Eve bites off too much

Ian Wishart is one of New Zealand’s more prominent creationists. In a recent book he takes on evolutionary biology, a task for which he seems ill-equipped.

In his latest book, Eve’s Bite (2007), Investigate magazine managing editor Ian Wishart has a chapter titled The Beagle Boys (sub-titled Darwinism’s last stand). In it he again attacks the well established edifice of organic evolution. He heads the chapter with a quote from Ann Coulter’s Godless: The Church of Liberalism, which is worthwhile reproducing here in full because it clearly reflects the key elements of Wishart’s (false) assessment of the scientific status of evolution:

Liberal’s creation myth is Charles Darwin’s theory of evolution, which is about one notch above Scientology in scientific rigor. It’s a make-believe story, based on a theory that is a tautology, with no proof in the scientist’s laboratory or the fossil record – and that’s after 150 years of very determined looking. We wouldn’t still be talking about it but for the fact that liberals think evolution disproves God.

Are Ann Coulter and Ian Wishart right? Is evolution a myth based on a tautology (the theory of natural selection)? Does evolution lack proof in the laboratory or in the fossil record? Does it disprove God?

The theory of natural selection (defined as “survival of the fittest”), claim anti-evolutionists, is a tautology because it is merely saying those who are fittest are the ones that survive. However, this is not how most biologists now view the term ‘fittest’. In brief, the fittest organisms are the ones possessing heritable features that enable them to leave the most offspring in a particular environment, physical and biological. In other words, there are criteria of fitness that are independent of survival.

Much of the confusion perpetrated by anti-evolutionists emanates from a too-simplistic notion of natural selection. “Survival of the fittest” is best regarded as a shorthand for a complex process. (Incidentally, it is Herbert Spencer’s phrase, not Darwin’s, although Darwin did eventually incorporate it into later editions of the Origin.) In fact, the theory of natural selection is far from being tautologous. For example, it can lead to testable hypotheses (predictions) relating to particular traits. As one evolutionist, Jason Rosenhouse, has observed, “there is nothing tautological about saying…that moths possessing dark coloration will be less visible than light colored moths to predatory birds when resting on dark-colored trees.” If the theory of natural selection is a mere tautology, supplementary testable hypotheses such as this one would be non-existent. Most importantly, regardless of how evolution has occurred, the evidence for it is overwhelming.

Evidence for the process, derived from laboratory observations and experiments, emanates from several fields of research, such as comparative anatomy (from an examination of fossil and extant organisms), embryology, molecular biology and genetics.

As for the fossil record, it is a treasure trove of evidence that evolution has occurred. Not only does it reveal morphological and other details of numerous creatures from the past, it also shows an overall pattern of similarity pointing to the reality of descent with modification. In addition, numerous transitional forms have been discovered (see below).


Does evolution disprove God? It is important to realise, in the current context, that biologists in doing science are practising methodological naturalism, so that supernatural explanations, because they are empirically non-testable, can have no role to play in science; they are scientifically worthless. Therefore the accusation by anti-evolutionists that evolutionists are deliberately atheistic (that in promoting evolution they are intentionally promoting atheism) is unwarranted. In fact, not all evolutionists are atheists.

It comes as no surprise, given her take on evolution, that Coulter, a lawyer and a conservative columnist, has drawn on what she calls “the generous tutoring” of intelligent design (ID) luminaries, Michael Behe, David Berlinski and William Dembski. If she genuinely wishes to learn something about evolution, the last people she should seek help from are ID proponents. In quoting Coulter, Wishart has set the tone and the level of argument of his chapter attacking evolution.

Wishart has adopted a familiar strategy used by anti-evolutionists in general – quoting eminent scientists purporting to be demonstrating that evolution itself is in crisis. It’s not, of course, but let’s see how he tries to convince his readers that it is, and that intelligent design is the only logical successor to an apparently discredited scientific theory.

