Option A: Human Nutrition and Health A.1 Components of the human diet. Study Questions: Red through your textbook & study guide and answer these questions in full sentences: What are nutrients? What are essential nutrients? Give 2 examples of essential amino acids Give 2 examples of essential fatty acids Give 2 examples of essential minerals Give 2 examples of essential Vitamins Why is water so important in the diet? What are non-essential amino acids? Give 2 examples. A.1 Components of the human diet. Define nutrient A nutrient is a chemical substance found in foods that is used in the body Example of nutrients in human: Carbohydrates; proteins; lipids (fats & oils); vitamins; dietary fibre; dietary minerals & water. •4 Essential nutrients in the human diet Nutrients that can not be synthesized by the body from other nutrients thus they must be included in the diet Examples: amino acids e.g. Phenylalanine & methionine; fatty acids e.g. omega 3 & omega 6; Minerals e.g. K, Na, Fe, Ca, P, I; vitamins e.g. A, B, C, D & folate and water. Non-essential nutrients in humans: Nutrients that can be synthesized by the body from essential nutrients or obtained from alternative sources. Dietary intake of nonessential nutrients reduces the need for biosynthesis thus saving the body energy. Examples: amino acid e.g. tyrosine & alanine; Carbohydrates (energy can be obtained from lipids & proteins); Vitamins e.g. E & K Biosynthesis: the production of non-essential nutrients in the body from components of essential nutrients, if these nutrients are present in the diet, the body does not need to expend the energy on biosynthesis. What is Malnutrition? the condition that results from taking an unbalanced diet in which certain nutrients are either lacking, in excess or in the wrong proportions Examples of malnutrition: Not enough food – starvation causing marasmus Too much food – overeating causing obesity Not the right type of food – protein malnutrition causing kwashiorkor All types of malnutrition lead to health problems. Malnutrition: Consequences of protein deficiency malnutrition :- Kwashiorkor These children are suffering from Kwashiorkor – protein deficiency. Explain why the children have swollen abdomens. Too low intake of protein could lead to protein deficiency malnutrition - a lack of essential amino acids. Essential amino acids are required for production of proteins, such as plasma proteins, extracellular proteins, DNA and plasma membranes in the body. Protein deficiency malnutrition is a key factor in kwashiorkor. Symptoms of kwashiorkor include: Stunted growth Muscle and skin problems Impaired mental development Immune system impairment Edema (swelling in the abdomen and legs) IB Exam Revision Questions: (a) Outline the consequences of protein deficiency malnutrition.  Phenylketonuria (PKU) Red through your textbook & study guide and answer the following questions in full: 1. What causes PKU? 2.What enzyme are sufferers of PKU unable to produce? What are the consequences of this (explain in full)? 3.How can PKU be controlled by early diagnosis? 4.How can PKU be controlled by diet? Phenylketonuria (PKU): PKU is a genetic disorder that is characterized by an inability of the body to utilize the essential amino acid – phenylalanine. It is caused by a mis-sense mutation in the PAH (phenylalanine hydroxylase) gene that codes for the enzyme tyrosine hydroxylase Phenylalanine cannot be converted to tyrosine, so it builds up to dangerous levels. PKU is progressive disorder i.e. its effects build up over time and lead to ongoing deterioration. Symptoms of PKU: skin disorders; intellectual disability; heart problems; microcephaly ( neurodevelopmental disorder in which the circumference of the head is smaller than that of an average person of the same age and sex) can also develop in severe cases. PKU Diagnosis: PKU Treatment: A blood test at birth A phenylalanine will detect the presence controlled diet is used or absence of the from. Foods containing enzyme tyrosine phenylalanine such as hydroxalase. dairy, aspartame sweeteners, breast milk, As PKU is a cumulative nuts and meat are disorder, the earlier it minimized. is diagnosed and the diet is started, the less Tyrosine rich foods such chance there is of as wheat, oats, banana, severe complications. avocado, beans, sesame, pumpkins may be used. IB Exam Revision Questions: (a) Explain how a special diet can reduce the consequences of phenylketonuria (PKU). (b)  Variation in the molecular structure of fatty acids Fatty acids have the same general structure, but there is variation in the bonds between carbon atoms. Saturated fatty acids have no C-C double bonds: all possible valences have been occupied. A