Health – DNA Testing
Cutting-edge science has gone commercial – you can now have your DNA analysed to find out if your health is at risk. But is it reliable?
Dancer, choreographer and RockingnHeels workout founder Nkateko “Takkies” Dinwiddy, 28, has 270k online followers. She also has a new baby, a big appetite and a sweet tooth she’d been indulging. So, when she was approached by a genetesting company in June with an offer to analyse her cell DNA, and “establish
scientifically” what exercise and eating routine was best suited to her, she leapt at it – as millions of people worldwide are now doing.
“The company had seen on my social media that I was trying a 14-day plantbased diet to reset my body,” Takkies says. “They said gene-testing could tell me if this was the best diet for my body and if my workout routine was right for me – I do combos of boxing, cardio and cross-fit, and my dance classes,” Takkies shares.
The gene-testing process was simple. She went to the company and in minutes, a swab was taken from her cheek. This was sent to a laboratory for DNA analysis and two weeks later, the company’s registered dietitian interpreted the results for her.
“She told me my plant-based diet was right for my genes. She advised me to fill my dinner plate with colourful veggies, and have legumes and eggs for protein, and cut back on sugar. It turns out I’m also doing the right exercises for my genes. She said I should just make more time for stretching and resting – not so easy with a year-old daughter! Takkies adds.
She’s delighted with her gene-testing experience. “It feels great knowing I’m doing what’s best for my DNA, and it has given me new motivation. I’ve stopped late-night snacking by going to bed earlier, and started cooking veggies in advance and putting them in the fridge. I’m going to take my mom in for gene testing!”
Deoxyribonucleaic acid is at the core of all our cells, and chunks of it make up our genes. It contains the code for everything that makes us who we are, from our eye colour to the speed with which we metabolise food. Patterns in a strand of DNA can indicate if we have a greater risk of certain diseases or birth defects – we inherit half our DNA from each parent, and if two people who carry a gene mutation for the same condition have a baby, that baby is at greater risk for it. Initially gene-testing focused on helping potential parents find out if they were carriers of mutations, when one partner had a family history of a genetically-linked condition such as muscular dystrophy or motor neuron disease. It also enabled those with strong family histories of potentially deadly conditions, such as breast or ovarian cancer, to take preventive measures and decide if they should consider a risk-reduction mastectomy or hysterectomy – which actress, Angelina Jolie, elected to have in 2013 and 2015.
But today gene-testing has grown in scope and become increasingly affordable and accessible (it’s available from around R3 000). American health economics researcher, Professor Kathryn Phillips
told CNBC business news recently that there are now more than 75 000 genetic tests, with more than 10 new tests entering the market every day. Some are for specific disease diagnoses, but most now focus on wellness and fitness, offered at genetic testing labs that are springing up all over. Many offer testing online, delivering cheek-swab kits in the mail. According to Global Market Insights, the genetic testing market is set to exceed $22 billion (R335 billion) in five years.
BLINDED BY SCIENCE?
But as genetic testing grows, so does controversy around it. “There are companies offering genetic tests that aren’t necessarily based on solid empirical evidence,” Associate Professor in the Department of Biomedical Sciences at Stellenbosch University, Craig Kinnear, says. “There’s been an explosion of directto-consumer genetic testing companies that promise clients diet plans and fitness regimes based on their genetic make-up. The problem is that you can send your sample to different companies and get different answers.”
Two years ago, American medical journalist, Rebecca Robbins, experienced this when she took two mail-order genetic tests that contradicted each other. They delivered “different interpretations of what certain regions of my genome meant for my risk for tendon injuries, for instance, or my propensity for high blood pressure”, she wrote on health news website, www.statnews.com. She added that the advice she was given “was either general – like stretch well before exercise – or oddly specific, like the menu I was given telling me to eat quinoa on Sundays”. Genetic tests had promised to help her achieve peak fitness.
The problem, Kinnear says, is that while there are strong genetic underpinnings for conditions such as breast and ovarian cancer, cystic fibrosis or muscular dystrophy (since inheriting these single gene mutations will result in you developing the disease), for complex traits such as obesity and fitness levels, very little is encoded by a single gene. “These complex traits are a result of the interaction between multiple genes and the environment (which includes behaviour like smoking and drinking alcohol). We still don’t know enough about human genes and their interaction with one another and the environment to be able to give accurate advice on the best diet to follow, or which exercise programme is best-suited to an individual,” Kinnear explains. In fact, he says, studies have shown that genetics play only a small role when it comes to the effects of diet and exercise, and behaviour matters much more. “A controlled trial published in the Journal of the American Medical Association found no difference in weight loss between groups of people who were matched to either a high-fat or a low-fat diet based on their genetic make-up. Similarly, an independent investigation of 38 genes frequently included in nutrigenomic tests (tests looking at the relationship between genes, nutrition and heath) provided by several private genetic testing companies found no association with dietary intake and any of these genes,” he says.
What’s more, different gene-testing companies use different tests, genes and scientific literature to reach their conclusions, Kinnear continues. “So the results of direct-to-consumer genetic tests, in particular those tests that tell you exactly which exercises to do and what to eat, should be taken with a grain of salt,” he adds.
THE BOTTOM LINE
GeneWatch UK, a not-for-profit group that monitors developments in genetic technologies, reports that for more than 15 years it has exposed companies making misleading claims about test results. “Genetic tests are not currently regulated,” it notes. “This means people could easily be misled about their health. Without proper regulation, genetic testing could be used to expand the drug market to healthy people identified as at high genetic risk; people would receive unnecessary medication; and the underlying cause of heart disease, cancer and obesity could be ignored, with serious implications for future health.” The group concludes that for most people, eating a balanced diet, getting enough exercise and not smoking are much more important in determining your health than your genes are. Talk to your doctor for diet advice or visit: www.adsa.org.za/Portals/14/ Documents/FoodBasedDietaryGuidelinesforSouthAfrica.pdf.