124567
The Association of Danish Biologist, FaDB
Claudia Girnth-Diamba and Dorte Hammelev
Lyngbyvej 32B, 6.mf, 2100 Copenhagen O
Email: [email protected]
Six a day
How much fruit and vegetables do you eat per day on average?
Aim
• To investigate how much fruit and vegetable students eat per day.
• To discuss the investigation method.
• To put the results into perspective focusing on what recent research
has discovered about antioxidants in fruit and vegetables in contrast to
antioxidants in pills.
Laura H. Hammelev and her fruit and vegetables.
Photo: Jan Herrstedt
1. Edition
October 2007
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Copyright © C. Girnth and D. Hammelev
The Association of Danish Biologist, FaDB
Six a day
Introduction
Healthy eating is a subject of big concern for the
authorities that care for people’s health. Lots of
ordinary people and especially young students of 16 –
19 care too. It is therefore a popular subject for pupils in
Danish schools and six form colleges. The latest Danish
advice on a healthy daily diet is formulated as follows:
• Fruit and vegetables - 6 pieces per day
(equivalent to 600 gram on average, ed.)
• Eat fish and fish products - several times a week
• Eat potatoes, rice or pasta, wholemeal bread
- every day
• Limit intake of sugar - particularly from soft
drinks, confectionary and cakes
• Eat less fat - particularly fat from meat and dairy
products
• Eat a varied diet - and maintain a healthy body
weight
• Drink water when you are thirsty
• Engage in physical activity - at least 30 minutes
per day
The Danish Nutrition Council
Why do we have to eat 600 gram of fresh or ccoked
fruit and vegetable every day?
We don’t know precisely, but the Danish Nutrition
Council has some interesting information on special
compounds in fruit and vegetables. Among these
are the water soluble vitamins, antioxidants, fibres
and other anti-cancer compounds. Antioxidants
are important because they work against the free
radicals that are produced when the metabolism
of the foodstuffs starts. However we do not know
the full consequences of the metabolic breakdown
of nutrients and it is even possible that eating too
much fruit and vegetables could have a negative
effect on metabolism. Fibres and their anti-cancer
effect is investigated in another unit on HUSK.
Here are some examples from certain
vegetables. Carrots are eaten all over the world and
are well known for the health giving compounds
they contain, like beta-carotene which is a precursor
for vitamin A and others. Carrots also contain
antioxidants. The carrot is closely related to Ginseng,
known for many years for its healthy effect though
we did not know the cause. A recent study has
shown that both roots contain poly-acetylenes,
which are known anti-cancer agents. However both
beta-carotene and poly-acetylenes are poisonous
in too high concentration. A special compound in
broccoli (glucosinolate) is meant to work as an anticancer compound to start the general detoxification
processes in cells. Garlic is known for its beneficial
effect on certain infectious bacterial diseases.
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Is 600 gram the right amount?
We don’t know. The British suggest 500 gram,
but the Japanese propose a much higher figure as
quoted in an article in The Guardian newspaper
(1). The ideas of Paracelsus, a doctor and alchemist
in the middle age (1493 – 1541) in Germany, might
help us answer the question. One of his theories,
which is still valid today, was that a chemical
compound is not poisonous as such, it is the
dose that determines whether it is poison or not.
This means that certain drugs can cure diseases when
taken in small amounts but can be poisonous in higher
concentrations. At the moment we do not know if 600
grams of fruit and vegetables are the right amount The
Danish Nutrition Council is pritty it is not too much.
Can fresh fruits and vegetables be replaced with pills?
Possibly not. Several investigations have failed to
provide evidence that taking these substances in
pill form has any positive effect. On the contrary,
it is possible that people have died from taking
too many of these dietar y supplements (2)
How to prove this scientific hypothesis?
It is very difficult and expensive to prove that a
certain compound has a special effect on the body.
To make this sort of investigation it is necessary to
test two fairly large groups of people with identical
lifestyles, ages etc. where only one factor is different,
the factor that is to be investigated. Due to the fact
that it is hard to find two such groups there are not
that many investigations of this type. Therefore it
would, in many cases, be more correct to talk about
assumptions rather than proven facts when talking
about for example the healthy effect of eating
Ginseng or Carrot.
