Transcript - SlideBoom

Mr. Lajos Papp
The British International School, Budapest
2012/2013
A.1 Components of the human diet
Nutrient: a chemical substance found in foods
that is used in the human body.
Define nutrient.
Essential nutrients are those that cannot be synthesized
by the body. Carbohydrates are not included because in
certain traditional human diets energy is obtained from
other sources without ill effect.
List the type of nutrients that are essential in the human
diet, including amino acids, fatty acids, minerals, vitamins
and water.
ESSENTIAL NUTRIENTS
NON-ESSENTIAL NUTRIENTS
(cannot be synthesised in the body from (can be synthesised in the body. Dietary
other nutrients, so must be included in the intake of these nutrients reduces the need for
diet)
biosynthesis.)
Water
Carbohydrates
Some fatty acids
Some fatty acids
Some vitamins
Some vitamins
Some minerals
Some minerals
Some amino acids
Some amino acids
http://en.wikipedia.org/wiki/Essential_nutrient
Non-essential amino acids can be synthesized in the
body from other nutrients.
Protein deficiency is shortage of one or more essential amino
acids. The consequences are:
 Stunted growth
 Muscle and skin problems
 Impaired mental development
 Immune system impairment
 Oedema (swelling in the abdomen and legs)
Outline the consequences of protein deficiency malnutrition.
1. PKU is the result of a missense mutation in a gene.
2. It is autosomal and recessive.
3. The gene codes for the enzyme tyrosine hydroxylase.
4. The essential amino acid phenylalanine cannot be
converted to tyrosine, so builds up to dangerous levels.
This disorder is progressive : its effects build up over time
and lead to ongoing deterioration.
Symptoms:
 skin disorders
 intellectual disability
 heart problems
 microcephaly can also develop in severe cases.
Diagnosis
a blood test at birth will detect the presence of absence
of the enzyme. As this is a cumulative disorder, the
earlier it is diagnosed and the diet is started, the less
chance there is of severe complications.
Treatment
A phenylalanine-controlled diet from birth is essential.
Foods
containing
phenylalanine
are
minimised,
including dairy, aspartame sweeteners, breastmilk, nuts
and meat. Tyrosine supplementation may be used.
Explain the causes and consequences of
phenylketonuria
(PKU)
and
how
early
diagnosis and a special diet can reduce the
consequences. Limit the causes to a mutation of
a gene for an enzyme that converts the essential
amino acid phenylalanine to tyrosine.
Outline the variation in the molecular structure of
fatty acids, including saturated fatty acids, cis and
trans unsaturated fatty acids, monounsaturated and
polyunsaturated fatty acids. Include omega-3 fatty
acids as an example.
Saturated fats
Cis-fatty acids
Sources: animal fats, - milk,
butter, cheese, red and white
Trans-fatty acids
Sources: vegetable oils such as
Sources: hydrogenated
olive oil and fish oils
vegetable oils, margarine
meat, eggs and palm oil
All contribute to dietary intake and excess consumption is related to weight gain and coronary
heart disease (CHD). Fat contains more energy per gram than carbohydrates or proteins.
- can
raise
cholesterol
harmful
LDL - may promote beneficial HDL - may have a greater negative
cholesterol and inhibit harmful effect on LDL cholesterol and
- lead to atherosclerosis and LDL
CHD
increased
- omega 3 fatty acids are linked sclerosis
to brain development
risk
of
athero-
and
CHD
than
saturated fats
- some natural trans – fats
may
have
impacts
less
harmful
Evaluate the health consequences of diets rich in the
different types of fatty acid. The link between
consumption of saturated fatty acids and coronary
heart disease is not a simple correlation and genetic
factors are also important.
Vitamins are organic compounds made by plants or
animals, whereas minerals are inorganic ions.
Distinguish between minerals and vitamins in terms of
their chemical nature. Limit this to minerals being
elements in ionic form and vitamins being organic
compounds.
Outline two of the methods that have been used to
determine the recommended daily intake of vitamin C.
Include brief details of one method involving human
subjects and another involving small mammals.
Vitamin C (ascorbic acid) is essential in the human diet.
It maintains mucus membranes as a component of
collagen, and promoted healing and skin growth.
Deficiency
of
vitamin
C
can
lead
to
scurvy,
characterized by bleeding hair follicles, gums and liver
spots on the skin. In extreme cases it can be fatal.
Recommended Daily Intake (RDI) of vitamin C have
been set at 45-60 mg/day. These levels were determined
based on a number of experiments into levels of vitamin
C that gave optimum benefit.
