Carbohydrates
�One of the three macronutrients
�Important source of energy for all cells
�Preferred energy source for nerve cells
�Composed of carbon, hydrogen, oxygen.
�Good sources: fruits, vegetables, grains
Glucose
�The most abundant carbohydrate
�Produced by plants through photosynthesis
Simple carbohydrates
�Referred to as sugars
�Contain one of two molecules
�Commonly referred to as sugars
Monosaccharides
Contain one molecule
ex: Glucose, fructose, galactose, and ribose
Disaccharides
Contain two molecules
ex: Lactose, maltose, and sucrose
Fructose
Sweetest natural sugar; found in fruit, high-fructose corn syrup
Galactose
Does not occur alone in foods; binds with glucose to form lactose
Lactose
Glucose + Galactose
�also called milk sugar
�Beta bond
Maltose
Glucose+ glucose
�Molecules join in food to form starch molecules; by-product of fermentation process
Sucrose
Glucose+fructose
�found in sugarcane, sugar beets, and honey
�Alpha bond
Oligosaccharides
contain 3 to 10 monosaccharides
Polysaccharides
Most consist of hundreds to thousands of glucose molecules
�Starch, glycogen, most fibers
Starch
Storage form of glucose in plants; found in grains, legumes, and tubers
Glycogen
Storage form of glucose in animals; stored in liver and muscles
�Not found in food and therefore not a source of dietary carbohydrate
Fiber
�Composed of long polysaccharide chains
Amylose
Straight chain of glucose
Amylopectin
Branched chain of glucose
Resistant starch (fiber)
Glucose molecules linked by beta bonds are largely indigestible
Dietary fibers
Non-digestible parts of plants
Functional fibers
non-digestible forms of carbohydrates extracted from plants or manufactured in a lab that have known health benefits
Total fiber
Dietary fiber + Functional fiber
Soluble fibers
�Dissolve in water; viscous and gel-forming
�Fermentable, digested by intestinal bacteria
�Regular consumption can reduce risk for cardiovascular disease and type 2 diabetes
�Pectin, gum, mucilage
�Found in citrus fruits, berries, oats, beans
Insoluble fibers
�Do not dissolve in water, non-viscous
�Cannot be fermented by bacteria in the colon
�Promote regular bowel movements, alleviate constipation, and reduce diverticulosis
�Ex: Lignins, cellulose, hemicelluloses
�Good sources: whole grains, seeds, legumes, f
Carbohydrate digestion
�It breaks down most carbohydrates into monosaccharides
�It does not occur in the stomach
�Stomach acids inactivate salivary amylase
�Most of it occurs in the small intestine
Salivary amylase
�Enzyme that begins starch digestion in the mouth
�Breaks starches down to maltose
Pancreatic amylase
�Enzyme produced in the pancreas and secreted into the small intestine
�Digests remaining starch to maltose
Maltase, sucrase, lactase
�Digest disaccharides to monosaccharides where they are absorbed into the mucosal cells lining the small intestine and then enter the bloodstream
Carbohydrate digestion Transport
�Glucose and galactose absorbed via active transport
�Fructose absorbed via facilitated diffusion (slower absorption)
Fructose and galactose
Converted to glucose in the liver
Glucose digestion
�Can provide immediate energy
�Can be stored as glycogen in the liver and muscles
�Liver glycogen used to maintain blood glucose and support brain, spinal cord, and red blood cells
�Muscle glycogen provides energy to muscles during exercise
Hormones regulating blood glucose levels
Insulin
Glucagon
Epinephrine
Norepinephrine
Cortisol
Growth hormone
Insulin
�Secreted by beta cells of the pancreas
�stimulates glucose transporters (carrier proteins) to help move glucose from the blood across the cell membrane
�Stimulates the liver and muscle cell to take up glucose and store it as glycogen
High blood glucose
�Insulin secretion
�Cellular uptake
�Glucose storage
Low blood glucose
�Glucagon secretion
�Glycogenolysis
�Gluconeogenesis
Glucagon
�Secreted by alpha cells of the pancreas
�Stimulates the liver to convert glycogen to glucose
�Assists in the breakdown of body proteins for gluconeogenesis, the production of glucose from amino acids
Epinephrine and norepinephrine
�Secreted by adrenal glands and nerve endings when blood glucose is low
�Increase glycogen breakdown in the liver, releasing glucose into the blood
�Increase gluconeogenesis
�Responsible for our "fight-or-flight" reactions to danger
Cortisol and Growth hormone
�Secreted by the adrenal glands to act on the liver, muscle, and adipose tissue