The method used
Though the recommended amount of 600 gram
per day is the result of certain assumptions we feel,
for educational purposes, it is still worthwhile for
students to investigate for themselves as precise as
possible how much they actually eat in the way of
fruit and vegetables. The assumptions can then be
used as a basis for discussion.
Photomontage Leif-H
Copyright © C. Girnth and D. Hammelev
The Association of Danish Biologist, FaDB
Six a day
Your investigation
How much fruit and vegetable do you eat per day on average? Do
the investigation for one week at a time. Fill in the tables on the next
pages:
Questionaire: How many pieces of fruit and vegetable
do you eat per day on average?
Do the investigation for one week at a time
Fruit
Yes
No
Do you eat fruit regulary?
If yes, how many whole pieces do you eat per day on
average?
Count one apple, pear, nectarines orange etc. as one piece each. One handful of grapes, cherries or
strawberries is counted as one piece.
Juice
Yes
No
Do you drink juice regulary?
If yes, how many glasses of juice do you drink per day
on average?
Lunch
Do you eat Vegetables for your lunch?
No never
Yes once a week
Yes twice a week
Yes three times a week
Yes four times a week
Yes five times a week
Yes six times a week
Yes seven times a week
If yes how many whole pieces do you eat at a time on average?
Count only in whole pieces. One tomato, one big piece of cucumber, one carrot, one portion of lettuce/
mixed salad
or raw food count each for one piece.
www.volvoxdk.dk
Copyright © C. Girnth and D. Hammelev
The Association of Danish Biologist, FaDB
Six a day
Dinner
Do you eat vegetables for dinner? - Both as salad as a side dish and cooked in a casserole
No never
Yes once a week
Yes twice a week
Yes tree times a week
Yes four times a week
Yes five times a week
Yes six times a week
Yes seven times a week
Either salad or cooked vegetables in a casserole or as side dish
No never
Yes once a week
Yes twice a week
Yes tree times a week
Yes four times a week
Yes five times a week
Yes six times a week
Yes seven times a week
Specification of points – Do the investigation for one week at a time.
Fruit/vegetables
All Together
Fruit, whole pieces (one piece = 1 point)
Juice (one or more glasses = 1 point)
Vegetables for lunch all together
(One piece = 1 point)
Salad or cooked vegetables for dinner
(one time = 1 point)
Both salad and cooked vegetables for dinner
(one time = 2 points)
Points all together
Points per day on average
Specification of points – Do the investigation for one week at a time
6 points or over:
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Congratulation! You fulfil the recommended advice of having 600 gram fruit and/or vegetables per day Between 4 – 5 points: You are on your way – and are better than the average Dane
3 points and under: It will be beneficial for your health to eat more fruit and vegetables
Copyright © C. Girnth and D. Hammelev
The Association of Danish Biologist, FaDB
Six a day
Facts about antioxidants
Vitamin C is an example of an antioxidant. There are also antioxidants that are
not vitamins. Antioxidants neutralize free radicals and other reactive oxygen and
nitrogen compounds. These compounds are produced in normal oxidative metabolic
processes like respiration. They are also produced in connection to smoking,
pollution, taking medicines and drugs, drinking alcohol and exposure to radiation.
These highly reactive compounds can be very injurious to health. They can change
the structure of cell membranes, lipoproteins, proteins, carbohydrates, RNA and
DNA. Oxidative stress is therefore believed to contribute to development of heart
disease and cancer.
Antioxidants in food:
- Vitamin C (ascorbic acid) – from fruit and vegetables
- Vitamin E – from vegetable oils, nuts, fat fish, egg yolk, whole grain cereals
- Carotenoids (for example beta-carotene) - from fruit and vegetables
- Flavonoids - from fruit and vegetables
- Phytoestrogens - from leguminous plants and whole grain cereals
- Zinc – from meat, dairy products and whole grain cereals
- Copper – from offal (highest content)
- Selenium – from fish, shellfish, eggs and offal
Interaction between antioxidants from both vitamins and non-vitamins is important
to obtain the optimal effect in neutralizing free radicals. When antioxidants work
together a synergy will occur. This means that the effect will be bigger than the sum
of the effect of individual antioxidants. This is the reason why it is so important to
have a varied diet
Facts about Free Radicals
A free radical is an atom or a molecule that has one or more unpaired electrons in
the outer shell. In a stable molecule the electrons circulate round the nucleus in
pairs. When free electrons are present the molecule becomes reactive. It will seek
out other molecules that either give an electron (the other molecule is reduced) or
accept an electron (the other molecule is oxidised). The molecules that reduce or
oxidise with free radicals either disintegrate or become free radicals themselves
– and a chain reaction is started.