Humans and guinea pigs cannot synthesise vitamin C,
so it is possible to measure the effects of varying
vitamin C doses in carefully controlled experiments.
Human trials
observe the symptomatic effects of varying doses of vitamin
C supplementation. 20 volunteers were used to measure the
effects of varying vitamin C concentrations.
Weeks 1-6: No vitamin C in foods, but all given 70mg
supplement.
Weeks 7-end (8 months): 3 kept on 70mg per day, 7 were
given 10mg per day and 10 were given no vitamin C at all.
Weeks 1-6: No vitamin C in foods, but all given 70mg
supplement.
Weeks 7-end (8 months): 3 kept on 70mg per day, 7
were given 10mg per day and 10 were given no vitamin
C at all.
Measurement
periodic incisions were made on volunteer’s thighs, and
healing time and strength of healed tissue were
observed. Blood and urine vitamin C concentrations
were recorded.
Outcomes
no ill effects were recorded in the 70mg or 10mg
groups. The 0mg group developed scurvy within 6-8
months and some serious side effects were recorded,
including one who experienced heart problems, which
were rectified after he was given vitamin C.
Guinea pig trials
observe the effect of vitamin C concentration on collagen
structure.
After
periods
of
varying
vitamin
C
supplementation and measurement of blood and urine
vitamin C levels, guinea pigs were sacrificed and the
structure of collagen fibres observed. Guinea pigs with
restricted vitamin C showed weaker collagen.
Recommended Daily Intakes (RDI) of vitamin C have been set at
45-60mg per day. These are based on controlled experiments
using human and animal subjects. There is some debate on
whether the RDI should be higher, with experts such as:
Nobel-winner Linus Pauling suggesting that megadoses (1000mg
or more) are required per day.
The Vitamin C Foundation recommend 3 doses of 1000mg per
day.
The evidence for the efficacy of these recommendations is
not strong, yet some have suggested it can boost the immune
system, prevent upper respiratory tract infections, decrease
susceptibility to cancer and speed healing and recovery from
illness. Large-scale, randomized and controlled trials of
these claims have not taken place.
Some adverse effects of high dose vitamin C regimes can include
intestinal problems and acidosis, but there is little data to suggest
long-term harm. It has also been suggested that rebound
malnutrition can occur as a result of systemic conditioning during
long periods of high-dose supplementation: the body is
accustomed to excreting large amounts of vitamin C and this
continues once supplementation stops, leading to deficiency. The
evidence for these claims is also weak.
Discuss the amount of vitamin C that an adult should consume
per day, including the level needed to prevent scurvy, claims
that higher intakes give protection against upper respiratory
tract infections, and the danger of rebound malnutrition.
Rebound malnutrition can occur when a normally adequate
intake of a vitamin follows a period of excessive intake and
excretion.
Vitamin D can be produced by skin as a response to
sunlight.
It also can be found in foods: fish with high fat content
(salmon, sardines), liver, eggs, some mushrooms and
some fortified cereals.
List the sources of vitamin D in human diets.
Vitamin D is required to allow uptake of calcium, which
is then used to produce bone matrix. Rickets, vitamin D
deficiency, results from low levels of vitamin D,
calcium or both. Symptoms of vitamin D deficiency
include bow legs and stunted growth.
There is a strong negative correlation between
increasing darkness of skin colour and vitamin D
synthesis. Historically, darker-skinned populations were
exposed to stronger sunlight for longer periods of time.
Darker skin produces vitamin D more slowly, but offers
protection against skin cancer (malignant melanoma).
Pale skinned people are more able to produce vitamin
D, yet more susceptible to skin cancer.
Risks of vitamin D deficiency can be negated with
supplementation or attention to dietary sources, whereas
the risk of skin cancer can be reduced by covering pale
skin, staying indoors or using sunblocks.
Discuss how the risk of vitamin D deficiency from
insufficient exposure to sunlight can be balanced
against the risk of contracting malignant melanoma.
Artificial supplementation can be used to ensure that a
population has adequate access to essential nutrients,
even if the supply of naturally-containing foods is
limited.
Some examples include adding fluoride to drinking
water
to
prevent
tooth
decay,
vitamin
D
supplementation of milk to prevent rickets or iodine
supplementation of salt to prevent thyroid problems
(hypothyroidism).
Iodine is essential in production of thyroxine, a
hormone responsible for regulating metabolic rate in the
body. Patients suffering from hypothyroidism are at risk
of mental retardation and goiter, an extreme swelling of
the thyroid glands in the neck.
It can cause birth defects and miscarriages. Worldwide
supplementation of edible salt with iodine has greatly
reduced incidence of iodine deficiency disorders, at
very low cost.
