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CLOSE THIS BOOKOutreach N 66 - Drugs - Part 3: Herbal Medicine (OUTREACH - UNEP - WWF, 40 p.)
VIEW THE DOCUMENT(introduction...)
VIEW THE DOCUMENTArticles on herbal medicines that have appeared in back issues of OUTREACH
VIEW THE DOCUMENTPlants that kill can often cure (plus exercise)
VIEW THE DOCUMENTThe effect of plant chemicals on animals
VIEW THE DOCUMENTA disappearing storehouse of medicinal plants
VIEW THE DOCUMENTThe effect of plant chemicals on humans
VIEW THE DOCUMENTWar on drugs: the tobacco connection
VIEW THE DOCUMENTTraditional herbal medicine and “modern” medicine
VIEW THE DOCUMENTUsing local plants to treat intestinal worms
VIEW THE DOCUMENTTreating cuts and wounds
VIEW THE DOCUMENTUnderstanding medicinal plants teaching materials available from World Neighbors
VIEW THE DOCUMENTTraditional medicine to graduate
VIEW THE DOCUMENTFilm: Jungle pharmacy
VIEW THE DOCUMENTIndigenous treatment for drug dependence in Thailand
VIEW THE DOCUMENTIdentifying health-protecting customs
VIEW THE DOCUMENTA simple and effective cough syrup we can prepare at little cost from the plants we find around us
VIEW THE DOCUMENTDiscovering the uses of medicinal plants in your neighbourhood
VIEW THE DOCUMENTFilm and teaching suggestions - Herbal medicine: fact or fiction?
VIEW THE DOCUMENTPills and potions
VIEW THE DOCUMENTRevival of traditional medicine in Amazonia
VIEW THE DOCUMENTDecode the drug
VIEW THE DOCUMENTBiodiversity and health
VIEW THE DOCUMENTBarefoot doctors
VIEW THE DOCUMENTHow a rainforest in Western Samoa was saved

The effect of plant chemicals on humans

World Wide Fund for Nature (WWF-UK)
Weyside Park,
Godalming, Surrey GU7 1XR

The activity below is taken from:
“Science for Survival: Plants and Rainforests in the Classroom” by Adam Cade, published in 1988 by the Richmond Publishing Co. Ltd. Copyright Adam Cade, Richmond Publishing Co. Ltd. WWF-UK.

This publication forms part of the WWF-UK Environmental Education Project. The activity may be reproduced for non-profit, educational purposes provided the source is acknowledged.

Scientists are continually discovering new properties of chemicals found in plants. This is true even for well-known chemicals such as caffeine. We know that caffeine, found in coffee beans, increases the pulse rate and acts as a stimulant, but recent research suggests that coffee may increase our blood cholesterol level, too. Other research has shown that caffeine may have an effect against certain viruses such as herpes.

In the investigation below, you will find out how caffeine affects your pulse rate:

You will need

1 cup of ordinary black coffee
1 cup of decaffeinated black coffee
1 cup of warm water

What to do

1. Three volunteer pupils (or multiples of three) should record their pulse rates over 1 minute.


2. Each volunteer must then drink one of the three drinks.

3. They must record their pulse rate again over 1 minute at intervals of 5. 10 and 15 minutes.

4. Copy and complete the following table.

Period (minutes)

Pulse rate per minute

ordinary coffee

decaffeinated coffee






% change in pulse rate (0 - 5 mins)

5. Draw a graph of the pulse rate over 15 minutes for each of the three volunteers.

Discussion of results

1. Does the pulse rate vary between the pupils before drinking?
2. Which drink produced the greatest change in pulse rate 15 minutes after drinking?
3. What are the limitations of this investigation?


1. Repeat the investigation, but do not tell the volunteers which drink they are being given. Does this affect the results?

2. Find out what the term placebo means. How is it related to the tests you have just done?

Note for teachers

1. Coffee can raise the pulse rate by up to 20%, often minutes after drinking.
2. Ideally, the temperature of each drink should be the same.