Unit 1: Carbs Flashcards
Monosaccharides
simple sugars which serve as the building blocks for all other carbohydrate (CHO) sources
Disaccharides
simple CHOs formed when two monosaccharides bond
Oligosaccharides
CHOs composed of a relatively small number of monosaccharide units; found in various plant foods
Polysaccharides
complex CHOs composed of long chains of monosaccharides; should comprise the majority of CHO intake due to their nutrient impact on health
also called complex carbohydrates, these form the basis of intake recommendations for athletes
Types of monosaccharides
glucose, fructose, galactose
Types of disaccharides
sucrose, lactose, maltose
High fructose corn syrup (HFCS)
man-made sweetener made from corn starch known to have a negative impact on metabolic health and body weight
Names of added sugars
anhydrous dextrose, corn syrup solids, invert sugar, malt syrup, molasses, nectars, sucrose, etc.
How much added sugar does the average American consume?
~22.2 teaspoons of added sugars per day = ~15% of daily calories (~355 kcals/day)
What is the American Heart Associations recommendation for daily sugar intake?
no more than 100-150 kcals/day
How much sugar does research estimate American consume per year?
150 lbs./year (1 soda a day = 32 lbs. a year)
Major sources of added sugar in American diet
- Processed grains
- Dairy desserts and milk products
- Fruit drinks
- Cakes, cookies, pies and other pastries
- Soft drinks and candy
Glycogen
storage form of CHO in the body (average skeletal muscle contains 300-400g; the liver contains 80-120g)
Starch
chains of sugars that are easily digested and metabolized for energy provision; accounts for >50% of CHOs consumed by athletes
Glycogen storage?
liver glycogen maintains blood glucose
muscle glycogen supplies energy during muscle contractions
Examples of starchy foods
bread, cereals, pasta, rice, potatoes, beans, chestnuts
Fiber
non-starch polysaccharide that resists digestion in the gut; associated with numerous health benefits and optimized weight management
Daily fiber recommendation for females
25-30 g/day
Daily fiber recommendation for males
30-40 g/day
Insoluble fiber
adds bulk to stool and helps food pass more efficiently through the intestines
Soluble fiber
attracts water and turns into gel, slowing the digestive process and positively impacting blood sugar management
Benefits of fiber
- Adds bulk (satiety)
- Decreases glycemic index- slows absorption
- Increases intestinal mobilization
- Decreases circulating cholesterol and triglycerides
- Removes intestinal carcinogens
- Balances intestinal pH and microbiota
- Aids weight management and body composition goals
Gastrointestinal microbiota
bacterial populations present in the gastrointestinal tract which can have a profound impact on health as well as risk for obesity
Satiety
sensation of fullness experienced following consumption of a meal
Examples of soluble fiber
oatmeal, lentils, apples, oranges, nuts, flaxseeds, beans, dried pears, cucumbers, celery, carrots
Examples of insoluble fiber
barley, couscous, brown rice, zucchini, broccoli, cabbage, green beans, dark leafy vegetables, root vegetable skins
Processed carbohydrates
manufactured CHO sources which are absorbed similar to simple sugars or starch; associated with obesity, inflammation, and lower nutritional value
Most forms have low nutrient bioavailability as they have been denatured for cost, palatability, and/or a longer shelf life
What impacts blood sugar dynamics?
type and timing of CHO intake before, during and after training or competition
Hypoglycemia
abnormally low blood glucose; begins at ~70 mg/dL
Hyperglycemia
abnormally high blood glucose; begins at ~200 mg/dL
What happens when blood sugar gets high?
After a meal blood glucose rises which facilitates a release of insulin from the pancreas to draw the sugar into tissues for use or storage
What happens when blood sugar gets low?
When blood sugar gets low due to training or a long period without nutrient consumption, glucagon is released from the pancreas to facilitate blood sugar release from the liver to reestablish normal blood sugar levels
Insulin
hormone released from the pancreas that facilitates glucose uptake from circulation; also serves various other anabolic roles
Glucagon
hormone released from the pancreas that promotes the breakdown of glycogen into glucose in the liver to increase concentrations in circulation; opposes the action of insulin
Pancreas
large gland that secretes digestive enzymes into the intestines and also secretes insulin and glucagon via specialized cells
Results of excess sugar and HFCS
- increases risk for weight gain and poor body composition
- body becomes less reliant on using fat stores for energy
- promotes hyperinsulinemia and metabolic disorder
- can lead to insulin resistance and increase the risk for metabolic disease
Hyperinsulinemia
excess insulin is present in circulation relative to blood glucose; caused by a variety of issues including diabetes as well as disordered or unhealthy eating behaviors
Glycemic index (GI)
measure of the blood-glucose raising potential of CHO content in a food
Glycemic Load (GL)
describes the blood-glucose-raising potential of the CHO in a food and the total quantity of CHO; calculated by multiplying the GI by the amount of CHO in grams and dividing the total by 100
Glycemic response (GR)
impact a food or meal has on blood glucose following consumption
Low-GI diets
Low-GI diets have been positively linked to a reduced risk for obesity, colon, and breast cancer, as well as raising healthy cholesterol levels
High-GI diets
High-GI CHOs are preferred during prolonged exercise and post-exercise when combined with protein
CHO management by Blood
transports 4-5g of glucose which maintains central nervous system function
CHO management by Liver
maintains 25% of glycogen storage (80-120g)
CHO management by Muscle
maintains 75% of glycogen storage (300-400g)
Central nervous system (CNS)
includes the brain and spinal cord; serves as the central control for voluntary (skeletal muscle) and autonomic functions throughout the body
Why does the body break down glycogen?