Explain
the
supplementation
benefits
as
a
of
artificial
means
of
malnutrition, using iodine as an example.
dietary
preventing
Dietary fibre includes the components of foods which
cannot be digested by the human body (egestion). This
is largely cellulose, a structural component of the plant
cell wall. Although it cannot be digested and absorbed
into the blood, dietary fibre plays an important role in
human health.
 Provides bulk in food, allowing one to feel full when eating
 Helps regulate blood sugar
 Reduces blood cholesterol
 Strengthens action of peristalsis in the intestine
 Reduces constipation
 Dietary fibre is sourced from vegetables, nuts, wholegrains and
some fruits.
Outline the importance of fibre as a component of a
balanced diet.
A.2 Energy in human diets
Compare the energy content per 100 g of carbohydrate, fat
and protein. Students should know that carbohydrates
contain approximately 1,760 kJ per 100 g, protein 1,720 kJ
per 100 g and fats 4,000 kJ per 100 g.
Compare the main dietary sources of energy in
different ethnic groups. Include ethnic groups using
rice, wheat, cassava, maize, fish and meat as their
staple energy source.
Region / Group
Main food energy source
Continental Europeans, USA
Wheat (bread or pasta)
UK & Northern Europe
Potatoes, wheat (bread), rye
Central Africa & Brazil
Cassava (sweet potato)
Americas & Africa
Maize (corn)
Asia
Rice
Eskimo tribes
Whale & fish meat
Isolated island populations
Fish
Explain the possible health consequences of diets rich
in carbohydrates, fats and proteins. The consequences
of an excess of each of the three types of nutrient
should be explained separately.
Carbohydrates
Proteins
Fats
As all macronutrients contain energy, high intake can lead to storage of excess energy
of fat, therefore gain weight, possible obesity and coronary heart disease. The ideal is a
balance of all three to ensure sufficient intake of all three nutrients.
- Carbohydrates are digested - Sufficient protein intake is - Strong correlation between
into monosaccharides which required to provide essential high fat intake and obesity, as
are
absorbed
into
blood. amino acids.
well as CHD.
Prolonged high intake can lead - There is a minimal risk in the - Saturated and trans-unsatuto diabetes as the liver become diet high in protein, though rated pose a higher risk than
less sensitive to insulin.
some kidney problems may be cis-unsaturated fats.
- Carbohydrates which cannot reported.
be digested (cellulose) count - Some
- some positive effects of diets
weight-loss
diets rich in cis-fats, with regard to
as fibre, which has health promote replacing carbohy- reducing harmful cholesterol.
benefits.
drates with proteins. These
may result in malnutrition as
nutrient rich foods are avoided.
Appetite is controlled in the hypothalamus of the brain.
Control is both nervous and hormonal: some hormones
trigger appetite-stimulating neurons, others trigger
appetite-inhibiting neurons.
An empty stomach releases a hormone, which triggers
appetite-stimulating hormones, leading to hunger. When
food enters the stomach, the hormone production is
stopped, reducing hunger.
Appetite is also inhibited when:
Food entering the intestine stimulates release of a hormone.
Carbohydrate and protein digestion stimulate release of insulin
hormone from the pancreas.
Fat storage stimulates release of a hormone from the pancreas.
This is enhanced by insulin.
These three hormones trigger appetite-inhibiting neurons in the
appetite control centre. There are strong links to malfunction of
any of these pathways and obesity, as the individual eats more
than is required.
Outline the function of the appetite control centre in the
brain. Only a simple account is expected. Hormones are
produced by the pancreas and small intestine after eating
and by adipose tissue in response to fat storage. These pass
to an appetite control centre in the brain, which makes the
person feel that they have eaten enough.
Calculate body mass index (BMI) from the body mass
and height of a person.
BMI = (mass in kg)/(height in m)2
Distinguish, using the body mass index, between being
underweight, normal weight, overweight and obese.
BMI Status
below 18.5
underweight
18.5–24.9
normal weight
25.0–29.9
overweight
30.0 and above
obese
Limitations of the BMI using this table:
Race, gender and age are not considered
No distinction is made on body fat/water/muscle
composition
Clinical obesity is an excess of body fat. Generally it is
caused by consuming more energy than is used in activity,
with the excess stored as body fat.
Obesity carries a reduced life expectancy, high risks of
CHD, diabetes, heart attacks and strokes.
The obesity epidemic is on the increase globally, in
developed nations in particular.
Food availability
Packaged, sugary or fatty foods
are energy-dense – they contain a
lot of energy per unit mass. A
large mass is consumed to feel
full, but an excess of energy is
also consumed.
