The next big thing: a diet tailored to your genes

Food fads come and go but one area of dietary research is expected to transform the way we eat and live. It is called nutrigenomics.

The unravelling of the human genome - once described as the greatest feat since the invention of the wheel - has spawned a new industry in nutritional advice based on our genes.

Food companies are gearing up for a commercial war in which they will exploit highly personal genetic information to sell their products.

At an international conference on nutrigenomics, which starts today in Amsterdam, geneticists and nutritionists will lay out their plans for a time when what we eat is largely determined by what we have inherited.

"Hypothetically, you may in the future choose your breakfast cereal based on your genes," said Peter Singer, director of the University of Toronto Joint Centre for Bioethics, which has published a joint study on nutrigenomics with the University of Guelph in Ontario. "It is hypothetical today but possible that if you have a particular gene, you will be advised to use a cereal that decreases your chance of heart disease and avoid another that would increase the chance of colon cancer," Dr Singer said.

Customised diets based on genetic tests will create unparalleled ethical and legal challenges, the study warns.

"As more is learnt about individual genetic susceptibility to disease, information from genetic tests may become increasingly attractive to outside parties who stand to gain from it," the study says.

Dr Singer said that a principal target will be the post-war "baby-boomers" now reaching their 50s and 60s who are trying to forestall the onset of age-related health problems such as heart disease, arthritis, menopausal symptoms and brittle bones.

Within the past few days, for instance, scientists have announced the discovery of genes that may increase the risk of clinical obesity and osteoporosis - both of which can be delayed or avoided by a concerted change in diet at an early enough age.

One British company, Sciona, is already offering a commercial genetic test for anyone concerned about how to adapt their diet to suit a set of seven genes they may have inherited.

The website of Sciona, a pioneer in the field of nutrigenomics, argues that the general dietary advice given to the public may not suit everyone. "Small differences in your genes can influence how well your body metabolises foods, utilises nutrients and excretes damaging toxins, all of which can affect your general state of health," Sciona says.

"By finding out if you have any of these small variations, [we] can provide you with specific dietary information that cannot be obtained from any other source."

But Tom Sanders, professor of nutrition at King's College London, warned that some aspects of nutrigenomics were being hyped and as a result the public could become victims of a hi-tech form of food fadism. "Tests are only really useful when the disease is clinically silent for a number of years before it erupts. The idea that you'll have a test to determine whether you should eat grapes or bananas is really nonsense," Professor Sanders said.

"One characteristic of humans is the huge variety of diets that we can live on quite well. A genetic test to fine-tune your diet is not going to undo the harm of sitting down and watching television for 50 hours a week," he said.

There are, nevertheless, studies being done on some serious genetic disorders that could be affected by a change in someone's diet. For instance, a substance called homocysteine, which is linked with heart attacks, can build up in some people with an inherited deficiency in a certain enzyme. A simple DNA test can identify people at risk who could be advised to take folate, a food additive that drives down homocysteine levels.

The Human Genetics Commission, Britain's watchdog on DNA testing, said that nutrigenomics aimed at such conditions could be potentially useful. "But we would be concerned if it became commercially available in the UK to the general public. The information and advice must be responsible and appropriate," a spokeswoman said.