to <10% calories evidence that they may also act synergistically with omega-3 to reduce CVD risk. Why is it so confusing?

9 Fat Digestion is complicated Oil & Water do not mix Enzymatic digestion of fat is more complex than simple molecular binding Enzyme Normal enzyme action on (e.g. starch) + + Starch Sugars Fat digesting enzyme action Water Fat Lipase Breakdown products Triglyceride Oil drop

10 Fat digestion disassembled Fat Tri glyceride polar lipids fatty acids bile salts lipase co-lipase mixed micelle Key stages of fat digestion in the small intestine Bile salt (BS) activated enzymatic breakdown of fat BS mediated transport of products (Fatty acids..) away from fat and through mucous layer Mucus layer Absorption of digestion products into epithelial cells Reassembly into oil droplets (chylomicrons or Lipoproteins) Gut epithelium cells

11 The Field Gun Run Original structure Limiting factors Enzyme action Transport & Uptake Reassembly

12 Fatty acids (FA) are not all the same Medium chain FA (partially water soluble) Long chain FA (insoluble) Some vegetable oils including palm kernel oil and coconut oil Animal fats Shorter fatty acids are more soluble, is this important? Unsaturated FA (insoluble) Vegetable oils olive, rape, sunflower etc Omega-3 FA (insoluble) Oily fish

13 Where do our fats end up? Shorter FA Gut wall cell Blood Used more rapidly for energy etc Longer FA Lymphatic system - HDL and LDL, excess fat is stored or may accumulate in blood vessels We can cope with moderate fat intake. Excess fat intake of modern diets overload the system. Excess long chain fatty acids lead to

14 Can we slow down fat digestion? Free fatty acids released, μm Lipase Bile salt Galactolipids Fat Protective film DGDG:PC=0:4 DGDG:PC=1:3 DGDG:PC=2:2 DGDG:PC=3:1 DGDG:PC=4: Time, s In the lab, Increasing galactolipid slowed down fat digestion. In humans, it is much more difficult

15 Fat release (µmol/ml) Back to the Future: Ancestral diets Faecal samples of digested almonds Ellis et al AJCN (2004) 80, m Plant cellular structures control release and bioavailability of nutrients Simple processing can control extent of fat release 10 8 Almond oil emulsion Milled particles mm mm Time (min) Utilise the natural resistance of plant tissues to control nutrient release 1-2 mm Separated cells

16 Summary Fats are essential nutrients, and healthy in moderation! Not all saturated fats are unhealthy Digestion of fats is a complex process. Controlling the digestion of fats and other food structures could have many health benefits: Reduce blood lipids and cholesterol Reduce appetite and help aid weight loss Reduce risk of obesity and related conditions (CVD, type 2 diabetes, cancer etc)

17 Acknowledgements Boon-Seang Chu, Fiona Husband, Roger Parker, Julia Maldonado- Valderrama, Mike Ridout, Louise Salt Myriam Grundy Peter Ellis Peter Butterworth Robert Gray Thank you Research Pavilion Stand RP57