Portion sizes
A trend to „supersizing” meals and
overeating contributes to intake of
excess energy.
Transportation
Increase of use of vehicles as
transport means less energy is
burned off than if one walked or
used pedal-power.
Sedentary lifestyles
Professions
are
increasingly
information-based and officecentred, so workers are less active.
Engagement in TV, video games
Food availability
Poverty
Genetic factors
Packaged, sugary or fatty foods
are energy-dense – they contain a
lot of energy per unit mass. A
large mass is consumed to feel
full, but an excess of energy is
also consumed.
Linked to food availability. Often
the cheapest option for the poor in
developed
countries
is
the
packaged, processed high-energy
alternative. Whole foods and fresh
ingredients tend to be more
expensive.
Genetic factors are strongly linked
to addiction, compulsive eating,
susceptibility to weight gain, heart
disease or diabetes or to problems
with appetite control mechanisms.
Outline the reasons for increasing rates of clinical
obesity in some countries, including availability of
cheap
high-energy
foods,
large
portion
sizes,
increasing use of vehicles for transport, and a change
from active to sedentary occupations.
Outline the consequences of anorexia nervosa.
Anorexia nervosa is an eating disorder in which the patient
severely limits food intake.
It is a medical condition with mental and physiological
causes.
It is closely associated with body image and meeting
aesthetic standards imposed by culture.
It is most common in females, but does occur in males.
Health consequences include:
Deficiency in some or all essential
Malnutrition
nutrients as a result of not eating can
lead to any of the effects below
Hormone imbalance
Periods stop, problems in pregnancy,
growth and development
Mental health
Mood swings, poor concentration,
phobias and paranoia
Blood
Anaemia and circulatory problems,
including heart weakness
Muscle and bone
Loss of muscle mass, lack of strength,
osteoporosis, more easily injured
Immunity and healing
Susceptible to infections, recovery
and healing are impaired
Skin problems
Death
Dry, easily damaged, discoloration
As a result of a prolonged, severe
starvation
A.3 Special issues in human nutrition
Distinguish between the composition of human milk
and artificial milk used for bottle-feeding babies.
Breastmilk
Present
in
first
Formula
feeds.
Colostrum
Not present
Stimulates newborn digestion.
Present in colostrums in high
Antibodies
Not present
doses, and subsequent milk.
Lower, but more easily digested Higher but harder to digest
Protein
and absorbed. Human.
and absorb. Bovine sources.
Breastmilk
Formula
Higher in lactose linked to Lower in lactose. May come
Carbohydrates
brain development.
from glucose.
Fatty acids
Human fatty acids.
Palm oil and alternatives.
Vitamins and
May be lower, but easier
Higher but harder to absorb.
minerals
to absorb.
Discuss the benefits of breastfeeding.
Benefit
Effect
Colostrum and early breastmilk contain
Immunity
high
concentrations
of
antibodies,
protecting the infant from infections.
Colostrum
Digestive function
stimulates
digestive
tract
function and eases defecation. Easier to
digest than formula milk.
Cost
Breastmilk is free and readily available as
long as the mother remains healthy.
Benefit
Bonding
Effect
Aids
in
mother-child
bonding
and
communication.
More complete than formula and changes
Nutrition
in composition to match the needs of the
infant.
Aids in weight-loss, reduces risk of breast
Mother’s health
cancer, type II diabetes and post-partum
depression.
Diabetes mellitus (type II diabetes) is also known as
adult-onset diabetes as it generally manifests in
adulthood. Receptors on the liver become resistant to
insulin
produced
by
the
pancreas,
complications with blood sugar control.
leading
to
Causes
Obesity can cause the receptors in the liver to ‘wear out’
or become resistant to insulin.
There is a very strong link with obesity. As the obesity
epidemic increases, the age of adult-onset diabetes is
also decreasing.
Genetics also plays a role. Some people are genetically
more susceptible to developing type II diabetes and
should use their family history as an indicator and take
preventative measures – largely a balanced diet and
exercise.
Symptoms
Glucose in the urine as the kidney is unable to reabsorb
all of the glucose back into the blood.
Deyhdration as water-balance is disrupted, coupled with
excessive urination.
Weight loss as insulin is less able to store fat.
Sleep loss and tiredness.
Blurred vision and potential blindness.
Outline the causes and symptoms of type II diabetes.
Explain the dietary advice that should be given to a
patient who has developed type II diabetes.
Dietary advice
Eat high fibre foods.
Explanation
High
fibre
makes
one
feel
without
providing too much energy. High fibre diets
can also help to reduce the effects of
diabetes.