mono-unsaturated fatty acid has C=C double bond. Polyunsaturated fatty acid has two or more C=C double bonds. Unsaturated fatty acids Unsaturated fatty acids varies in their structure: cis- isomers have the hydrogen atoms on the same side of the C=C double bond; trans- isomers have the hydrogen atoms on opposite sides. Most trans- fatty acids are created artificially through hydrogenation. In unsaturated fatty acids, the omega-number indicates the position of the first double bond, from the CH3 group. An omega-3 fatty acid has the C=C double bond at the third bond along the chain. Oleic acid (CH3(CH2)7CH=CH(CH2)7 COOH) is an omega-9 fatty acid, it is a component of olive oil in its cis- form. Hydrogenation is a process which is used to create trans- fatty acids from cis- fatty acids. Hydrogen is used to saturate some of the double bonds in an oil, making solid fats from liquid oils e.g. making margarine from vegetable oil. Oleic acid isomer, elaidic acid (trans-oleic acid) is found in hydrogenated vegetable oil. Copy and complete this table to outline the differences between the different structures of fatty acids: Name of fatty acid Saturated fatty acids Cis unsaturated fatty acids Trans unsaturated fatty acids Mono unsaturated fatty acids Poly unsaturated fatty acids Diagram of structure Description of structure Foods that contain them Health implications Health consequences of diets rich in the various types of fatty acid: IB Exam Revision Questions: (a) Explain possible health consequences of diets rich in fats.  (b) Outline the variation in the structure of fatty acids.  (c) Explain why the difference between saturated fats and unsaturated fats is important in a healthy diet.  Fat diets across the world: introduction Read your textbook pp 210-213, your guide pp 111 & search the internet (http://www.ific.org/foodinsight/2005/jf/fatconsfi105.cfm? renderforprint=1)and answer the following questions: What are the benefits of eating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish and fish oils? What is hydrogenation? Why is it done? HDL stands for High Density Lipoproteins (often called “good cholesterol). LDL stands for Low Density Lipoproteins (“bad cholesterol). Using this information, explain why hydrogenation is thought to be bad for health. Fat diets across the world: Mediterranean diets How does eating a diet rich in olive oil help reduce the levels of Coronary Heart Disease (CHD) in Mediterranean populations? What else is in the Mediterranean diet that might help reduce CHD? How does the article say they protect cells from damage? What are the other benefits of MonoUnsaturated Fatty Acid (MUFA)? Fat diets across the world: Eskimo and Japanese diets Give 3 examples of fatty, cold-water fish. What useful substances do they contain? What health benefits might this account for? How can you tell that it is not just Japanese genetics that gives them these health benefits? What study led experts in the US to define a weekly consumption of 1-2 servings of fish as consistent with good health? Fat diets across the world: Analyzing the studies Summarise the other dietary components and non-dietary factors that contribute to the health and well-being of the Mediterranean and Japanese ethnic groups. Do you think there is enough evidence to support the claims made by the studies in the Mediterranean and Japan? Look at this website (http://www.stop-transfat.com/benefits-of saturated_fats.html)before you answer! Vitamins and Minerals Distinguish between the chemical structure of Vitamins and Minerals – use Page 194 of your text book. What does RDI stand for? What is the older method for calculating RDI? What is the more modern method? Vitamins Vitamins are organic compounds made by plants or animals e.g. vitamin C Minerals minerals are inorganic ions they can be found in water, soil and many organic food types as a result of uptake e.g. K+, Na+, Ca2+, Fe2+, P & I- IB Exam Revision Questions: (a) Distinguish between minerals and vitamins in terms of their chemical nature.  Vitamin C (Ascorbic Acid): Read your text book Pp 214-216, your guide pp 110 and webpage (http://www.healthyeatingclub.com/info/books- phds/books/foodfacts/html/data/data4i.html) then answer the following questions: What is the Vitamin C deficiency disease? Discuss how to cure it. What is the difference between RDI, RDA and DRI? How much Vitamin C is needed to “saturate” the body? What happens to any excess? The RDA of Vitamin C has changed over the years. Why? What are the benefits and dangers / adverse effects of taking more than the RDI of Vitamin C? (Give details) Vitamin C 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 Intakes (RDI) of vitamin C have been set at 45-60mg day-1. These levels were determined based on a number of experiments into levels of vitamin C that gave optimum benefit. Humans and guinea pigs cannot synthesize vitamin C, so it is possible to measure the effects of varying vitamin C doses in carefully controlled experiments. Human trials: Conscientious objectors from WWII volunteered to take part in a series of medical trials in Sheffield over a four-year period. symptomatic effects of varying doses of vitamin C supplementation were observed Experiment: 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. 