Components of the Human Diet

Components of the Human Diet
Option A: Human Nutrition & Health
Stephen Taylor
Image: 'Banana - Isolated'
http://www.flickr.com/photos/53507547@N06/5129712590
Found on flickrcc.net

Assessment Statements Obj.
A1.1 Define nutrient. 1
List the types of nutrients that are essential in the human diet, including
A1.2 1
amino acids, fatty acids, minerals, vitamins and water.
State that non-essential amino acids can be synthesised in the body from
A1.3 1
other nutrients.
A1.4 Outline the consequences of protein deficiency malnutrition. 3
Explain the cause and consequences of phenylketonuria (PKU) and how
A1.5 3
early diagnosis and a special diet can reduce the consequences.
Outline the variation in the molecular structure of fatty acids, including
A1.6 saturated fatty acids, cis and trans fatty acids, monounsaturated and 2
polyunsaturated fatty acids.
Evaluate the health consequences of diets rich in different types of fatty
A1.7 3
acid.

Command terms: http://i-biology.net/ibdpbio/command-terms/ Assessment statements from: Online IB Biology Subject Guide

Assessment Statements Obj.
Distinguish between minerals and vitamins in terms of their chemical
A1.8 2
nature.
Outline two of the methods that have been used to determine the
A1.9 2
recommended daily intake of vitamin C.
Discuss the amount of vitamin C that an adult should consume per day,
including the level needed to prevent scurvy, claims that higher intakes
A1.10 3
give protection against upper respiratory tract infections and the danger of
rebound malnutrition.
A1.11 List the sources of vitamin D in human diets. 1
Discuss how the risk of vitamin D deficiency from insufficient exposure to
A1.12 sunlight can be balanced against the risk of contracting malignant 3
melanoma.
Explain the benefits of artificial dietary supplementation as a means of
A1.13 3
preventing malnutrition, using iodine as an example.
A1.14 Outline the importance of dietary fibre as a component of a balanced diet. 2

Command terms: http://i-biology.net/ibdpbio/command-terms/ Assessment statements from: Online IB Biology Subject Guide

Nutrients are chemical substances found in
Components of the Human Diet food that are used in the body
Nutrition Information:

Food energy: from carbohydrates, proteins, fats.
Units: food calories (kcal) or kilojoules (1kcal = 4.18kJ)
daily needs vary by individual based on gender, age, size and activity.

Fats (lipids) can be saturated or unsaturated.
Trans fats are particularly unhealthy.

Sodium (salt): keep it low.
Carbohydrates are polymers of sugars (an energy source).
Sugars are absorbed easily into the blood
Dietary fibre (cellulose) cannot be digested (healthy).

Proteins are polymers and sources of amino acids.
They are used to build new proteins in cells.

Vitamins are organic compounds that are essential in small
amounts in the diet.

Minerals are mineral ions (elements) that are also essential.

http://www.wolframalpha.com/input/?i=big+mac+nutrition

Nutrient: a chemical substance found in foods that used in the body.

Essential Nutrients Non-essential Nutrients
Cannot be replaced or Can be replaced or synthesised
synthesised by the body, so must by the body, so are not necessary
be taken in the diet. in the diet.
• Water • Carbohydrates/ sugars (energy could
• Minerals come from proteins or fats)
• Some vitamins • Other minerals and some vitamins
• Some unsaturated fatty acids • Saturated fatty acids
• Some amino acids • Some amino acids.

Dietary fibre is also necessary, though as it is Dietary fibre is also necessary, though as it is
not absorbed it is technically not a nutrient. not absorbed it is technically not a nutrient.

Image: 'La Boqueria'

Protein-deficiency malnutrition
Kwashiorkor: “The disease of the first child
when the second is born.”
Link: NCBI PubMed Health

Caused by a lack of essential amino acids as a result of extremely
low protein intake (such as when breastfeeding ceases for one
child and the diet switches to low-protein sources of energy).
http://www.youtube.com/watch?v=P-POKztF9ns
Essential amino acids are therefore not available to make new
proteins - enzymes, pumps, antibodies – that are necessary for
normal cell function, growth and immunity.

Edema (severe swelling) results as fluids gather in tissues and
cannot be returned to the blood effectively. Growth is severely
stunted and mental development can be impaired.

Risk factors:
• Extreme poverty, overpopulation, large family sizes
• Drought, war, poor infrastructure

http://en.wikipedia.org/wiki/Kwashiorkor

Phenylketonuria (PKU)
Inherited, progressive, degenerative.
Genetics Review
1. Is this disorder autosomal or sex-linked?
•

2. What is a mis-sense base-substitution
mutation?
•

3. What is the chance of a child having PKU if
both parents are asymptomatic carriers?
•

http://en.wikipedia.org/wiki/Phenylketonuria

Genetics Review
1. Is this disorder autosomal or sex-linked?
• Autosomal (chromosome 12)

1. What is a mis-sense base-substitution
mutation?
• One base in the allele has been replaced by
another, resulting in one different amino
acid being used in protein synthesis.

