Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Be smart!
Should I believe all that the advertisements say?
Teacher’s Version (with video exemplars)
NOS/STSE Features
1. Science is based on skepticism.
2. Scientists should be open-minded.
3. Scientific knowledge is tentative.
4. Ethical considerations are always important in
scientific research.
You can click an icon like this
to access the activities in this package.
You can click an icon like this
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You can click an icon like this
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Table of Contents
Introduction
(i)
Activity 1: Do you require a high protein diet?
P.1
Activity 2: How much protein does a food product contain?
P.4
Activity 3: Incredible food: Soy (soya) Protein - What does the
advertisement say?
P.8
Appendix 1: Advertisements for extension activity
P.12
Appendix 2: Lesson Plan
P.19
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Introduction
Rationale
More and more health food products are available in the market. Yet there have been few
regulations on the claims of their advertisements. How can people analyze these claims? And
how can people decide whether they need the health food products? The package uses
protein-rich health food products as examples to incorporate students’ scientific knowledge
into daily life. Students can also learn the tentative nature of scientific knowledge and how to
choose a suitable test for a scientific investigation.
Level of study
Number of lessons
Form 3 – Form 7
4 lessons (each lesson 35-40 minutes)
Contents
1. Applying scientific knowledge in reading advertisements
2. Measuring protein content in food products
3. Analyzing claims in advertisements
Teaching package includes
1. Worksheets (Teacher’s Version and Student’s Version)
2. A Teaching PowerPoint
(i)
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Activity 1
Do you require a high protein diet?
What kind of diet do you need?
Notes: Students may be asked for examples of well known
athletes or movie stars such as Lee Lai Shan, Guo Jingjing,
Jackie Chan, to discuss the dietary requirement of different
people. Also to brainstorm different kinds of occupations,
and how they differ in terms of dietary requirement.
Do you require protein supplements? There are many protein
products on the market. Below are the advertisements for two of them:
Notes: Students may be divided into groups. Half of the groups read Ad 1 and
answer Q1-3. Others read Ad 2 and answer Q1, 2 and 4.
Ad 1
Source﹕Volleyball Association
of Hong Kong, China
“… the most useful protein supplement ever, it enlarges
every muscle that you want it to… contains the best
quality nutrients, it facilitates protein uptake after
exercise and improves muscle strength, you will
certainly love it ”
Ad 2
Remarks: The two advertisments are real advertisements found on the internet. Teachers can
show the following websites for students to read the advertsiements.
Ad 1: http://www.owbfitness.com/ (This ad is no longer exist in 2007 but similar products can be
found in the website)
(N.B. The English version of the website is greatly different from the Chinese version.
Teacher can discuss why the Chinese version is very different from the English one. This is
probably due to the differences in regulatory control of claims on nutritional functions in
different countries.)
Ad 2: http://www.fancl-hk.com/products/foods/essential/5008.asp (Last visited: 23/5/2006)
P.1
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Q1 Which kinds of people may need the products?
People who require a lot of protein (e.g. pregnant woman, children, strength
athletes, bodybuilders) may need the products.
Remarks: Strength athletes e.g. weightlifting athletes, shot putters who need to
gain muscle size will require more proteins than other athletes e.g. runners.
Q2 Why is protein so important to our bodies?
Protein provides materials for growth and repairs.
It acts as an energy reserve.
Enzymes and hormones for regulation of body functions are made of protein.
It is one of the components of cell membranes and cytoplasm.
Some important biomolecules e.g. haemoglobin, and antibodies are partly protiens
(The answers may vary with students’ level of knowledge.)
Q3 Those people who want to add volume to their muscles (get larger muscles)
usually eat a high-protein diet or consume protein supplements like the one
in Ad 1. Can all protein consumed be stored in the body for muscle
building? Are there any other factors that could contribute to increasing
muscle size?
No. Excess protein cannot be stored.
Amount and duration of exercise contribute in increasing muscle size. People must exercise to
strengthen the muscles and provide better heart health and blood supply. (The amino acids are
added to muscle fibres as part of the repair processes following exercise – all exercise does
some muscle damage, but in training, this is a good thing if not taken too far!!)
Genetic factors, diet, rest, etc. are also factors that affect the muscle size of a person.
Additional information: After birth, the number of muscle fibres cannot increase. One cannot
make muscle more effective just by making it bigger. The increase in muscle size is due to the
increase in the size of each muscle cell and due to more development of blood vessels to
oxygenate the cells and take away waste more efficiently. An athlete requires more protein
mainly for the repair of muscle cells.
Notes: Teacher can link this part to the NSS Science curriculum “science in a sprint”. Teacher
