Carbohydrates: love m m or leave m? The glycemic index explored

Transcription

1 Carbohydrates: love m m or leave m? The glycemic index explored Current trends Louise Gagné M.D. Family Physician, Saskatoon Community Clinic Clinical assistant professor Department of Community Health and Epidemiology University of Saskatchewan Type 2 diabetes has become an epidemic The prevalence and magnitude of obesity is rising dramatically What do carbohydrates have to do with it? The glycemic index (GI) low 55 medium high 70 The glycemic load (GL) Glycemic load= GI x carbohydrate (gm per serving) divided by 100 Low 0-10 low medium high >20 1. Factors that influence the GI: rate of stomach emptying Slowing the rate of stomach emptying: soluble fiber acids protein fat GI 80 GL cup watermelon GI 72 GL 25.6 ½ bagel

2 2. Factors that influence the GI: amylose vs amylopectin Foods high in amylose starch: Basmati rice, kidney beans, lentils Foods high in amylopectin starch: potatoes, wheat flour, sticky rice 3. Factors that influence the GI: starch gelatinization Gelatinization of starch increases the rate of digestion Sticky rice, Jasmine rice Pasta cooked 20 minutes Amylose starch molecules take longer to be acted upon by digestive enzymes than amylopectin starches 4. Factors that influence the GI: physical barriers Physical barriers to digestion: whole grains are more resistant to action by digestive enzymes than finely pulverized flours What happens when we eat a high glycemic index food? The rapid rise in blood glucose causes a spike in insulin output Bulgur 46 Whole wheat bread 69 Baguette 95 Insulin Insulin is released from the pancreas when blood glucose levels are elevated Insulin lowers blood glucose by facilitating the entry of glucose into cells Insulin promotes the storage of glucose as glycogen (in muscle and liver) and as fat The glycemic index low <55 medium high >70

3 The spike in insulin release lowers blood glucose levels The glycemic index As blood glucose falls, stress hormones, and glucagon are released low <55 medium high >70 Low blood glucose and the release of stress hormones can lead to Trembling, heart palpitations, irritability, anxiety, sweating and increased appetite Physiologic response to a low glycemic index meal Slower rise in blood glucose Moderate release of insulin Longer period of satiety No reactive hypoglycemia The glycemic index low <55 medium high >70 High insulin secretors People who are high insulin secretors lose more weight when they follow low glycemic load, higher fat diets. (Than when they follow high glycemic load, low fat diets) In one study, high insulin secretors lost ~13 lbs (5.8 kg) versus 2.6 lbs (1.2 kg) Low glycemic load diets also have beneficial effects on lipids: they increase HDL cholesterol and lower triglycerides

4 Nutrigenomics Percent of diseases potentially preventable with diet and lifestyle change Diet influences gene expression! Balancing Life-Style and Genomics Research for Disease Prevention by Walter Willet Glycemic index and gene expression Low glycemic index diets have been found to down regulate 71 different genes, resulting in: lower insulin levels and increased resistance to obesity lower risk of type 2 diabetes High glycemic index diets have been found to up regulate 62 different genes, resulting in increased inflammation and oxidative stress GI/GL and weight loss Overweight and obese people have been shown to lose the most weight on low GI/GL diets compared to other diets This is thought to be because of a longer period of satiety after meals The aftereffects of breakfast and lunch A study of obese teenage boys found that a high GI breakfast and lunch led to excessive hunger and overeating for the rest of the day The boys who ate a low GI breakfast and lunch were less hungry and spontaneously ate less for the rest of the day What makes us less likely to become obese? Eating low glycemic index carbohydrates Eating breakfast Eating more fruits and vegetables Getting adequate protein Getting enough calcium and vitamin D Eating less fat and more fiber Eating out less often Moving around more (even people who fidget weigh less) Getting enough sleep

