NUTR 1010 Midterm 1 Aerobic Metabolism - Without the presence of oxygen, ONLY glucose can make ATP 1. In the presence of oxygen, glucose, fatty acids, and amino acids can be metabolized to produce acetylCoA (C-C-CoA) 2. Acetyl – CoA is broken down by the citric acid cycle to yield carbon dioxide (CO2) and high–energy electrons 3. The electrons are shuttled to the electron transport chain, where their energy is used to generate ATP and they are combined with oxygen and hydrogen to form water Macronutrient Catabolism - Glucose turns into Acetyl CoA through GLYCOLYSIS - Fatty acids turn into Acetyl CoA through BETA-OXIDATION - Amino acids turn into Acetyl CoA through Deamination Monosaccharides - Free glucose and fructose found naturally - “Simple” Carbs or sugars - Basic units of carbohydrates - Found in honey, fruit vegetables and milk EX. Glucose, Fructose and Galactose - Often added as sweeteners to processed foods ex. Glucose, fructose - Each contains 6 Carbons, 12 Hydrogens and 6 Oxygen atoms Disaccharides - “Simple” Carbs or sugars - Two monosaccharides linked together - sucrose=table sugar - Maltose is naturally found in beer and is used as a food additive - Lactose is milk sugar - Lactose is less sweet than sucrose - MALTOSE = 2 glucose - SUCROSE = 1 glucose+1 fructose - LACTOSE = 1 glucose+1 galactose Polysaccharides - ‘Poly’ =many - “Complex” Carbs - Three Polysaccharides: 1. STARCH - plant energy - Long strings of monosaccharides - Storage form of CARBOHYDRATES for plants - EX. grains, potatoes, legumes 2. GLYCOGEN - animal energy (only when alive) - Found in liver and muscle - Liver -> Keeps blood glucose levels stable - Muscle -> Fast energy for exercise - NOT a dietary source of carbohydrate 3. FIBRE - plant energy - Often made of glucose but can be other monosaccharides - Provides structure to the leaves, stems and seeds of plants - Lots in whole grains, vegetables, fruit and seaweed - Cannot be digested by the digestive enzymes our bodies produce Carbohydrate Digestion - STARTS in the mouth by salivary amylase - breaks starch into glucose and smaller polysaccharides - NO carbohydrate digestion occurs in the stomach - Small intestine: - Pancreatic amylase - Starch turns into glucose and maltose - Sucrase: sucrose -> glucose and fructose - Maltase: maltose -> 2 glucose molecules - Lactase: lactose -> glucose and galactose Carbohydrate Absorption - Monosaccharides -> intestinal cells -> blood - The blood delivers the nutrients into the liver - All monosaccharides go into the hepatic portal system - Glucose can be burned for energy or stored as glycogen in the liver - Glucose gets converted into Acetyl-CoA and then parts of Acetyl-CoA into citric acid cycle and then high energy electrons transfer to the Electron Transport chain and is converted to ATP Fat Digestion - Mouth: chewing and LINGUAL LIPASE - Stomach: churning into small droplets + GASTRIC LIPASE in the stomach (ZERO fat absorption in the stomach) - - Bile separates the fat from other foods in the stomach Small Intestine: this is where the fat is absorbed - Pancreatic Lipases break fatty acids off the glycerol - Free fatty acids and monoglycerides - Bile emulsifies fats into smaller droplets called micelles (bile separates out the fat particles) - 3 forms of lipase so far: Fat Absorption - In the small intestines bile emulsifies fats while enzymes digest them. - intestinal cells absorb the fats - Long-chain fatty acids form a large lipoprotein structure called a chylomicron that transports fats through the lymph system - Fats have to be repackaged in the liver but don’t go through the hepatic portal system (blood system) will be delivered through the blood however Barrier Function of the GI Tract - Barrier function: - Protective role of gastrointestinal cells - Limits the absorption of harmful substances such as toxins and disease-causing organisms - Helps to protect against foreign viruses and agents that attack - GI Tract contains some special immune cells: 1. Phagocytes = by ingesting harmful substances (come along and eat the offender, then take a little piece of the offender and put it outside of the phagocytes as a flag) 2. T cells (lymphocytes) = cell-mediated immunity 3. B cells (lymphocytes) = antibody-driven immunity - A)The barrier function can detect Antigens: - - foreign substances that, when introduced to your body, stimulate an immune response B)The first immune cells to respond are called Phagocytes: - They target any invader, engulf it, destroy it by breaking it up inside the phagocyte, and present Antigens on the phagocyte surface. - C) The broken-up antigens are then detected by B cells. - - D) T cells are another immune component of the Barrier Function. - - B Cells produce and secrete protein molecules into circulation called Antibodies T cells bind directly to infected or foreign cells, and destroy them The lymphatic system also helps us fight infections – get rid of body toxins, waste & unwanted materials - Transport