Some products containing nano-sized particles are already on the market. In America and Europe, nano-sized ingredients have been added to some fruit juices, processed meats, diet milkshakes and baby food. But consumers would not know, as there are no requirements to label the presence of nanoparticles in food. Concerns are also growing about the possible harmful effects of nano-sized materials on human health and the environment.

In a comprehensive review of the issue, a British researcher, Dr Qasim Chaudhry, and his team conclude there are major gaps in knowledge about the safety of nanoparticles. "The toxicological nature of hazard, likelihood of exposure and risk to consumers from nanotechnology-derived food and food packaging are largely unknown," says Chaudhry, of Britain's Department for Environment, Food and Rural Affairs' Central Science Laboratory. Their study is published in this month's Food Additives and Contaminants journal. Evidence that nanoparticles are more chemically reactive than larger particles, and that some are toxic to cells has prompted the environmental group Friends of the Earth, as well as the NSW Greens, to call for a moratorium on the use of nano-sized ingredients in food, food packaging or surfaces that can come into contact with food. Friends of the Earth spokeswoman, Georgia Miller, says it is possible nano-sized ingredients are already present in Australian food, but without labelling or regulations it is impossible to know. "There is no way for anyone to choose to eat nano-free," says Miller, co-author of a report called Out Of The Laboratory And Onto Our Plate, Nanotechnology In Food And Agriculture.

Food Standards Australia New Zealand says it is not aware of any commercially sold foods in Australia that have been developed using nanotechnology, and says "robust regulatory arrangements to ensure the safety of food" are in place. As part of its national nanotechnology strategy, the Federal Government has also commissioned a review of regulations covering nanotechnology. Professor Graeme Hodge, of Monash University, who helped carry out the review, says Australia is one of the few countries to have done this. People should not overreact to concerns about nanofoods because a host of standards guarding food safety are already in place: "We're not coming at the question of nanotechnology from a blank slate."

He says a sophisticated middle road needs to be trodden between premature bans and a laissez-faire attitude, starting with an international agreement on a definition for nanomaterials. It is also vital the public is involved in debates about the safety and regulation of nanomaterials in consumer products such as cosmetics, foods and medicines, Hodge says. Chaudhry points out that the public knows very little about nanofoods, and there could be a backlash, as with genetically modified foods.

"The food industry could consider voluntarily declaring the use of nano-additives, especially where free engineered nanoparticles have been introduced into food and drinks, and where such products are likely to be consumed in large quantities and or by a large proportion of the population," he says. One of its first uses in food has been the addition of nutritional supplements. The German company Aquanova produces ball-like structures about 30 nanometres across, called micelles, inside which additives - such as vitamins or antioxidants - can be placed for better absorption.

Another German company, BASF, produces a nano-sized synthetic tomato colouring for soft drinks and baking mixtures. Nanostructures made from soya bean extract, that protect nutrients during manufacture and storage, are under development, as are nanotubes made from milk protein, says Chaudhry. These methods could be used to develop colourless and tasteless drinks that the consumer controls with a particular microwave frequency. "This would lead to the activation of selected nanocapsules, while the others remain latent, releasing only the preferred flavour, colour or nutrients." By making ingredients tiny, products such as low fat mayonnaise or ice-cream could be produced that are as smooth in texture as high-fat ones, he says.

The nanofood sector is led by the US, followed by Japan and China. Asian countries, particularly China, are expected to be the biggest market for nanofood by 2010. Food packaging using nanotechnology is more advanced than nanofoods, with products on the market that incorporate nanomaterials that scavenge oxygen, fight bacteria, keep in moisture or sense the state of the food.

Plastic incorporating nanoparticles of clay or oxides of metals such as zinc and titanium have already been used to package meats, cheese, confectionery, beer, fruit juice and soft drink overseas. Nanoparticles of silver are being used to coat the inner surfaces of fridges as well as cutlery and chopping boards, with the promise of keeping the environment clean and hygienic. The Friends of the Earth report has identified more than 100 nanoproducts used in food, packaging and agriculture. "We believe this to be just a small fraction of the total number of products now available worldwide," says Miller.

The main concern to consumers from nanoparticles in food packaging is through their migration into food and drinks, says Chaudhry. "However, such migration data are not currently available." Few studies have been carried out on the toxic effects of nanoparticles, and most deal with the risks of breathing them in, rather than consuming them, he says.

Yet evidence is growing that they can cross into cells and increase the risk of oxidative damage. It has also been shown that particles smaller than 70 nanometres can reach the nucleus of the cell and possibly disrupt the DNA. Although one of the benefits of nanotechnology may be to increase absorption of nutrients from food, there are unknown consequences, such as a possible change in the balance of nutrients in the body. "It is also of concern that the introduction into foods of nanoparticles designed to carry dietary supplements could lead to the introduction of foreign substances into the blood," says Chaudhry.

Nanosilver, for example, is good at killing bacteria. But no research has been published about the possible effects of consuming it on the beneficial bacteria in our guts. The question of whether nanoparticles can cause an inflammatory response from the body is also poorly understood, he says.

"There is an urgent need for research into the behaviour of foodstuffs, both manipulated and processed at the nanoscale and the properties of manufactured nanoparticles introduced into foods whether deliberately or as the result of contamination." In Europe the Institute of Food Science and Technology, as well as the British Royal Society have recommended nanoparticles be treated by regulators as new, potentially harmful materials until they are proven safe. Miller adds that apart from the safety issues, nanofood will make it even more unlikely that people will eat fresh, sustainably produced food.

A free public forum on nanotechnology will be held at the State Library of NSW on Thursday April 3 at 6pm.