Fight strategy
Question: When I have been ill with a high temperature, my wife has tried to
persuade me to take paracetamol to reduce my temperature. However, I prefer to
take nothing because I have heard that the body increases its temperature to
fight the infection. Which of us is right?
Answer: You are probably right. There is considerable experimental evidence
indicating that fever is an adaptive response that facilitates host resistance
and slows the growth of the pathogen. The fact that fever evolved hundreds of
millions of years ago (it is a common response to infection in vertebrates, as
well as in many invertebrate species) indicates its adaptive value.
Elegant studies in lizards conducted by Matthew Kluger some 25 years ago
showed that, in general, moderate fevers decrease morbidity and increase
survival rate. Lizards, like other 鈥渃old-blooded鈥� animals, develop fever by
moving to a warmer environment. A rise in body temperature after experimental
bacterial infection increases host survival (Science vol 188, p 166).
Furthermore, blocking fever with antipyretic drugs such as sodium salicylate
increased the mortality rate from bacterial infection (Science vol 193,
p 237).
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Antipyretic drugs may help us to feel better but probably not because of the
reduction in our body temperature. It is more likely to be their profound
analgesic and anti-inflammatory properties that perk us up. If an increase in
body temperature made us feel ill, why would people enjoy saunas, where their
core temperature can go up by a couple of degrees?
Alexander Gourine
Department of Physiology
Royal Free and University College Medical School
London
Answer: A fever occurs in response to substances called pyrogens, derived
from bacteria or viruses that enter the body. The presence of the pyrogen causes
an increase in the temperature at which our body maintains itself.
The pyrogens entering the body are attacked by cells of the immune system
called macrophages. Macrophages release chemicals called interleukins that sound
the alarm to other immune cells throughout the body and trigger responses that
contribute to feeling crummy. The interleukins also raise the set point for our
body鈥檚 heat production and trigger the production of prostaglandins, which
contribute to fever and inflammation.
Aspirin and paracetamol are potent inhibitors of prostaglandin synthesis,
which explains how the drugs return the set point to normal and make us feel
better. But while they can eliminate the symptoms, they do not cure the
disease.
Barinu Rashid
Oldham
Answer: Lowering body temperature during a fever can do harm rather than
good. Evidence for this comes from experiments with fish housed in
interconnected tanks with different water temperatures. Fish prefer a particular
water temperature when healthy, but choose a higher temperature when infected.
If they are not allowed to move between tanks, their mortality is higher. This
story is set out in Kluger鈥檚 Fever: Its biology, evolution, and function
(Princeton University Press, 1979).
John Forrester
By e-mail, no address supplied
Water everywhere
Question: People are currently obsessed with drinking 2 litres or more of
water every day. Is there any evidence that this 鈥渄etoxifies鈥� you or is in
general good for you, as many people believe? If so, how does this work? How
much water do we really need?
Answer: The minimum volume of urine required by the kidneys to excrete the
waste products of metabolism is about half a litre per day. Since we lose
another half litre via sweat, breathing and faeces, the net intake required to
maintain water balance is about one litre per day under normal conditions.
Drinking more than this simply results in more dilute urine鈥攖he same
absolute amount of 鈥渢oxins鈥� will still be excreted.
The rationale behind the common injunction that the 鈥�2 litres or more a day鈥�
should be pure water escapes me. After all, once a water molecule has been
absorbed across the gut, how can the body tell whether it originated from pure
water or a more interesting flavoured beverage? There are minor diuretic effects
from alcohol and components of tea and coffee, but provided we drink when we
feel thirsty, these are easily compensated for.
I am also mystified by the concept of 鈥渄etoxification鈥�, especially when
applied to individual organs or, indeed, parts of organs. Our metabolism
produces plenty of toxins, which the kidney does a good job of excreting. It is
true that the symptoms caused by kidney failure can be helped by changes in
diet, but this is a fairly extreme situation. I fail to see how drinking more
water than the minimum needed would make any significant difference to the
elimination of waste products for the vast majority of us who have normal renal
function.
David Oliveira
Department of Renal Medicine
St George鈥檚 Hospital Medical School
London
Answer: According to a 1994 newspaper article (Columbus Dispatch, 16 May),
the US National Academy of Sciences first mentioned water intake in the second
edition of its US Recommended Daily Allowances, published in 1945: 鈥淎 suitable
allowance of water for adults is 2.5 litres (83 ounces) daily in most instances.
An ordinary standard for diverse people is one millilitre for every calorie of
food. Most of this quantity is contained in prepared foods.鈥� Somehow the final
sentence has been lost to most women鈥檚 magazines and health 鈥渆xperts鈥�.
This information was found at www.urbanlegends.com.
Paul Hynch
Victoria Park
Western Australia
This week鈥檚 question
Sink stoppage: A European friend of mine likes to rail against the American
habit of compulsive bathing. He claims the skin鈥檚 natural oils contain
components that kill off stink-producing bacteria and insists that if I simply
stop bathing and allow my body鈥檚 natural odour defences to recover, I will be
free of the inconvenience of daily showers. Is there any scientific basis for
this? And how long would I have to forgo bathing before I saw an effect?
Hal Plunkee
Madison, Wisconsin
Colour bind: If I buy mauve, yellow and white cut freesias, the mauve ones
always die first, then the yellow ones and finally the white ones. This happens
regardless of the time of year. Why?
Faye Jackson
Birmingham