can mention “fast & slow twitch” muscles if there are athletes among the students.
Reference: Muscle fibres are classified into different types including fast and slow twitch muscle
fibres. Fast twitch muscle fibres (快縮肌纖維)contract quickly but get tired rapidly. Slow twitch
muscle (慢縮肌纖維) fibres contract slowly but can remain contracted for a longer period.
Athletes participating in different sports may have different proportions of fast and slow twitch
muscle fibres.
http://www.hksports.net/hkpe2000/human_body/anatomy/muscular/fiber_type.htm (Chinese)
http://www.bbc.co.uk/science/humanbody/body/factfiles/fastandslowtwitch/soleus.shtml(English)
P.2
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Q4 Some protein supplements like the product in Ad2 target at vegetarians.
Do you think vegetarians especially need the product or other protein
supplements? Explain.
Vegetarians do not necessarily need to consume the products.
Proteins are made up of amino acids. Our bodies manufacture proteins according to the base
sequences of DNA by using amino acids. We cannot produce some proteins if we lack certain
amino acids. We can produce most of our own amino acids while some “essential” amino acids
have to be consumed. Meat, fish and eggs can provide all these essential amino acids but some
plant foods cannot. However, by mixing different kinds of plant foods, even vegetarians can get
all the amino acids they required.
Remarks: Most vegetarians do eat milk and eggs. Only those called vegans (嚴守素食主義的人)
must ensure that they can get enough essential amino acids. Vegans do not eat any animal
products.
Reference:
http://www.bbc.co.uk/health/healthy_living/nutrition/basics_protein.shtml#types_of_protein
(Last visited: 23/5/2006)
P.3
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Activity 2
How much protein does a food product contain?
From activity 1, we learnt that some people do require more protein in their diet for various
reasons. However, news reports on health problems caused by low-quality milk are not
uncommon. So, even though you are sure that you need protein supplements, you have to
make sure that the products contain the right amount of proteins that you are looking for.
Imagine that you have just bought a milk product. You want to check if the milk product
contains the same amount of protein as specified on its food label.
Notes: Teacher may ask students to bring their own food products which they think are
protein-rich.
Below are two methods for testing protein. Read the information carefully and choose one
which is best suited for the above purpose. Explain your choice. (If necessary, your
teacher may describe the methods to you in greater detail using the PowerPoint slides.)
General
information
Detection limit
P.4
Biuret test
Albustix paper
(PowerPoint slide 10)
(PowerPoint slide 13)
Biuret reagent is a blue solution.
It reacts with protein to give a
purple solution. The intensity of
the purple colour is proportional
Albustix paper is used for testing
the presence of protein in urine.
The paper contains an indicator
dye. At a constant pH, protein
to the protein concentration.
reacts with the dye giving a
green-blue colour. The colour is
proportional to the concentration
of protein.
0.2 – 50 µg
0.15 - 20 g/L
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Testing procedure
Biuret test
Albustix paper
1. Prepare a set of standard
solutions (0, 2, 4, 6, 8 mg/ml)
by using bovine (cattle) serum
albumin.
2. Pipette 1 ml standard solution (8
mg/ml) to a test-tube containing
2 ml Biuret solution.
3. Repeat the above step for the
1. Dip the Albustix paper into a
solution of the test sample.
2. Remove excess liquid from the
test paper.
3. Wait for 60 seconds for the test
paper to dry
4. Match the colour of the test
paper with those on the standard
rest of the standard solutions
colour chart found on the bottle.
and the test sample.
5. Protein concentration of the
4. Mix the contents inside each of
sample is estimated by
the tubes well. Wait for 15
comparing the colour of the
minutes.
paper with the colour chart
5. The intensity of the purple
provided on the bottle of
colour of the contents inside
Albustix paper.
each of the tubes is determined
by measuring the amount of
light transmitted through the
solution using a colorimeter.
6. A standard curve is plotted with Remarks: Alkaline food products
may give a false-positive result with
light transmittance versus
the Albustix paper.
concentration of protein.
7. Protein concentration of the test
sample can then be determined
from the standard curve after
obtaining the light transmittance
value from the calorimeter.
Limitations
P.5
It is only applicable to soluble
The Albustix test is only a
proteins and colourless solution.
semi-quantitative method. The
result is only an estimated value
since the colour chart provides
only the test results of certain
protein
concentrations.
The
concentration between two values
cannot be measured.
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Discuss the criteria for a scientist to choose a test method.
Criteria for choosing a test method:
1) Will it work for the particular food product;
2) Accuracy in relation to the purpose;
3) Cost
(Notes: This question may be answered by a whole class discussion.)
Which test will you choose to estimate the protein content in the milk product? Explain your
choice below.
Albustix test is advised. Biuret solution is not applicable to the milky solution. Besides, there is
no need to use such a sensitive test as the Biuret test for estimating protein content in milk.
