Carrots and pumpkin might reduce your risk of cancer, but beware taking them in pill form

A diet rich in fruit and vegetables is more than just a sum of its individual nutrients. From www.shutterstock.com

Simon Chapman, University of Sydney

In February this year, ABC’s Four Corners broadcast a critical and compelling program on complementary medicines, Swallowing it: How Australians are spending billions on unproven vitamins and supplements.

The program certainly tapped into a growing trend. The value of the global vitamins and dietary supplements market is predicted to reach US$59.6 billion by 2020; in Australia in 2014-15, 49% of women and 34% of men had bought vitamins in the past six months. Companies like Swisse and Blackmores have a lot riding on keeping up this demand.

Yet, the vast majority of this mass consumption, often helped along by celebrity endorsement, is just generating oceans of very expensive urine; relatively few people have medical conditions requiring specific nutrient supplements.

So why do so many people waste their money?

Seduced by reductionism

Scientific reductionism is the seductive “mental shortcut” or cognitive heuristic that assumes you can understand complex phenomena by analysing each of its elements: the whole is just the sum of its parts.

In reductionist reasoning, a piece of fruit is nothing more than the sum of all the compounds it contains. So if you don’t have enough time to buy, cook and eat a diet rich in the sources of vitamins and minerals we all need, you can buy a set of pills containing the vitamins and other nutrients that go to make up a carrot, a fish or a banana.

Right? No, actually.

A good example of the simplistic appeal of reductionism is the assumption that because tobacco smoke has over 70 known carcinogens, removing some of them will make smoking less dangerous. A no-brainer?

This is what three major US tobacco companies once tried to imply when they chemically engineered “reduced carcinogen” brands.

But a study of cigarette smoke emissions across different brands concluded that reducing some carcinogens in the smoke mix had two effects – “risk swapping”, when one specific carcinogen exposure was reduced at the cost of another’s exposure increasing, or “risk shifting”, when a specific exposure was reduced at the cost of that exposure increasing within another carcinogen group.

The impact on actual carcinogenic risk remains unknown when tobacco companies manipulate the presence of one or several carcinogens but sell products with all the 68 or so others intact.

Dietary reductionism

Reductionist thinking flourishes most in popular understanding of nutrition and is at the very epicentre of the appeal of complementary medicine. The vitamin and supplement shelves of pharmacies and complementary medicine shops are groaning with single and multi-vitamin and supplement bottles all promising swallowing their contents daily just must be good for you.

Perhaps the most famous of all salutary tales about the folly of reductionist thinking in medicine concerns beta-carotene. Beta-carotene is an organic red-orange pigment abundant in plants and fruits. It is a member of the carotenoid group, the main source of vitamin A in our diets (along with retinol in liver, butter, cheese and chicken skin). Beta-carotene levels in the diet are seen as a good indicator of overall fruit and vegetable consumption. Carrot, orange sweet potato and pumpkin are the richest sources of beta-carotene, with spinach and kale and any brightly coloured fruits and vegetables also good sources.

Studies of the diets of whole populations and their sub-groups (such as vegetarians) had long observed those who ate the most beta-carotene tended to have lower population-wide rates of several cancers.

Could beta-carotene pills prevent cancer?

By the early 1980s, leading epidemiologists like Oxford University’s Richard Doll and Richard Peto were speculating that diets high in beta-carotene protected people from developing cancer. This speculation stimulated several long-term trials of whether taking beta-carotene supplement pills might influence cancer rates.

The most famous was the Carotene and Retinol Efficacy Trial (CARET). In this study, people – including those at high risk of cancer like those exposed to asbestos at work, and smokers – were given daily 30mg of beta carotene plus 25,000IU of retinol and followed for an average four years between 1983 and 1997.

In May 1996, the bombshell results from the study were published in the New England Journal of Medicine. A total of 388 new cases of lung cancer were diagnosed. And the clanger? The study participants randomised to receive the beta-carotene and retinol supplements had a 28% higher incidence of lung cancer than those given placebos. As a result, the trial was stopped 21 months early.

The study provoked intense interest and commentary. In 2008, a meta-analysis of four studies of beta-carotene supplementation involving 109,394 people taking an average of 20-30mg of beta-carotene supplements a day confirmed the CARET results. It found that in smokers, those taking the supplements had a 24% increased risk of lung cancer. Beta-carotene was found in 70% of 47 common multivitamins used by people in the studies.

The beta-carotene supplementation story is a textbook illustration of the folly of reductionist thinking in preventive health. As one letter writer to the New England Journal of Medicine put it:

Beta-carotene was also acting as a marker of increased fruit and vegetable consumption and thus of many other components that have cancer-preventing potential (Vitamin C, folate, other carotenoids, polyphenols, and many plant compounds).