But first, a point of clarification. It is necessary to distinguish between Darwin’s theory of descent with modification, establishing the reality of the process, and his theory of natural selection. The distinction is important because, almost invariably, scientists are quoted by anti-evolutionists questioning aspects of theories relating to the mechanism(s) of evolution. But it suits Wishart (and others) to convey the impression that evolution itself is in serious doubt in scientific circles (hence his subheading: “Darwinism’s last stand”).

A passage by Niles Eldridge (American Museum of Natural History), a prominent opponent of ID creationism, extracted from his 1995 book, Reinventing Darwin (p. 95), according to Wishart, is supposed to demonstrate “the lack of fossil support” for evolution. It reads in part as follows:

No wonder paleontologists shied away from evolution for so long. It never seems to happen. Assiduous collecting yields…the very slight accumulation of change-over millions of years, at a rate too slow to really account for all the prodigious change that has occurred in evolutionary history. When we do see the introduction of evolutionary novelty, it usually shows up with a bang, and often with no firm evidence that the organisms did not evolve elsewhere! Yet that’s how the fossil record has struck many a forlorn paleontologist looking to learn something about evolution.

On the face of it, pretty damning comment surely? To understand what really concerns Eldridge we need to consider the above passage in context. It appears in a chapter devoted to a discussion of the Eldridge/Gould concept of punctuated equilibria which, as Eldridge himself describes it, “is a melding, in essence, of the pattern of stasis [as revealed in the fossil record] with the recognition that most evolutionary change seems bound up with the origin of new species-the process of speciation.” By ‘stasis’ is meant the tendency for species not to change very much, often over millions of years. Long periods of stasis (or stability) are punctuated by shorter periods of comparatively rapid change, the process of speciation. Because of its somewhat short duration (geologically speaking) in small populations on the outskirts of an ancestral species’ range, the chance of recording a speciation ‘event’ in the record of the rocks is substantially reduced.

Two points to note here. Eldridge is not denying the reality of evolutionary change-that new species and groups arise over time through the influence, essentially, of natural selection. What Eldridge and Gould have brought to the attention of fellow evolutionists is that it is possible to reconcile what palaeontologists have observed in the fossil record, in Eldridge’s words “its gappiness, and uncertainties about where its fossilized animals and plants might have come from”, with how species originate over time. This reconciliatory theory brings into question the view of gradual (imperceptible) change over eons of time in the production of new species. Most importantly, the theory of punctuated equilibria is very much concerned with rates of change, the tempo of evolution.

To repeat, what it does not bring into question is the reality of evolution itself. This is not the place, nor is it necessary, to discuss the merits or otherwise of punctuated equilibria theory or of phyletic gradualism. What the theory has done (going back to Eldredge’s statement quoted above) is show that palaeontologists do have a role to play in the elucidation of the mechanisms and patterns of evolutionary change. And we should not overlook the role long played by palaeontologists in the discovery and painstaking excavation and preparation of numerous fossils that have provided such a rich lode of evidence for the ‘fact’ of evolution.

Transitional fossils

Which brings us to Wishart’s take on the subject of transitional fossils as evidence for evolution. There aren’t any, he contends, among the 250,000 fossil species now identified and catalogued: “Nowhere, are there fossils that show a weasel-cat, or a deer-giraffe, or any other of the alleged half-breed species said to have existed. In fact, a search of the literature on giraffe evolution has failed to find a single example of a short-necked giraffe at all. The long ones just suddenly appeared.”

Let’s briefly examine each of these examples. First the ‘weasel-cat’. Weasels and cats belong to different families within the mammalian Order Carnivora (Mustelidae and Felidae respectively). Should we expect these two families to be linked by a transitional ‘weasel-cat’? Well, no. The fossil and morphological evidence together point to separate ancestral groups among the earlier carnivores. What about a deer-giraffe link? Such a link between the Cervidae and Giraffidae is conceivable, but the inter-relationships of these two families are not firmly established. The apparent absence of such a link in the fossil record does not, of course, rule out a possible future discovery.