Glycogen is broken down in the body to create the energy needed for anaerobic sport performance (e.g., high-force strength and explosive power actions)
What is the result of inadequate CHO consumption?
If inadequate CHOs are consumed, the body will lose its protein-sparing mechanism defense system and be forced to promote gluconeogenesis at the expense of bodily proteins and muscle
Gluconeogenesis
creation of new glucose via the liver for release into circulation to meet energy needs and/or regulate blood sugar
Protein-sparing mechanism
preference of the neuroendocrine systems to spare bodily proteins for energy provision unless inadequate CHOs are available to fuel the CNS
How are CHO needs determined?
CHO needs are primarily determined by body size and activity frequency, intensity, and duration
What were early CHO recommendations for athletes? (no longer used)
60-70% of the diet; this lacks accuracy as it fails to consider body mass or any activity variables
CHO intake for overall Light (low of skill-base activities)
3-5 g/kg of athletes body weight/d
CHO intake for overall Moderate (moderate exercise program, ~1 h/d)
5-7 g/kg/d
CHO intake for overall high (endurance program, 1-3h/d moderate to high-intensity exercise)
6-10 g/kg/d
CHO intake for overall very high (extreme commitment, >4-5 h/d moderate to high-intensity exercise)
8-12 g/kg/d
CHO intake for general fueling up (preparation for event <90 in of exercise)
7-12 g/kg/24 h for daily fuel needs
CHO intake for carbohydrate loading (preparation for events >90 min of sustained/intermittent exercise)
36-48 h of 10-12g/kg body weight/24 h
CHO intake for speedy recovery (<8 h recovery between 2 fuel-demanding session)
1-1.2 g/kg/h for first 4 hr then resume daily fuel needs
CHO intake for pre-event fueling (before exercise >60 min)
1-4 g/kg consumed 1-4 h before exercise
Recommended CHO intake during brief exercise (<45 min)
not needed
Recommended CHO intake during sustained high-intensity exercise (45-75 mins)
small amounts, including mouth rinse
Recommended CHO intake during endurance exercise, inlduing “stop-and-start” sports (1-2.5 h)
30-60 g/h
During ultra-endurance exercise (>2.5-3 h)
up to 90 g/h
What is the benefit of mixing CHOs?
Mixing CHOs provides the best outcomes for events lasting longer than 60 min
How can you improve performance during prolonged competition?
~30-60g of CHO/hour in the form of a 6-8% CHO solution comprised of sucrose, glucose, and/or maltodextrin can greatly improve performance during some prolonged competition
Rapidly-oxidized CHOs (~1 g/min)
- glucose
- sucrose
- maltose
- maltodextrins
- amylopectin
Slowly-oxidized CHOs (~0.6 g/min)
- fructose
- galactose
- isomaltulose
- trehalose
- amylose
Three of the most common strategies for carbo loading
- depletion method
- taper method
- single bout method
Benefit of CHO loading before competition
CHO loading before competition increases glycogen stores and improves performance for events >90 min
Major CHO loading mechanisms
- Increased glucose transport and glycogen synthesis
- Improved anabolic hormone secretion
- Increased CHO metabolism
Depletion Method
Implemented in the week leading up to the event
First 3 days consist of hard, fatiguing exercise while consuming minimal CHOs (~10% kcals); next 3 days (up until event) involve minimal exercise and intake of 8-10 g/kg
Science behind the strategy: athlete depletes his/her CHO stores, this heightens specific enzyme activity to expedite glycogen storage
Benefits: some athletes observe a 180-200% increase in stores
Risks: may predispose the athlete to injury, illness, psychological issues, and/or excess fatigue
General mechanisms of depletion method
Implemented in the week leading up to the event
First 3 days consist of hard, fatiguing exercise while consuming minimal CHOs (~10% kcals); next 3 days (up until event) involve minimal exercise and intake of 8-10 g/kg
Science behind depletion method
athlete depletes his/her CHO stores, this heightens specific enzyme activity to expedite glycogen storage
Benefits of depletion method
some athletes observe a 180-200% increase in stores
Risks of depletion method
may predispose the athlete to injury, illness, psychological issues, and/or excess fatigue
Taper Method
Most commonly recommended technique among endurance athletes
Eliminates the depletion phase while promoting a similar increase in glycogen stores
Involves a short, 3-day tapering of exercise and rest prior to competition while consuming CHO at 8-10 g/kg of body weight
Single Bout Method
Less commonly used for endurance sports, but promotes advantages for team sports and anaerobic events
The athlete performs an intense, but brief, bout of anaerobic exercise 24 hours before the event, and then consumes CHO at 10-12 g/kg of body weight over the next 24 hours via continuous grazing (higher-GI sources for first 4 hours, mixture after)
The same muscle groups used during competition are used during the intense bout of exercise to enhance tissue-specific glycogen saturation
Cycling may be superior to running to prevent eccentric muscle damage, inflammation, and impaired glucose uptake during the loading period
Muscle soreness may be the greatest risk associated with this technique
Dynamics of CHO loading for female athletes
Females may be slightly less sensitive to CHO-loading but can still benefit from increased intake before an event at >8 g/kg of body weight each day
Females tend to store greater glycogen during their luteal phase (later phase) of menstruation
Does CHO loading provide additional enhancement to muscle girth for bodybuilders?
No, clinical trials have suggested that CHO loading provides no additional enhancement to muscle girth among bodybuilders getting ready for competition
However, when pre-competition diets are evaluated, greater CHO intake was found among placing-competitors compared to losers
Potentially due to maximized anabolic hormone activity and minimized lean mass losses
