Option A: Human Nutrition and Health

1. Option A:Human Nutrition and Health

2. A.1 Components of the human diet.

3. 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.

4. 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.

5. 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.

6. Non-essential nutrients in humans: • Nutrients that can be synthesized by the body from essential nutrients or obtained from alternative sources. Dietary intake of non-essential 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

7. 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.

8. 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.

9. Malnutrition:

10. Consequences of protein deficiency malnutrition :- Kwashiorkor • These children are suffering from Kwashiorkor – protein deficiency. • Explain why the children have swollen abdomens.

11. 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)

12. IB Exam Revision Questions: • (a) Outline the consequences of protein deficiency malnutrition. [2]

13. Phenylketonuria (PKU) Red through your textbook & study guide and answer the following questions in full: • What causes PKU? • What enzyme are sufferers of PKU unable to produce? What are the consequences of this (explain in full)? • How can PKU be controlled by early diagnosis? • How can PKU be controlled by diet?

14. 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.

16. 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.

17. PKU Diagnosis: PKU Treatment: • A blood test at birth will detect the presence or absence of the enzyme tyrosine hydroxalase. • As PKU is a cumulative disorder, the earlier it is diagnosed and the diet is started, the less chance there is of severe complications. • A phenylalanine controlled diet is used from. Foods containing phenylalanine such as dairy, aspartame sweeteners, breast milk, nuts and meat are minimized. • Tyrosine rich foods such as wheat, oats, banana, avocado, beans, sesame, pumpkins may be used.

18. IB Exam Revision Questions: • (a) Explain how a special diet can reduce the consequences of phenylketonuria (PKU). [4] • (b)

19. Variation in the molecular structure of fatty acids

20. Fatty acids have the same general structure, but there is variation in the bonds between carbon atoms. • Saturatedfatty 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.

21. 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.

22. 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)7COOH) is an omega-9 fatty acid, it is a component of olive oil in its cis- form.

23. 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.

24. Copy and complete this table to outline the differences between the different structures of fatty acids:

25. Health consequences of diets rich in the various types of fatty acid:

26. IB Exam Revision Questions: • (a) Explain possible health consequences of diets rich in fats. [2] • (b) Outline the variation in the structure of fatty acids. [3] • (c) Explain why the difference between saturated fats and unsaturated fats is important in a healthy diet. [3]

27. 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.

28. 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)?

29. 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?

30. 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-trans-fat.com/benefits-of saturated_fats.html)before you answer!

31. 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?

32. Vitamins Minerals • Vitamins are organic compounds made by plants or animals • e.g. vitamin C • 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-

33. IB Exam Revision Questions: • (a) Distinguish between minerals and vitamins in terms of their chemical nature. [2]

34. 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)

35. 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.

36. 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.

37. 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.

38. 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.

39. 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.

40. 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.

41. IB Exam Revision Questions: • (a) Outline a method used to determine the recommended daily intake of vitamin C. [3] • (b) Discuss the amount of vitamin C that adults should consume per day. [4]

42. Vitamin D:

43. 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.

44. 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

45. IB Exam Revision Questions: • (a) List two dietary sources of vitamin D. [1] • (b) Discuss exposure to sunlight as a source of vitamin D. [3] • (c) Suggest how environmental conditions cause malnutrition [2]

46. 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: • How is iodine used in the human body? • What are the symptoms of iodine deficiency? • What would be the benefits of dietary supplementation with iodine? • Would it be feasible to develop a world wide programme of dietary iodine supplementation? • Are there other mineral deficiencies that are widespread causes of malnutrition?

47. IB Exam Revision Questions: • ( a) Explain the benefits of artificial supplementation of iodine in the diet. [3]

48. 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

49. IB Exam Revision Questions: • (a)Explain the importance of fibre in the diet. [2] • (b)

50. A.2 Energy in human diets