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D1 Human Nutrition

A balanced diet is essential to human health

Essential idea:

D1 Human Nutrition

Understandings

D1 Human Nutrition

Applications and Skills

D1 Human Nutrition

Do Now

The relative energy content of carbohydrates, proteins and fats are as follows:

Carbohydrates – 1,760 kJ per 100 grams;

Proteins – 1,720 kJ per 100 grams

Fats – 4,000 kJ per 100 grams

D1 Human Nutrition

Comparing Energy Content

D.1 S1 Determination of the energy content of food by combustion

Energy (joules) = Mass of water (g) × 4.2 (J/gºC) × Temperature increase (ºC)

Measure exact amount of water (5ml)

Measure exact amount of food (5g)

Measure exact amount of water (1ml)

Measure exact amount of food (1g)

• Energy content is the amount of heat produced by the burning of 1 gram of a substance, and is measured in joules per gram (J/g).
• where H = heat energy (in J), Δt = change in temperature (in °C), m = mass (in g), and Cp = specific heat capacity (4.18 J/g°C for water).
• Dividing the resulting energy value by grams of food burned gives the energy content (in J/g).
• The biggest source of error in calorimetry is usually caused by the unwanted loss of heat to the surrounding environment
• The food sources should be burnt at a constant distance from the water to ensure reliability of results
• The initial temperature and volume of water should also be kept constant (1 g of water = 1 cm³ or 1 ml)

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D1 Human Nutrition

D.1 S1 Determination of the energy content of food by combustion

Molecules that cannot be synthesised by the human body and must be consumed in the diet are known as essential nutrients. They include:

• essential amino acids
• essential fatty acids
• minerals
• most vitamins

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D1 Human Nutrition

Define ‘essential’ as related to dietary nutrients

D.1.U1 Essential nutrients cannot be synthesised by the body, therefore they have to be included in the diet

Glucose, starch and other carbohydrates are all non-essential because they are used in respiration and lipids can be used instead.

• Conditionally non-essential amino acids, are a group of amino acids that the human body can typically synthesize on its own under normal circumstances.
• Eg. arginine, cysteine, glutamine, tyrosine, glycine, proline, serine, and ornithine

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D1 Human Nutrition

Define ‘essential’ as related to dietary nutrients

D.1.U1 Essential nutrients cannot be synthesised by the body, therefore they have to be included in the diet

D1 Human Nutrition

D.1.U4 Some fatty acids and some amino acids are essential.

D.1.U5 Lack of essential amino acids affects the production of proteins.

A shortage of one or more essential amino acids in the diet will prevent the production of specific proteins. This is known as protein deficiency malnutrition and the health effects will vary depending on the amino acid shortage

 usually not essential, except in times of illness and stress.

It can be caused by an improper dietary intake of nutrients – e.g. overnutrition (too much) or undernutrition (not enough)

It can be caused by the inadequate utilisation of nutrients by the body – e.g. due to illness or disease

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D1 Human Nutrition

Outline two causes of malnutrition.

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D.1.U6 Malnutrition may be caused by a deficiency, imbalance or excess of nutrients in the diet

Stunting

Wasting

Obesity

D1 Human Nutrition

State the difference between a vitamin and a mineral.

D.1.U3 Vitamins are chemically diverse carbon compounds that cannot be synthesised by the body.

Dietary minerals are chemical elements required in small quantities as essential nutrients by organisms. Usually ionic in nature.

Minerals present in common organic molecules are not considered essential – e.g. C, H, O, N, S

Minerals include calcium (Ca), magnesium (Mg), iron (Fe), phosphorus (P), sodium (Na), potassium (K) and chlorine (Cl)

D1 Human Nutrition

State the difference between a vitamin and a mineral.

D.1.U3 Vitamins are chemically diverse carbon compounds that cannot be synthesised by the body.

Vitamins are essential organic molecules with complex chemical structures that are quite diverse and hence categorised by groups

Water soluble vitamins need to be constantly consumed as any excess is lost in urine (e.g. vitamins B, C).

Fat soluble vitamins can be stored within the body (e.g. vitamins A, D, E, K). Vit A is hydrophobic, contains a hydrocarbon ring and chain.

