an autodidact meets a dilettante…

Oh,rats – they’ve exposed the conspiracy!

Food irradiation is a well-known process for preserving food and eliminating or reducing bacteria. It’s used for much the same purpose that pressure cooking of tinned food is used, or the pasteurization of milk. All food used by NASA astronauts in space is irradiated, to reduce the possibility of food-borne illness.

advantages and disadvantages of irradiation

According to the US Department of Health’s Center for Disease Control and Prevention (CDC), irradiation, if applied correctly, has been clearly shown to reduce or eliminate food pathogens, without reducing the nutritional value of the food. It should be noted that irradiation doesn’t make food radioactive. I’ll look at the science of irradiation shortly.

Of course it’s not a cure-all. For example, it doesn’t halt the ageing process, and can make older fruit look fresher than it is. The reduction in nutritional value of the food, caused by the ageing process, can be masked by irradiation. It can also kill off bacteria that produce an odour that alerts you that the food is going off. Also, it doesn’t get rid of neurotoxins like those produced by Clostridium botulinum. Irradiation will kill off the bacteria, but not the toxins produced by the bacteria prior to irradiation.

how does food irradiation work?

Three different types of irradiation technology are used, using gamma rays (cobalt-60), electron beams and x-rays. The idea is the same with each, the use of ionising radiation to break chemical bonds in molecules within bacteria and other microbes, leading to their death or greatly inhibiting their growth. The amount of ionising radiation is carefully measured, and the radiation takes place in a special room or chamber for a specified duration.

When radioactive cobalt 60 is the energy source, it’s contained in two stainless steel tubes, one inside the other, called ‘source pencils’. They’re kept on a rack in an underground water chamber, and raised out of the water when required. The water isn’t radioactive. Food products move along a conveyor belt into a room where they’re exposed to the rack containing the source pencils. Gamma rays (photons) pass through the tubes and treat the food. The cobalt 60 process is generally used in the USA.

An Electron-beam Linear Accelerator generates, concentrates and accelerates electrons to up to 99% of light-speed.These electron beams are scanned over the product. The machine uses energy levels of 5, 7.5 or 10 MeV (million electron volts). Again the product is usually guided under the beam by a conveyor system at a predetermined speed to obtain the appropriate dosage. This will clearly vary with product type and thickness.

The X-ray process starts with an electron beam accelerator targeting electrons on a metal plate. The energy that isn’t absorbed is converted into x-rays, which, like gamma rays, can penetrate food containers more than 40cms thick. Shipping containers, for example.

Most of the radiation used in these processes passes through the food without being absorbed. It’s the absorbed radiation, of course, that has the effect, destroying microbes and so extending shelf life, and slowing down the ripening of fruits and vegetables. The potential is there for food irradiation to replace chemical fumigants and fungicides used after harvest. It also has the potential, through the use of higher doses, to kill contaminating bacteria in meat, such as Salmonella.

Food irradiation is a cold treatment. It doesn’t significantly raise the temperature of the food, and this minimises nutrient loss or changes in texture, colour and flavour. The energy it uses is too low to cause food to become radioactive. It has been compared to light passing through a window. Food irradiation uses the same principle as pasteurization, and can be described as pasteurization by energy instead of heat, or cold pasteurization..

the use of food irradiation in Australia

Due largely to fears about irradiation having to do with radioactivity and nuclear energy, the process isn’t used as widely in Australia (or indeed the USA) as it could be. Irradiation is used in some 50 countries, but the level of usage varies for each country, from very limited in Austria and other EU countries, to a very widespread usage in Brazil. Food Standards Australia New Zealand (FSANZ) summarises our situation thus:

In Australia and New Zealand, only herbs and spices, herbal infusions, tomatoes, capsicums and some tropical fruits can be irradiated.

FSANZ has established that there is a technological need to irradiate these foods, and that there are no safety concerns or significant loss of nutrients when irradiating these foods.