Dietary advice
Eat low GI foods.
Explanation
Some foods release energy more slowly –
they have a lower glyceimic index. Eating
these reduces “spikes” in blood sugar.
Cut out sugars and refined These are high GI foods – they are broken
carbohydrates.
down into sugars and absorbed quickly,
causing blood sugar to rise quickly. They
include sugary snacks, white bread and
pasta.
Dietary advice
Small, regular meals.
Explanation
Smaller
releases
of
energy
more
frequently result in less dramatic blood
sugar changes than large, infrequent
meals.
Choose “diabetic” alternatives. Some packaged foods may be labelled
to show that they have reduced sugars
or carbohydrates, suitable for diabetics.
Read the food labels.
Learn how to read and interpret food
labels to avoid eating unsuitable foods.
Discuss the ethical issues concerning the of eating of animal
food products, including honey, eggs, milk and meat.
Animal products are a major component of the human diet,
though they are not without their ethical concerns. As populations
grow, demand for food increases, including meat and animal
products. Concerns arise with regard to ethical treatment of
animals and environmental sustainability.
Food
product
Advantages
Ethical concerns
Source of proteins, •Animal-welfare issues in intensively-farmed cattle,
some vitamins and poultry. Pain and suffering in slaughter.
minerals.
•Growth of antibiotic-resistant bacteria and new
strains of viruses as a result of overuse of
medication. Use of growth hormones may affect
Meat
human health, such as earlier onset of puberty.
•Huge demand for land and water to grow crops to
feed animals is no longer sustainable and results in
clearing of rainforests and habitat destruction.
Methane
and
other emissions
from
farming
livestock contribute to global warming.
Source of proteins •Many
fish
and helpful fatty overfishing.
Fish
species
are
endangered
due
to
Food
product
Advantages
Ethical concerns
•Animal-welfare issues in intensivelyfarmed cattle, poultry.
•Growth of antibiotic-resistant bacteria
and new strains of viruses as a result of
overuse of medication.
Source
Milk
of
energy,
•Huge demand for land and water to
grow crops to feed animals is no longer
protein and calcium. sustainable and results in clearing of
rainforests
Methane
and
and
habitat
destruction.
other emissions
from
farming livestock contribute to global
warming.
Food product
Advantages
Ethical concerns
•Cholesterol health risks associated
with
too
much
egg
yolk
chickens
fed
consumption.
Source of fats and protein,
Eggs
•Battery
farmed
a „meat” alternative in hormones, in cramped conditions
some cultures.
and can be treated inhumanely.
Living spaces can be dirty and
encourage spread of illness.
Farmed bees compete with local
Honey
Honey
is
a
natural insect and bee populations for
sweetener. Bees pollinate nectar. Artificial selection of bees
many flower species.
will result in a genetic shift in bee
populations.
Cholesterol is needed in small amounts in the body to
produce hormones and plasma membranes. In excess it
is thought to contribute to atherosclerosis by forming
deposits in the arteries. Rupture of plaques can cause
clots, or CHD.
It has been suggested that the link between dietary
cholesterol intake and CHD is not logical, and that the
more likely cause of CHD is a diet high in saturated
fats. Diets high in saturated fats tend to be high in
cholesterol, so there is a correlation without necessarily
causation.
With moderate cholesterol intake, the body is able to
remove excess with no harmful effect – dietary
cholesterol is not necessarily converted into plasma
cholesterol.
Plasma cholesterol can be HDL (not
harmful), or LDL (plaque-forming).
Extreme intakes may lead to a greater build-up of LDL
in atherosclerosis. Although there is a small risk of
cholesterol leading to CHD, the risks of smoking,
inactivity and heredity are much stronger and more
closely related to CHD.
Although a cholesterol-controlled diet may slow or
reduce the risk of atherosclerosis, it must be combined
with a healthy diet and lifestyle if it is to have a
significant effect on reducing the risk of CHD.
Evaluate the benefits of reducing dietary
cholesterol in lowering the risk of coronary
heart disease.
Food miles are a measure of the distance a food product
travels from ’plough to plate’. It is an indicator of the
environmental impact of the foods we eat, as this travel
involves costs in fuel, emissions, packaging and time:
the further a product travels, the less sustainable it is.
Some imported foods cost more in energy per gram for
their transport than they provide for the consumer.
Some consumers prefer to choose locally grown or
farmed food products to reduce the costs, use of
packaging and preservatives, use of oil/fuel and
emissions. They may also hope to encourage outlets to
use local providers of produce rather than imported
goods.
Discuss the concept of food miles and the reasons for
consumers choosing foods to minimize food miles.