Scientists do not always choose the most accurate test. Requirement of accuracy is
different from one test to another. (For example, we use a 4-digit balance to weigh
chemicals but not our body weight). A perfect assay never exists. We may choose one test
over another because of ease but sometimes the choice is dictated by specific scientific
limitations or cost.
Science-Technology-Society
Albustix paper is used for testing the presence of protein in
urine. Normally, urine contains no protein but kidney diseases
may result in the presence of protein in urine. The invention of
the Albustix paper has provided a convenient assay for doctors
to measure protein in urine. People can even perform the test at
home. So, science and technology are affecting our lives!
Science is ever improving
Scientists have developed many methods to determine
protein concentration accurately e.g. the Kjeldahl method,
and the Bradford Assay. Scientists often try to improve their
methods of investigation. They improve or develop new
techniques to get more reliable and accurate results.
P.6
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Having decided on which test you will be using to estimate the protein content of the milk
product, now work out the detailed procedure in the space below to show how you are going
to estimate if the milk product contains the same amount of proteins as specified on its food
label. (Hint: Dilution of the milk product may be required.)
(Notes: Students may require guidance in the dilution of sample and the calculation of the
protein content. In the biuret test, dilute the sample by ten times if the sample exceeds the
highest concentration of standards.)
Now, try to estimate the protein content in the milk product! Is it the same as stated in the
food label?
Notes: Teacher may link up Activity 2 with Activity 3 by saying that, “In Hong Kong, there is a
food label ordinance governing the accuracy of information on nutritional contents of the food
products. The claims made on the food label are likely to be true. However, there is no similar
legislation governing the claims made in advertisements of food products. This is especially a
problem for those claimed to be ‘health foods’.
Notes: Lower vitamin C content than claimed was found in Ribena in Australia, a popular drink
worldwide. Teacher may use PowerPoint slides 21-23 to discuss the issue with students.
P.7
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Activity 3
Incredible food: Soy (soya) Protein - What does the
advertisement say?
Soya has been one of the most popular foods in Asia (China and Japan) and is said to be a
good protein source for vegetarians. The proteins in Soya have been investigated for many
years for benefits to health apart from muscle building. Recently, a new food supplement
made from Soya has been produced. Advertisements in a local newspaper are shown below.
(The brand name is covered.)
Optional exercise:
People talk about different kinds of cholesterols. Do you know about them? Are all
cholesterols bad? Find it out from the following website!
http://www.bbc.co.uk/health/conditions/cholesterol1.shtml (English)(Last visited on 2/3/2006)
http://www.healthcare2u.com/cd_chole.html (Chinese) (Last visited on 2/3/2006)
Cholesterol is a kind of lipid molecule which is an important part of cell membranes as well
as the precursor of steroid hormones e.g. sex hormones.
P.8
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Let’s take a look into the suggestions by U.S. Food and Drug Administration (FDA)
about soy protein!
Remarks: The original FDA statement about soy protein:
http://www.cfsan.fda.gov/~lrd/tpsoypr2.html (Last visited on 2/3/2006)
The Soy Health Claim – 1999
In October 1999, FDA approved a health claim that can be used on labels of soy-based 1
foods to support their healthy-heart benefits. The agency reviewed research from 27
studies that showed soy protein's value in lowering levels of total cholesterol and
low-density lipoprotein (LDL, or "bad" cholesterol).
Food marketers can now use the following claim, or a reasonable variation, on their 5
products: "Diets low in saturated fat and cholesterol that include 25 grams of soy
protein a day may reduce the risk of heart disease.”
Foods made with the whole soybean, such as tofu, may qualify for the claim if they
have no fat other than that present naturally in the whole bean.
Q1 Does the FDA allow the health claims made in the advertisement for the product?
The FDA only approved the health claim about lowering the risk of heart diseases but not
others.
Is soy protein so
Q2 What evidence did the FDA use to decide on approving
incredible?
the health claim?
Reviewed a large number of research papers.
Now, look at the following statement about the effects of soy protein.
Soy protein shows little effect on "bad" cholesterol - 2006
News
Soy protein in the diet or from nutritional supplements has little or no effect on the risk
factors for heart disease, according to a new American Heart Association scientific
1
statement published in 2006.
After analyzing 22 studies, it is found that large amounts of soy protein in the diet
reduced low-density lipoproteins (LDL) or “bad cholesterol” by only 3 percent and had
no effect on high-density lipoproteins (HDL), or “good cholesterol”, no effect on
lipoprotein or blood pressure.
In a statement released in the year 2000, adding soy protein to a diet low in saturated fat
and cholesterol was recommended. However, the statement is re-evaluated after the
recent, well-controlled studies, noted above were added to the knowledge base.
P.9