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: Observation of 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 Based on controlled experiments using human and animal subjects, RDI of vitamin C have been set at 45-60 mg day-1 There is some debate on whether the RDI should be higher, with experts such as: Nobel-winner Linus Pauling suggesting that mega doses (1000 mg or more) are required per day; The Vitamin C Foundation recommend 3 doses of 1000 mg 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. Danger of rebound vitamin C malnutrition. 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. IB Exam Revision Questions: (a) Outline a method used to determine the recommended daily intake of vitamin C. (b) Discuss the amount of vitamin C that adults should consume per day.   Vitamin D: Questions: Answer Vitamin D is soluble in? Vitamin D is needed for? Where is vitamin D is made? What else is needed to make it? What foods contain vitamin D? What are vitamin D deficiency disease in children? What are vitamin D deficiency diseases in adults? Issues surrounding getting sufficient Vitamin D to avoid deficiency disease Name: Description: Names: Description: Sources of vitamin D in human diets: Vitamin D can be produced by skin on exposure to UV light from sunlight. (next slide)** It also can be found (in a slightly different form) in foods: fatty fish e.g. Nile perch, lung fish, cat fish; fish oils e.g. cod liver oil & fish liver oil; fortified cereal; eggs yolk and dairy product e.g. milk, cheese & yoghurt. In some countries, milk is supplemented with vitamin D. Exposure to sunlight as a source of vitamin D: UV light from sunlight on skin causes chemical production of vitamin D UV light is too low in winter in high latitudes Vitamin D is stored in liver so the body can make enough to last several months through winter Too much UV light can damage skin and cause skin cancer so exposure needs to be limited Use of sun-block will inhibit vitamin D production; Covering skin with clothing prevents UV light from reaching the skin IB Exam Revision Questions: (a) List two dietary sources of vitamin D.  (b) Discuss exposure to sunlight as a source of vitamin D.  (c) Suggest how environmental conditions cause malnutrition  Dietary supplements Iodine is an essential mineral in the diet. In many parts of the world children show symptoms of iodine deficiency. Find out the answers to these questions: 1. How is iodine used in the human body? 2. What are the symptoms of iodine deficiency? 3. What would be the benefits of dietary supplementation with iodine? 4. Would it be feasible to develop a world wide programme of dietary iodine supplementation? 5. Are there other mineral deficiencies that are widespread causes of malnutrition? IB Exam Revision Questions: ( a) Explain the benefits of artificial supplementation of iodine in the diet.  Importance of fibre as a component of a balanced diet. Dietary fibre includes the components of foods which cannot be digested by the human body, largely cellulose, a structural component of the plant cell wall. Dietary fibre plays important roles in human body such as: 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 IB Exam Revision Questions: (a)Explain the importance of fibre in the diet. (b)  A.2 Energy in human diets Comparison of energy content per 100 g of carbohydrate, fat and protein Type of Nutrient Energy content Kj/100g carbohydrate 1760 fat 4000 protein 1720 Various units of energy can be used on food labels, but we use the unit kJ (kilojoules). One food Calorie is equivalent to 4.18kJ. Note that fats contain more than double the energy per unit mass than carbohydrates or proteins. Comparison of main dietary sources of energy in different ethnic groups. Dietary energy can come from various sources, carbohydrates, proteins or fats, depending on the foods available to a population. Staple foods make up the bulk of a population’s diet, and are generally crops. Map showing some of the main staple crops around the world Possible health consequences of diets rich in carbohydrates, fats and proteins: Energy and Ethnicity: Staple foods is a food that