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Irwig L, Irwig J, Trevena L, et al. Smart Health Choices: Making Sense of Health Advice. London: Hammersmith Press; 2008.

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Smart Health Choices: Making Sense of Health Advice.

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Chapter 2Be sceptical

What has not been examined impartially has not been well examined. Scepticism is therefore the first step towards truth.

Denis Diderot, Pensées Philosophiques

This chapter forms the basis of making ‘smart health choices’ because it encourages you to ask questions about the health advice that you receive – whether it comes from a television advertisement, a friend or a health professional. It will give you some of the tools to be sceptical, a critical thinker who can sift the misleading advice from that which has a genuine basis.

First, it is important to understand how our own biases can influence us. It is human nature to be tempted to believe explanations because they sound plausible, or because they agree with a prior belief or fit in with our value systems. Similarly, it can be difficult to give up a long-standing belief, even if not supported by the available evidence.

An example of this comes from the history of the tomato, which originated from South America and became a popular food in Europe by the mid-1500s. However, North Americans did not cultivate it until the twentieth century. They believed it to be poisonous, because it belongs to the Nightshade family, which includes some poisonous plants. The fact that Europeans had been eating tomatoes safely for centuries did not change their view.1

There are many examples of people’s health suffering because of practitioners’ failure to change their thinking in response to new medical evidence. It has been estimated, for example, that tens of thousands of premature babies around the world died or suffered health problems that could have been prevented had doctors been quicker to act on research evidence showing the benefits of giving corticosteroid drugs to expectant mothers going into premature labour.

On the other hand, new tests and treatments can be adopted too quickly, sometimes as a result of commercial pressure and sometimes for political reasons.

It is important to be critical of your own decision-making processes. Are you choosing or avoiding a particular treatment simply because that is what you or your family have always done, without investigating its harms and benefits or whether it is your best option? Be aware that healthcare practitioners also have their own personal and professional biases; a chiropractor will take a different approach to back pain to a surgeon, whereas cardiologists may have different views from liver specialists about the health impact of alcohol.

But perhaps you should reserve your most sceptical thinking for what you read or hear in the media. Consider a news report that cites a professor saying that the latest research suggests that drug x is a breakthrough new treatment for high blood pressure. If the professor’s views are being disseminated as part of a campaign by the drug’s manufacturer, this is unlikely to be mentioned in the news story. Similarly, if you read a report where an expert is sounding the alarm about the safety of a certain drug, it may well be that the expert’s views are being disseminated as part of a campaign funded by the manufacturer of an opposition drug. Again that will not necessarily be mentioned in the news story. Such stories often do not put the experts’ claims into a broader context – for example, looking at how they compare with other research in the area. And they rarely look critically at what evidence might be available to support the experts’ claims. Clearly, it would not be wise to take such stories at face value.

However, many consumers and even health professionals rely on the news media for information about health. The problem with this is that ‘news’, by its very definition, is that which is unusual, sensational, scandalous or stirring. The media’s preoccupation with rare, sensational events tends to make us lose perspective of what is normal. News is also susceptible to distortion and misinterpretation. The media are more likely to report studies with a ‘positive’ finding, such as those linking power lines to childhood cancer. ‘Negative’ studies – those finding no link – are much less likely to be reported. It is unusual for the complexities of health information to be accurately or fully conveyed in the media.

The media may report a new ‘breakthrough’ study showing that one treatment increased the survival of people with cancer by 10 per cent. It may not mention, however, that what this actually meant was that, one year after treatment, 110 of 1000 patients were alive instead of the 100 of 1000 who would have survived without treatment. Furthermore, it may not mention that what this meant for longer-term survival was unclear, and that the usefulness of the treatment was still uncertain because of its side effects.

Media coverage of health-related news can have significant effects on people’s health behaviour. After Kylie Minogue’s diagnosis of breast cancer there was a 20-fold increase in average daily television time given to breast cancer over a 2-week period. Messages during this time emphasised that breast cancer can ‘strike at any age’. Although to some extent this is true, this message fails to point out that, while breast cancer does occur in women under the age of 40, it is much less common than in older women. Accompanying media messages at this time were critical of the government for not extending free mammograms to women of all ages. However, they neglected to explain that mammography is not a very accurate test in the breasts of younger women who have not yet reached the menopause. They also neglected to mention that mammography, as with most tests, is not entirely without risks. After this publicity the number of women booking mammograms went up by 40 per cent. But the increase was much higher in women aged 40–49 years compared with older women aged 50–69 years (25 per cent increase).2 In other words, the intense media focus on Kylie Minogue’s breast cancer seems to have made some younger women overly anxious about their risk of the disease.

Most journalists and media managers are not qualified to assess scientific data and to discriminate between high-quality studies and the many studies that are of poor quality and dubious value. You can be more confident of the validity of a study if it is reported as being published in a well-known medical or scientific journal, but this is no guarantee. Reports of such single studies often fail to include the broader context, so that the results are reported as if conclusive fact, whereas they may be tentative and not in line with other valid studies.

