Cancer, diabetes markers - the real value of DNA tests lie in knowing what's potentially ahead, not what's in your past

PHOTO: Unsplash

DNA testing is well and truly mainstream, and is on offer from health clinics, wellness centres and gyms. You can even pick up a consumer test kit from food and drug retailers.

Go online and, for as little as US$99 (S$136), you can get an astounding amount of information - from where your ancestors may have lived to lengthy personalised health reports. The wealth of data is incredible, but it can be overwhelming.

If you go it alone - as I did four years ago, sending off for a 23andMe test in Britain - you need to be prepared for an avalanche of information. And it doesn't stop.

23andMe regularly updates you with new findings based on your DNA and new DNA matches. A few months after getting my results, I turned off the notifications because I really didn't need to be distracted by the discovery of a new fourth cousin.

A DNA test telling Kate Whitehead she has more Neanderthal DNA than 85 per cent of other customers. PHOTO: South China Morning Post

Last week, after a long abstinence, I logged onto my account and learned that I have more Neanderthal DNA than 85 per cent of other 23andMe customers.

That DNA has specific traits which, in my case, mean I'm less likely to have a fear of heights and more likely to have a poor sense of direction.

I answered a swathe of seemingly random questions on the site four years ago - Do you sneeze after eating plain chocolate?

Do you have dandruff? - and based on my answers and those of many thousands of other 23andMe customers, scientists were able to identify associations between Neanderthal DNA variants and human traits.

"So much about Neanderthals has been discovered over the last decade, and we're really starting to understand that they were probably a lot like us," said Samantha Ancona Esselmann, 23andMe ancestry product scientist.

My closest DNA match - a third cousin - has 98 per cent more Neanderthal DNA than most, so clearly it runs in the family. You can really go down the rabbit hole with this.

PHOTO: Pixabay 

While I was tickled by the Neanderthal finding (though I'm none the wiser as to whether it accounts for my hairy toes), it was the second update that gave me the chills - a slightly increased risk of age-related macular degeneration (AMD). That's irreversible vision loss.

The site goes to great lengths to stress that test results are not a diagnosis and that many people with the same result will not develop AMD. But it still got me worrying about what might happen in 15 or 20 years.

What if I'd landed an even scarier finding? Say an increased risk of "the Big C"? Had I properly weighed up the impact of getting such a result?

Graeme Bradshaw is the director of the Integrated Medical Centre in Central in Hong Kong. PHOTO: South China Morning Post 

Graeme Bradshaw, director of the Integrated Medical Centre in Central in Hong Kong, has been using DNA reports as part of his practice for the last six years. He advises patients to think carefully about how much information they want. The correct answer depends on the person.

"What people do if they are anxious types and get a high-risk factor, then they turn it into a new stress for themselves. If they've chosen to do a test where they are getting a load of information, they will start to worry themselves a lot," Bradshaw says.

DNA test results are not a fixed outcome. The environment influences about 70 per cent of whatever our genetic make-up is expressed as. Even in identical twins, only about 30 per cent of the same illnesses will show up, says Bradshaw.

In the last few years, 23andMe has improved the information it provides on this front and it now lists lifestyle and other factors that can influence the chance of developing certain conditions. It advises me to eat more green leafy vegetables, nuts and grains to reduce the AMD risk.

Bradshaw suggests that a good time to take a DNA test is in your mid- to late 40s, the age at which predispositions to diseases such as cardiovascular disease, diabetes and Alzheimer's will begin to show up.

He says it's about looking at the health markers for potential problems before they occur rather than when the symptoms start manifesting, as then the damage is already done.

Kate Whitehead took a 23andMe test in Britain four years ago. PHOTO: South China Morning Post 

The actionable DNA insights are the true value of these reports - they give you a head start on better managing your health and averting possible ill health ahead.

Of course, we should all be eating plenty of green leafy vegetables, exercising lots and getting enough sleep, but having a report that spells it out is a great motivator.

DNA testing is still the preserve of the rich.

There are a host of firms that produce affordable reports - AncestryDNA, CircleDNA and 23andMe to name just a few - and they will give you buckets of information, but unless you are prepared to do a lot of homework, you're best advised to work with a genetic counsellor to get the real value out of it.

DNA testing is a fast-moving field and someone who knows their way around the reports can not only swiftly sift through the volumes of data and focus on the key areas, but also point to the next steps.

"If you are at risk of Alzheimer's and don't know what to do about it, that's very disempowering. But if you do know what to do - control blood sugars, use antioxidants that protect the blood vessels from becoming damaged - that can be empowering," says Bradshaw.

This article was first published in South China Morning Post