5 Heart disease Large spikes in postprandial glucose (after meal blood sugar) are associated with: Two times higher all cause mortality Three times higher cardiovascular mortality High GI/GL diets are linked to: increased risk of heart attack increased inflammation (hs-crp) Lower GI/GL diets are associated with lower total cholesterol, LDL cholesterol and triglycerides Type 2 Diabetes People who consume a high glycemic index diet are 1.4 times more likely to develop type 2 diabetes Low fiber & high glycemic index People who eat a high glycemic index, low fiber diet are 2.5 times more likely to develop type 2 diabetes Pregnancy and high glycemic index/load diets Women who eat a high glycemic load, low cereal fiber diet, have more than twice the risk of developing gestational diabetes Neural tube defects are twice as likely to occur if pregnant women consume a high GI diet Macular degeneration People in the highest quintile of dietary GI have been found to have a significantly higher risk of age related macular degeneration (AMD) and have increased severity of AMD Researchers have concluded that 20% of AMD may be prevented by low GI diet Non-alcoholic fatty liver disease Mice fed standardized diet which differed only in type of starch (calories were equal) had the same weight gain, but High GI diet mice had 2x adipose tissue, 2x hepatic triglycerides and increased plasma insulin and triglycerides

6 Increased cancer risk? Some studies show a link between high GI/GL diets and increased cancer risk Colon, endometrium, ovary, stomach, breast and pancreas Confounding factors What is bread, rice, breakfast cereal, pasta? How is the food normally eaten? Adding peanuts or vinegar can lower the 1 hour glucose response by 55% French baguette (GI 95) eaten with chocolate spread (GI 72) Nutrient density/quality Is there an ideal proportion of carbohydrate? Apple GI 37 High fat ice cream GI 37 What is your lifestyle and genetic profile? Most recommendations are for 40-65% of caloric intake However, low fat vegan diets containing 75% carbohydrates have been found to support weight loss and improve diabetic control However, these diets consist primarily of vegetables, fruits, grains and legumes and are low glycemic index/high fiber diets, in addition to being low fat and vegan Diet quality #1 How to use the GI/GL Studies have found that low carb/high fat diets generally have lower diet quality Healthy eating index (HEI), low carb diet= 44.6 whereas high carb diet= 82.9 In population studies, high fat/low carb diets are associated with higher BMI s, whereas people on high-carb diets are more likely to have BMI <25 High fat/low carb diets are less likely to produce sustained weight loss Use the GI/GL to choose what starchy foods to eat in each category Consider switching from: Instant oatmeal to large flake oats or quinoa Cornflakes to All Bran Whole wheat bread to wholegrain sourdough Potatoes to (al dente) pasta Minute rice to Basmati rice

7 Good carbohydrate choices Breads: 100% whole grain breads, pita bread, sourdough breads Rice: Basmati rice, Uncle Ben s converted rice Pasta: al dente Cooked grains: quinoa, bulgur, steel cut oats, large flake oats Cereals: All Bran Other foods that contain slow burning carbohydrates Legumes Vegetables Most fruits Dairy products Foods with a very low GI Nuts Oils Fish Meat Eggs Less good carbohydrate choices Most breads, bagels and other flour products Puffed grains Most cold breakfast cereals Potatoes Gooey starches #2: Combine high GI with low GI foods French bread and lentil soup Peanuts and vinegar sprinkled over a Vietnamese Bun #3: Choose smaller portions of high GI/GL foods

8 #4: Add healthy fats, proteins, soluble fiber and acids Try drizzling olive oil (combined with ginger and garlic) over vegetables Include a protein food with each meal Add foods rich in soluble fiber: apples, okra, beans, oatmeal, flax Squirt some lemon juice or vinegar on vegetables, noodles, fish, etc #5 Choose high quality carbohydrates High quality carbohydrates: Whole foods/unprocessed Nutrient dense High fiber Low in saturated fats Zero trans fats #6 Don t forget to eat lots of fruits and vegetables! In summary High postprandial glucose levels are harmful to health If you are overweight or obese, be especially careful to choose low glycemic index/load carbohydrates Staying healthy Choose healthy carbohydrates Choose healthy proteins Choose healthy fats Eat lots of fruits and vegetables! Recommended reading The Glucose Revolution by Brand-Miller, Wolever, Colagiuri and Foster-Powell The New Glucose Revolution by Brand- Miller, Wolever, Foster-Powell and Colagiuri The Low GI Diet Revolution by Brand- Miller, Foster-Powell and McMillan-Price

9 Recipes The Low GI Diet Cookbook: 100 Simple, Delicious Smart-Carb Recipes-The Proven Way to Lose Weight and Eat for Lifelong Health by Jennie Brand-Miller