basic principles of nutrition and healthy eating Flashcards
digestion definition
the process by which foods are broken down into smaller molecules or nutrients
absorption
the uptake of nutrients and how the body utilises these nutrients to perform a wide range of bodily functions
Excretion
the means by which the body removes unwanted, unnecessary or harmful substances from the body once it has extracted what it needs
the body’s two mechanisms for breaking down food consumed
mechanical
chemical
mechanical digestion
chewing/mastication
also involves rolling of tongue to create small balls of mixed food = ‘bolus’
not limited to mouth - continues throughout digestive system using ‘peristalsis’
the smooth muscle tissue of the walls of digestive organs involuntarily contract to push foods along. cylindrical shape of digestive tract is optimal for this process.
chemical digestion
how the body breaks down foods into simpler nutrients using enzymes
enzymes are protein molecules that accelerate specific chemical reactions
speed up rate of digestion - would be too slow to sustain life without them
the digestive tract
also known as alimentary tract, alimentary canal, gastrointestinal tract
mouth to anus
transit time = time for food to pass through the tract
for healthy adult transit time 24-72 hours
av tract is 9meters long
3 functions saliva
1) moistens food so tongue can form ‘bolus’
2) starts carbohydrate digestion - contains amylase which breaks it down into glucose
3) be present in food consumed
pharynx
has both digestive and respiratory functions
forms passageway connecting the mouth and nose to oesophagus and larynx
3 diff muscles
primary structure for swallowing ~ a reflex ~ 1-3 seconds
oesophagus
approx 10 inches in length
connects throat to stomach
runs parallel to trachea
protected by cartilage called ‘epiglottis’ ~ seals the trachea so food is transported to stomach and not lungs
with medium bolus take about 5-8 seconds for food to get to stomach
stomach
J shaped
can expand 8 times the size
located just left to centre of chest - below sternum
3 layers of tissue
gastric juices with food creates chyme
hydrochloric acid kills invading bacteria - so corrosive that stomach lined with mucus to prevent digesting itself
pepsin - breaks down protein - can only work in vv acidic conditions
emptying of stomach takes 3-4 hours depending on food consumed, hydration and physical activity levels
moves onto small intestine
alcohol is only substance that is directly absorbed into stomach
functions of pancreas
producing and releasing enzymes for digestion (trypsin, amylase, digest
creating and releasing blood regulating hormones (insulin and glucagon)
produces bicarbonate - neutralises acidity
Gall Bladder and Bile Duct
below liver
gallbladder stores bile produced by liver and delivers to small intestine via bile ducts
the liver
storage of carbs in form of glycogen hormone production blending and emulsification of fats excretion of old blood cells production of bile storage in the gall bladder production of cholesterol filters and neutralises toxins storage of some vitamins and iron
small intestine
longest of intestinal tracts - 5-6 metres first section (10 inches) is the duodenum second section (3-4 metres) is the jejunum = most nutrient absorption takes place final section (3-4 cm) is the ileum = remaining nutrients absorbed inside the small intestine are cilia - hair like structures that provide large surface area to increase rate of absorption - they have a rich blood supply food absorbed goes to liver which is good for nourishing it but bad when has to detoxify from substances like alcohol to prevent cellular damage. takes bout 3-4 hours for food to pass through SI - but varies according to different factors
large intestine
1.5 metres av time of waste matter to stay in colon is 36 hours reabsorbs water from waste matter manufacturing of vitamins b and k excretion of waste
what is a calorie
one calorie is the amount of energy it take to raise one gram of water by one degree
metabolic rate
BMR does not take into account increased energy required to stay awake and therefore resting metabolic rate is more accurate for estimating a persons needs
BMR and RMR decreases with age because lean tissue decreases which reduces the amount of energy the body burns = body’s energy needs reduced
males higher metabolism - more testosterone = more lean muscle
carbs
complex and simple
complex - essential for anyone regularly exercising = slow and sustained release of energy
simple - sugary = quick supply of energy ~ not sustainable - kept to minimum except for micronutrients
free sugars
form of simple carb added to food or drink for flavour
also naturally present in honey, syrup and fruit juice
glucose and glycogen
carbs are broken down into glucose and absorbed into bloodstream but if additional blood glucose is not required the glucose is stored in the liver and/or skeletal muscles as glycogen
functions of carbs
body’s preferred source of energy
1g carbs = 4kcals
carbs are the only source the brain and nervous system can use as energy in form of blood glucose
higher levels of glycogen stores are linked with increased aerobic performance
help maintain a healthy metabolism by preventing the use of muscle protein for energy = muscle tissue sparing
carbs also needed for water storage
1g glycogen in muscles and liver is with 3g water
55-60%
fibre
plant based carbs - not digested in small intestine
absorbs water - bulks out food
transports waste and good through gastrointestinal tract
protein
animal products contain amino acids that plants do not so plant based people should insure they get a range
veg protein = incomplete
10-12%
functions of protein
growth and repair of bodily tissues
production of hormones and enzymes
transports oxygen and regulates blood clotting
used as energy source when there is insufficient carbs - this is undesirable as results in loss of learn tissue
1g protein = 4kcals
fats
1g fat = 9kcals saturated and unsaturated saturated - gen solid at room temp ~ animal and dairy sources. soft and low density substance that sticks to inside of blood vessels - can restrict transit of blood = increased blood pressure also heart strain unsaturated = gen liquids at room temp plant sources fat - 25-30% 15-20% from unsaturated
functions of fat
can only be burned in presence of oxygen (aerobically) fats are essential for transporting vitamins a,d,e,k
provides protection to vital organs
controls body temperature
manufacturing hormones
cholesterol
soft waxy substance found among fats in the bloodstream and in body’s cells
used to form cell membranes, some hormones and a number of essential functions
water
45-70% bodyweight
cannot be used directly as source of energy but used in energy releasing and metabolic reactions
rec 2-2.5litres depending - increased for exercise
euhydration
state of optimal hydration
functions of water
regulating body temperature reducing strain on cardiovascular and regulates blood pressure delivers nutrients in blood plasma elimination of waste from body lubrication of joints and tissues protection of foetus constipation relief
micronutrients
help body release energy from food regulation of cell function building blocks for cells and organs healthy teeth and bones aid with muscle function/contraction vision transport oxygen in red blood cells regulate and maintain water balance
vitamins
‘organic compounds’
no energy content
can be broken down by heat, air or acid during metabolism
body cannot manufacture vitamins so they have to be supplied in diet
minerals
‘inorganic compounds’
regulatory and structural roles in body
not broken down - maintain their chemical structure
some form part of bones and teeth, some for nerve function, enzyme secretion, formation of red blood cells
no energy but essential for energy-related processes
health risks of poor nutrition
vitamin and mineral deficiency increased risk of osteoporosis digestive disorders loss of muscle mass weight gain fatty acid deficiencies depression and low confidence lethargy some cancers lower immune
positive energy balance (weight management)
results when the energy consumed is greater than that required by the body and thus weight is gained
negative energy balance
energy consumed is less than that required by the body and thus weight is lost
an energy equilibrium
energy consumed is equal to what body requires = maintain weight
