IB Biology, Human Health & Nutrition Notes

7/29/2019 IB Biology, Human Health & Nutrition Notes

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Click4Biology: Option A Human Nutrition and health

Stephen is also author of theScienceVideos.wordpress.com which has excellent links

A.1.1 Define nutrient.

A nutrient is a chemical substance found in foods that is used in the body.

A.1.2 List the types of nutrient that are essential in the human diet

A.1.3 State that non-essential amino acids can be synthesized in the body from othernutrient

Biosynthesis is the production of non-essential nutrients in the body from components of essentialnutrients.

If these nutrients are present in the diet, the body does not need to expend the energy onbiosynthesis.

A.1.4 Outline the consequences of protein deficiency malnutrition
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If the intake of protein is too low, it could lead to a protein deficiency malnutrition - a lack of

essential amino acids. These amino acids are required for production of proteins, such as plasmaproteins, extracellular proteins, DNA and plasma membranes in the body.Protein deficiency malnutrition is a key factor in kwashiorkor. Symptoms include:

Stunted growth Muscle and skin problems

Impaired mental development Immune system impairment Edema (swelling in the abdomen and legs as plasma proteins responsible for balancing

tissue fluids are not produced, so fluid builds up)

A.1.5 Explain the causes and consequences of phenylketonuria (PKU) and how earlydiagnosis and a special diet can reduce the consequences

1.PKU

is theresultof amis-

sensemutation

in thePAHgene.

2. Itis

autosomaland

recessive.

3. The PAH gene codes for the enzyme tyrosine hydroxylase .

4. The essential amino acid phenylalanine cannot be converted to tyrosine, so builds up todangerous 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:


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a blood test at birth will detect the presence of absence of the enzyme. As this is a cumulativedisorder, the earlier it is diagnosed and the diet is started, the less chance there is of severecomplications.

Treatment:

A phenylalanine-controlled diet from birth is essential. Foods containing phenylalanine areminimised, including dairy, aspartame sweeteners, breastmilk, nuts and meat. Tyrosinesupplementation may be used.

A.1.6 Outline the variation in the molecular structure of fatty acids, cis- and trans-unsaturated fatty acids, monounsaturated and polyunsaturated fatty acids.

Fatty acids have the same general structure, but there is variation in the bonds between carbonatoms.Saturated fats have no double bonds: all possible valences have been occupied. A mono-

unsaturated fatty acid has C=C double bond, whereas as polyunsaturated fatty acid has two ormore C=C double bonds.

There is also variation in the structure of unsaturated fatty acids. cis- isomers have the hydrogen

atoms on the same side of the C=C double bond, whereas trans- isomers have the hydrogen atomson opposite sides. Most trans- fats are created artificially.

In unsaturated fatty acids, the omega-number indicates the position of the first double bond, fromthe CH3 group. An omega-3 fatty acid has the C=C double bond at the third bond along the chain.


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(i) Hydrogenation is a process which is used to create trans- fatty acids from cis- fatty acids.

(ii) Hydrogen is used to saturate some of the double bonds in an oil, making solid fats from liquidoils: making margarine from vegetable oil.

(iii) Although this has benefits with regard to storage and mass-production, it has health effects.

(iv) Oleic acid (CH3(CH2)7CH=CH(CH2)7COOH) is an omega-9 fatty acid. It is a component ofolive oil in its cis- form. Its isomer, elaidic acid (trans-oleic acid) is found in hydrogenatedvegetable oil.

A.1.7 Evaluate the health consequences of diets rich in the various types of fatty acid


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Dietary studies are difficult to control sufficiently to gain really reliable data. Where data are

produced it may not be possible to conclude causal relationships from correlation. Care must betaken to think critically about nutrition-based news stories and articles.

A.1.8 Distinguish between vitamins and minerals in terms of their chemical structure

Vitamins are organic compounds made by plants or animals, whereas minerals are inorganic ions.Minerals can be found in water, soil and many organic food types as a result of uptake.

A.1.9 Outline two of the methods that have been used to determine the recommended

daily intake of vitamin C

Vitamin C (ascorbic acid) is essential in the human diet. It maintains mucus membranes as acomponent of collagen, and promoted healing and skin growth. Deficiency of vitamin C can lead to


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scurvy, characterized by bleeding hair follicles, gums and liver spots on the skin. In extreme casesit can be fatal.

Recommended Daily Intakes (RDI) of vitamin C have been set at 45-60mg day-1. These levelswere determined based on a number of experiments into levels of vitamin C that gave optimumbenefit.

Humans and guinea pigs cannot synthesise vitamin C, so it is possible to measure the effects ofvarying vitamin C doses in carefully controlled experiments.