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
5
10
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Q3 Compare the statements made by the FDA and the American Heart Association. Why has
the knowledge about the health effects of soy protein been re-evaluated?
Scientists gather new evidence / knowledge from well-controlled studies becomes available.
Q4 This kind of change is common in the scientific world. Can you name another scientific
knowledge/theory that has ever changed?
Yes.
Examples of change in scientific knowledge:
- Evolution theory, identification about the nature of the pathogen causing SARS
(Paramyxovirus, Coronavirus)
- Evidence about cause of stomach ulcer
Scientists should keep an open mind and can modify their views when new
evidence comes along. Scientists usually evaluate old evidence in light of the new
ones.
Q5 Soy is regarded as a healthier source of protein than meat since it contains little or no
cholesterol. But are there any drawbacks from eating so much soy? Think!
Students should be encouraged to express different views. Students can be allowed to search for
information.
Examples of drawbacks:
-
Some soya bean varieties are genetically modified so their long-term effects on human
health is unknown (relating to GM, not to the protein)
-
There are some chemicals in the soya bean (e.g.
isoflavones) that may have bad health effects for
certain people.
Scientists should keep an open mind until there is enough evidence to
make decisions.
Remarks: Isoflavones are a group of chemicals whose chemical structures are similar to
estrogen. Some scientists have suggested that isoflavones might help in preventing cancers but
there is also indirect evidence showing that isoflavones may promote growth of certain cancer
cells. The studies concerning the risks and health effects of isoflavones are not well established.
P.10
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Extension activity: Are advertisements about food products always true?
Many health products, just as that in activity 3, have made a number of health claims. Are
they really true? How can you verify the claims?
Remarks: Advertisements of some other health products are provided for students. A copy of the
advertisements with additional information is attached in Appendix 1.
You are scientists working for the Consumer Council. Your task is to design an investigation
to assess the health claims made by the products. Present the design of your investigation to
the class. In your presentation, include possible problems and limitations of the design.
(Technical procedures are not required.)
Include ethical considerations in your design. How do scientists overcome such concerns?
Notes: Teachers may guide students to think about the problems of animal/human testing and
ask them to search for alternatives to animal test such as tissue culture.
Scientists should act ethically.
Summary of the lesson
P.11
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Appendix 1: Advertisements for extension activity
Extension activity: Are advertisements about food products always true?
Advertisement for a vitamin C product (Brand name is covered.)
You may include the following questions in your discussion.
1. What is vitamin C? What are its functions in the body?
Vitamin C is a weak acid, also known ascorbic acid. It is essential in preventing scurvy
in humans and to maintain the health of teeth and gums.
2.
What are the claims in the advertisement?
The product can help in improving immunity, reducing the severity of colds. The
product can release vitamin C bit by bit slowly over an 8-hour period so as to avoid
damaging the stomach.
3.
Are the claims valid based on your knowledge?
Vitamin C will not damage the stomach.
4.
P.12
How to test the effect of the product on health?
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Advertisement for a sliming product (Brand name is covered.)
You may include the following questions in your discussion.
1. What is chitosan?
Chitosan (蟹殼素/殼聚糖) is a
Chitosan is a polysaccharide produced commercially
from chitin, the protein making up the hard shells
(exoskeletons) of crustaceans and insects.
polysaccharide produced
commercially from chitin which
comprises the exoskeleton of
crustaceans (e.g.crabs and shrimp).
2. What are the claims in the advertisement?
The product can absorb fats and expel the fats out from the body.
People will not absorb any fats from meal after using the product.
3. How to test the effect of the product on health?
P.13
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe
all the advertisement say?
Advertisement for a collagen product (Brand name is covered.)
You may include the following questions in your discussion.
1. What is collagen (膠原蛋白)? What are its functions in the body?
Collagen is a protein which is the main component of connective tissues such as
ligaments and cartilage.
(Notes: For lower form students, teacher may explain what collagen is before any
discussions.)
2.
What are the claims in the advertisement?
By drinking the product, people can improve their skin quality.
3.
Are the claims valid based on your knowledge?
Collagen will be digested into amino acids in the body. New collagen can only be
synthesized from amino acids available according to the genetic code in their DNA.
4.
P.14
How to test the effect of the product on health?
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe all the advertisement say?
Appendix 2: Lesson Plan
Activity 1: Do you require a high protein diet?
Time
15 min
Intended Learning Outcomes
Students should be able to


