Transcript Diet and Food Production

Diet and Food Production
Learning Outcomes
• Define the term balanced diet.
• Explain how consumption of an
unbalanced diet can lead to
malnutrition, with reference to obesity.
Starter Question
• Nutrition come from the food we eat.
• What advantages are gained from
eating well?
– E.g. better health
• Stronger immune system
• Ill less often
• Learn more effectively
• Make you stronger
• Make you more productive.
Next question
• List the seven components of a
balanced diet
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Carbohydrates
Proteins
Fats
Vitamins
Minerals
Water
fibre
The macronutrients
Nutrient
Elements
present
Use in
body
Good food
sources
Source of Rice, potato,
Carbohydrate Carbon,
hydrogen, energy
bread
oxygen
Fats and oils
Protein
Carbon,
Source of Butter, milk,
hydrogen, energy
cheese, egg
oxygen
Insulation yolk
Carbon,
hydrogen,
oxygen,
nitrogen
Growth
and
tissue
repair
Meat, fish,
eggs, soya,
milk
Requirements of a balanced
diet
• Sufficient energy for our needs
• Essential amino acids
• Essential fatty acids
• Micronutrients – vitamins and minerals
• Water
• fibre
Guidelines (17 year old girl)
Nutrient
Mass/g per day
Carbohydrates
250
Fats
80
Proteins
60
Minerals
9.2
Fibre
12
Vitamins
Traces
water
variable
Looking at the guidelines
• Are these the same for everyone?
• What factors will influence the energy
requirements of different people?
Energy intake
• It is recommended that energy intake
come from
– 57% carbohydrates
– 30% fats
– 13% protein
• In an active person the amounts of
each of these will increase
Malnutrition
• Malnutrition is caused by eating an
unbalanced diet
– This could mean eating much more than
is needed or much less
Eating too little
• A person who does not eat enough
– Lacks energy
– Shows signs of protein energy malnutrition
– Can have deficiencies that impair health
• Vitamin D – rickets
• Vitamin C – scurvy
Eating too much
• Obesity is defined as when excessive
fat deposition impairs health.
• Body mass index > 30
– This is an indication that body weight is
20% or more above that recommended
for your height.
– BMI = mass in kg/(height in m)2
Health risks associated with
obesity
• Cancer
• Type 2 diabetes
• Coronary heart disease (CHD)
Body Mass Index
BMI
Category
<18.5
Underweight
18.5 – 24.9
25 – 29.9
30 – 34.9
Acceptable
Overweight
Obese (class 1)
35 – 39.9
>40
Obese (class 2)
Morbidly/severely obese
(class 3)
Prevalence of obesity
• Increasing in affluent countries
– People eat more than they need
– Take less exercise
• In the UK
– 25% men obese
– 20% women obese
Learning Outcomes
• Discuss the possible links between diet
and coronary heart disease (CHD).
• Discuss the possible effects of a high
blood cholesterol level on the heart
and circulatory system, with reference
to high density lipoproteins (HDL) and
low density lipoproteins (LDL).
Coronary Heart Disease
• CHD is a degenerative condition
• It involves the build-up of fatty tissue in
the walls of the arteries that supply the
heart muscle.
Atheroma
CHD
• As a result of the build up
– Arteries become narrow
– Flow of blood decreases
– Supply of nutrients and oxygen to heart
muscle is restricted
– The muscle does not release enough
energy
– The heart becomes weak
CHD
• Heart attack / myocardial infarction
– A blood clot in the coronary artery cuts off the
blood supply to an area of heart muscle.
• Cardiac arrest
– Severe heart attack / heart stops
• Angina
– Pain when exercising
• Thrombosis
– Development of a blood clot
Lipoproteins
• Lipoproteins
– Made in the liver
– Move cholesterol around the
bloodstream
• As cholesterol is water soluble, it is
coated with phospholipids and
proteins so that they can travel in
blood plasma
Structure of a lipoprotein
• Phospholipids and
protein coat
• Centre
– Cholesterol
– Triglycerides
– Other lipids
Two types of lipoprotein
• There are two types of lipoprotein
– Low-density lipoprotein (LDL)
• Transports cholesterol to the tissues
– High-density lipoproteins (HDL)
• Remove cholesterol from tissues and return it
to the liver
• HDLs have less lipid than LDL
Cholesterol and CHD
• If there is a tear in the endothelial lining
of coronary arteries
– LDLs enter the inner layer of the arteries
– The cholesterol and fat that they carry are
oxidised and build up
– This forms an atheromatous plaque
– This enlarges the wall, giving the arteries a
rough lining
Atheromatous plaque
HDLs – “good” fat
• Appear to protect against CHD by
removing cholesterol from the tissues,
including the tissues in the walls of
blood vessels.
It’s all about proportions
• Health professionals are now less
concerned about the quantity of
cholesterol in the body
• The focus is now on the proportions of
HDLs and LDLs
– The more HDLs - the less chance of heart
disease
Fats in diet
• Diets rich in saturated fats tend to
increase the cholesterol concentration
of the blood due to a high LDL
concentration
• Polyunsaturated fats in foods, e.g. fish
oils help protect against heart disease
and lower the concentration of
cholesterol in the blood.
