A1 Nutrition Flashcards
Nutrient
a chemical substance found in food that is used in the human body
Diet
total sum of all nutrients eaten
Essential nutrients
cannot be synthesized by the body; Fatty acids Vitamins Minerals Amino acids (BUT non-essential amino acids can be sythesized by the body from other nutrients) Water
Fat Velociraptor Markets Arty Water
Protein deficiency malnutrition
cause: inadequate supply of one or more ESSENTIAL AMINO ACIDS
key factor in the development of kwashiorkor
- swelling of the abdomen - one of the most visible consequences - caused by tissue fluid retention (oedema) due to a lack of plasma proteins in the blood
- skin flaking
- hair lacking pigmentation
- children: retardation of physical and mental development
Phenylketonuria (PKU) - cause
genetic disease
deficinecy / complete lack of enzyme TYROSINE HYDROXYLASE, because of a mutation of a gene coding for this enzyme
–> tyrosine hydroxylase catalyses the reaction of synthetizing PHENYLALANINE (an essential amino acid) into TYROSINE (non-essential)
—> as phenylalanine cannot be converted into tyrosine, it is converted into PHENYLPYRUVIC ACID, causing high leve;s of KETONES in blood
Phenylketonuria - consequences
retarded mental and physical development
skin rashes
eczema
Phenylketonuria - diagnosis
simple blood test for the levels of phenylalanine (soon after birth)
phenylketonuria - treatment
early diagnosis + special diet (low in phenylalanine, should include fruits, grains, vegetables, and special milk)
can prevent most harmful effects
Fatty acids
- all have a carboxyl group (COOH) and a hydrocarbon chain
- vary in the bonding between the carbon atoms and the number of hydrogen atoms bonded to the carbon
Saturated Fatty Acids
all carbon atoms connected by a SINGLE covalent bond
Unsaturated fatty acids
Monounsaturated = 1 double bond Polyunsaturated = multiple double bonds
Cis-unsaturated - hydrogen atoms bonded to carbon atoms on the same side of a double bond
Trans unsaturated - hydrogen atoms bonded to carbon atoms on opposite sides of a double bond
Health consequences of a diet rich in saturated fatty acids
high levels = high Coronary Heart Disease mortality
BUT correlation =/= causation - it could be e.g. low fiber content of most diets high in saturated fatty acids that causes CHD
Health consequences of a diet rich in Cis-monounsaturated fatty acids
Mediterranean diet - rich in olive oil (Cis-monounsaturated fatty acids)
rates of CHD low
BUT apart from the amount of fats in diets, other factors vary between people, too
Omega-3 fatty acids
Much of the eye and brain tissue is made up of long-chain fatty acids, synthesized in body from essential fatty acids, including Omega-3 fatty acids
BUT no clear evidence that Omega-3 dietary supplements improve brain and eye development
trans fatty acids
high levels = high incidence of coronary heart disease;
- analysis has shown that other factors cannot explain this correlation, leaving trans fats as the only risk factor (cause)
- autopsies after death of CHD: most of fat in arterial plaque = trans fat
- raised LDL and reduced HDL levels, associated with CHD
Minerals
usually INORGANIC elements
in ionic form (e.g. NA+)
Vitamins
ORGANIC compounds made by plants and animals
e.g. vit. A
Recommended daily intake
the amount of a nutrient that should be consumed per day to ensure health
Recommended daily intake of vitamin c
50 mg
- probably sufficient
- eliminates the risk of rebound malnutrition, associated with higher intakes (body adjusts to high rates of intake by excreting the excess, so that the intake drops to normal levels BUT when the intake is lowered such high excretion continues, causing SCURVY)
1000 mg
- Linus Pauling, Nobel-winning chemist, argued to increase the RDI to such level
- reason: it may give protection against cold (upper respiratory tract infection), although there’s little evidence for that
Methods to determine the recommended daily intake of vit. C (2)
1) GUINEA PIGS fed with diets of different amounts of vit. C for a trial period
- level of vit. C in blood plasma and urine measured
- strengths of collagen in bone and skin measured to test for scurvy
- results used to estimate the amount of vit. C by humans per kilogram of body tissue
2) VOLUNTEERS
during WW2 experiments conducted in Britain on a group of conscientious objectors to military service
- 6 weeks: all volunteers given a diet lacking vit. C + a daily supplement of 70 mg
- 8 months: divided into 3 groups and given 70mg, 10mg, or 0mg vit. C per day
- tests: skin cuts to test wound healing
results:
- 70 mg, 10 mg - no scurvy
- 0 mg - developed scurvy
suggest that 10 mg vit. C is sufficient, but in most countries much higher daily intakes are recommended to give a safety margin so that the risk of scurvy is minimized + to consider variations between individuals in their general health and in their ability to absorb and use vit. C
Source of vit. D
oily fish eggs milk butter cheese liver NOT IN PLANT PRODUCTS, but often added to soya milk or breakfast cereals
synthesis of vit. D
- can be synthesized in skin, but only in presence of ultra-violet light (UV)
- in winter: intensity of UV light too low in high latitudes to allow for vit. D synthesis, BUT the liver can usually store enough vit. D during summer to avoid winter deficiency
- inhibited by:
- avoiding exposure to sunlight
- covering skin with thick clothing
- applying sun creams to block UV light
Malignant melanoma
- form of skin cancer
- can be fatal
- UV light can cause mutations, which turn cells into tumor cells
– one should always find a delicate balance between over-exposure and under-exposure to UV light
Deficiency of vit. D
skeletal deformities, slower growth due to calcium deficiency (rickets) - vit. D is required to allow calcium uptake
