Carbohydrates
Body’s preferred energy source Human brain uses it exclusively 2 categories
• simple• complex
Found in plants and dairy products
Carbohydrates
Simple sugars• monosaccharides• disaccharides• sweet
Complex sugars• polysaccharides• not sweet
Glucose
Fructose
Galactose
Found only as part of lactose
Sucrose
Lactose
Maltose
Absorbed directly into blood stream without digestion Glucose (plant sugar) - 4 kcal/g
• from starch digestion or hydrolysis Other forms of CHO are converted
into glucose - needs insulin for take up Dextrose- monohydrate of glucose
• used in IVF (3.4 kcal/g)
Fructose- fruit and honey Sweetest of all sugars Used almost exclusively in soft drinks Can be used in very small amounts
to hide after taste in diet drinks
Galactose Appears in nature only as part of
lactose “milk sugar” Changed to glucose for energy Reaction is reversible During lactation glucose
reconverted to galactose for use in milk production
Compounds used in medications Cardiac glycosides - digitalis Steroids Antibiotics - streptomycin,
erythromycin Deoxy sugars - DNA
Derivatives- sugar ETOH Sorbitol side effects: diarrhea, gas,
abdominal discomfort Helps with dental caries Sorbitol occurs naturally in prunes,
apple juice, etc. Liquid medications
Glucose
Fructose
Galactose
Found only as part of lactose
Sucrose
Lactose
Maltose
Maltose = glucose and glucose Plant sugar found in germinating cereal grains Used in some infant formulas and
cereals Highly significant in human
nutrition as intermediate product of starch digestion
Pairs of simple sugars linked together Sucrose = glucose and fructose Sugar beets, sugarcane, molasses,
maple syrup Fructose converts to glucose in body 7-11% total kcal in American diet NO difference between honey and sugar
Lactose=glucose and galactose Principle CHO of milk Lactose intolerance common
-no lactase or digestive enzyme in digestive system-can be transient after illness
Starch, glycogen, dextrin, dietary fiber
Starch- hundreds of linked glucose units
Amylopectin and amylose-ratios and structures differ
~80-85% amylopectin- insoluble ~15-20% amylose-soluble
Amlyopectin- thickening agent Amylose - slow even rate of
digestion Amylase-digestive enzyme Cereal grains, legumes, potatoes Dextrin-intermediate product from
breakdown of starch-makes maltose
Glycogen
Stored energy Found in liver and muscle
tissue Important link in energy
metabolism Sustains normal blood sugars
during fasting
Oligosaccharides
Small portions of partially digested starches (3-10 monosaccharides)
Infant formulas Special dietary formulas Sports drinks Faster and easier to digest
Dietary fiber
Soluble and insoluble Celluloses, pectins, mucilages,
gums, lignin Need 20-35 grams/day Have laxative effect, soften
stools Increase transit time, influence
blood lipid levels
Dietary fiber
Increase satiety Bulk helps with weight control,
constipation, diverticulosis Undesirable effects-
binds Fe++, Ca++, & Zn++
Produce colon bacteria-volatile short chained fatty acids/GAS
Insoluble-Cellulose & Lignin
Cellulose-not digestible• has no nutrients• produces bulk • grains, fruits, vegetables
Lignin is non-carbohydrate fiber• binds bile acids and metals• whole grain, strawberries, mature
vegetables
Insoluble
Soften stools Regulates bowel movements Increase fecal weight Increase transit time Reduce risks of diverticulosis,
hemorrhoids, and appendicitis
Non-cellulose fiber
Soluble-Absorbs water Slows gastric emptying Binds bile acids Adds some bulk Found in
• pectin• gums • mucilage
Carbohydrate Digestion
Polysaccharides are broken down to
Disaccharides are broken down to
Monosacharides which are absorbed through intestinal mucosa and transported to the liver
Carbohydrate Metabolism
In the liver:• Fructose and Galactose converted to
Glucose Blood sugars rise Insulin secreted Insulin moves glucose out to bloodstream and into cells
Carbohydrate Metabolism
Muscle cells convert glucose to glycogen if storage CHO is needed.
IF energy needed, glucose is burned in cells.
Glucose not needed for energy or glycogen is used to make DNA, RNA, or converted to fatty acids and stored as triglycerides.
Carbohydrate Function
Provides energy-especially to brain, nervous system, used by muscles
4 kcalories per gram Spares protein Prevents ketosis Quickly digested-principle site is
small intestine
Glycogen
Immediate fuel for muscle actions 1200-1500 kcal on board 2/3 stored in muscle/ 1/3 in liver 2.7- 3.4 g of water stored with
every gram of glycogen
Glycogen
Minimum of 100g CHO/ day to prime citric acid cycle
to prevent keto-acidosisto prevent excessive tissue
protein breakdown Symptoms from lack of CHO :
fatigue, dehydration
Healthy Diet
CHO 50-60% of daily diet 10% of this amount should be
sweets Fiber intake 20-35 grams/day CHO alone does not cause obesity
• remember fat and activity levels
Chronic Diseases
Diabetes-Type 2 related to body fatness• 95% of DM are Type 2
Heart Disease-fat not sugars
Sugar behavior-unproven
Nutrients in 100 Kcalories
Food Protein Calcium Sugar (2T) 0 g trace Cola (1 C) 0 g 6 mg Milk (1 c) 8 g 300 mg Bread ( 1 slice) 3 g 48 mg Pinto Beans (1/2 c)
7 g 41 mg
Sugar Alcohols
Used in chewing gums 2-3 kcal per gram Examples:
• Sorbitol• Isomalt• Xylitol
Artificial Sweeteners
Saccharin-pros and cons Aspartame-Equal Acesulfame K- Sunette & Sweet
One Sucralose-Splenda Use as replacement, not addition,
if used for weight control
Glycemic Response
Effect of a particular food on blood glucose reduced to a number
Factors:• Amount of fat and fiber• Method of preparation• Amount eaten
Use for fine tuning meal planning with DM patients and athletes
GI Food Pyramid
Refined Grains Potatoes Sweets
Unrefined Grains Pasta
Dairy Lean Protein Nuts Legumes
Fruits Vegetables
Fat & Energy
Used to meet 50% of energy needs• Most cells can utilize fat for energy
• Not brain cells or nerves
Fat cannot be converted to glucose
Ketosis?
Ketone bodies• Acidic, fat related
compounds formed from incomplete breakdown of fat when no carbohydrate is available.
Protein and Energy
Protein used for energy when• glycogen depleted• Body starts to auto-digest
CHO has protein sparing effect