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Carbohydrates I

Terms in this set (31)

Americans
50% of calories in American diet
-recommendation: 60%
Dietary fiber: 15g/day
-recommendation: 25g+/day
Simple sugars: 100g/day
-recommendation: <50g/day
Types of Carbs
simple and complex
-all must be converted to glucose in liver to be used
-high glucose foods more quickly available (no conversion). good for athletics, bad for diabetics
Carbs in diet
-in some situations one type better than the other!!!
-depends on timing (sport vs. rest)
-diet should be high in complex CHO due to addition nutrient value
-during/after competition, prefer simple CHO to give us quick boost
Simple Carbs
monosaccharides
disaccharides
polysaccharides
Complex Carbs
contain more than just sugar
-sources: potatoes, pasta, bread, beans
-1000s of molecules together, starch in plants, glycogen in animals
-can be digestible or non-digestible
monosaccharides
6:12:6 C:H:O
-glucose
-galactose
-fructose
disaccharides
12:24:12 C:H:O
-sucrose = glucose + fructose, table sugar
-lactose = glucose + galactose, milk and dairy
- maltose = 2 glucose, starches and beer
polysaccharides
natural and manufactured, thousands C:H:O
-big accumulation of monosaccharides
-sport specific substance
-gatorade, gummy blocks, gel
Fiber
Complex carb, part of plant cells humans cannot digest.
-fruit, bran, veggies, beans,
-food for out colonic bacteria, thus, we form GAS with high fiber content
Fiber example
Kernel of Grain: bran (outer), starch (inner), germ (V&M)
-whole grain foods have all! refined grains have only start and germ mixed up.
-total fiber = sum of DF (dietary fiber) and FF (functional fiber)
dietary fiber vs functional fiber
dietary: grain ex is cellulose
functional: isolated, ex is pectin, gum
Fiber benefits
-regularity
-improve cholesterol
-improve blood glucose
-anti colon cancer
soluble fiber
dissolves in water, bind to bile acids and transport out of body
-found in beans, oat bran, pectin, guar gums
insoluble fiber
does not dissolve in water, triples stool volume, makes stools easier to pass
-cellulose
Beneficial effects of fiber
reduced risk for...
-GI problems (water insoluble) by adding bulk to stool, reducing retention of undigested foodstuffs in color (reduce bowel inflammation, risk for diverticulitis)
-obesity and related conditions (low GI foods & lower intake), low in calories and high in bulk, making you feel full and reducing caloric intake.
reduced absorption of...
-cholesterol and carcinogens (water soluble), binding to bile salts containing cholesterol or carcinogens and flushing them out
increased SCFA production in large intestine that may have both GI and systemic effects (water soluble), provide "food" for gut bacteria
Carb needs in diet
-essential for brain and muscle function, brain (2% body mass) uses 50% of body's glucose/carbs
-45-65% of daily energy intake
-<25% from simple sugars
fiber needs by sex
-fiber for males: 38g/day to 50, 30g/day over 50
-fiber for females: 25g/day up to 50, 21g/day over 15.
-current avg intake: 15g
CHO digestion and absorption
-mouth: salivary amylase breaks down CHO
-stomach: nothing happens here from a CHO standpoint
-small intestine: pancreatic amylase is primary enzyme for CHO. converted to disaccharides, then maltase, lactase and sucrase)

where does each conversion happen at?

-monosaccharides converted to glucose in liver
-brush border location of absorption
High intake of simple CHO
-can lead to reverse osmosis, water going into GI, causing diarrhea
-selection of intake during exercise very important
Glycemic index (GI)
how quickly CHO source gets digested and absorbed (as compared to pure glucose)
-high GI = quick
-low GI = slow
Factors affecting GI
physical form (coarse or fine), serving method (raw, sauteed, fried, baked)
Fruits and GI
Fruit GI depends on ratio of
Glucose:Fructose:Sucrose
-apple: 7% to 40% to 25%
-grape: 40% to 30% to 10%
-more GLU = higher GI
based upon CHO release, insulin response.
Ways to Keep CHO in the body
-muscle and liver glycogen stores, maximize this
-blood glucose, needs to stay normal, if decrease, so does mental function
-gluconeogenesis, production of new glucose in liver (slow)
-dietary carbs, maximize this, carb consumption protocol
CHO during rest and exercise
-rest: blood glucose used in brain, liver releases via GNG to match it, liver forms new CHO
-exercise: consumes muscle glycogen. after used up, blood glucose used, liver releases glucose, but GNG cannot keep up.
therefore need some from diet!!!
-exercise over 90 mins requires CHO intake
-goal of athlete: maximize amt of stored CHO, take in during exercise, recovery
Carb metabolism
process of building and breaking down carbs
Muscle glycogen
storage form of CHO
Glycogenesis
build glucose stores on glycogen chain
-body can store about 500g of carbs in liver and muscle
-7% of liver weight and 1% of muscle weight
-athletes can store up to 750g
-requires glycogen synthase and branching enzyme
-rest and digest
Glycogenolysis
break down glucose off the glycogen chain for energy
-when we need energy or have lower blood glucose
-requires glycogen phosphorylase and debranching enzyme
-exercise
Carb loading
the process of increasing the amount of glycogen stored in the body prior to a race or competition
Glycolysis
process of breaking down glucose to form 2 pyruvate
-lactic acid system: Pyr to Lactic acid, net 2 or 3 ATP
-oxygen energy system: Pyr to mitochondria to krebs cycle to ETC, net 36 or 37 ATP
-depends on energy demand
Gluconeogenesis
form new glucose, opposite of glycolysis
-from pyruvate, amino acids, other substances
-occurs in liver (slow)
-important during long term exercise: if no CHO intake, will exhaust liver glycogen, run out of glucose for blood.
-helps maintain BG levels
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