Others argued the dose of beta-carotene in the CARET study pill was too high. Others argued the specific form of beta carotene likely used in the CARET trial (all-trans-beta-carotene) was just one of 272 different isomers of beta-carotene and was probably chosen because it was the only one made commercially in large quantities (by BASF, Hoffmann-La Roche, and Sumitomo) and available for purchase. Perhaps the people who conducted the study, they argued, picked the wrong beta-carotene?

All these “what ifs?” may well have substance and we may one day find the holy grail of cancer preventing agents. But when the results are highly unlikely to be much different to the preventive effects of eating a mixed diet emphasising fruit and vegetables, I know which plan to continue to follow.

Simon Chapman, Emeritus Professor in Public Health, University of Sydney

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

Which supplements work? New labels may help separate the wheat from the chaff

Ken Harvey, Monash University

New proposals from Australia’s drug regulator should give you a better idea if your complementary medicines do what they say on the packet.

One change proposed by the Therapeutic Goods Administration (TGA) is a “stamp of approval” on the packaging and promotional material of some vitamins, minerals, herbs and other supplements to tell you there is enough evidence to back health claims.

Other proposals include reducing the number of often unsubstantiated indications that manufacturers of complementary medicines currently make on their TGA application, which are then used as the basis for advertising claims.

The TGA also proposes incentives for companies to develop and market products with new active ingredients, or make new claims based on research.

The proposed changes, which are out for public consultation, follow the recent ABC Four Corners program, which highlighted long-standing problems with the way complementary medicines are currently regulated.

ABC Four Corners’ documentary “Swallowing it” highlights the shortcomings of how complementary medicines are regulated in Australia.

What’s the problem?

The TGA’s proposals are urgently needed to fix three major shortcomings of the current regulatory system.

First, consumer organisations and health professionals have lost confidence in the complementary medicines industry’s ability to regulate its own advertisements, and in the TGA’s ability to apply adequate sanctions when companies don’t follow the rules.

Second, there is little incentive for the manufacturers of complementary medicines to research new innovative products or prove existing ones work.

There are about 11,000 listed complementary medicines on the Australian Register of Therapeutic Goods (indicated by Aust L on packaging). Listed medicines are meant to contain pre-approved, relatively low-risk ingredients, produced with good manufacturing practice and only make “low-level” health claims for which evidence is held. However, the TGA does not check these requirements before the product is marketed; post-marketing surveillance and upheld complaints show high levels of regulatory non-compliance.

But there are only 35 registered complementary medicines (indicated by Aust R on packaging) the TGA says have been thoroughly assessed for safety, quality and efficacy (there is also debate about whether many of these older products should still be on this TGA list). There are fewer products on this list because research to meet registration requirements is expensive, the public doesn’t understand the subtleties between an Aust L and Aust R product and a better return on investment comes from promotional hype and celebrity endorsement of listed products.

Third, the TGA provides only limited transparency about companies and products that fail post-marketing evaluation or have complaints upheld. This information is currently regarded as commercial-in-confidence, fuelling the perception the TGA is more concerned with helping industry than protecting consumers.

How could the new measures help?

The proposal to restrict companies to only making pre-approved, “low-level” indications and claims for a product, such as, “may relieve the pain of mild osteoarthritis”, will minimise the risk of misleading consumers. But it is not yet clear how the list of allowed indications will be established nor how a specific product will be matched with an appropriate allowed indication.

The regulator also proposes manufacturers apply for “intermediate-level” health claims falling outside the permitted list (outlined above). An example might be, “our formulation of cranberry reduces the frequency of recurrent urinary infections in women”. For this, the TGA would have to assess the evidence substantiating the claim for a particular product. If the evidence stacks up (and there’s a debate about the type of evidence needed), the product could then carry a TGA “stamp of approval” on the label and any promotional material. But it is not clear what this “stamp of approval” will be. Is it text, a symbol or both?

Not everyone agrees a TGA ‘stamp of approval’ should be in the form of a symbol, like this.
(Unofficial mock-up created by Ken Harvey)

In preliminary TGA stakeholder consultations, consumer representatives supported a prominent visual identifier (like a logo or symbol) because of the failure of the existing Aust L and Aust R labelling to inform consumers. But industry representatives were concerned a highly visible identifier for a small number of evidence-based complementary medicines might affect sales of the bulk of listed products without one.

The TGA’s proposals encourage innovation because they will stimulate companies to engage in research to qualify for a TGA “stamp of approval”. The proposal also suggests companies that develop a TGA approved evidence-based claim would be awarded a three-year period of data protection to stop others freeloading on their research.

But the proposed changes do not yet address the need for greater transparency in the regulatory process. For instance, it is not clear whether the TGA’s assessment of evidence to back higher-level health claims for complementary medicines will be publicly available, as they are for prescription medicines.

What happens next?

