CRAIG VENTER is developing the ultimate in individually tailored diets. The American scientist, famous for his role in decoding the human genome, is close to another scientific first — mapping all of his own DNA — and the results are already changing what he eats and the way he lives.

As he becomes the first person to have all six billion letters of their individual DNA decoded, Venter is opening the door to a future in which one day “gene maps” will be a guide to living longer and more healthily.

Recently Venter, 60, has started to breakfast on a bowl of oatmeal and skimmed milk with “just a little” brown sugar. The analysis of his DNA, he says, shows he has an above average risk of a heart attack, prompting him to adopt a healthier start to the day with a high-fibre, low-fat diet. The genetic predisposition may have been inherited from his father, who died at 59 from cardiac arrest.

Venter still enjoys a steak in the evening, however, because his DNA also shows that he has a gene associated with a low risk of susceptibility to mad cow disease.

He also has OCA2, one of thousands of genes on his 46 chromosomes that is probably responsible for his blue eyes. Unfortunately he also has a mutation in one gene, CFH, which may quadruple his risk of going blind.

Venter made his name as head of Celera Genomics, a private company that raced to decode the human genome. He now heads a scientific centre, the non-profit J Craig Venter Institute in Rockville, Maryland.

Once his researchers have completed decoding his DNA, the entire code will be made available through a computer database to help other researchers studying the links between genes and health.

“This research is extremely important, but the importance is in understanding the basic pathogenesis of disease (rather than it’s immediate application to Venter),” said Dr Ron Zimmern, director of the Public Health Genetics Unit. “The holy grail of public health is that — at some stage, probably 20, 30, 40 years downstream — you can segment the population into groups of different genetic risk.”

Some companies are already dangling such prospects before the public. One called Sciona will analyse a swab from your mouth for genetic traits thought to be connected with breast cancer, osteoporosis and even to the effects of high levels of caffeine.

However, Sciona scans for a mere 19 genes, and many experts doubt the worth of DNA analysis. “Some of the information drawn from these susceptibility tests is grossly over-interpreted,” said Dr Frances Flinter, a member of the Human Genetics Commission and senior lecturer in clinical genetics at King’s College London.

“You can sequence the DNA of an individual but you can only interpret that DNA if you have mapped many other people’s and looked at their lives. For most of the medical conditions we can develop, we don’t know which genes are responsible.”

Venter, for example, is renowned as an aggressive and bold businessman; yet researchers have found his “dopamine D4 receptor” is not the version that some research has associated with risk-taking.

Zimmern is even blunter: “You can get all these tests done and they send back a piece of paper saying eat more broccoli, eat fruit five times a day as that’s what your genetic profile says. It’s a waste of everybody’s money.

“We all know too much fat is bad for us so, despite the fact that you’ve got a few genes that might predispose you to having higher levels than other people, the message isn’t different: everybody should be eating less fat.”

Venter dismisses the critics, saying his gene map will be the first of many. Harvard University has called for seven volunteers to have their DNA decoded, and a Californian foundation is offering a $10m prize to anyone who finds a much faster way of decoding DNA. Stephen Hawking, the Cambridge physicist, is to have his DNA decoded as part of that project.

As decoding speeds increase, costs fall and research accumulates, the chances of unravelling the secrets of DNA will rise. And if it proves Venter right, choosing your breakfast cereal will one day never be the same again.

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