Human trials: observe the symptomatic effects of varying doses of vitamin C supplementation

Conscientious objectors from WWII volunteered to take part in a series of medical trials in Sheffield

over a four-year period.In one of these, 20 volunteers were used to measure the effects of varying vitamin Cconcentrations.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 givenno vitamin C at all.

Measurement: periodic incisions were made on volunteers thighs, and healing time and strength ofhealed 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 developedscurvy within 6-8 months and some serious side effects were recorded, including one whoexperienced heart problems, which were rectified after he was given vitamin C.

Another example of a human trial took place in a prison in Iowa, and the outcome was similar, witha recommended intake of around 30mg day-1.

Guinea pig trials: observe the effect of vitamin C concentration on collagen structureAfter 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.

A.1.10 Discuss the amount of vitamin C that an adult should consume per day,including the level needed to prevent scurvy, claims that higher intakes protect againstupper respiratory tract infections, and danger of rebound malnutrition.

Recommended Daily Intakes (RDI) of vitamin C have been set at 45-60mg day-1.These are basedon 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 perday

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 tocancer and speed healing and recovery from illness. Large-scale, randomized and controlled trialsof 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


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malnutrition can occur as a result of systemic conditioning during long periods of high-dosesupplementation: the body is accustomed to excreting large amounts of vitamin C and thiscontinues once supplementation stops, leading to deficiency. The evidence for these claims is alsoweak.

A.1.11 List the sources of vitamin D in human diets.

Vitamin D can be produced by skin as a response to sunlight. It also can be found (in a slightly different form) in foods: fatty fish, fish oils, liver, eggs and

some mushrooms. In some countries, milk is supplemented with vitamin D.

A.1.12 Discuss how the risk of vitamin D deficiency from insufficient exposure tosunlight can be balanced against the risk of contracting malignantmelanoma.

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 ofvitamin D deficiency include bow legs and stunted growth.

There is a strong negative correlation between increasing darkness of skin colour and vitamin Dsynthesis. Historically, darker-skinned populations were exposed to stronger sunlight for longerperiods of time. Darker skin produces vitamin D more slowly, but offers protection against skincancer (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 usingsunblocks.

A.1.13 Explain the benefits of artificial dietary supplementation as a means ofpreventing malnutrition, using iodine as an example.

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 addingfluoride to drinking water to prevent tooth decay, vitamin D supplementation of milk to preventrickets or iodine supplementation of salt to prevent thyroid problems (hypothyroidism).


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Iodine is essential in production of thyroxine, a hormone responsible for regulating metabolic ratein the body and therefore body temperature. Patients suffering from hypothyroidism are at risk ofmental retardation and goiter, an extreme swelling of the thyroid glands in the neck. It can causebirth defects and miscarriages.

Worldwide supplementation of edible salt with iodine has greatly reduced incidence of iodinedeficiency disorders, at very low cost and with minimal objection.

Genetic engineering is also being used to produce enhanced crops, such as beta-carotene richgolden rice, though there is more ethical debate concerning these methods.A.1.14 Outline the importance of fibre as a component of a balanced diet

Links to3.2,3.8.6and6.1

Dietary fibre includes the components of foods which cannot be digested by the human body. This

is largely cellulose, a structural component of the plant cell wall. Although it cannot be digested anabsorbed 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 peristalisis in the intestine Reduces constipation

Dietary fibre is sourced from vegetables, nuts, wholegrains and some fruits.

A.2.1 Compare the energy content per 100g fat, carbohydrate andprotein.

Various units of energy can be used on food labels, but we use the unit kJ (kilojoules).

Notice that fats contain more than double the energy per unit mass than carbohydrates orproteins.

Some food labels use Calories, which is the more common term in public science.One calorie is the energy required to raise the temperature of 1kg water by 1oC.One food Calorie is actually 1000 calories (1kcal). One food Calorie is equivalent to 4.18kJ.

Students might like to consider what the link is between the energy content of fats and their

metabolism in respiration? Refer to the role of CoA.

A.2.2 Compare the main dietary sources of energy in different ethnic groups.
http://click4biology.info/c4b/3/Chem3.2.htmhttp://click4biology.info/c4b/3/Chem3.2.htmhttp://click4biology.info/c4b/3/Chem3.2.htmhttp://click4biology.info/c4b/3/Chem3.8.htm#sixhttp://click4biology.info/c4b/3/Chem3.8.htm#sixhttp://click4biology.info/c4b/3/Chem3.8.htm#sixhttp://click4biology.info/c4b/6/hum6.1.htmhttp://click4biology.info/c4b/6/hum6.1.htmhttp://click4biology.info/c4b/6/hum6.1.htmhttp://click4biology.info/c4b/6/hum6.1.htmhttp://click4biology.info/c4b/3/Chem3.8.htm#sixhttp://click4biology.info/c4b/3/Chem3.2.htm


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Dietary energy can come from various sources, carbohydrates, proteins or fats, depending on the

foods available to a population. These staples make up the bulk of a populations diet, and aregenerally crops.