is eaten regularly and in such quantities as to constitute the dominant part of the diet and supply a major proportion of energy and nutrient needs. Different cultures have different staple foods due to availability, cultural preferences, wealth, life style and traditions. Diets high in carbohydrates or proteins or fats can affect health in different ways Make a table showing different staple foods from around the world and the cultures that eat them. Health consequences of diet Rearrange this table so the information it shows is correct: Diet contains lots of… Health consequences Fat Makes you feel full faster and for longer. Can also be used for energy if necessary although this does require the kidneys to excrete more urea which could damage them. Protein Provides lots of energy which is beneficial before a big sporting event. Excess can be turned into fat causing obesity. Carbohydrate Contains lots of energy which could cause obesity. Also linked to cancer of the colon. IB Exam Revision Questions: (a) Compare the energy content of carbohydrate, protein and fat.  Function of the appetite control centre in the brain: Appetite is controlled in the hypothalamus of the brain by both nervous and hormonal. Some hormones trigger appetite-stimulating neurons while others trigger appetite-inhibiting neurons. An empty stomach releases the hormone gherin, which triggers appetite-stimulating hormones, leading to hunger. When food enters the stomach, gherin production is stopped, reducing hunger. Appetite is also inhibited when: Food entering the intestine stimulates release of PYY3-36 hormone. Carbohydrate and protein digestion stimulate release of insulin hormone from the pancreas. Fat storage stimulates release of leptin hormone from the pancreas. This is enhanced by insulin. These three hormones trigger appetite-inhibiting neurons in the appetite control centre in hypothalamus of the brain. When sufficiently stimulated, the appetite control centre sends nerve signals to another region of brain to create a feeling of “being full” There are strong links to malfunction of any of these pathways and obesity, as the individual eats more than is required. Appetite control Copy and complete the flow chart on the next slide to explain how appetite is controlled in the brain Add annotations to explain what happens when parts of this system stop working. Start eating Hormones from ___________ and __________ travel via the blood to the… The ______ _______ _______ in the ________ in the brain detects that no more food needs to be eaten. Stop eating _______ Gene creates leptin in _______ tissue __________ tissue sends ________ to the brain to tell it________ ___________________ ___________________ IB Exam Revision Questions: (a) Outline how appetite is controlled.  (b) Outline the role of the brain in how appetite is controlled.  Body Mass Index: Do a survey of your friends, school mates and family members and work out their BMI. (Ask permission first!). Investigate one of the following R.Q: Is being underweight in humans (Homo sapiens), dependent on age? or Is being overweight in humans (Homo sapiens), dependent on gender? Present your findings in a lab report, DCP & CE criteria will be assessed. Classify your participants as underweight, normal weight, overweight or obese using the BMI categories in the textbook page 225. Work out the BMI of the following people: Participant Name Sarah Mass (kg) 70 Height (m) John 60 1.85 Jacob 67 1.50 Ann 63 1.70 1.40 BMI Obesity is on the increase. Why? State and explain four reasons for the trend in the data shown on the graph. Use assessment statement A.2.7 on p 220 of your textbook to guide you. Reasons for increasing rates of clinical obesity in some countries; Clinical obesity is an excess of body fat generally caused by consuming more energy than is used in activity, with the excess stored as body fat. Sometimes obesity is caused due to mutation of the leptin gene resulting in overeating. Obesity carries a reduced life expectancy, high risks of CHD, diabetes, heart attacks and strokes. The obesity epidemic is on the steady increase globally, in developed nations in particular. IB Exam Revision Questions: (a) Outline the reasons for increasing rates of clinical obesity in some countries.  