The functions of vitamins are as diverse as their structure, although many function as cofactors, antioxidants or hormones.

Many vitamins are essential as they cannot be synthesised by the body and their absence may cause a deficiency disease

D1 Human Nutrition

Compare the properties of water soluble and fat-soluble vitamins.

• potent antioxidant and also plays an important role in immune function
• is also involved in the synthesis of collagen (a structural protein) and in the synthesis of lipoproteins
• Helps in wound healing
• Ascorbic acid is made internally by most mammals from monosaccharides – but it is not produced by humans
• scurvy and a general weakening of normal immune function
• include citrus fruits and orange juice.

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D1 Human Nutrition

Ascorbic acid is a form of vitamin C that is required for a range of metabolic activities in all animals and plants

D.1. A1 Production of ascorbic acid by some mammals, but not others that need a dietary supply.

D1 Human Nutrition

Ascorbic acid is a form of vitamin C that is required for a range of metabolic activities in all animals and plants

D.1. A1 Production of ascorbic acid by some mammals, but not others that need a dietary supply.

D1 Human Nutrition

Ascorbic acid is a form of vitamin C that is required for a range of metabolic activities in all animals and plants

D.1. A1 Production of ascorbic acid by some mammals, but not others that need a dietary supply.

Vitamin D is involved in the absorption of calcium and phosphorus by the body – which contribute to bone mineralisation�

This can lead to the onset of diseases such as osteomalacia (where bones soften) or rickets (where bones are deformed)

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D1 Human Nutrition

D.1.A3 Lack of Vitamin D or calcium can affect bone mineralization and cause rickets or osteomalacia

What? Where? How?

Why?

https://quizizz.com/admin/quiz/6385956ddf979b001eec8529?source=quiz_share

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D1 Human Nutrition

D.1.A3 Lack of Vitamin D or calcium can affect bone mineralization and cause rickets or osteomalacia

D.1.U3 Dietary minerals are essential chemical elements

Magnesium is an important component of chlorophyll (required for photosynthesis)

Potassium is an inorganic salt found within the sap of a plant (maintains water potential)

D1 Human Nutrition

Minerals in Plant Development

D.1.U3 Dietary minerals are essential chemical elements

It is an autosomal recessive disease caused by a mutation to the gene encoding the enzyme phenylalanine hydroxylase

Phenylalanine hydroxylase (PAH) normally converts excess phenylalanine within the body into tyrosine

In people with PKU, the excess phenylalanine is instead converted into phenylpyruvate (also known as phenylketone)

This results in a toxic build up of phenylketone in the blood and urine (hence phenylketonuria)

�Untreated PKU can lead to brain damage and mental retardation, as well as other serious medical problems

Infants with PKU are normal at birth because the mother is able to break down phenylalanine during pregnancy

Diagnosis of PKU is made by a simple blood test for elevated phenylalanine levels shortly after birth

D1 Human Nutrition

Phenylketonuria (PKU) is a genetic condition that results in the impaired metabolism of the amino acid phenylalanine

D.1.A2 Cause and treatment of phenylketonuria (PKU)

The body takes in phenylalanine from the digestion of protein in the gut.

�PKU is treated by enforcing a strict diet that restricts the intake of phenylalanine to prevent its build up within the body

This low-protein diet should include certain types of fruits, grains, vegetables and special formula milk

This diet should be supplemented with a medical formula that contains precise quantities of essential amino acids

Patients who are diagnosed early and maintain this strict diet can have a normal life span without damaging symptoms

Screening for PKU

All babies born in the UK and other developed countries are routinely screened for high phenylalanine levels.

This is done using the heel prick test and is carried

out during the first week of a baby’s life (within 24

hours).

During the test, a blood sample is taken from the

baby’s heel to test for a number of rare but serious

conditions, including PKU.

D1 Human Nutrition

There is evidence to suggest dietary deficiencies of these fatty acids may be linked to impaired brain development (e.g. depression) and altered maintenance of cardiac tissue (e.g. abnormal heart function) and eye development – although this evidence is contested

�Foods rich in essential fatty acids (omega-3 and omega-6) include fish, leafy vegetables and walnuts�

D1 Human Nutrition

D.1.U4 Some fatty acids and some amino acids are essential.