lymph, a fluid containing infection-fighting white blood cells - Lymph Nodes swell up when fighting infections Nutrient Transport into Cells - Via the cell membrane - A cell membrane maintains the integrity of the cell and surrounds cell contents (cell membrane regulates what goes in and out) - - Nutrients are transported into cells by: - Simple Diffusion - Facilitated Diffusion - Active Transport SIMPLE DIFFUSION: the movement of substances from an area of higher concentration to an area of LOWER concentration. - No energy or carrier are required - EX. CO2, O2 and water - FACILITATED DIFFUSION: The movement of substances across a cell membrane from an area of high concentration to an area of low concentration with the aid of a carrier molecule - - No energy is required, requires a carrier molecule - Ex. Transport of sugars (FRUCTOSE) into the cells ACTIVE TRANSPORT: the transport of substances across the cell membrane with the aid of a carrier molecule AND the expenditure of energy [from an area of lower to an area of higher concentration] - - Ex. transport of glucose (also sugar) OSMOSIS: the passive movement of water across a semipermeable membrane in a direction that equalize the concentration that equalize the concentration of dissolved substances on both sides [from an area of lower to an area of higher substance concentration] - Ex. if there is a high concentration of sugar in the intestine, water will move into the intestine to help dissolve the sugar - ONLY PERTAINS TO WATER Macronutrient DRIs - What are the 6 Dietary Reference Intakes (DRIs): 1. Estimated Energy Requirements - Calculated for both men and women based on height, weight, age and activity level the amount of kcalories needed to maintain a stable weight 2. Acceptable Macronutrient Distribution Ranges - Used to see if you're getting the right proportion of macronutrients 3. Estimated Average Requirements 4. - Based on SOLID evidence, that meets 50% of the population - Tool for adequately assessing the population, NOT for an individual Recommended Dietary Allowance - Meets the requirements of 98% of the population - Much more accurate for an individual assessment - A GOAL for individuals to meet 5. Adequate Intake 6. - For some nutrients there is not enough evidence to set an EAR or an RDA - The AI is the mean intake of a healthy population - A goal for individuals if a RAD does not exist Tolerable Upper Intake Level - The highest average daily nutrient intake level that poses a risk of adverse (toxic) health effects - - As intake increases about the UL, the risk of potential adverse effects can increase - Refers to over consumption ADMR: Acceptable Macronutrient Distribution Range - Carbs: 45-65%, Lipids: 20-35%, Protein: 10-35% How to Calculate Macronutrient Calories or Grams as a Percentage of Total Caloric Intake - Calculation of calories for: - Carbs: 2,300 x 0.50 equals 1,150. I eat 1,150 calories worth of carbs each day (hello, extra slice of toast). - - Protein: 2,300 x 0.25 equals 575, so I get 575 calories worth of protein. - Fats: 2,300 x 0.25 equals 575. I also get 575 calories comprised of dietary fat. To calculate the actual gram amounts: - Carbs (4 calories per gram): 1,150 divided by 4 equals 287.5 grams of carbs. - Protein (4 calories per gram): 575 divided by 4 equals 143.75 grams of protein - Fat (9 calories per gram): 575 divided by 9 equals 63.8 grams of fat. What Influences Blood Sugar - Controlling blood glucose (sugar) levels decreases your risk of developing complications like diabetes (if we maintain a balance of macronutrients we can avoid diabetes and further complications) - Glycemic Index (GI) is a measure of carbohydrate quality - Classifies dietary carbohydrates based on a scale of 0-100 - LOW GI is <55, MEDIUM GI is 56-69, HIGH GI is >70 - lOW GI foods result in a more gradual INCREASE of blood glucose levels after meals - A low GI helps to control blood sugar and low GI foods can also help to control appetite - USUALLY high-fibre foods are low GI but not always Fibre - Benefits of fibre include: - Lower risk of: - Constipation - Obesity (fibre is filling; slows release for sugar into blood) - Diabetes (fibre slows down CHO digestion, stabilizes blood sugar levels) - Colon cancer (fibre moves stool down the GI tract faster, limiting toxins taken in and exposure to the cells in the GI tract) - Hemorrhoids Function of GI Tract - Your digestive system does four things: 1. Digestion: breaking down food into tiny pieces 2. Absorption: moving the tiny pieces from the inside of your intestine into the bloodstream 3. Elimination: getting rid of the waste 4. - Barrier Function: preventing the absorption of harmful substances Digestion begins in the mouth through MECHANICAL DIGESTION (your teeth break up the food) and CHEMICAL DIGESTION (enzymes in saliva work to break down the food… SALIVARY AMYLASE breaks up CARBS and LINGUAL LIPASE breaks up FATS) which turns the food into a bolus - The bolus gets passed