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L3 Nutrition > carbs > Flashcards

carbs Flashcards

1
Q

what carbs are broken down into

A

they are broken down to form glucose and deposited in blood for energy or deposited in the liver and skeletal muscles for storage as glycogen

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2
Q

glycogen stores

A
  • when blood glucose levels drop, glycogen stores are used to top up circulating blood glucose to ensure brain and nervous system have the energy they need.
  • liver supplies most of the glycogen required to manage blood glucose levels
  • skeletal muscles supply glycogen to fuel muscle contraction
  • muscles can only use glycogen that is stored in their own muscle cells and so they need to be maintained with a diet rich in wholesome carbs
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3
Q

functions of carbs

A
  • each g of carbs yields 4 kcals
  • blood glucose is only energy for brain and CNS
  • natural and unrefined sources add bulk to food which assists it through digestive system to alimentary canal
  • helps preserve body’s protein reserves (esp lean muscle tissue)
  • serve as a metabolic primer = facilitates metabolism of fat - when low in carbs body can’t release energy from fat stores efficiently
  • post exercise carb consumption helps replenish depletes glycogen stores
  • carbs are needed for water storage in body. each gram of glycogen stored is paired with 2.7ml water
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4
Q

types of simple carbs

A
  • monosaccharides and disaccharides
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5
Q

types of complex carbs

A
  • polysaccharides
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6
Q

monosaccharides

A
  • single units of sugar
  • rapid absorption into bloodstream
  • glucose, fructose, galactose
  • fruit, energy drinks, honey, milk, jams
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7
Q

disaccharides

A
  • 2 molecules of sugar
  • moderate absorption into bloodstream
  • sucrose, lactose, maltose
  • table sugar, cakes, biscuits, breakfast cereals, pastries
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8
Q

polysaccharides

A
  • many molecules bound together
  • slow absorption into bloodstream
  • glycogen, starch and fibre
  • wheat, bread, pasta, oats, corn, rice, barley, potatoes
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9
Q

sources of carbs

A
  • naturally the originate from plant based foods which contain micronutrients and water
  • refined sources like soft drinks and confectionary are called empty calories because they lack essential micronutrients
  • refined sources result in fluctuations in blood sugar which cause sugar lulls and triggers hunger cues even tho the body has an abundance of energy = why people overeat on them
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10
Q

blood glucose levels (normal)

A
  • BGLs vary throughout day depending on physical activity levels and carbs consumed
  • body must quickly respond when BGLs are out of the normal range of 4.4 and 6.1 mmol per litre of blood
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11
Q

hyperglycaemia

A
  • blood glucose concentration spikes after simple carbs are ingested = hyperglycaemia (too much sugar in blood)
  • the pancreas secrets insulin because high blood glucose can be toxic, which moves glucose into muscles and liver for storage as glycogen
  • can temporarily stabilise BGLs but can also create a sugar lull which can lower BGLs to below what is required by brain and CNS = hypoglycaemia
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12
Q

hypoglycaemia

A
  • low blood sugar levels

- pancreas secretes glucagon which releases glucose back into body

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13
Q

blood glucose regulation and complex carb sources

A
  • complex carbs give a slower and more gradual release of sugar into blood
  • this provides endocrine system with more time to manage increasing glucose concentration
  • under these conditions insulin is released in smaller quantities which helps maintain stable BGLs
  • prevent likelihood of hypoglycaemic or hyperglycaemic state
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14
Q

insulin resistance

A
  • lots of people release excessive insulin in response to over consumption of simple carbs.
  • repeated exposure to elevated insulin levels reduces the effect the insulin has on the body, meaning it has to manufacture more insulin to produce the same effect
  • these people are more likely to develop type 2 diabetes, becoming obese/overweight because increased concentration of insulin accelerates glucose
  • this mechanism occurs at the expense of fat metabolism and promotes a greater storage of fats in adipose tissue
  • regular exercise = improves insulin sensitivity which reduces quantity of insulin needed
  • exercise also promotes fatty acid metabolism and positively influences increasing calorie expenditure
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15
Q

fibre

A
  • non starch polysaccharide
  • primarily found in unrefined foods
  • located in outer walls of plants and seeds
  • more common in complex carbs
  • not many in simple - except fruit
  • crucial role in maintaining healthy digestive system and aiding excretion of waste and toxins from body
  • excessive intake can result in flatulence and digestive discomfort
  • insufficient fibre intake can result in constipation, and if prolonged to more serious including colon cancer and IBS
  • RDI = 30g
  • not absorbed directly into bloodstream
    technically not a nutrient
  • 2 forms = soluble and insoluble
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16
Q