These proposed changes, which are out for public consultation until March 28, 2017, sit alongside other recommendations aimed at improving the advertising complaints system.

If the TGA implements this package of recommendations, Australia will be a world leader in how complementary medicines are regulated. Despite the substantial and increasing use of supplements, no other country has developed a system that helps consumers and health professionals separate the evidence-based wheat from the chaff, improves confidence in the industry, stimulates more evidence-based products and has the potential to boost exports.

Ken Harvey, Adjunct Associate Professor, School of Public Health and Preventive Medicine, Monash University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

Appeal to tradition

by Tim Harding

Appeal to Tradition or argumentum ad antiquitatem (also known as ‘appeal to common practice’) is a common informal fallacy that occurs when it is assumed that something is better or correct simply because it is older, traditional, or ‘has always been done.’  For example, arguments of this type often begin with phrases like ‘It has been a long-standing tradition that…’ on the assumption that such words are persuasive.

The placebo industry (aka ‘alternative medicine’) relies heavily on this fallacy by appealing to the notion that ‘traditional medicine’ or some rare berry or plant root has been used for thousands of years, often in a hidden valley in some exotic Eastern country.  Strangely, this argument is regarded by the placebo industry (and gullible consumers) as more persuasive than any evidence that the product actually works.  This fallacy is often comitted in combination with the Appeal to Nature fallacy.

This sort of reasoning has the following form:

Premise: P has always been done.

Conclusion: Therefore P is right or good.

This argument is fallacious because the conclusion does not logically follow from the premise.  There are plenty of counterexamples where something that has always been done or believed in is now regarded as wrong or false such as:

• Belief in the pseudoscience of astrology is thousands of years old;
• People believed that Sun revolved around the Earth (rather than vice versa) until only a few hundred years ago;
• The idea of the Flat Earth is much older than the idea that the Earth is round;
• Slavery was considered normal until only a couple of hundred years ago;
• Women have continuously been treated like second class citizens in certain parts of the world.

The opposite of an appeal to tradition is an appeal to novelty – claiming something is good because it is new.  This type of advertising hook is often used to sell new technology, such as software updates, when many of us know of new operating systems that have actually been inferior to their previous versions.

Since false beliefs tend to be rooted out over time, the long-term persistence of a belief can provide some degree of inductive evidence for its credibility, but not sufficient to qualify as a cogent argument. There are lots of ancient ideas that have persisted to modern times, but they are still false e.g. astrology, quackery, beliefs in the paranormal etc. 

An appeal to common practice can be valid if the cost of abandoning the practice or switching to an alternative outweighs the benefits of doing so. For example, re-defining the direction of the flow of current in electrical circuits to match the direction of the flow of electrons might aid education by reducing confusion, but doing so would come with the significant cost of re-writing text books and translating any technical material that covered the topic.  Another example is that the cost of changing the calendar to a year zero other than the birth of Jesus would be far greater than the benefits.  Non-Christians would be wiser to stick with the familiar Christian calendar dates.

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The David and Goliath Fallacy

by Tim Harding

The biblical parable of David and the Goliath is taught to many children throughout the Western world and the Middle East.  Goliath was a huge armoured and weapon-carrying champion, who was defeated by a small shepherd boy using only a slingshot and stone.  This parable is often cited to show how an underdog with ‘right on his side’ can defeat much a more powerful opponent.

In some cases, this parable is extended into a logical fallacy that attempts to paint large and powerful organisations as bad or wrong because they are large and powerful.  For example, anti-science advocates often disparagingly refer to ‘Big Pharma’, implying that the pharmaceutical industry is bad, at least in part, because it is big.  Never mind that, in terms of retail sales dollars, the placebo industry (or so-called ‘alternative medicine’) is of a similar order of magnitude these days.  Similar disparagements are made against medical science, the medical profession and even government agencies on the grounds of their size and influence.

The David and Goliath Fallacy takes roughly the following form:

   Premise 1: There is a conflict between two organisations A and B.

   Premise 2: A is much larger and more powerful than B.

   Conclusion: Therefore, A is bad or wrong, compared to B which is good or right.

Like all logical fallacies, this argument is invalid because the conclusion does not necessarily follow from the premises.  Small organisations can be bad and/or wrong; and large organisations can be good and/or right. In some ways, the David and Goliath Fallacy can be viewed as a perverse over-correction of the aphorism ‘Might Makes Right’.

One of the consequences of this fallacy is that claiming underdog status against a more powerful ‘Goliath’ can give moral licence to poor behaviour during conflicts, to create a ‘more even contest’.  For example, small organisations like the so-called Australian Vaccination-skeptics Network frequently make false or unsubstantiated claims, with the lame excuse that they do not have the resources to back up their claims with evidence. The David and Goliath Fallacy has been used during ideological debates in attempts to justify intellectual property theft and even terrorism.

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