Lecture 6 - Carbohydrates continued.docx

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Foods and Nutrition
Foods and Nutrition 4471A/B
Mac Kaisel

Chapter 4 Carbohydrates (Part 2) How do our cells get energy from glucose? Inside a cell, enzymes split glucose molecules in half (breaking the bonds between the carbon atoms), a process called glycolysis o Releasing some energy from breaking glucose These halves can be put back together to reform glucose or broken further If broken down further, they cannot be reassembled to form glucose (the point of no return) Splitting 6 carbon unit to release energy Water is also released in this process What if you dont consume enough carbohydrates? The body must get energy from other sources o Muscle protein begins to be broken down to use as a source of calories Diverting protein from critical functions of its own o Adequate dietary carbohydrates prevent the use of protein for energy This is the protein-sparing action of carbohydrate Lose lean tissue from muscles Bare minimum for the brain The minimum intake of carbohydrates to feed the brain is 130 grams a day o If you consume less than 130 g, fat is broken down to form ketone bodies which can be used to feed the brain o Ketone bodies are the only other thing besides glucose the brain will accept to be used for energy Ketosis o Compromised mental function (dizziness, fainting) o Breath may smell fruity or foul because of the odour of ketone bodies o Occurs when low-carb, high-protein diets begin using fat for energy Storing Glucose as Glycogen After a meal, as blood glucose rises, the pancreas releases insulin o Insulin signals the bodys tissues to take up glucose When blood glucose concentration drops and cells need energy, the pancreas produces glucagon o Enzymes in the liver break down glycogen releasing it into the blood as glucose o If more glucose is needed, protein may be broken down (from blood, muscle, organs) Since glycogen is highly branched, allows for enzymes to easily attack it and break it apart leading to a surge of glucose in blood Where is glucose stored as glycogen in the body? 2/3 of the bodys total glycogen is stored in and used by muscles A small emergency store is found in the brain (1-2 hours worth) The remainder is stored in the liver, which makes it available to the body as blood glucose (4-6 hours worth) Sugar Crash When you have a empty stomach and grad something that is high in sugar to tie you over Your blood sugar will go dramatically high and it quickly absorbed Insulin is quickly surged o Leads to decrease in blood sugar level o And results in crash Sugar in Drinks Highest amount per 250 mL o Crush 34g (8 tsp) o Coke, Mountain Dew and Yop Yogurt tied at 30 g o Lemonade 29 g o Chocolate milk 28 g o Apple juice 24 g o Powerade 15 g Powerade is designed for rehydration and has the ideal amount of sugar for reabsorption Would a boiled potato or a glass of orange juice raise your blood sugar faster? Potato is higher on the glycocemic index because: o It has starch that breaks down to maltose which is made of 2 glucose o Orange juice contains fructose so takes longer than glucose to absorbThe Glycemic Response The glycemic index (GI) is a measure of the ability of a food to elevate blood glucose and insulin levels o Scores are compared with a standard, usually white bread or glucose (which score 100) Important to know because if you want to keep your blood sugar stable youll want to pick foods with a lower glycemic index value A foods score depends on several factors o The monosaccharide in the food o What else is in the food (fat or protein) Figured it out by giving participants with 50 g of sugar and theyd mark how quickly it took the body to absorb glucose o Not entirely accurate because: We are all individuals so body size and weight and blood volume and metabolic rate all have an impact on how blood sugar will respond to a food This means that absorption will be different in each person Also depends on how ripe fruit is, what other foods accompany it in the meal and how food is prepared Glycemic Index Lower on th
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