Is Wishart correct? Is there no example of a short-necked giraffe fossil? Here Wishart really comes to grief. He couldn’t have searched very far. Here is what Prothero (New Scientist, 1 March 2008) has to say: “Most fossil giraffes looked more like the short-necked okapi, a shy white-and-brown-striped denizen of the African rain forests, and the only other living giraffid.” More recently, a fossil giraffe has been described from the late Miocene and early Pliocene. “Its neck is a perfect intermediate between the short-neck ancestors and their long-neck descendants.”

Wishart somewhat sarcastically refers to “half-breeds”. However, “half-breed” is best regarded as an offensive term pertaining to a person whose parents are of different ‘races’. The term has nothing whatever to do with transitional or intermediate forms. In fact, the fossil record contains numerous examples of transitional forms, between species and between higher groups.

Before we leave the subject of transitional fossils, a brief word about whale evolution. Wishart continues to ignore the impressive fossil evidence-a series of forms beginning with a semi-aquatic predator (Pakicetus), probably derived from the hippo-pig lineage of artiodactyls, and ending with modern whales.

The Cambrian Explosion

He again raises what is colloquially called the Cambrian explosion. The Cambrian period saw the first appearance in the fossil record of many of the major phyla of multi-cellular animals. Naturally, creationists like to take ‘explosion’ literally, depicting this period as a time of sudden or instant creation, and hence supporting the creationist scenario. (The fact that many groups preceded them, and many have arisen subsequently, seems not to concern them!) It was nothing of the sort. In brief, new groups appeared in the Cambrian over tens of millions of years. One of the chief reasons for the variety of new fossils during this period is clearly the arrival of hard-shelled invertebrates conducive to fossilisation.

There are many more examples of misconceptions and distortions about evolution in Wishart’s chapter, too numerous to expose here. The key message to take away from this critique: if you decide to read Ian Wishart or Ann Coulter on evolution, or any other ID proponent on the same subject, keep a salt cellar handy!

For previous critiques of Ian Wishart on evolution, see NZ Skeptic, winter 2002; summer 2003.

Recommended additional reading: Donald R. Prothero (2007). Evolution. What the Fossils Say and Why It Matters. Columbia University Press, New York.

Hokum Locum

Drink your way to good health

Don’t scoff. A magazine as authoritative as Woman’s Day reports a case where a woman treated her breast cancer by drinking her own urine. Following a mammogram and ultrasound examination the patient reports: “I was introduced to a surgeon who said I needed to have both my breasts removed right away.” This is complete nonsense as no surgeon would ever perform a bilateral mastectomy without a tissue sample confirming the diagnosis. It is quite clear that she never had cancer at all, but a condition colloquially known as lumpy breasts or benign fibrocystic breast disease.

Such people are a godsend for cancer quacks. There’s nothing easier than curing somebody who was never ill in the first place. In fact, that’s the whole basis of ‘alternative medicine’.

I googled the subject of urine drinking and there are a surprising number of articles on the subject. My favourite was a reference to the Koryak tribe of Siberia who used to get stoned by consuming the fly agaric toadstool, Amanita muscaria. The hallucinogens are excreted in the urine and as the account goes: “those who cannot afford the fairly high price (of the fungi) drink the urine of those who have eaten it, whereupon they become intoxicated.” (Wasson, quoted in Murder, Magic and Medicine, by John Mann)

Hyperbaric Oxygen-I don’t think so!

A local clinic offers “Hyperbaric Oxygen Therapy” at a cost of $60-$110. The pamphlet says:

“A cleanse with intraceuticals products first followed by a deep exfoliation. Oxygen Therapy applied with serums suitable to skin condition – a relaxing soothing treatment incorporating lymphathic (sic) drainage for a complete rejuvenation/brightening or reduction of fine lines. Also treats acne, rosacea, eczema and open pores-super hydrates. Complimentary home care product if a course of six treatments (weekly) booked.”

This clearly constitutes false advertising as well as an affront to grammar and spelling. Hyperbaric oxygen means oxygen under pressure and this requires either a pressurised mask or a chamber which can be pressurised. I have contacted the Commerce Commission over this false claim and I will keep you posted.

