D1 Human nutrition Flashcards
define nutrient
a chemical substance that can be used by the human body
what is an essential nutrient
cannot be synthesized by the body = has to be included in diet
examples of essential nutrients 4
minerals, vitamins, amino acids, fatty acids
what are non-essential nutrients + example
made in the body / have a replacement nutrient
eg carbohydrates as respiratory substrates
name the 2 types of fatty acids the body cant synthesize
- omega-3 fatty acids
- omega-6 fatty acids
what benefits does omega-3 fatty acids have 2
controlling blood clotting
building cell membranes in the brain
is omega-3 fatty acid saturated? why?
NO – has a double bond between 3rd and 4th carbon (from opp end of OOH grp)
where can omega-3 fatty acids be found
plant and fish oils (fatty fish like salmon)
benefits of omega-6 fatty acids 3
- lower LDL (low density lipoprotein) cholestrol levels (‘bad’ cholesterol)
- reduce inflammation
- protect against heart disease
how many essential amino acids can humans not synthesize
nine
what is an essential amino acid in infants
arginine
what amino acid is essential if phenylalanine is absent
tyrosine
how many amino acids does protein synthesis require in most living organisms
20
why is calcium required in the diet
major constituent of structures like bones, teeth + needed for muscle contraction
why is iron needed in the diet
needed to form haemoglobin
why is phosphate needed in the diet
needed to make DNA, cell membranes
why are sodium and chloride ions needed in the diet
control of composition of body fluids, propogation of nerve impulse
words used to describe how much of an element a body needs: m______ vs t______
macro vs trace
why are vitamins essential nutrients?
they cant be manufactured in the body
- absence from diet = deficiency diseases
- complex chem structures
what are the 2 types of vitamins
water-soluble vitamins – excess=excreted in urine
fat-soluble vitamins – stored in body, excess=problems!
are the following vitamins soluble in water or fat?
1. B
2. C
3. D
4. E
- water
- water
- fat
- fat
define a balanced diet
contains accepted and defined portions of carbs, fats, proteins, vitamins, minterals, and water essential good health
define malnutrition
condition that occurs when diet does NOT contain right amt of nutrients
what is malnutrition caused by 3
deficiency – lack
imbalance – inadequate intake (not enough)
excess – disproportionate intake (too much)
(of nutrients in the diets)
where is appetite controlled from?
the hypothalamus (appetite control centre!)
3 hormones used in controlling appetite
- Leptin
- Ghrelin
- PYY3-36
what is starvation caused by
a severe reduction in caloric energy intake
how does starvation lead to the breakdown of body tissue 5
- diets very low in energy rich foods = body exhausts glycogen stores
- body respires AA deprived from protein digestion (instead of building and maintaining tissues)
- muscle proteins break down, body wastes away – eg muscle wastage
- prolonged starvation = permanent organ damage and death
- vitamin deficiency = deficiency diseases (anaemia, beriberi, pellagra, scurvy)
does the number of fat cells change in adults
no, not significantly
how does leptin control appetite? 3
- overeat = fat cells fill with lipids = secrete more LEPTIN
- reaches appetite centre, suppressing hunger sensation
- fat cells empty = less leptin = hunger experienced
(long term)
leptin is associated with the ____-term regulation of eating
LONG
how does ghrelin work 2
- stomach empties = ghrelin secreted
- stimulates appetite control centre to create a WISH to FEED
how does PYY3-36 work 4
- released after eating
- from upper intestines + pancreas
- early in digestion process – reaches appetite centre = suppresses hunger
- hunger is temporarily overcome
(short term)
what diets lead to protein deficiency
- based on carbs (cassava, plantain, sweet potato)
- starvation: too little food intake = proteins used for energy, AAs respired
protein-deficient malnutrition leads to?
lack of blood plasma proteins
= water retained in tissue
symptoms of protein deficiency 2
- fluid retention
- swelling in abdominal area
name the 2 types of protein deficiency
Kwashiorkor: swelling of legs and abdomen
Marasmus: wizened, underweight body
can humans synthesize vitamin C?
NO
why cant some animals synthesize vitamin C?
mutation in the GLO gene (codes for an enzyme needed for last step of synthesis of vitC)
what is vitamin C needed for? 2
- production of collagen: involved in synthesis of AA hydroxyproline (15% of collagen)
- synthesis of lipoproteins: makes lipids soluble for transport in blood plasma
lack of vitamin C leads to?