Anorexia nervosa Anorexia nervosa is an eating disorder in which someone has firm conviction that he/she is overweight even when their BMI indicate that they are normal or underweight. Anorexia affects mainly teenage girls & women but also affects few boys and men. Someone who has anorexia becomes chronically underweight because of following strict a diet and exercise pattern. What are the physiological consequences (effects on the body) of anorexia in relation to: Muscle mass? Hair growth? Blood pressure? Fertility? Menstruation? Dental health? Anorexia nervosa What are the consequences for the family and friends of someone who develops anorexia? Read this article: http://www.mediaawareness.ca/english/issues/stereotyping/women _and_girls/women_beauty.cfm What are your views on magazines using young ultra thin models for advertising? Is it acceptable? What could the consequences be? How can we build a society where healthy body shape is valued? Consequences of anorexia nervosa Hormonal imbalance; periods stops, problems in pregnancy, growth & development Mental health; mood swings, phobias & paranoia Muscle & bone; loss of muscle mass, lack of strength & osteoporosis Circulatory system; anemia, heart weakness & circulatory problems Immunity & healing; susceptible to infections, healing is impaired. IB Exam Revision Questions: (a) Describe the consequences of anorexia nervosa.  (b) A.3 Special issues in human nutrition Breast feeding Design a leaflet to persuade new mothers to breastfeed their babies rather than use formula (artificial) milk. It should include: The difference between breast and artificial milk The benefits of breast feeding Reassurance that breast feeding in public is acceptable This should be a biased piece of writing! Breastfeeding Read the article on this website: http://www.breastfeeding.com/advoca cy/advocacy_boycott.html Explain as fully as you can the reasons why someone may boycott buying Nestle products. Are you convinced to boycott Nestle? Breast feeding Remember – breastfeeding doesn’t work out for every mother! Read this article for a (slightly) less biased view!) http://kidshealth.org/parent/growth /feeding/breast_bottle_feeding.html Differences in composition between human milk and artificial milk used for bottle-feeding babies Human milk Artificial milk contains human proteins contains soya or bovine fatty acids are derived from human butterfat has antibodies thus provides immunity contains lactose Contains less iron proteins fatty acids are derived from vegetable oils No antibodies thus does not provide immunity Does not contain lactose contains more iron Benefits of breastfeeding. IB Exam Revision Questions: (a) Distinguish between the composition of human milk and artificial milk for bottle-feeding babies. (b)  Type II diabetes also called adult-onset diabetes as it generally manifests in adulthood. Receptors on the target cell such as liver cells become resistant to insulin produced by the pancreas, leading to failure by the body to correctly regulate blood glucose. It is common in people aged over 35 years, often in those who have become overweight or obese. Diabetes The cause and treatment of Diabetes is covered in the core syllabus in sections 6.5.11 and 6.5.12. You may like to read Pg 196 in your text book & pg 55 in your guide to get an overview. Briefly outline the difference between Type I and Type II diabetes (you do not have to give any details of the cause or treatment). How can the two types of diabetes be managed (controlled)? Type II Diabetes 1. 2. 3. 4. 5. Read Pp 233 - 234 in your text book and pp 113 of your guide, then answer the following questions: What are the other names of type II diabetes? What are the causes of type II diabetes? What are the symptoms of Type II diabetes? What dietary advice is given to people with Type II diabetes? Which ethical groups have higher incidences of type II diabetes? Causes of type II Diabetes: body becomes resistant i.e. not responsive to insulin pancreas does not produce enough insulin dietary factors e.g. prolonged intake of high-energy foods genetic predisposition certain ethnic groups e.g. Pima Indians are more prone (50% of people aged 30 years & above) lack of exercise, there is a very strong link of type II diabetes with obesity Symptoms of Type II Diabetes: high glucose content in blood (hyperglycemia) Feeling thirsty all the time frequent urination slow-healing sores (wounds) Tiredness (fatigue) Red swollen gums blurred vision, blindness in extreme cases Kidney & back pains nerve damage glucose in urine erectile dysfunction Dietary advice to patients with type II diabetes: moderate portions of food to avoid fluctuations in blood sugar levels regular mealtimes to avoid fluctuations in blood sugar levels include unrefined carbohydrates because they are more slowly absorbed include carbohydrates with a low glycemic index include fibre-rich foods to slow absorption of sugar limit saturated & trans fats because diabetes increases risk of coronary heart disease IB Exam Revision Questions: (a) State one cause of type II diabetes.  (b) List two symptoms in a patient with type II diabetes. (c) Outline the causes and symptoms of type II diabetes.   Animal food products Ethical issues concerning the of eating of animal food products: Animal products such as honey; milk; eggs & meat are a major component of the human diet; Animal products provide energy, protein, fatty acids, dietary minerals & vitamins though they are not without their; As human population grow, demand for food increases, including animal products raising certain ethical concerns; Concerns include ethical treatment of animals and environmental sustainability. Religious reasons; Islam & Judaism do not eat meat from certain animals such as pig and animals has to be slaughtered in a certain (non-violence) way Environmental reasons; More grains needed to feed animals for meat production, hence more land needed thus clearing more rainforests to create farmland Ethical reasons; Bio-industry does not give animals decent life Transporting animals cause a lot of stress to them Some slaughtering procedures cause animals a lot of stress & pain Health reasons; People belief that it is healthier to avoid animal products Economic reasons; Animal products such as meat are relatively expensive than plant products in certain countries To Meat or not to Meat Explain why some people prefer not to eat animals or animal products. Cholesterol and heart disease Read P 235 in your textbook & your guide p 114, then answer the following questions: 1. What is cholesterol? 2. What is cholesterol needed for? 3. Explain how cholesterol can cause a heart attack or stroke. 4. Explain the change in thinking about the relationship between dietary cholesterol and serum (blood) cholesterol. 5. How is cholesterol transported in the blood? 6. Complete the diagrams on the next two slides. Benefits of reducing dietary cholesterol in lowering the risk of coronary heart disease Cholesterol is needed in small amounts in the body to produce steroid hormones and plasma membranes. Excess cholesterol is thought to contribute to atherosclerosis by forming deposits in the arteries. Although there is some risk of cholesterol leading to CHD, other risks factors such as smoking, inactivity, high blood pressure and heredity are much stronger and more closely related to CHD. Dietary cholesterol is not necessarily converted into plasma cholesterol such as HDL (not harmful), or LDL (harmful). Extreme intakes of cholesterol may lead to a greater buildup of LDL in atherosclerosis. Transport of cholesterol Cholesterol in blood • • • • • • Transported by __________ (good cholesterol) Liver Cholesterol broken down Can be increased by: E__________ Not s__________ W________ loss Omega 3, _________________________ A diet containing a lot of _________ and limited amounts of _______. • Moderate use of a__________??? (not proven!) Transport of cholesterol Transported by __________ (bad cholesterol) Cholesterol in blood Cholesterol can cause plaques • • • • • • Liver Can be increased by: No E__________ S__________ Putting on w________ trans _________________ A diet containing too little _________ and lots of _______. Food miles Read the article on this website: http://www.bbc.co.uk/food/food_matters/foodmiles.s html Discuss the concept of food miles and the reasons for consumers choosing foods to minimize food miles Concept of food miles: Is a measure of the distance the food is transported from site of production to the consumer It is used to assess environmental impact of food we eat Locally produced food has lower environmental impact Some imported foods cost more in energy per gram for their transport than they provide to the consumer Food miles does not take into account number of trips from source& other costs such as machinery used, fertilizers, & pesticides which may also need to be transported from where they are produced to the farms Transportation is associated with CO2 emissions, with some transport producing more than others e.g. planes During famine & natural disasters transport of food is justifiable whatever the food miles on humanitarian grounds Should consumers choose foods to minimize food miles? Advantages: Disadvantages: less consumption of reduction in choice i.e. less aviation fuel , so less fossil fuel used per food unit; Reduction in air pollution & road congestion; food will be fresher since it is produced locally; access to exotic foods; reduction in access to foods out of season; reduced international trade between developed and developing countries; might be more expensive in short-term; How far should we transport food and in which circumstances should we do it? IB Exam Revision Questions: (a) Outline the concept of food miles.  (b) Discuss whether consumers should choose foods to minimize food miles.