And most journalists and media managers are looking for a ‘story’; the stronger and more exciting they can make the findings sound, the more chance that their story will be displayed prominently. One journalist expresses it this way:

Scientists who do poor studies or overstate their results deserve part of the blame. But bad science is no excuse for bad journalism. We tend to rely most on ‘authorities’ who are either most quotable or quickly available or both, and they often tend to be those who get most carried away with their sketchy and unconfirmed but ‘exciting’ data – or have big axes to grind, however lofty their motives. The cautious, unbiased scientist who says, ‘Our results are inconclusive’ or ‘We don’t have enough data yet to make any strong statement’ or ‘I don’t know’ tends to be omitted or buried someplace down in the story.

Victor Cohn3

Advertisements also have a powerful impact on our healthcare, whether by influencing a doctor’s decision about what drug to prescribe or by persuading you to buy a particular food or pill. Tips for avoiding the tricks and traps of advertising can also be useful for evaluating other forms of health advice.

And, of course, there’s the internet! An ever-increasing amount of health information is now available to everyone online. More and more, people are turning to the internet to look up health information, to try to find out more about either their own health problem or the health of a family member, perhaps to double-check information that they’ve received from a health practitioner or to ‘chat’ with people who have the same health problem via discussion groups and ‘blogs’. Health programs can be downloaded via pod-casts and played through i-pods while walking the dog.

Below are some of the common strategies used in selling health messages, why they can lead you astray and how to evaluate them.

If it works on a rat, it will work on you

Many reports claim that a certain product has been scientifically proven to have various benefits. But the fine print reveals that the results come from laboratory or animal experiments. It cannot be assumed that these results will be relevant for humans. Different species respond differently to various treatments.

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For years many scientists were convinced that taking supplements of the antioxidant, beta carotene, related to vitamin A, would reduce the risk of certain cancers and heart disease. One of the reasons for their optimism was that animal studies had suggested that vitamin A was protective against cancer in some situations. The theory was strengthened by observational studies showing that people with higher blood levels of beta-carotene had lower rates of cancer and heart disease. But when proper trials were done – randomly allocating individuals to beta-carotene or placebo supplements (dummy pills) – the results surprised many. An analysis of 47, well-conducted, randomised controlled trials showed that antioxidant supplements (beta-carotene, vitamins A, C and E, and selenium) do not reduce your chance of dying. In fact taking beta-carotene or vitamin A or E appeared to increase it.4 To add further weight to this, another summary of the effect of beta-carotene on preventing cancers of the bowel, liver, stomach and pancreas also showed that it increased your chance of dying! It seems that, in humans, taking beta-carotene, vitamin A and vitamin E (alone or in combination) may do you more harm than good.5–7


You need to know the evidence proving that the product works on humans – and that its effect is relevant to your needs and situation.

Here’s how it works

A remedy which is known to work, though nobody knows why, is preferable to a remedy which has the support of theory without the confirmation of practice.... The question to which we must always find an answer is not ‘should it work?’ but ‘does it work?

Richard Asher8

People selling health messages, especially advertisers, love to tell you ‘how their product works’. This strategy can be very convincing because it seems to make ‘good sense’ that, if we understand the mechanism by which something might work, the hoped-for outcome will automatically follow. But knowing how something is supposed to work is not proof that it does work.

For example, knowing that a substance changes the lining of your stomach, or plumps out your skin cells – these are examples of markers which are sometimes called surrogate or intermediate measures – may be intriguing, but is certainly no proof that you will have better digestion or smoother skin. These outcomes that matter to you are often called ‘person-centred outcomes’. And on a more serious note, remember the story of flecainide, the drug that was meant to reduce deaths by treating irregular heart rhythms, but in fact increased the risk of death. What we really need to know is whether a product or treatment will improve our quality of life or help us to live longer.

Similarly, we should not discard treatments that have been proven to have benefits, simply because we do not understand how they work. Many thousands of women and their babies probably suffered unnecessarily because the medical profession was reluctant to accept that the anticonvulsant, magnesium sulphate, was an effective treatment for eclampsia because they did not see how it could possibly work. Eclampsia causes swollen feet, high blood pressure and fits in pregnant women, and accounts for about 10 per cent of all maternal deaths worldwide – about 50,000 deaths a year. A summary of the results of six randomised trials has shown that magnesium more than halves the risk of eclampsia and was better than other anticonvulsants, although there is a small increased risk of caesarean section (5 per cent).9

People who dismiss alternative health therapies because their mechanisms ‘do not make sense’ may be as misguided as those who believe a therapy will work because its mechanism suggests it ought to.


You need to know whether an intervention works in practice (empirical evidence). This can come only from seeing what actually happens to people who have the intervention. We get this information from good quality trials on people rather than from theory alone. Person-centred outcomes describe how an intervention affects your quality or length of life.

Blind you with science

Product promotions aimed at the general public and at doctors are notorious for using inconclusive or misleading research, wrapped up in scientific jargon, in an attempt to inspire support for a product.

And even if valid research is cited, you cannot assume that it will be quoted accurately or fairly. Consider this advertisement aimed at medical practitioners for a cholesterol-lowering drug called Zocor or simvastatin. In 1993 the pharmaceutical company brochure included this quote from a 1991 independent medical report:

HMG-CoA reductase inhibitors such as simvastatin ... are the most effective in lowering cholesterol levels and are more acceptable to patients than the bile acid resins....