- iron deficiency
- anaemia (bc low blood haemoglobin lvls)
- scurvy
whats a good source of vitC!
citrus fruits
how was vitamin C discovered? (scurvy)
1753: sea captain reported SCURVY could be avoided by including ORANGES AND LEMONS in the diet
1907: norwegian scientists Axel Holst and Theodor Frolich – animal model (guinea pigs) for scurvy
case control vs cohort study
case control: look at outcome first, then work backwards and look at the factors
cohort study: subject normal indivs to condition to yield results
8 symptoms of scurvy
- bleeding gums
- lack of energy
- weight loss
- extreme fatigue
- mood swings depression
- chronic join pain (bc bleeding in the joints)
- suppressed immune system
- slow wound healing
what is the full name of PKU
phenylketonuria
phenyl keton uria
how does phenylketonuria (PKA) work
- mutation in gene coding for phenylalanine hydroxylase (recessive)
- inability to convert phenylalanine into tyrosine
- Phenylalanine accumulates
4 medical consequences of PKU
- intellectual disability
- reduced growth of head
- lack of skin and hair pigmentation
- seizures
treatment of PKU? 2
- early diagnosis (within 24 of birth) – Heel prick test
- restriction of diet to supply only amt of phenylalanine that body needs for protein synthesis
(may still dev learning difficulties)
2 important roles of Vitamin D
- maintain skeletal calcium balance – promoting calcium absorption in intestines
- maintain calcium and phosphate levels for bone formation
what does a vitamin D deficiency lead to?
softening or malformation of bones
names of vitamin C deficiency in adults and children
adult: Osteomalacia (milder)
child: Rickets (more serious)
what foods can vitamin D be found in?
oily fish (salmon, herring, tuna), egg yolk, liver, dairy products
how can the synthesis of vitamin D be triggered in humans
exposing human skin to UV light (wavelength 290-310) = triggers syn of vitamin D
out of carbs, lipids, proteins, rank the amt of energy each yields
lipids
carbs
proteins
what is the BMI (body mass index)
value used to determine if a patient is within normal parameters of weight
how to calculate BMI?
weight in KG / (height in M)^2
what BMI is clinical obesity
30 and over
how do people become overweight / obese (2)
- diet w excess lipids and fatty acids = more energy rich items than body requires
- storage of excess fat in adipose tissue
why does obesity lead to enhanced likelihood of type II diabetes 3
- islet of Langerhans: B cells produce sufficient insulin
- BUT! insulin receptors on target cells are less sensitive (insulin resistance)
- pateient raised blood glucose level
symptoms of type II diabetes 4
- incr glucose levels (blood and urine)
- frequent need to urinate
- tiredness and fatigue
- loss of. weight
main 3 health consequences of obesity
enhanced likelihood of…
1. type II diabetes
2. hypertension
3. coronary heart disease
how does obesity lead to hypertension
- persistently raised blood pressure
- accelerates onset of atherosclerosis
- incr workload of heart
- makes brain haemorrhage more likely
(can be. treated using drugs)
what is hypertension
persistently raised blood pressure (damages heart, blood vessels, brain, kidneys)
what is coronary heart disease
plaque builds up inside coronary arteries
how does obesity lead to coronary heart disease
- saturated fatty acids deposited inside arteries
- deposits combine with cholesterol = atherosclerosis = hypertension
saturated vs unsaturated fatty acids
saturated = bad – raises LDL cholesterol
(low-density lipoprotein bc saturated = easier to arrange)
why is cholesterol important 4
- for metabolism
- component in plasma membranes of all cells
- needed to produce sex hormones
- bile salts (involved in lipid transport) synthesised from cholestorl
how does high cholestrol lead to atherosclerosis
strands of low-density lipoproteins are deposited under the endothelium of arteries
cholesterol in blood is an indicator of?
coronary heart disease
how is high cholesterol treated
- reducing dietary intake = limtied effect
- DRUGS! statins (drugs that lower cholesterol lvls) more effective
what are statins
a class of drugs used to lower cholesterol levels
how do statins/cholesterol lowering drugs work
inhibits ENZYME HMG-CoA reductase
(catalyses 2nd step in Acetyl CoA –> cholesterol pathway)
how can the energy content of food be determined
combustion – burning a known mass of food to test
steps to find energy content in food
- burn a known mass of food under a test tube with water
- heat liberated absorbed by known value of water
- record rise in temp
- energy value /g = temp rise x mass of water x 4.184 or 1 calorie
IS units system units for energy 3
energy – Joules (J)
food related – kilojoule (kJ)
kilocalorie (kcal)
kcal conversion to kJ
1 kcal = 4.184 kilojoules
benefits of high fibre diet
maintains bowel health
lowers cholesterol levels