In the body it is the free oxygen-radicals that have the biggest affect. Oxygenradicals are produces all the time in connection to metabolism.
Free radicals attack many elements in the body for example DNA, proteins, fatty
acids and LDL-cholesterol. The fats that are oxidised will become rancid – the same
will happened to the cholesterol, which in an oxidised state will stick to the blood
vessels where it can cause arteriosclerosis. Free radicals will make meat rancid.
Free radicals can start harmful processes in the body that in the end can result in
cancer or other diseases. On the other hand our immune system uses free radicals to
fight off infections.
The body defends itself against free radicals with the help of antioxidants from a
whole range of vitamins, minerals and other plant products. These antioxidants
absorb free electrons or whole radicals so they cannot harm the body.
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Copyright © C. Girnth and D. Hammelev
The Association of Danish Biologist, FaDB
Six a day
Pedagogical tips
Other sources of information
It is a good idea to wait with delivering the scheme
for point counting to after the students have filled
in the first schemes (page 3 and 4). Then you
avoid students to focus on how many points they
have got from they have made the investigation.
1. The antioxidant myth: a medical fairy tale. Look
Waterson in The Guardian May 25 2006
2. Is five a day enough? Lisa Melton in New
Scientist Aug. 05 2006
3. Carotenoids in health and disease. Red. af
Norman I. Krinsky m.fl. Marcel Dekker, 2004, 568
sider. (Oxidative stress and disease)
4. Dragsted, L.O.: Antioidants in fruits and
vegetables: Final report for evaluation of the
FØTEK 2 programme “Health evaluation of
biologically active nonnutrive components in
foods: Antioxidants in fruits and vegetables”
5. HUSK. another package of Volvox materials.
Before answering
When the students answering the questionnaire they
should think about what they have been eating within
the last month due to the fact that there can be season
variations in the consumption of fruit and vegetables.
- Make the students aware that they registrar fruit and
vegetables eaten both on weekdays and in weekends.
Use this information later in the follow up discussion.
- Potatoes do not count in this scheme
- Give the students an explanation on the difference
between “both salad and cooked vegetables” and
“either salad or cooked vegetables” to be sure they
understand the difference.
Some of the students will possibly think their
consumption of vegetables at the dinner/evening
meal is underestimated in the point specification,
but with a simple scheme like this it is not possible
to look at the size of portions too as basis for an
estimation of how much they eat. On group level
over- and underestimation will possibly equalize
but on the individual level there will be both underand overestimation of the intake. Discuss therefore
the meaning of that in connection to selection of
investigation method.
Starting at the “Six a day” project there can be a talk
about different antioxidants, souces to antioxidants,
recommendations and the background for individual
needs compared with recommendations on food and
food-supplements.
Acknowledgement
This material is based on some parts of the Danish
material "Hvorfor bliver frugten brun og kødet gråt?
..."written by: Claudia Girnth-Diamba, FaDB,
Liselotte Unger, BioInfo, Hanne Thomsen, The
Chemistry teachers Association, Karen Lunden,
HTX and Marie Kielsgaard, Lykke Thostrup, Michael
Bom Frost, Lone Brinkmann Sørensen all academic
staff from KVL, now Institute for Human Nutrition
Copenhagen University. The material, which is in
Danish, can be downloaded from: www.kvl.dk/
forskning/oevelseshaefte.aspx
We would like to thank the group for the posibillity
to adapt this material for the Volvox project.
Thanks very much too to John Watson, European
School, Luxembourg for waluable help with
adaptation and the English translation.
This practical was adapted for the Volvoc project,
which is funded under the Sixth Framework
Programme of the European Commission.
Preparation and timing
This activity can be carried out within one - two
lessons.
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Copyright © C. Girnth and D. Hammelev