Carbohydrates Chapter 4 BIOL1400 Dr. Mohamad H. Termos

Carbohydrates - Main fuel source for brain, nervous system and red blood cells - 4 kcal per gram - Carbohydrates are readily available as fuel for all cells in the form of: - Blood glucose - Glycogen : Stored in muscles and liver . Helps maintain blood glucose

Simple carbohydrates or sugars - Monosaccharides: most common forms: Glucose, Fructose (fruit sugar), and Galactose - Disaccharides: two mono bonded together. Examples: 1- Sucrose: the table sugar 2- Lactose: milk sugar 3- Maltose Two glucose molecules bonded together Used in liquor industry Cereal grains broken down to maltose Note: Food labels lump all simple sugars (mono and disaccharides) into one group called "sugars" Sucrose is made up of glucose and fructose and it is also found in sugarcane, sugar beets, honey and maple syrup. It is not produced by animals. Lactose is made up of glucose and galactose.

Complex carbohydrates or starches Polysaccharides are 1000 or more glucose units bonded together in chains Found mostly in grains, vegetables and fruits Food label calls them "other carbohydrates“ - Plants store carbohydrates in two forms that are digestible by humans: Amylose and Amylopectin. - Enzymes break down Amylopectin faster and raise blood sugar quicker than Amylose

Forms of complex carbohydrates Glycogen: - Carbohydrates are stored as glycogen in animals - About 1800 kcal - Major storage sites are liver and muscles. Fibers: - Differ from starches in that the bonds that hold the sugar units together are indigestible by humans so they are not absorbed - Forms of non-starch polysaccharides that food labels call "dietary fiber“: cellulose, pectins, and gums Major storage sites of glysogen: - Liver (400 kcal), used to maintain blood glucose and - Muscle (1400 kcal), used to fuel muscle cells especially during high-intensity or endurance exercises

Forms of Fiber Insoluble fiber Do not dissolve in water Not metabolized by intestinal bacteria Include cellulose and lignin Found in wheat, vegetables, wheat bran.

Forms of Fiber Soluble fiber Dissolve or swell in water Fermented by intestinal bacteria Pectins and gums Found in fruits and vegetables

Carbohydrates in foods - Table sugar, honey, jam, fruit and plain baked potatoes contain most of their kcal as carbs. - Rice, bread, noodles, corn flakes are about 75% carbohydrate - Foods with no carbohydrate include meat, fish, eggs and oils

Digestion and Absorption Help make carbohydrates available for body use: Digestion: Starch digestion starts in the mouth. Salivary amylase produced by salivary glands breaks down starch into disaccharides (maltose) Note: Salivary amylase will be inactivated by stomach acid

Digestion Small intestine - Pancreas releases pancreatic amylase to breakdown to di and monosaccharides - Enzymes attached to intestinal cells digest disaccharides to monosaccharides Maltase acts on maltose Lactase acts on lactose Sucrase acts on sucrose

Absorption - Most monosaccharides are actively absorbed - Requires a specific carrier and energy - Glucose and galactose are absorbed with sodium - Fructose undergoes facilitated absorption. Attracts water in the small intestines and can cause diarrhea - Transported to the liver via the portal vein

Absorption - Liver transforms galactose and fructose into glucose - Liver then has 3 options Releases glucose into the bloodstream Produces glycogen for storage Produces fat Note: Only about 10% of sugars escapes absorption, traveling to the large intestine where it's fermented by bacteria which promotes intestinal health

Simple carbohydrates functions in the body A- Yielding energy - Supply kcal to fuel the body - Red blood cells can only use simple carbohydrates - Brain and CNS use glucose but can use ketones - Muscles fueled by glucose but can also use fat

Simple carbohydrates functions B- Sparing protein from use as an energy source and preventing ketosis - Under normal circumstances, CHO is used as energy and protein is reserved for building and maintaining vital organs - When not enough CHO is consumed Proteins are converted to glucose. Fats are not metabolized completely and ketones are formed and can disturb acid-base balance

Regulating this energy source Blood glucose is regulated in a very narrow range by the liver and pancreas Pancreas releases insulin when blood glucose rises Insulin directs liver to store glucose as glycogen Insulin directs muscle, adipose and other cells to take up glucose

Regulating this energy source Pancreas releases glucagon when blood sugar falls Keeps blood sugar from falling too low Prompts liver to breakdown glycogen to glucose Adrenal gland also plays a role during stress Located on kidneys Releases epinephrine causing quick conversion of glycogen to glucose in the liver This complex regulatory system safeguards against high blood glucose (hyperglycemia) and low blood glucose (hypoglycemia)

Failure of Blood Glucose Regulation Diabetes mellitus - Type 1 Diabetes - Often occurs in childhood but can occur at any age - Usually admitted with high blood glucose and ketosis - Decreased release of insulin - Glucose spills into urine

Type 1 Diabetes Pathology Treatment Most cases begin with immune system disorder destroying the insulin producing cells of the pancreas Pancreas loses ability to synthesize insulin Treatment Insulin therapy: injections or pump Following suitable dietary recommendations: such as taking 3 meals and one or more snacks and consuming a regulated ratio of CHO: protein: fat

Type 1 Diabetes Risks associated with type 1 diabetes - Cardiovascular disease - Excessive ketone production Ketones in urine Pull sodium and potassium into urine with them Can lead to dehydration, ion imbalance, coma and death - Nerve deterioration Mostly in extremities Loss of sensation means not recognizing sores or problems Increased risk of infection and amputation

Type 2 Diabetes Disease characteristics - Usually occurs after age 40 Most common type, 90% of cases Pathology Inactivity and obesity especially abdominal Genetically linked Insulin receptors on cell surfaces become insulin resistant and glucose is not taken up by the cells as well

Type 2 Diabetes Pathology (cont.) High blood glucose Insulin production increases, insulin is high at the onset of disease Pancreas can't keep up and insulin production is significantly reduced

Type 2 Diabetes - To decrease risk, those with family history should avoid obesity, animal and trans fat intake, simple carbohydrates and inactivity Treatment - Achieve healthy weight - Oral insulin therapy or injections - Regular physical activity - Dietary therapy (regular meals, calorie control, etc.)

Hypoglycemia Reactive hypoglycemia Symptoms occur 2-4 hours after eating Symptoms include: headache, dizziness, sweating, confusion Unclear cause possibly overproduction of insulin

Hypoglycemia Fasting hypoglycemia Diagnosis Nutrition therapy Rare and usually caused by pancreatic cancer Blood glucose falls after fasting 8-24 hours Diagnosis Low blood glucose with symptoms Low blood glucose is 40-50 mg per 100 ml Nutrition therapy Eat regular meals Include protein, fat and complex carbohydrates at meals Moderate caffeine and alcohol intake

Dental caries - Cavities are created when bacteria in mouth metabolize carbohydrates into acid that dissolves tooth enamel - Worst offenders are sticky gummy carbohydrates like caramel - Snacking regularly on sweets or chewing sugar gum between meals contributes greatly - Fluoridated water and toothpaste decrease dental caries - Cheese, peanuts and sugar free gum may decrease acid on teeth