Cancer Diversions

A friend has been unlucky enough to develop bowel cancer last year and then go down with breast cancer this year. She has faced up to all of this with equanimity. Another acquaintance of mine, a doctor, has been diagnosed with a form of cancer which is likely to be terminal. This person is now on a vegetarian diet with no alcohol and is described by friends as “doing very well.”

It’s hard to imagine the fear and horror of being diagnosed with cancer. It leads to all sorts of irrational thinking, even by doctors. If I ever got cancer I would take up smoking again, use hard drugs, drink as much as I liked and indulge myself in dangerous sports. Go out with a bang, not a whimper! Such a strategy could well see cancer cells shrinking against an onslaught of nasty substances.

“Magical” thinking about cancer extends to psychological issues. An Australian study comprehensively debunked the idea that mental attitude has anything to do with beating cancer. For example, women who were preoccupied about their cancer were more likely to get a relapse. The researchers found that such women had the worst tumors-they were anxious and preoccupied for a reason! This sort of analysis is at the heart of skepticism – looking at the facts and coming up with the most likely explanation-not some horribly deprivational diet that denies people meat, wine and what little enjoyment of life they have left.

The chief executive of the Cancer Council Australia, Professor Ian Olver said that he had been involved with a smaller study with lung cancer and had reached a similar conclusion. Marlborough Express 4 June

Bogus Body Enhancer

Winston and Sylvia Gallot were ordered to pay $632,500 and $130,000 costs after being convicted of breaching the Fair Trading Act. Their weight loss product, Body Enhancer, was described by the judge as being ineffective. The High Court dismissed the quacks’ appeal but reduced the fines to $394,500.

Never mind, the couple must be laughing all the way to the bank as it was estimated that about $5 million of the product had been sold. If you google the offending product there is a wealth of material to review. I particularly enjoyed the Judge’s descriptions as follows:

“Mr Gallot was described as a man of considerable intelligence, style and charm, but he was exposed as ‘calculatedly dishonest’ and blamed everyone but himself.”

Judge Moore referred to a “succession of blatant untruths” by Mrs Gallot in trying to launch Body Enhancer in Britain.’

Marlborough Express 30 May

Another useless product

The Commerce Commission successfully prosecuted another useless product which claimed to “melt away fat and cellulite.” A judge said anyone who purchased Celluslim wasted their money.

The company had claimed that the product “had been scientifically tested by a fictitious doctor at the fictitious Saint Alto Research Centre in Switzerland.” When their useless product ran out they merely substituted honey, garlic and apple cider vinegar pills.

Marlborough Express 30 May

Amalgam again

A local dentist missed out on a health contract because of his opposition to dental amalgam. The amalgam debate has raged for decades and has parallels with the pure water crackpots who oppose fluoridation. Amalgam is a stable compound that is not ideal but it is the most cost effective agent at present. When something better comes along it will be superseded. I have a mouth full of amalgam fillings-a legacy of growing up without fluoridation. My mother gave fluoride tablets to the remaining four siblings who all have perfect teeth. People who elect to have their amalgam fillings removed expose themselves to a great deal of mercury which is released during destruction of their fillings. Those of us who sensibly live with our existing amalgam fillings can rest assured that our major mercury exposure comes from fish and chips.

Marlborough Express 25 March

Body Talk

I will have to rethink my theory that “wacky ideas are promoted by people who are bald and have beards”. After rubbishing body talk in an earlier column I was stunned to see that this ludicrous nonsense has arrived in Blenheim. Get this-straight from the reporter:

“I lie down on the consultation table and she holds my hand loosely over my stomach. A series of yes or no questions are asked and she lifts my hand in a circular motion each time, sensing resistance or acceptance of the question. It’s when she picks up on a positive response; she places my hand over my sternum and then taps me several times on the head, then taps me on my heart zone.”

The reporter accidentally stumbles across the mechanism when reporting: “It bears a resemblance to the ‘laying on of hands’ popular among some born again Christian groups.”