�Cortisol increases gluconeogenesis and decreases glucose use by muscles and organs
�Growth hormone decreases muscle glucose uptake, increases fatty acid mobilization and use,
Glycemic Index
�A food's potential to raise blood glucose
�Not always easy to predict
�Food's absorption rate varies type of carbohydrate, preparation methods, and its fat and fiber content
�Most foods are eaten in combination in a meal, ____ of total meal becomes more
Glycemic Load
�May be more useful than Glycemic Index
�Used to determine the effect of a food on a person's glucose response
�Grams of carbohydrates in a food are multiplied by the glycemic index
�Glycemic index and glycemic load remain controversial
Value of Lower Glycemic Load
�Higher fiber foods help to regulate blood glucose
�Risk reduction for heart disease and colon cancer
�Fiber helps to decrease fat levels in the blood
�Ex: Legumes, fresh vegetables, whole wheat
The role of carbohydrate (energy)
�Each gram of carbs= 4 kcal
�Red blood cells use only glucose for energy
�Brain and nervous tissue rely primarily on glucose
�Both carbohydrates and fats supply energy for daily activities
�Glucose is especially important for energy during exercise
The role of carbs (Ketosis)
�Alternative fuel source for the brain
�Breakdown of stored fat during fasting, low carb intake, or vigorous exercise forms ketones
�Excess ketones increase blood acidity and cause ketoacidosis
�Sufficient energy from carbohydrates prevents ketone product
Carbohydrates spare protein
�Gluconeogenesis occurs when the diet doesn't provided enough carbohydrates
�The body will make its own glucose from breakdown of body proteins
�Amino acids from these proteins cannot be used to make new cells, repair tissue damage, support the immune sys
Health benefits of fiber
�May prevent chronic and digestive diseases
�Helps prevent intestinal problems
�Reduces the risk of diverticulosis
�May reduce the risk of colon cancer
�May reduce the risk of heart disease
�May lower the risk of type 2 diabetes
�May enhance weight loss
How much carbohydrate
�Recommended Dietary Allowance (RDA) is 130 grams/day
�Acceptable Macronutrient Distribution Range is 45% to 65% of daily calories
�Focus on fiber-rich carbohydrate foods
Diets high in simple sugars
�Contribute to tooth decay
�May increase "bad cholesterol"
�May decrease "good cholesterol"
�May contribute to diabetes and obesity
Enriched foods
Foods in which nutrients that were lost during processing have been added back so the food meets a specified standard
Fortified foods
They have nutrients added that did not originally exist in the food (or existed in insignificant amounts)
Fiber intake
Adequate intake of this is
�25g per day for women
�38g per day for men or 14g of fiber for every 1,000 kcal per day
Non-nutritive sweeteners
Limited use is not harmful within Acceptable Daily Intake
�Saccharin
�Acesulfame-K
�Aspartame
�Sucralose
�Neotame, Stevia, and Advantame
Diabetes
�Impaired blood glucose regulation
�Type 1 diabetes
�Type 2 diabetes
�Gestational diabetes
�Uncontrolled diabetes can cause nerve damage, kidney damage, blindness, and can be fatal
�Hyperglycemia = higher-than-normal blood glucose levels
Diabetes type 1
�Accounts for 10% of all cases
�Most cases are diagnosed in adolescence
�Body does not produce enough insulin
�Causes hyperglycemia (high blood glucose)
�Classified as an autoimmune disease
�Requires insulin injections
Diabetes Type 2
�Obesity can trigger cascade of changes resulting in this
Insulin insensitivity (insulin resistance)
cells become less responsive to insulin
Impaired fasting glucose
Higher than normal blood glucose, also called pre-diabetes
Metabolic syndrome
A cluster of risk factors that increase the risk for type 2 diabetes
Academy of Nutrition and dietetics strategies
�Eat meals and snacks at regular and planned times
�Eat about the same amount and types of food
�Follow Dietary Guidelines for Americans or USDA Food Patterns
�Seek advice of a registered dietitian/nutritionist
Hyperglycemia
�Low blood glucose may cause shakiness, sweating, anxiety, weakness
Reactive hypoglycemia
Pancreas secretes too much insulin after a high-carbohydrate meal
Fasting hypoglycemia
Pancreas produces too much insulin, even when someone has not eaten
Lactose intolerance
�Insufficient production of lactase to digest lactose-containing foods
�Not to be confused with milk allergy
�GI symptoms: gas, cramping, diarrhea
�Variations in extent of intolerance
�Need alternate sources of calcium