D.1 HUMAN NUTRITION Flashcards
DIET CONSISTS OF
carbohydrates
lipids
proteins
dietary minerals
vitamins
water
fibre
CARBOYDRATES
these are a source of energy but can be replaced by lipids
LIPIDS
most fatty acids can be synthesised in the body
GLYCEROL
lipid
can be synthesised from glucose
ESSENTIAL FATTY ACIDS
omega 3 (fish oils) omega 6
linoleic acid (sunflower seeds)
ESSENTIAL AMINO ACIDS
- Histidine
- Valine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Tryptophan
CONDITIONALLY ESSENTIAL AMINO ACIDS
threonine
arginine
ARGININE
can be syn if AA phenylalanine is present
THREONINE
essential AA for infants but adults can syn it
LACK OF ESSENTIAL AA MEANS
that certain proteins cannot be synthesised
NUTRIENT
chemical substances found in foods use in human body
ESSENTIAL
foods are the only possible source of the nutrient-calcium/water
NON-ESSENTIAL
another nutrient can be used for the same purpose or can be made in the body from another nutrient-glucose/starch/carbohydrates
CONDITIONALLY ESSENTIAL
vitamin K produced by metabolism of symbiotic bacteria in the intestine in adults only
Infants do not have colonies of such bacteria= require supplementary injections
MALNUTRITION CAUSES
deficiency of nutrients (proteins)
imbalance of nutrients (insufficient vitamins/ minerals)
excess of nutrients
FIBRE
cellulose cannot be digested but is imported for maintaining the strength of the gut muscles for peristalsis
ESSENTIAL VITAMINS
A B C
CONDITIONALLY ESSENTIAL VITAMINS
D
can be synthesised in the skin in sunlight
NON-ESSENTIAL VITAMINS
K H
syn in large intestine
DIETART MINERALS
essential
calcium-bones/teeth
Na/K/Cl
APPETITE CONTROL CENTRE
in hypo makes us feel satiated
When APCC receives insulin, PYY3 and leptin
it reduces desire to eat: avoid overeating
ACC AND SI
S.I secretes hormone PYY3-36 when full
ACC AND PANCREAS
Pancreas: insulin when blood glucose > conc
ACC AND ADIPOSE TISSUE
Adipose tissue: hormone leptin when amount of stored fat increases
OVERWEIGHT CAUSES
Diets rich in fat/ low in fibre
overeating
lack of exercise
genetic factors-metabolic R
OVERWEIGHT AND TYPE I
➢ Auto-immune destruction of insulin-secreting cells in the pancreas (type 1)
OVERWEIGHT AND TYPE II
➢ Decreased responsiveness of body cells to insulin due to ‘burn-out’ (type 2)
o Elevated blood glucose
o Glucose in urine
o Dehydration an thirst resulting from excretion of large volumes of urine
OVERWEIGHT AND ATHEROSCLEROSIS
narrowing of arteries by fatty deposits
OVERWEIGHT AND HYPERTENSION
Raised blood pressure
Weight gain→ higher cardiac output which can raise blood pressure
Abdominal obesity can increase vascular resistance which can raise blood pressure
Weight gain is associated with arteries becoming stiffer and narrower→ raise blood P
OVERWEIGHT AND CHD
narrowing of the coronary arteries with risk of <3 attack
Link between high cholesterol, high conc of LDL and low conc of HDL
Clear correlation between excessive weight gain and hypertension
abnormally >blood P
STARVATION EFFECTS
- Body access glycogen stores
- Break down its own muscle to utilise the resulting AA as E
a. If no glucose is available - AA → liver→ converted to glucose
- Loss in muscle mass = BREAKDOWN OF BODY TISSUE
STARVATION CAUSES
due to severe lack of intake of essential nutrients
PKU CAUSES
⇒ Genetic disease caused by mutation of a gene coding for the enzyme that converts phenylalanine into tyrosine
⇒ Mutation produces alleles of the gene that code for enzymes unable to catalyse the conversion reaction
⇒ Only occurs with 2 recessive mutant alleles→ RECESSIVE MUTATION
⇒ Phenylalanine accumulates in body→ deficiency in tyrosine
PKU CONSEQUENCES
⇒ Reduced growth of head/brain
⇒ Mental retardation of young children
⇒ severe learning difficulties/ hyperactivity/ seizures
⇒ lack of skin/ hair pigmentation
PKU TREATMENTS
⇒ early diagnosis/treatment: test 24 hours after birth
⇒ diet low in phenylalanine for the rest of person’s life (meat/fish/nuts/cheese/peas/beans only in small quantities)
⇒ tyrosine supplements may be needed
ANOREXIA
Voluntary starvation and loss of body mass
→ Amounts of carbohydrates and fat consumed are too small to satisfy the body’s energy requirements
→ so protein/other chemicals are broken down
ANOREXIA CONSEQUENCES 6
⇒ Wasting of muscles = loss of strength
⇒ Hair becomes thinner/drops out/ Skin becomes dry/bruises easily
⇒ Blood pressure is reduced→ slow heart rate and circulation
⇒ Females: infertility→ no ovulation/ menstrual cycle
⇒ Skeletal muscle is digested + heart muscle deteriorates
⇒ Lack of protein/micronutrients= deterioration of muscle fibres
⇒ Both skeletal/cardiac muscle do not contract normally
VITAMIN D DEFICIENCY
Lack of vitamin D or calcium can affect bone mineralization and cause rickets or osteomalacia
VITAMIN D SOURCE
oily fish/eggs/liver
VITAMIN D SYNTHESIS
⇒ Can be synthesised by the skin
o Only when light is 290-310 nm
⇒ Enough time spent outside = no diet supplement
VITAMIN D USE
r calcium absorption from food in intestines → similar symptoms as calcium lack
VITAMIN D DEFICIENCY SOL
Children/pregnant/elderly = daily supplement
CHOLESTEROL
normal component of plasma membranes
CHOLESTEROL AS HARMFUL
because research has shown a correlation between high levels of cholesterol in blood plasma and an increased risk of coronary heart disease CHD
LDL
• Much research has involved total blood cholesterol levels but only cholesterol in LDL is implicated in CHD
REDUCING DIETARY CHOLESTEROL
• Reducing dietary cholesterol often has a very small effect on blood cholesterol levels and therefore has little effect on CHD rates
CHOLESTEROL LEVELS AND LIVER
Liver can synthesise cholesterol so dietary cholesterol is not the only source
GENETIC AND CHOLESTEROL LEVELS
Genetic factors are more important than dietary intake
DRUGS AND CHOLESTEROL LEVELS
Drugs can be more effective at reducing blood cholesterol levels
CHD AND SATURATED FATS
There is a +ve correlative between dietary intake of saturated fats and intake of cholesterol
Saturated fats, not cholesterol, cause the increased risk of CHD