Irradiated food or ingredients must be labelled clearly as having been treated by ionising radiation.

food irradiation, health and safety

Since 1950 hundreds of studies have been carried out on animals fed with irradiated products, including multi-generational studies. On the basis of these studies, food irradiation has been approved by the World Health Organization, the American Dietetic Association, the Scientific Committee of the European Union and many other national and international monitoring bodies. Of course this hasn’t stopped many individuals and organisations from complaining and campaigning against the practice. Concerns include: chemical changes harmful to the consumer; impairment of flavour; the destruction of more ‘good’ than ‘bad’ bacteria; and that it’s an unnecessary process which runs counter to the movement towards regional product, seasonality and real freshness. I’ve already mentioned other problems, such as that it can mask spoiled food, and that it doesn’t destroy toxins already released by bacteria.

opposition from the organic food movement

Food products  must be irradiation-free if they are to certified as ‘organic’, in Australia and elsewhere. Now, I’ve fairly regularly expressed irritation with the ‘organic’ food ideology, most particularly in this post, but I recognise that it appeals to a very diverse set of people, with perhaps a majority simply believing, on faith, that ‘organic’ food will be more nutritious, safer and better for the environment than conventional food. Most of those people wouldn’t know much about food irradiation, but hey, it sounds dodgy, so why not avoid it? I’ve no great argument to make with such people, apart from the old ‘knowledge is power’ arguments, but there are a few individuals and organisations trying to get food irradiation banned, based on what they claim to be evidence. Unsurprisingly, most of these critics are also ‘organic’ food proponents. I’ll look at some criticisms from Eden Organic Foods, a US outfit, which admittedly represents the extreme end of the spectrum (nature before the fall?).

Firstly, in their ‘factsheet’ on irradiation, linked to above (and reprinted verbatim here by another alarmist organisation, the Center for Food Safety), they waste no time in informing us that the beams used are ‘millions of times more powerful than standard medical x-rays’. This sounds pretty scary, but it’s a bogus comparison. Irradiation is designed to kill bugs and bacteria, whereas medical x-rays are for making visible what is invisible to the naked eye. Clearly, the first and foremost concern in testing and studying the technology is to make sure that the chemical changes it induces are safe for humans. Comparisons with medical x-rays are more than irrelevant to this concern, as the author of this factsheet well knows.

Next comes this disturbing claim:

Radiation can do strange things to food, by creating substances called “unique radiolytic products.” These irradiation byproducts include a variety of mutagens – substances that can cause gene mutations, polyploidy (an abnormal condition in which cells contain more than two sets of chromosomes), chromosome aberrations (often associated with cancerous cells), and dominant lethal mutations (a change in a cell that prevents it from reproducing) in human cells. Making matters worse, many mutagens are also carcinogens

Wow. So much for the poor people of Brazil – they’re obviously done for. But how is it that the world’s top scientific agencies missed all these mutagens and carcinogens? Let’s take a closer look.

The term ‘radiolytic products’ simply means the products created by chemical changes that occur when food is irradiated. Similarly, the products created by heat treatment, or simply cooking, might be called ‘thermolytic products’. These are not ‘strange’, they’re quite predictable, for irradiation would be totally ineffective if it didn’t bring about some chemical changes. One of the differences is that radiolytic products are generally undetectable and produce only minor changes in the food compared to the major operation we call cooking. It is, of course, precisely these products that the scientific community scrutinises when determining the safety of irradiated foods.

Interestingly, in an article, dating back to 1999, called ‘Scientific answers to irradiation bugaboos’, for 21st Century Science & Technology magazine, Marjorie Mazel Hecht has this to say:

The July 1986 report of the Council for Agricultural Science and Technology (CAST), which reviewed all the research work on food irradiation, defined unique radiolytic products “as compounds that are formed by treating foods with ionizing energy, but are not found normally in any untreated foods and are not formed by other accepted methods of food processing.”

The report states that “on the basis of this definition no unique radiolytic compounds have been found in 30 years of research. Compounds produced in specific foods by ionizing energy have always been found in the same foods when processed by other accepted methods or in other foods” (Vol. 1, p. 15).

This slightly contradicts the factsheet put out by Idaho University’s Radiation Information Network, which acknowledges the existence of such products while insisting on their nugatory nature:

Scientists find the changes in food created by irradiation minor to those created by cooking. The products created by cooking are so significant that consumers can smell and taste them, whereas only a chemist with extremely sensitive lab equipment may be able to detect radiolytic products.