This whole mélange of hocus pocus is of course a placebo. It is staggering that such nonsense can gain credence and it beggars belief that a newspaper should even bother reporting it. How ridiculous does something have to be before an editor would reject it?

Saturday Express 24 May

Anti-oxidants: the key to nutritional success?

Extravagant claims are often made for the health-giving effects of anti-oxidants in the foods we eat. But sorting out the truth from the hype is not at all easy.

In the window of a health-food shop, I saw an advertisement extolling the merits of Goji berries. The advertisement said that an ‘ORAC test’ had shown that Goji berries have a lot of anti-oxidants in them. ‘ORAC test’ has a scientific ring about it-Goji berries must be good!

Anti-oxidants have attracted a reputation as beneficial ingredients of foods, nutritional supplements and cosmetics. So I thought I would try to describe what anti-oxidants are, and explain what the ORAC test is and its limitations. I’ll also give some examples of anti-oxidants in fruits and vegetables, and make some comments as to whether it’s worthwhile taking supplements containing these anti-oxidants in an attempt to get more of them inside you than is usual from a healthy diet.

What are anti-oxidants? Let’s start with oxidation and move onto food. Oxidation is a process in which electrons are removed from atoms and molecules. Oxygen is the classic oxidising agent. Digestion of food and extraction of energy from it is essentially an oxidative process. It occurs over many steps but one of the final outcomes is the transfer of electrons to oxygen (which is why our existence is dependent on a supply of this gas*). When the electrons are passed to oxygen, water is formed but oxygen ‘radicals’ are also formed as a side effect. Radicals are atoms or molecules which have one or more unpaired electrons. By virtue of the unpaired electrons, radicals (sometimes referred to as ‘free radicals’) are extremely reactive. The oxygen radicals are no exception and if not mopped up will cause all sorts of havoc by reacting with molecules that they shouldn’t react with. In short, oxygen radicals are toxic.

An example of an oxygen radical generated in our bodies is the ‘superoxide radical’: O2.-, two oxygen atoms linked together to form a molecule that has an unpaired electron (the dot) and a negative charge (the dash). It’s been estimated that an adult weighing 70 kg makes about 1.7 kg of superoxide radicals a year. This is equivalent to about one percent of total oxygen consumption.

Molecules that can neutralise free radicals are called anti-oxidants. Anti-oxidants do not react only with oxygen radicals. Other ‘reactive species’ capable of causing oxidative damage and that react with anti-oxidants may contain, for example, nitrogen and sulphur. Barry Halliwell and John Gutteridge give a more formal definition of an anti-oxidant in Free Radicals and Biology in Medicine (2007), which is: “any substance that delays, prevents or removes oxidative damage to target molecules”.

Reactive species in addition to oxygen radicals also end up in our bodies. Cigarette smoke, for example, contains free radicals. Given the toxicity of oxygen radicals and other reactive species, it’s not suprising that anti-oxidants are considered a good thing, and that it’s thought a good idea to make sure we have as much of them inside our bodies as possible. Fortunately, our bodies have a number of built-in anti-oxidant systems to protect us against oxygen radicals formed as we breathe, and other reactive species. I am not going to deal with these systems but will confine my attention to dietary sources of anti-oxidants as it is these which are usually discussed in dietary advice and turn up in nutritional supplements. These anti-oxidants are, by and large, derived from plants.

Measuring Anti-oxidants

The ORAC test is one of the principal assays used to estimate the anti-oxidant content of such materials. (If all this seems a bit dry, bear with me because the nature of assays for anti-oxidants is central to claims that supplements, foods, etc, contain a lot of them.)

When an analyst is faced with developing a chemical assay to find out how much of something is in a sample of fruit or vegetable, one approach is to find some reagents which when added to the sample react with the substance(s) in question and in so doing exhibit a measurable change in some property of the mixture, eg an increase in colour intensity. Hopefully the technique is sufficiently sensitive (will measure quantities that are of interest to the analyst), selective (ideally the reagents react only with the substance(s) in question) and quantitative (the properties of the mixture change in a regular way as the amount of substance changes). Many assays are quite selective; others only give an indication of the amount of a class of compound. The ORAC test is of this latter type.