insoluble fibre

A
  • travels through body with almost no absorption
  • arrives at large intestine for excretion in almost same state it was ingested
  • promote growth of healthy bacteria within gut and gives bulk to faeces
  • larger and softer faeces makes them easier to pass through the intestines = reduces risk of constipation
  • because waste materials pass through the body much faster in the presence of insoluble fibre, toxins are unable to accumulate and fester within the intestines
  • this is important in prevention in diseases such as bowel cancer, other cancers, IBS, haemorrhoids and diverticulitis
  • can be found on skins of fruit, vegetables, wholegrain cereals and rice
17
Q

soluble fibre

A
  • also called water soluble fibre
  • absorbed and fermented by water in the digestive tract
  • gives bulk and roughage to faeces
  • helps lower total blood cholesterol by inhibiting the digestion of fat and LDL cholesterols
  • also helps control blood sugar in those suffering from diabetes
  • can found in flesh of fruits, oats, kidney beans and sweetcorn
18
Q

glycaemic index

A
  • a technique that originates from the treatment of diabetics and is used to rank foods according to their effect on blood sugar
  • the glycaemic value of a food is presented as a percentage of the glucose response that food elicits
  • glucose therefore has a GI of 100
19
Q

GI classifications

A
  • high GI foods = index value of 70-100
  • moderate GI foods = index value of 56-69
  • low GI foods = index value of 0-55
    (high GI does not always represent poor nutritional value ~ many fruit, vegetables and some grains have high GI and yield rich quantities of fibre, vitamins, minerals and water
20
Q

GI and meals/portion sizes

A
  • a food’s glycaemic response is influenced by a variety of factors including portion size, the way food is prepared, other foods consumed at or around the same time and the fat and fibre content
  • foods are rarely eaten individually. the combination of individual foods has a significant influence on the subsequent glycogenic response. moderate and low GI foods = net glycaemic response reduced
21
Q

glycaemic load

A
  • preferred technique by many to determine the actual response a food will have on the blood sugar levels based on the GI of the food(s) and portion size
  • the GL therefore, represents the amount of available carbs in that serving and can be calculated using:
    GL = GI/100 x g of carbs
22
Q

GL classifications

A
  • low when the GL is less than 10
  • medium when the GL ranges between 11 and 19
  • high when the GL is greater than 20
23
Q

long term consumption of foods with high GL

A

can dramatically increase the risk of obesity, insulin resistance, type 2 diabetes and coronary heart disease

24
Q

carb loading

A
  • technique often used by endurance athletes to maximise the availability of muscle and liver glycogen for athletic performance
  • there are variety of methods that have been used by athletes to maximise glycogen storage, however many can disrupt the digestive system
  • the most effective technique requires the athlete to taper their activity levels 3 to 4 days prior to the competitive event while increasing their consumption of high carb foods (8 to 10g per kg of body weight)
  • this technique typically provides an additional 20-30% of available glycogen which provides boost to endurance performance during the event
25
Q

carbs and exercise

A
  • carbs are body’s most readily available fuel
  • during exercise, esp at higher intensities they represent the most dominant fuel
  • muscle glycogen and blood glucose contribute most of the energy used during high intensity exercise, as well as at the onset of exercise, when insufficient oxygen is available.
  • during maximal exercise intensities, carb contribution to energy production dramatically increases because carbs are the only source of energy that can be burned anaerobically
  • as exercise continues and glycogen stores deplete, the metabolism of fat starts to rise, which sees the total carb contribution diminish, the extent of which largely depends on pre-exercise nutrition and the exercise intensity and duration
  • when skeletal muscles and liver are unable to supply the exercising muscles with sufficient glucose to fuel the exercise intensity, physical performance will decline, even if sufficient oxygen is present. despite availability of fat, the body is unable to continue exercising under these conditions ~ because carbs are metabolic primer of fat
26
Q

how much carbs to eat based on energy intake

A
  • for sedentary people and those engaged in moderate levels of physical activity or exercise, carbs should supply about 50-60% of daily energy
    eg 2500 x 55% = 1375
    1375/4 (4 kcals p/ gram) = 343g
  • for those involved in heavy and intense physical training, esp endurance type, carbs should make up total of 70%
27
Q

how much carbs based on body weight and activity level

A
  • when an individual partakes in intense and prolonged periods of exercise. their tdee may be as much as double that of a sedentary individual. so the energy intake model would not work because the large amount of carbs would be difficult to reach from solid foods, and would exceed the level required by the body to maintain optimum glycogen storage
28
Q

how much carbs based on body weight and activity level table

A 
activity level ~ g carb p/kg BW 
3-5 hours p/week ~ 4-5
5-7 hours p/week ~ 5-6 
1-2 hours p/day ~ 6-7 
2-4 hours p/day ~ 7-8 
more than 4 hours p/day ~ 8-10
e.g. a 75kg man who is active for 1 hour per day 75x7g = 450g

L3 Nutrition (14 decks)

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