By Lissa Cook
BBC 5live Report
More and more people in the UK are following America's lead in spending hundreds of pounds on private genetic tests.
The tests analyse a fraction of the genes which make up human DNA
Such personalised DNA analysis, which calculates susceptibility to common illnesses, such as cardio-vascular disease, Alzheimer's, cancer and osteoporosis, claims to help people live longer, feel better and avoid disease.
Kits are ordered online or over the phone and users send a swab of saliva to a laboratory for analysis.
The laboratory in turn sends back a report giving an individual their genetic profile with personalised advice on improving diet and lifestyle.
But is it worth the money?
Peace of mind
Ben Hudson, a 44-year-old house husband from Sussex whose mother is a heavy smoker and whose father died from cancer, ordered a DNA test which analysed more than 40 gene variations.
"It's reassuring," he said.
"If someone said you've got a risk of this and that and you've got to change your diet and lifestyle, surely it's got to be easier than ending up in the doctors with a whole list of problems."
Ben was told he was at low risk of illnesses like cardio-vascular disease, Alzheimer's, and cancer. It cost nearly ú1,000, but he said it meant peace of mind.
But genetics is a science in its infancy.
In an investigation for the BBC's 5live Report, the bio-ethicist Tom Shakespeare, from Newcastle University, talked to experts concerned about the lack of regulation of such tests.
The tests analyse just a fraction of the 25,000 or more genes which make up human DNA, and predict risk of susceptibility to a range of common complex diseases.
They are common because they are the things most of us die from. They are complex because they are affected by dozens of genes, but also by environment and lifestyle.
Other health influences
Dr Ron Zimmern, director of the Foundation for Genomics and Population Health in Cambridge, is one of those with concerns that long-term studies of the tests involving large numbers of people have not been completed.
"I think it is certainly too early to start offering the test both directly to the public or indeed through a physician," he said.
"My main problem is that clinical studies that try to see what the predictive value of these studies is at the individual level, just have not been done."
Dr Sian Astley, communications manager for the European Nutrigenomics Organisation, said the science is sound but added that we do not yet know enough and there are more important things that influence our health.
"Not smoking, drinking alcohol in moderation, maintaining an appropriate weight for your height, regular exercise - just keeping those four things in place is far more likely to have an impact on your risk of age-related diseases than your genetic background."
Dr Astley said you could get equally useful advice from your GP or a dietician without paying for a genetic test.
5Live Report found six British companies selling different types of tests. One clinic offered a skin cancer test and another tested for chances of getting breast cancer. The prices ranged from ú100 to ú1,000.
Ben Hudson used Genetic Health, which sells a variety of tests.
Their website claims that based on individual genetic profile, one of their medical experts will be able to advise people on which lifestyle changes to make, and which supplements to take that "will improve your quality of life, extend the active period of your life and most possibly will enable you to live longer".
Their medical director, Dr Paul Jenkins, said: "I think we do have the evidence.
"All of the genes we analyse have been published in very large-scale studies in the most eminent medical studies and show a clear association between those polymorphisms [genetic variations] that individuals possess and their risk of having a disease."
'Anxiety and stress'
But what if someone gets bad results?
Dr Paul Martin, from the University of Nottingham's Institute for Science and Society, is worried about testing for illnesses like Alzheimer's, for which there is no available treatment.
"There's no way of using that information usefully," he said.
"All it does it tell you you're at greater risk of getting the condition, and I think the international consensus is that this isn't useful and, if anything, it would cause a certain amount of harm - the anxiety and stress - when people could do nothing about it."
But Dr Jenkins defended selling such tests to the public.
"These are not diagnostic tests and that is a point I make very firmly to all the patients.
"We're not guaranteeing either they will or they will not develop a disease, but I think individuals have a right to know whether they are at increased risk genetically, in the same way that knowing you have high blood risk puts you at increased risk of heart disease."
The Human Genetics Commission offers advice to anyone considering an over-the-counteráDNA test. Purchasers with questions and doubts are advised to seek professional medical advice before buying.
5live Report: DIY DNA was broadcast on Sunday 28 October. Listen online or get the podcast at the 5live Report website. The programme was made by All Out Productions.