There are dozens of molecules that can be classed as anti-oxidants and it would be a lengthy and expensive task to identify the compounds in a sample every time an estimate of the overall level of anti-oxidant activity was required. Tests like the ORAC assay are used to estimate overall activity in a sample, the amount of activity being expressed as ‘equivalent to’ an amount of a ‘standard’ anti-oxidant compound.

ORAC stands for Oxygen Radical Absorbance Capacity. The basic premise behind this assay is that the ability of a sample to neutralise free radicals indicates the presence of anti-oxidants. When exposed to light, a substance called fluorescein emits light of a longer wavelength than that shining on it; this ‘fluorescence’ can be measured using a fluorimeter. Fluorescein also has the useful property that its fluorescence is diminished in the presence of free radicals. We would have the basis of an assay if we mixed our sample with fluorescein and a source of free radicals and saw that the decrease in fluorescence was less than in the absence of the sample because of the protective effect of anti-oxidants. This wouldn’t get us very far as about all we could do would be to say that one sample had more or less anti-oxidant activity than another. The assay could be made more quantitative if we were able to compare estimates of activity from various samples with those obtained using a known standard anti-oxidant. A commonly used one is Trolox, a synthetic analogue of vitamin E.

So in the complete assay we would measure the fluorescence coming from a series of solutions containing increasing amounts of Trolox but constant amounts of fluorescein and free radicals. If we run everything correctly there will be a regular and positive relationship between the fluorescence emitted and the amount of Trolox present. We would also measure the fluorescence coming from solutions containing the free radicals and our extract of Goji berries (no Trolox), and calculate that a measured amount of Goji berries contained an anti-oxidant activity equivalent to that provided by a known amount of Trolox. Another way of looking at this is that we have estimated so many grams of berries as having the same ability as a certain amount of Trolox to protect fluorescein from oxidation by the free radicals.

Remember that the ORAC test only gives a measure of the ability of our extract to protect fluorescein from the action of free radicals in vitro (in vitro-in the test tube; in vivo-in the living body). It says nothing about the anti-oxidant activity of the extract once it has been ingested (in vivo). A high ORAC value simply tells us that the extract contains molecules that might have some anti-oxidant activity in vivo.

The principal value of an assay of this type lies in the ability to compare different samples of plants, foods etc according to a single property. The table below contains some ORAC values for anti-oxidant levels in some fruits and vegetables. These values have been taken from a larger set published by the United States Department of Agriculture (USDA, 2007).

The units of measurement are µmol Trolox Equivalents per 100 g fresh weight (FW) of fruit or vegetable. Fresh weight is the weight of the leaf, fruit etc as it is harvested with no adhering dirt, fully hydrated but with no surface drops of water. A mole (abbreviated as mol) is a measure of the amount of Trolox and 1 µmol of Trolox has a mass of 0.00025 g. So, if a vegetable has an ORAC value of 1000 TE per 100 g FW, then 100 g FW of the vegetable has the same ability, in the test-tube, to neutralise free radicals as 1000 µmol or 0.25 g of Trolox.

µmol TE / 100 g FW
Turmeric 119346
Curry powder 6665
Blueberries 6552
Apples, Granny Smith, raw with skin 3898
without skin 2573
Cashew nuts, raw 1948
Avocadoes, Hass 1933
Onions, raw 1034
Green peppers, raw 923
Bananas,raw 879
Carrots, raw 666
Cabbage,raw 508
Tomatoes, raw 367
…and Goji berries? It’s not easy to find a reputable ORAC value but it does seem to be considerably higher than most other plants tested.

Examples of anti-oxidants

What are these anti-oxidants of plant origin? Here are a few examples, with some comments as to whether they exert a beneficial effect in vivo.