Needless to say, alarmists thrive on these contradictions. So what evidence is there of mutagenic irradiation byproducts? Well, there are radiolytic byproducts of fatty acids in meat, called alkylcyclobutanones (2-ACBs), first detected a few decades ago, and the research done on them seems to be so far inconclusive. A book entitled Food Irradiation Research and Technology, the second edition of which was published last year, states that ‘knowledge about the toxicological properties of 2-ACBs is still scarce’, and that ‘it may be prudent to collect more knowledge on the toxicological and metabolic properties of 2-ACBs in order to quantify a possible risk – albeit minimal.’ The book describes a number of studies on rats and humans, going into more detail than I can comprehend, but the results have been difficult to interpret and generally not easily replicable in other studies, indicating very minute and hard-to-measure effects. No doubt such studies will be ongoing. As far as I know, 2-ACBs are the only products about which there is any concern.

What is obvious though, in looking at the research material available online, is the difference between the caution, skepticism and uncertainty of researchers compared to the adamantine certainty of such critics as the Center for Food Safety.

But what about polyploidy? Polyploid cells contain more than two paired sets of chromosomes. Eukaryotic cells, those of multicellular creatures, are diploid (two sets), and prokaryotic, bacterial cells are haploid (one set). Polyploidy is regarded as a chromosomal aberration, common in many plants and some invertebrates, but relatively rare in humans. However it is present in humans, and the percentage varies from individual to individual, and within individuals from day to day and week to week, depending on a range of factors including diet, age, and even circadian rhythms. Levels of up to 3-4% in human lymphocytes have been found in healthy individuals, though some researchers have claimed much higher percentages, in liver cells. The overall finding so far is that fluctuations in polyploidy are the norm, and no clear correlation has been found so far between these fluctuations and health profiles. It seems that the biological significance of polyploidy isn’t known.

Critics of irradiation have been going on about polyploidy and other mutations supposedly caused by irradiation for decades, and unsurprisingly, some are fanatically obsessed with the issue, accompanying their rants with long reference lists, mostly from like-minded activists. However, the text Safety of irradiated foods, 2nd edition discusses polyploidy in some detail, with particular reference to a study of malnourished Indian children fed irradiated wheat, a study regularly cited by anti-irradiation activists. It turns out that there were many problems with the study. First, not enough cells were counted to validly pinpoint an effect, such as a change in diet. Secondly, polyploidy is notoriously difficult to detect – superimposed diploid cells can be easily mistaken for polyploid cells under a microscope (in fact when two independent observers looked at the same microscope slides, one found 34 polyploid cells, the other found 9). Further, the study only gave group results rather than individual results, so it wasn’t possible to know whether the polyploidy was restricted to one or two individuals rather than spread over the group. Another problem was that the reference or control group was found to have no polyploidy at all, a very strange finding given that other researchers always found some degree of polyploidy in their subjects, regardless of irradiation or other effects. In fact, the study was so poorly written up that it’s impossible to replicate – for example the exact diet given the children wasn’t described. How was the wheat fed to the children?. Presumably it was prepared in some way, but how? The omission is crucial. The study also didn’t take into account the effect of malnutrition itself on chromosomal abnormalities. And so on.

You get the picture, and it’s the same with other claims about mutations and carcinogens. Every time you look into the claims you find the same problems that no doubt other scientific watchdog organisations have found – poorly conducted studies that either can’t be replicated or haven’t survived replication. That, of course is no reason for complacency, and at least the activists can assist, in their sometimes muddle-headed ways, in improving our knowledge of 2-ACBs, polyploidy and other biological effects, just as the creationists who bang on about a lack of transitional forms, or ‘irreducible complexity’, help us to focus on refutations, clarifications and further evidence.

Finally, food irradiation, while clearly not the zappo-horrorshow that activists are determined to make it, doesn’t replace proper handling techniques and a good instinct about food quality. The fact is, though, that it does increase shelf life, and is a useful tool in our increasingly global economy, where food is shipped from here to there and everywhere, in season and out. If you prefer to eat locally, with fresh and seasonal produce, fine, and we can argue about the sustainability of that approach on a worldwide scale, but let’s none of us pretend that food irradiation is other than what it is. Let the evidence, properly evaluated, be your guide.