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– Carbohydrates– Proteins– Fats– Vitamins– Minerals– Water – fibre

The macronutrients

Nutrient Elements

present

Use in body

Good food sources

Carbohydrate

Carbon, hydrogen, oxygen

Source of energy

Rice, potato, bread

Fats and oils

Carbon, hydrogen, oxygen

Source of energyInsulation

Butter, milk, cheese, egg yolk

Protein 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 Acceptable

25 – 29.9 Overweight

30 – 34.9 Obese (class 1)

35 – 39.9 Obese (class 2)

>40 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

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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

• Bacteria– Cheese– Yoghurt

• Fungi– Cheese– Single celled protein / mycoprotein

• Yeast– Brewing – Winemaking– Bread making

Micro-organisms in food production

Advantages of using micro-organisms

• Low fat foods – free from saturated fat and cholesterol

• No ethical issues• Quick growth, high yields, fast

production

Disadvantages of using micro-organisms

• 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:– 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