How do you fancy tucking into a bowl of ice cream that has no more fat than a carrot? Or eating a burger that will lower your cholesterol? If you are allergic to peanuts, perhaps you'd like to fix your food so that any nut traces pass harmlessly through your body. Welcome to the world of nanofoods, where almost anything is possible: where food can be manipulated at an atomic or molecular level to taste as delicious as you want, do you as much good as you want, and stay fresh for ... well, who knows? A world where smart pesticides are harmless until they reach the stomachs of destructive insects; where food manufacturers promise an end to starvation; where smart packaging sniffs out and destroys the micro-organisms that make good food go bad. In short, a food heaven to those who see it spelling the end of obesity and poor diet. Food hell to those who believe the case for nanofood safety is still far from proven. One thing is certain: after the controversy that surrounded genetically modified foods, nano is set to become the next kitchen battleground.

Nanotechnology has its roots in a talk delivered in 1959 by physicist Richard Feynman to the American Physical Society. He predicted a time when individual atoms and molecules might be used as the building blocks for a set of tools that could then make a smaller set, and so on. The scale he was talking about strains the imagination. A nanometer - nm - (from the Greek word nanos, dwarf) is one-billionth of a metre. To help you visualise how small that is, a red blood cell is about 7,000nm across, a human hair 80,000nm wide and a water molecule slightly less than 0.3nm in diameter. The science of nanotechnology generally inhabits the region of 0.1nm to 100nm.

The science behind the theory became a reality in the 1980s with the invention of specialist microscopes which allowed scientists to see how atoms and molecules behaved in different conditions. By manipulating those conditions - say, with other chemicals, heat, moisture, electromagnetism and so on - they could encourage atoms and molecules to form useful shapes.

This resulted in the creation of new nanomaterials built at the atomic level that promise to revolutionise everything from chemistry to aeronautics. Some nanotechnology products are already on the market - sunscreens, for example, make use of titanium oxide, TiO2. At larger scales TiO2 is white, opaque and good for blocking ultraviolet light. However, at the nanoscale it becomes transparent while retaining its UV-blocking properties, making it perfect for protection against the sun's harmful rays.

Others look set to follow. Carbon nanotubes, for example, could revolutionise the construction industry. Seamless tubes of graphite one atom thick and 10,000 long (to the naked eye, large quantities would look like soot), carbon nanotubes are up to 100 times stronger than steel but around eight times lighter. They can be teased into a twine that can be woven into sheets and, potentially, mixed with composites to eventually overhaul the way - and the height to which - we build. And those buildings could be covered with solar cells made from nanomaterials that could supply all their energy needs. In medicine, "nanocapsules" containing pharmaceuticals that can be programmed to release their cargoes only on contact with, say, cancer cells, are promising new and improved treatments. Not surprising, then, that the proponents of nanotechnology predict that it will lead to a new industrial revolution.

In food, however, the excitement is being matched by health and environmental concerns at all three stages of production: farming, processing and packaging. In its report, Down on the Farm, the ETC Group, an independent Canadian technology watchdog, predicts: "From soil to supper, nanotechnology will not only change how every step of the food chain operates, but it will also change who is involved. At stake is the world's $3 trillion food retail market, agricultural export markets valued at $544bn, the livelihoods of 2.6 billion farming people, and the wellbeing of the rest of us who depend upon farmers for our daily bread."

Nano-futurists don't dispute that, one day, nanofoods will be everywhere. They envisage a day when tiny sensors called motes or smart dust will radio information to the farmer detailing what is going on in his field, inside his crops and in the bodies of his animals so that he can optimise his yields. While such "precision farming" is some way off, nanotechnology is already here in the form of smart pesticides, or nanocides. Syngenta, Monsanto and BASF are among companies that have either developed or are researching pesticides on the nano-scale that they claim will be more stable, longer-lasting and deadlier to pests.

Several of these have already passed safety tests and are licensed for use in Britain and the US. Their active ingredients have been around for years without causing problems; only the delivery method has changed. This involves controlled-release systems that use small polymer capsules which can be more evenly diluted in liquid, be programmed to "stick" to the parts of plants where they are needed, and even remain inert until activated by the alkaline content of a certain insect's stomach; only then do they burst open and kill the pest. Agrochemical companies argue that this means the pesticides are smarter, need lower concentrations of active ingredients, can be programmed not to harm "friendly" insects, and are more easily and safely broken down in the environment.

Packaging, too, may change. Coatings made from smart nanoparticles that can sniff out the telltale gases given off by deteriorating food will trigger colour changes on labels. The label will also tell you when something is ripe. It's called intelligent packaging.

But there is a problem. There are signs that consumers will recoil from any food to which this new technology is applied. Several years ago, the big food companies were happy to talk about products that might be in the pipeline. Famously, Kraft Foods described a tasteless, odourless drink that might contain dozens of flavours, colours and nutrients in billions of microcapsules that could be activated - possibly by microwave - at home. You might turn it into a strawberry-flavoured drink, while I might opt for lemon and lime. Then came the consumer opposition to GM. Nowadays it is difficult to get food companies even to admit they are conducting researching into nano.

However, one firm of German technology analysts, the Helmut Kaiser Consultancy, estimates that hundreds of food companies are conducting research into nanotechnology. Its latest report says: "The nanofood market [soared] from $2.6bn in 2003 to $5.3bn in 2005 and is expected to reach $20.4bn in 2010. The nano-featured food-packaging market will grow from $1.1bn in 2005 to $3.7bn in 2010. More than 400 companies around the world are active in research, development and production. The US is the leader, followed by Japan and China. By 2010, Asia, with more than 50% of the world population, will become the biggest market for nanofood, with China in the leading position."