Diet and CHD
• Antioxidants e.g. vitamin C and E
– Protective and reduce the risk of
developing CHD
– Fresh fruit and vegetables are rich sources
Question time!!
• A study followed 639 people with a
family history of CHD over a period of
14 years. Some has an LDL:HDL ratio of
more that 8, while some had an
LDL:HDL ratio of less than 8. The graph
shows the probability of survival of a
person in each of these groups over
the 14 years of study.
The questions
• Explain why the survival probability is
100% at 0 years
• Suggest why the graph is drawn so
that it goes down in steps rather than
in a smooth line.
• Describe the conclusions that can be
drawn from these data.
The answers
• This means that everyone was alive at the start of
the study
• Data collected once a year
– Researchers did not know what happened in between
– If one or more people died in a year the graph goes down
by a step
• Clear difference between results for people with
high LDL:HDL ratio and the lower LDL:HDL ratio
– The lower ratio had the greater probability of survival
Learning Outcomes
• Explain that humans depend on plants for
food as they are the basis of all food chains.
• Outline how selective breeding is used to
produce crop plants with high yields,
disease resistance and pest resistance.
• Outline how selective breeding is used to
produce domestic animals with high
productivity.
Food Chains
• Food chains represent feeding
relationships between living organisms
• Plants are the basis of all food chains
– Autotroph
• Use an external energy source and simple
inorganic molecules to make complex
organic molecules
• Photosynthesis
Food Chains
• All other organisms in the food chains
are consumers
– Heterotroph
– Take in complex organic molecules as a
source of energy
• Your diet depends on plants
Food Production
• We can increase food production by
making food chains more efficient
• Plants
– Improve growth rate of crops
– Increase yield
– Reduce losses due to pests and diseases
• Animals
– Increase rate of growth
– Increase productivity
– Increase resistance to disease
Selective Breeding
• Artificial selection is the intentional
breeding of certain traits
– Humans apply the selection pressure for
the change in the population
• Stages
– Isolation
– Artificial selection
– inbreeding
Selective Breeding in Plants
• Examples
– Tomatoes
• Bred with improved disease resistance
– Apples
• Varieties with improved texture and flavour
– Better quality
• Nutritional value
• flavour
Selective breeding in Animals
• Increase in the yield of meat, milk and eggs
• Faster growing breeds
– Farmed salmon
• reduce time to market
• Production of lean (low fat) meat
• Egg laying chickens can lay up to 300 eggs
per year
Learning Outcome
• Describe how the use of fertilisers and
pesticides with plants and the use of
antibiotics with animals can increase
food production
Fertilisers
• Replace the minerals in the soil that
are removed when crops are
harvested.
• Help to increase growth rate and the
overall size of the crops
Fertilisers
• Artificial fertilisers contain
– Nitrogen (ammonia or nitrate ions)
• Make amino acids
– Magnesium ions
• Make chlorophyll
– Potassium ions
• Enzyme co-factors
• For Guard cells to open stomata
– Phosphate ions
• Make DNA, RNA and coenzymes
Pesticides
• Pesticides are chemicals designed to
kill pest species
– Herbicide
– Fungicide
– Insecticide
• Organic farmers use methods of crop
rotation and biological control to
control the number of pests
Antibiotics
• Antibiotics can be used to:
– Reduce the spread of disease among
intensively farmed animals
– Add to animal feed to reduce the activity
of gut bacteria (banned in EU)
Learning Outcomes
• Describe the advantages and
disadvantages of using
microorganisms to make food for
human consumption.
• Outline the methods that can be used
to prevent food spoilage by
microorganisms.
Micro-organisms in food
production
• Micro-organisms are used in food
technology, where they act as
production agents
– Turning ingredients into food
– Modifying food ingredients
Micro-organisms in food
production
• Bacteria
– Cheese
– Yoghurt
• Fungi
– Cheese
– Single celled protein / mycoprotein
• Yeast
– Brewing
– Winemaking
– Bread making
Advantages of using microorganisms
• Low fat foods – free from saturated fat
and cholesterol
• No ethical issues
• Quick growth, high yields, fast
production
Disadvantages of using microorganisms
• Infection
• Contamination of fermenters by
competitors
• Fungi, yeast and bacteria all use plant
substrates
• Purification
• Palatability – taste and texture
Micro-organisms and Food
Spoilage
• Food spoilage begins as soon as an
item is picked, slaughtered or
manufactured.
• Food poisoning is the presence of
microbes or their toxins that cause
illness or death
Micro-organisms and food
spoilage
• Visible growth (e.g. bread mould)
• External digestion process
• Clostridium botulinum produces botulin
(toxin) - 1μg is enough to kill
• Can cause infection e.g. Salmonella
present in poultry
• Aspergillus – produces carcinogenic
toxins
Preventing food spoilage
• In order to grow micro-organisms need:
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Organic material
Water
Suitable temperature
Oxygen
Suitable pH
• Food preservation removes one or several of
these conditions.
Preventing spoilage
• Cooking
• Pasteurising
• Salting
• Pickling
• Freezing
• Irradiation
Preventing contamination
• To prevent further contamination
– Canning
– Vacuum wrapping
– Plastic or paper packaging