Coronary Heart Disease

Arteries supplying the heart become narrowed and the blood supply to cardiac tissues is reduced

Heart has to work harder to force blood through narrowed vessels / blood pressure increases

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Angina

Chest pain due to severe shortage of blood to the heart muscle - cells do not die

Pain only occurs during activity but not at rest

Caused by narrowing of coronary arteries (atherosclerosis)

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Heart attack (myocardial infarction)

When a coronary artery is totally blocked by a thrombus/embolus

No blood supply to heart muscle and cells die - often fatal

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Heart failure

Blockage leads to damage of heart muscle and to gradual weakening of muscle

Less efficient pumping

Often accumulation of blood on right side → enlargement of heart

D1 Human Nutrition

D.1.A5 Cholesterol in blood as an indicator of the risk of coronary heart disease

Fats and cholesterol cannot dissolve in the bloodstream and so are packaged with proteins (to form lipoproteins) for transport

Low density lipoproteins (LDLs) carry cholesterol from the liver to the body (hence raise blood cholesterol levels)

High density lipoproteins (HDLs) carry excess cholesterol back to the liver for disposal (hence lower blood cholesterol levels)

The mix of fatty acids consumed as part of a diet directly influences the levels of cholesterol in the bloodstream:

Saturated fats increase LDL levels within the body, raising blood cholesterol levels 

Trans fats increase LDL levels and lower HDL levels, significantly raising blood cholesterol levels

Cis-polyunsaturated fats raise HDL levels, lowering blood cholesterol levels��High cholesterol levels in the bloodstream lead to the hardening and narrowing of arteries (atherosclerosis). When there are high levels of LDL in the bloodstream, the LDL particles will form deposits in the walls of the arteries

The accumulation of fat within the arterial wall leads to the development of plaques which restrict blood flow. If coronary arteries become blocked, coronary heart disease (CHD) will result – this includes heart attacks and strokes

D1 Human Nutrition

D.1.A5 Cholesterol in blood as an indicator of the risk of coronary heart disease

• Cholesterol has important functions and is needed for
• Vitamin D production in skin
• Sex hormone production in gonads and adrenal glands
• Making cell membranes
• Make bile acid (salts)
• Cholesterol is transported in the blood from the liver (where it is synthesized) to the tissues
• Safe transport is needed due to its insolubility
• This is achieved by lipoproteins, which are soluble fatty proteins
• These are wrapped around the cholesterol
• Usually, only small amounts of free cholesterol escape
• Fatty streaks adhere to wall of arteries - /plaque forms Atheroma/atherosclerosis(hardening of the arteries)
• Narrows lumen of artery
• Damages endothelium
• Can lead to formation of thrombus/blood clot

D1 Human Nutrition

D.1.A5 Cholesterol in blood as an indicator of the risk of coronary heart disease

D1 Human Nutrition

D1 Human Nutrition

• The heart may also develop dangerous arrhythmias and become physically diminished in size
• Electrolyte imbalance – concentrations of calcium, potassium and sodium are affected.
• Skeletal muscle mass reduces faster than cardiac mass
• Both these muscles do not contract normally.

D1 Human Nutrition

Symptoms of anorexia

D.1.A4 Breakdown of heart muscle due to anorexia

The recommended daily intake for a nutrient (RDI) is the daily dietary level required to meet the requirements of health

It is an estimate only and will vary according to age, gender, activity levels and medical conditions

The recommendations are based on a daily energy intake of 8400 kJ (2000 kcal) for healthy adults

On food packages, this information is usually presented as a percentage of a daily total (based on identified serving size)

Recommended Daily Intake (RDI)

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Dietary intake can be recorded and compared against levels of energy expenditure in order to monitor weight change

There are a variety of online databases and software programs that can be used to calculate dietary intake and expenditure

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D1 Human Nutrition

D.1 S2 Use of databases of nutritional content of foods and software to calculate intakes of essential nutrients from a daily diet