In its original form, what the report actually said was:

HMG-CoA reductase inhibitors such as simvastatin and pravastatin are the most effective in lowering cholesterol levels and are more acceptable to patients than the bile acid resins although their longterm safety and effectiveness in terms of morbidity and mortality have yet to be demonstrated.10

Another example of how science can blind comes from an advertisement for Ponstan, a non-steroidal anti-inflammatory drug. The product was advertised to doctors in Pakistan as providing:

... unsurpassed efficacy compared to acetaminophen [paracetamol] in fever control and better tolerance.

When challenged by the Medical Lobby for Appropriate Marketing (MaLAM),11 the company agreed to withdraw its claim of better tolerance from future advertising. But it defended the claim of unsurpassed efficacy on the grounds that this meant it was equivalent, not superior, to other products – although most general readers might not understand it this way. MaLAM has been renamed ‘Healthy Skepticism’ and their website has some excellent examples of misleading advertising that you may wish to look at via


Just because it sounds scientific doesn’t mean that it is valid. And don’t assume that individuals or groups with vested interests will be objective.

Personal testimony and celebrity endorsement

Often an individual’s experience is used to sell products. A leaflet for a homeopath’s practice, for example, says that people such as the Royal Family, Mahatma Ghandi, Mother Theresa and Tina Turner visit homeopaths. So what if they do? Celebrities don’t always get it right. Just because one person has had a good experience with a product or treatment does not mean that others can expect the same outcomes, or even that that person’s recovery was a result of their use of the product. Anecdotal evidence can sound compelling, but is not a valid guide for decision-making, whether it comes from the experience of your next-door neighbour or a personal testimony published in an advertisement. Of course, such advertisements never publish the negative experiences with their product. What is needed is evidence from high-quality studies such as randomised controlled trials. For reasons that we discuss later, randomised controlled trials, in which people are allocated randomly to the treatment or an alternative treatment or placebo, are the most effective studies for evaluating the risks and benefits of health interventions.


As compelling as it may sound, anecdotal information can be unreliable as a basis for predicting an outcome. Ask to see evidence of randomised controlled trials.


  • Just because a product works on rats, or cells in a laboratory test tube, does not mean that it will improve your health. The outcomes of a treatment or intervention should be relevant to people. They should tell you about quality and length of life rather than some biological measure that is supposed to predict well-being.
  • Knowing how something is supposed to work is not necessarily proof that it does work in practice. We need evidence from high-quality studies on groups of people rather than from theory alone.
  • Don’t be blinded by ‘science’. All too often what is marketed as ‘scientifically proven’ is based on questionable research. And be aware of the vested interests of information sources.
  • What matters is not whether someone famous recommends a particular product, but whether there is evidence from randomised controlled trials showing that it is more likely to do good than harm.


Goodwin J, Goodwin J. The tomato effect – rejection of highly efficacious therapies. JAMA. 1984;251:2387–90. [PubMed: 6368890]
Chapman S, McLeod K, Wakefield M, Holding S. Impact of news of celebrity illness on breast cancer screening: Kylie Minogue’s breast cancer diagnosis. Med J Australia. 2005;183:247–50. [PubMed: 16138798]
Cohn V. News and Numbers. Iowa: Iowa State University Press; 1989.
Bjelakovic G, Nikolova D, Gluud L, Simonetti R, Gluud C. Mortality in randomised trials of antioxidant supplements for primary and secondary prevention. JAMA. 2007;297:842–57. [PubMed: 17327526]
Hennekens C, Buring J, Manson J, et al. Lack of effect of long-term supplementation with beta carotene on the incidence of malignant neoplasms and cardiovascular disease. N Engl J Med. 1996;334:1145–9. [PubMed: 8602179]
Omenn G, Goodman G, Thornquist M, et al. Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. N Engl J Med. 1996;334:1150–5. [PubMed: 8602180]
Bjelakovic G, Nikolova D, Simonetti R, Gluud C. Antioxidant supplements for preventing gastrointestinal cancers. Cochrane Database of Systematic Reviews. 2006 [PubMed: 18677777]
Asher R. Apriority. The Lancet. 1961:12–6.
Duley L, Gulmezoglu A, Henderson-Smart D. Magnesium sulphate and other anticonvulsants for women with pre-eclampsia. Cochrane Database of Systematic Reviews. 2006 [PubMed: 12804383]
Anonymous. Merck Sharp & Dohme’s promotion of Zocor (simvastin) MaLAM Australian News. 1994.
Medical Lobby for Appropriate Marketing (MaLAM) Adelaide, Australia: 1996;14:7/8.
Copyright © 2008, Professor Les Irwig, Judy Irwig, Dr Lyndal Trevena, Melissa Sweet.

All rights reserved. No part of this publication may be reproduced, stored in any retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the publishers and copyright holder or in the case of reprographic reproduction in accordance with the terms of licences issued by the appropriate Reprographic Rights Organisation.

Bookshelf ID: NBK63648


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