I approached five of the world's largest food companies, Kraft, Cadbury Schweppes, Unilever, Nestlé and HJ Heinz. Cadbury Schweppes said it was "keeping a watching brief" but was not actively researching nanofood; Heinz had no plans to use nanotechnology; and Kraft and Nestlé made no comment. Unilever, however, was willing to provide a food manufacturer's perspective.

Charles-François Gaudefroy, whose job title - head of consumer confidence and sustainability for research and development - is indicative of the task ahead of him, says there is much hype about nanofood. "There are some people who say nanotechnology is everywhere," he says. "Well, I'd like to see it first. We do not have it in food at the moment, but the potential is manifold, particularly in stabilising foods and enhancing their nutritional properties. For example, if you squeeze an orange and drink it now, you will get vitamin C from it, but if you leave it a while, all the vitamin C will vanish. Putting the vitamin C in nanocapsules can allow it to be released only when it is drunk.

"And [it could be useful in] stabilising nutrients in food. For example, iron and essential fats such as omega-3 do not remain stable in liquids; they oxidise and that changes the colour, odour, the taste of the product ... You could use nanotechnology to stabilise the nutritional properties of products and that would be of benefit to people with deficiencies - anaemia, for example."

Food companies, he says, are also excited by the prospect of intelligent packaging and the ability to give foods a longer shelf life. "In Africa, there is food, but part of the issue is bringing it to the table and increasing its nutrition profile to give children a better start. Stabilisation of nutrients and enabling longer shelf life are areas of development that can reduce suffering."

In Europe, any nanofoods would have to gain approval under a European Commission directive on new foods and ingredients that was introduced in 1997 to regulate genetically modified products or those manipulated at a molecular level. The directive requires such products to be assessed by member states before a licence can be granted. In Britain, the EU and the US, moves have been made to introduce voluntary codes of practice for research and manufacturing in nanotechnology, but hard legislation is lagging behind.

So what about safety? A report by the Royal Society and the Royal Academy of Engineering in 2004 expressed concern that little was known about the behaviour of nanoparticles in the environment and recommended that waste containing them should be treated as hazardous until proven otherwise. Since then, the Royal Society and the Council for Science and Technology (CST), the government's main advisory body on science issues, has criticised ministers for failing to put measures in place for assessing the environmental risks. "There is a pressing need for a programme of central government spending [on research] into the toxicology, health and environmental effects of nanotechnologies," the chairman of the CST's nanotechnologies sub-group, Professor John Beringer, said in March last year. "Without a substantial home research endeavour, the UK risks being left out in the cold in future international collaboration. To put it bluntly, the safe development of a new technology should not depend on whether an academic wins a highly competitive research grant."

The US's Environmental Protection Agency has set up a committee to develop a framework for safety legislation, but the tendency so far has been to accept nano-manipulated materials as being no different from their larger relatives. But any chemist will tell you that materials behave differently at different sizes. Aluminium, for example, is stable in everyday concentrations, but becomes explosive at micro-fine levels.

"I think the authorities know this and they are concerned, but they've been caught flat-footed," says Pat Mooney, the executive director of ETC. "I met a guy who said his company was shipping carbon nanotubes but they'd started limiting the shipment to a couple of kilos at a time because in concentrations of more than that they tended to become explosive. His company didn't know why. That inevitably raises questions about nanotechnology in pesticides and food."

Lynn Frewer, professor of food safety and consumer behaviour at Wageningen University in the Netherlands, acknowledges the potential benefits nanotechnology could bring, but when I ask her about the risks, she says: "The problem with the digestion of nanoparticles is that we don't know where in the body they would end up. If they are small enough to travel through the wall of the gut, which some nanoparticles would be designed to do, they could end up anywhere. And how will they accumulate and travel through the food chain? We simply don't know."

Dr Mike Bushell, Syngenta's research head, disagrees, arguing that nano-sized particles are more easily and safely degraded in the environment. There is, then, much disagreement in an industry still in its infancy, an industry that hasn't yet got international standards of safety. There isn't even an internationally accepted lexicon of nanotechnology.

Last year, the Woodrow Wilson International Centre for Scholars in Washington, an independent Washington-based research institute, published a report entitled Nanotechnology in Agriculture and Food. It expressed concern at the lack of research, concluding: "Neither industry nor government appears to be doing its homework. Products could end up in the market without a proper assessment of risk or end up indefinitely halted at the threshold of commercialisation."

Whether nano-engineered foodstuffs land on our tables will, to a large extent, depend on consumers. If it proves as controversial as GM to many food buyers and environmentalists, then marketing it could be difficult - something of which the industry is well aware. Unilever's Gaudefroy says: "There are areas where debate is vital and it is only just beginning. Much of this is driven by what happened with GM. We have to explain to consumers the good side of nanotechnology and what benefits it can bring them.

"Food regulations, in particular the EU's novel-foods directive, prescribe stringent environmental and safety evaluation before anything is introduced to the market. I can see areas where people could be afraid of nanotechnology - in weaponry, for example. But in food? No. I really don't see mad scientists doing mad things."

· This article was amended on Thursday April 3 2008. In the article above we originally said that any nanofood product would have to be approved and licensed under a European directorate. We meant directive, not directorate. This has been corrected.