through the esophagus and starts the process of PERISTALSIS which are waves of contractions that move the food - Food moves into the stomach through the lower esophageal sphincter - The stomach then churns the food by chemical digestion and through the mixing of gastric juices turns the bolus into chyme - Pepsin breaks down the protein - Chyme gets delivered through the PYLORIC SPHINCTER from the stomach to the duodenum (1st part of small intestine) - the liver, the gallbladder and the pancreas are involved - Bile is made in the LIVER and stored in the GALLBLADDER - The pancreas produces and adds Bicarbonate ions to neutralize the acid in the chyme (creating an alkaline environment) - The large intestine does not participate in digestion. It absorbs water and some micronutrients and participate in the elimination of waste - Nutrients get imported into the bloodstream and are transported to organs and tissues around the body Constipation: - Fewer than 3 bowel movements per week - Abdominal pain, bloating, gas Causes: - Traveling (schedule disruption); changes in diet (e.g. low fibre, fluid);side effects of some medications (e.g. antidepressants); lack of physical activity - Disorders affecting the nervous system E.g. Parkinson’s; spinal cord injury How to prevent it: - Eat lots of fibre – provides bulk and holds onto water - Drink lots of water – keeps everything soft (hot liquids) - Increase physical activity - Probiotics help too Diarrhea: - More than 3 bowel movements a day; passage of loose watery stool - Cramping, abdominal pain, bloating, blood in stool, nausea, fever Causes: - Bacteria; viruses, parasites; stress, medications; food intolerances; irritable bowel syndrome, Celiac disease - Causes dehydration and loss of electrolytes - Can I eat differently to prevent/treat diarrhea? – Probiotics may help! Managing Diarrhea: - Decrease caffeine; decrease lactose; decrease alcohol; decrease fat; small frequent meals; increase soluble fibre (dried beans, peas, lentils, oats; some fruit like bananas, apples, oranges); foods with probiotics Irritable Bowel Syndrome (IBS): - Cause unknown; Irregular bowel patterns - Symptoms: abdominal pain, cramping, bloating, gas, constipation, or diarrhea - 5 million Canadians currently suffering - Affects more women than men - Managing symptoms: Exercise and rest, and eliminate stress; probiotics; keep a food diary Where do I get Probiotics? : - Foods that contain live bacteria cultures or yeasts - Yogurt, kefir, soy yogurt, dietary supplements How do they work? - Increase number of good bacteria - Encourage growth of healthy bacteria in colon - Increase production of short-chain fatty acids, which promote water and electrolyte absorption in colon (decrease severity of diarrhea) - Help fight bad bacteria, viruses, etc. Lipids and Fatty Acids - Nutrients move throughout the body through blood but if you add fat to blood it won’t mix. Thats where LIPOPROTEINS come in - Types of Lipoproteins - Chylomicrons - Made in the cells of the small intestine - Carries dietary fat to the LIVER and the rest of the body for burning or storage - Other types are made in the LIVER - a) Very Low Density Lipoproteins (VLDL) - b) turn into low density lipoproteins (LDL) in the bloodstream - c) High Density Lipoproteins (HDL) “Healthy” lipoprotein - Transports fats to and from the liver - Thinks of VLDL and LDL as transporting lipids through blood to cells around the body and think of HDL as removing lipids from cells around the body, so they can be excreted - Why do we need lipids? - For structure and lubrication - Provide insulation • In addition to storing energy as fat, adipose tissue (fat cells) insulates the body from changes in temperature - Protect bones, joints and organs •Provide a cushion to protect internal organs against shock - Very important for our the nervous system •Form an insulating coating around nerves called the myelin sheath - Lubricate body surfaces •i.e.glands in the skin and eyes release oils that lubricate For cell structure - Lipids make up cell membranes - Phospholipids keep membranes fluid Regulation of body processes - Regulation of body processes - There are lipids we need for things like: - Vitamin absorption (A, D, K and E) - Making hormones - Blood pressure regulation - As a building block to make other fats - - - Regulating blood clotting - ATP production for energy - 1g of fat provides 9kcal of energy - High fat foods have high energy content - Your cells burn fat at rest and during exercise The Essential Fatty Acids - Linoleic acid (aka omega-6) - - 18:2 ω-6 Alpha(α)-Linolenic acid (aka OMEGA 3) - - Some fats are essential - need to be consumed through the diet 18:3 ω-3 These are necessary for: - Regulating blood clotting - Regulating inflammation in the body - Normal brain development How much fat do you need? - All based on how much ESSENTIAL FATTY ACID you need to keep clotting under control - For a healthy adult, use the AMDR for fat which is 20-35%