Vitamin C or ascorbic acid: This is an essential nutrient, famous for its role in the prevention of scurvy. It is an anti-oxidant in vitro but it is uncertain as to whether it has any major effects as an anti-oxidant in vivo. Sufficient vitamin C to maintain health can be obtained from a diet including fruits and vegetables. With such a diet, there is no evidence of beneficial effects of supplementary doses.

(Scurvy is a deficiency disease of connective tissue. The role of vitamin C here is not that of an anti-oxidant but to ensure that enzymes involved in the synthesis of connective tissue function effectively.)

Vitamin E: Vitamin E was first defined as a fat-soluble ‘factor’ necessary for reproduction in rats. It is not a single compound, a number of substances having vitamin E activity. The principal ‘natural’ form is α-tocopherol. Mixtures of tocopherols are found, for example, in soybean, corn, walnut and rapeseed oils. The evidence for anti-oxidant effects in well-nourished humans is limited.

Carotenoids: These are orange and yellow pigments found in plants, most typically in carrots. ß-carotene is a common carotenoid. There is only weak evidence that they have an anti-oxidant role in vivo. (They do have an important role in the diet for other reasons, principally as a precursor for vitamin A.)

Polyphenols: Polyphenols are compounds that have groups of six carbon atoms linked together in rings. The rings have hydroxyl groups (-OH) attached to them. Polyphenols of plant origin are excellent anti-oxidants in vitro, but it does not follow that they have the same effect in vivo. This group contains the compounds found in blueberries and blackcurrants and some have become quite well known through discussion of their potential anti-oxidant properties, eg resveratrol from red wine, quercetin in teas and onions, and curcumin from turmeric.


There is evidence from epidemiological studies of correlations between anti-oxidant levels in the body and good health, and between good health and diets rich in fruit and vegetables. Correlations however do not prove causation and it remains uncertain whether the correlations observed are due to compounds exerting anti-oxidant effects in vivo. A further problem in interpreting epidemiological studies is that it is difficult to be accurate about the relationship between dietary intake and incidence of disease, particularly when studies seek to understand data gathered across different countries. Intervention studies

Intervention studies (where one group of subjects is provided with a supplement, and their health and physiological status is compared to a matched group receiving a placebo) might help us decide whether supplements are worth taking, but it has proved difficult to obtain evidence of a cause and effect relationship in these. Halliwell & Gutteridge (2007) describe the literature on intervention studies seeking to demonstrate a link between diet and supplementary anti-oxidants as a “morass of confusing data”.

Some clarity on the effects of supplements of some anti-oxidants (ß-carotene, vitamins A, C, E) and selenium has been given by a recent Cochrane review (Bjelakovic et al., 2008). This review considered 67 trials, involving 232,550 people, of the effects of taking supplements of these anti-oxidants. The principal conclusion from consideration of all this data was that overall, there is no evidence for an effect of these supplements on mortality in healthy people or those with various diseases. When the effects of different supplements were looked at separately, there was an increased risk (which only just reached statistical significance) of mortality associated with supplements of vitamins A, E and beta-carotene. There were no significant effects on mortality from vitamin C or selenium supplementation. (Selenium is an essential nutrient and is a component of several enzymes, some of which are thought to have anti-oxidant functions.)


What to do? If we take the epidemiological evidence as our guide, eating lots of fruit and vegetables is sensible advice. They have established beneficial effects, such as being enjoyable to eat, providing fibre and helping to maintain adequate levels of vitamins and minerals. The anti-oxidants they contain might exert a direct beneficial effect in vivo. At this point in our knowledge of dietary anti-oxidants and their effects in vivo, there seems little, if any, point in spending money on supplements of anti-oxidants.

Alan Hart spent over 30 years doing biology research. The last 15 were spent developing assays of various kinds. He has an interest in the meaning and practice of biological measurement.

*An excellent and readable account of the role of oxygen in our world, including a discussion of oxygen radicals and anti-oxidants, is Nick Lane, 2002: Oxygen, The molecule that made the world, Oxford University Press.