This map shows some of the main staple crops around the world

A.2.3 Explain the possible health consequences of diets rich in carbohydrates, fats andproteins.
http://www.topazmaps.com/about/mapsforscience3.htmlhttp://www.topazmaps.com/about/mapsforscience3.html


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A.2.4 Outline the function of the appetite control centre of the brain.

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 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:

1. Food entering the intestine stimulates release of PYY3-36 hormone.2. Carbohydrate and protein digestion stimulate release of insulin hormone from the

pancreas.3. 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.There are strong links to malfunction of any of these pathways and obesity, as the individual eatsmore than is required.


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A.2.5 Calculate body mass index (BMI) from the body mass and height of a person.

e.g. 1: 70kg man, 1.8m tall. BMI = 70 / 1.8 = 21.6

A.2.6 Distinguish, using the body mass index, between being underweight, normalweight, overweight and 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

Examples:


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A.2.7 Outline reasons for increasing rates of clinical obesity in some countries,including availability of cheap high-energy foods, large portion sizes, increasing use ofvehicles for transport, and a change from active to sedentary occupations.

Clinical obesity is an excess of body fat. Generally it is caused by consuming more energythan is used in activity, with the excess stored as body fat.

Obesity carries a reduced life expectancy, high risks of CHD, diabetes, heart attacks andstrokes.

The obesity epidemic is on the increase globally, in developed nations in particular.There are many contributing factors:

A.2.8 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 aest-hetic standards imposed by

culture. It is most common in females, but does occur in males.

Health consequences include:


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http://www.womenshealth.gov/faq/anorexia-nervosa.cfm.


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A.3.1 Distinguish between the composition of human milk and artificial milk used forbottle-feeding babies.

A.3.2 Discuss the benefits of breastfeeding.

A.3.3 Outline the causes and symptoms of type II diabetes.

Diabetes mellitus (type II diabetes) is also known as adult-onset diabetes as it generally manifests in adulthood. Receptorson the liver become resistant to insulin produced by the pancreas, leading to complications with blood sugar control.

Causes:

Obesity, and prolonged intake of high-energy foods can cause the receptors in the liver towear 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 typeII diabetes and should use their family history as an indicator and take preventativemeasures largely a balanced diet and exercise.


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Symptoms:

Glucose in the urine as the kidney is unable to reabsorb all of the glucose back into theblood.

Deyhdration as water-balance is disrupted, coupled with excessive urination. Weight loss as insulin is less able to store fat. Sleep loss and tiredness are also symptoms. Blurred vision and potential blindness.

A.3.4 Explain the dietary advice that should be given to a patient who has developedtype II diabetes.

Type II diabetes can be controlled through careful diet and healthy lifestyle. An obese oroverweight patient would be advised to reduce their weight and exercise more.

A.3.5 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 animalproducts. Concerns arise with regard to ethical treatment of animals and environmentalsustainability.


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A.3.6 Evaluate the benefits of reducing dietary cholesterol in lowering the risk ofcoronary heart disease.

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. Ruptureof plaques can cause clots, or CHD. However, this is a paradigm that is being challenged and ithighlight the correlation-cause argument.

In a review of studies, it has been suggested that the link between dietary cholesterol intake andCHD is not logical, and that the more likely cause of CHD is a diet high in saturated fats. Diets highin saturated fats tend to be high in cholesterol, so there is a correlation without necessarilycausation.


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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 beHDL (not harmful), or LDL (plaque-forming).

Extreme intakes may lead to a greater buildup of LDL in atherosclerosis. Although there is a small

risk of cholesterol leading to CHD, the risks of smoking, inactivity and heredity are much strongerand more closely related to CHD.

Although a cholesterol-controlled diet may slow or reduce the risk of atherosclerosis, it must becombined with a healthy diet and lifestyle if it is to have a significant effect on reducing the risk ofCHD.

A.3.7 Discuss the concept of food miles and the reasons for consumers choosing foodsto minimize food miles.

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 infuel, 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 theconsumer.

Some consumers prefer to choose locally grown or farmed food products to reduce the costs, useof packaging and preservatives, use of oil/fuel and emissions. They may also hope to encourageoutlets to use local providers of produce rather than imported goods.

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