1. What is the chance of a child having PKU if
both parents are asymptomatic carriers?
• 1 in 4


Cause
Autosomal recessive, disease-causing allele:
mis-sense base-substitution mutation on the gene
for the enzyme phenylalanine hydroxylase.

Result
Phenylalanine (Phe) cannot be metabolised into
tyrosine. Phe builds up in the brain, and competes
with other amino-acids related to transport.

Effect
Mental development is retarded.

Detection
Heel-prick (Guthrie test) of newborns to test
concentration of Phe and Phe:Tyr ratio.


Detection
Heel-prick (Guthrie test) of newborns to test
concentration of Phe and Phe:Tyr ratio.
http://youtu.be/2ODyeOBrkao
Treatment
Strict low-Phe diet: no dairy, meat, breastmilk, nuts
or aspartame (artificial sweetener).
Lots of medication.

http://en.wikipedia.org/wiki/Neonatal_heel_prick

There is no cure for PKU.

Genetic counseling would be sought by prospective
parents who suffer from or are suspected carriers of
the disease-causing PKU allele.
http://youtu.be/CEiOYSYhnhY

Fatty Acids CH3(CH2)nCOOH

• High-density energy storage
• Usually solid at room temp • Usually oils at room temp
• Animal products, palm and • Usually plant sources, e.g.
coconut oil olive oil
• High contribution to • Lower contribution to CHD
coronary heart disease (CHD)

Image: 'Ã–l 2'

High-density (efficient) energy storage
Metabolism of fatty acids in cell respiration skips glycolysis.
Coenzyme A* cuts off carbon atoms from the fatty acid in the link
reaction and carries them to the Krebs cycle.

Therefore: longer chains are a greater store of potential energy.

*Coenzymes assist enzymes and are made using vitamins. It’s all connected!

Fatty Acids
Important components of the plasma membrane

http://en.wikipedia.org/wiki/Cell_membrane

Have other diverse functions.

Triglycerides are efficient energy stores.
g fatty acids
l
saturated
y
c
e mono-unsaturated
r
o
poly-unsaturated
l

“Good Cholesterol”: High Density Lipoproteins Lipid Hormones
• Transport triglycerides out of the blood • Steroid hormones, such as
and so reduce the risk of CHD. testosterone and cortisol, are
made using lipids.
“Bad Cholesterol”: Low Density Lipoproteins
• Hormones are chemical
• Raise blood triglyceride levels and blood
messengers.
pressure, increasing risk of CHD.

http://en.wikipedia.org/wiki/Triglyceride

Saturated, mono-unsaturated or poly-unsaturated?
Describe these fatty acids If they’re unsaturated, what’s their omega-number?
Are the unsaturated fatty acids cis- or trans-fats?

O H H H H H H H H H H H

C C C C C C C C C C C C H

HO H H H H H H H H H H H

O H H H H H H H H H H


HO H H H H H H H H H H

H H H H H H H H H H H O
H C C C C C C C C C C C C
H H H H H H H H H OH

Saturated, mono-unsaturated or poly-unsaturated?
Describe these fatty acids If they’re unsaturated, what’s their omega-number?
Are the unsaturated fatty acids cis- or trans-fats?

O H H H H H H H


HO H H H H H H H H H H H

O H H H H H H H H


HO H H H H H H H H H H

H H H H H H H H H H H O
H C C C C C C C C C C C C
H H H H H H H H OH

Should we ban trans fats?
Nutrition Information:

California bans trans fats
http://youtu.be/WHcg_zoo1oc

Doctors demand ban on man-made trans fats:
http://www.guardian.co.uk/society/2010/jan/18/trans-fats-ban-health-faculty

Watch out for trans fats on your food labels (or
search your favourite foods on Wolfram|Alpha).

http://www.wolframalpha.com/input/?i=big+mac+nutrition

Vitamins & Minerals Minerals are elemental ions found in food.

http://tinyurl.com/35d6qyq
Vitamins are complex
organic compounds
(contain C, H and O).
Some can be made by
the body, but others are
essential in the diet.

http://en.wikipedia.org/wiki/Vitamin_C

http://whqlibdoc.who.int/publications/2004/9241546123.pdf

http://www.youtube.com/watch?v=dcw1m31zuTE

Understanding Vitamin D

http://highered.mcgraw-
hill.com/sites/0072507470/student_view0/chapter25/animation_ http://www.youtube.com/watch?v=onSPZ0aBUKM
_b_vitamins.html

http://www.mja.com.au/public/issues/175_05_030901/grover/grover.html

http://whqlibdoc.who.int/publications/2004/9241546123_chap7.pdf

http://www.ted.com/talks/michael_specter_the_danger_of_science_denial.html

Image: 'Banana - Isolated'

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