Identify the protein requirement
of different people


State the importance of protein
to the body



Teaching Flow
Students discuss the dietary requirement of people
with different occupations.
Students read the advertisements on the internet /
worksheet
Students discuss the people who need the products
most and answer Q1 to Q2.
Students discuss the factors contributing to the
increase in muscle size (Q3).
Students discuss the claims in Ad2 and discuss
whether a vegetarian needs protein supplements.


Materials
Activity 1
worksheet
PowerPoint
Slides 2 - 8
Remarks
The Chinese and
English version of
the website showing
health food products
may be different. In
the English version,
not many claims are
made. Teacher may
discuss this
difference
phenomenon with
students.
Teacher may
emphasize the point
that what students
learn in science can
easily apply into
daily life and it
would help them to
make decisions (e.g.
the principle of
getting larger
muscles)
P.19
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe all the advertisement say?
Activity 2: How much protein do the food products contain?
Time
70 min
Intended Learning Outcomes
Students should be able to

describe the criteria for
choosing a specific test for
scientific investigation

point out that there is no perfect
test

point out that scientists do not
necessarily always choose the
most sensitive test but one
which can serve the intended
purpose, and at the same time is
more convenient and/or less
costly








Teaching Flow
Students are given food products with nutrition

labels. (Or students can bring the products from
home)

Teacher introduces Biuret test and Albustix test.
Students discuss the choice of test.
Students work out their plan of investigation using
Albustix test for testing protein.
Teachers may guide students by the following

questions:
Q: How to measure its protein concentration if the 
sample is in solid form?
Q: How to prepare the food samples if they exceed
the detection limits?
Students perform the test.
Teacher asks students whether their results are
consistent with the protein concentration claimed for
the products.
Teacher points out that there is no perfect test and
scientists do not necessarily always choose the
most accurate test but also take into consideration
other factors like cost and ease of administration
Materials
Activity 2
worksheet
Materials for
the
investigation
(stated in
Appendix 2)
PowerPoint
Slide 9 - 20
PowerPoint
Slide 21-24
(Ribena
vitamin C
content was
lower than that
claimed)
Remarks
The protein test in
this activity is not an
experiment, but a
kind of measurement
called an “assay”.
Students are
expected to find out
that Biuret test
cannot measure the
protein concentration
in this case since the
colour of the milk
will interfere with
the colour of the
Biuret reagent.
Teacher may discuss the issue of improper food
labelling by using the case of Ribena vitamin C content.
P.20
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe all the advertisement say?
Activity 3: Incredible food: Soy (soya) Protein - What does the advertisement say?
Time
15 min
Intended Learning Outcomes
Students should be able to

point out that scientists review
evidence to justify a claim.

point out that scientific
knowledge is subject to
changes and scientists usually
evaluate old evidence in light
of new ones.







P.21
Teaching Flow
Students read the advertisement of the soy protein 
product.
Students identify the health effect of soy protein in 
the advertisement.
Students read the FDA’s suggestions about soy
protein.
Students discuss how the FDA approved the claim
of soy protein. Emphasis is put on how scientists
justify the validity of certain claims.
Students read the statement of the American Heart
Association and compare the two statements.
Students discuss the reasons for the changes of
scientific knowledge. They are encouraged to give
examples of other changes in well-known scientific
knowledge.
Students can discuss the drawbacks from eating too
much soy.
Materials
Activity 3
worksheet
PowerPoint
Slide 24 - 29
Remarks
Teacher may explain
the difference
between LDL and
HDL cholesterol to
students.
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.
Senior Form Biology – Be smart! Should I believe all the advertisement say?
Extension Activity: Are advertisements about food products always true?
Time
35 min
P.22
Intended Learning Outcomes
Students should be able to

apply their scientific
knowledge in analyzing claims
in different products

be aware that ethical problems
may be involved in scientific
investigations




Teaching Flow
Students are divided into groups and each group is
given an advertisement of a health product.
Students discuss the validity of the claims on the
advertisement based on their scientific knowledge.
Students design a test to verify the claims on the
health product.
Students present their design to the class. Teacher
may discuss the ethical problems in their design.



Materials
Remarks
Extension
activity
worksheet
Advertisement
of food
products
PowerPoint
Emphasis can be put
30-32
on the fact that
students should not
believe all claims of
the advertisements
but should try to
verify the claims
based on scientific
evidence.
©2007 The University of Hong Kong – Faculty of Education. All rights reserved.