Why get your genes tested? Some myths and misconceptions explained

I must say before I wrote The Genetics of Health (Simon and Schuster, 2017) I myself was a bit sceptical about the value of getting genetic testing done for dietary nutrients. After all, while humans have adapted to the environment over the past 50,000 years (with skin colour changes due to the battle between vitamin D and folate that I explained in Skin, a Biography), and our diets have changed (things like the higher prevalence of lactose intolerance in Asians can be explained by ancestral hunter-gatherer diets) -- overall our genome has not changed. So why is nutritional and drug metabolism gene-testing important?

Almost every day a medical study comes up with a new finding (“coffee is good for you”; “coffee is bad for you”; “alcohol is good for you”; “alcohol is bad for you” etc.) How is this possible?

I chose the genetics of coffee as my first study not just because I drink a cup every day. The gene that metabolises caffeine, the CYP1A2 gene is a recent gene (because consumption of coffee/caffeine only began around the 10th century. When we look at the population studies of the gene that breaks down coffee (or indeed most nutrients or drugs) we end up with a U-shaped graph – some high-risk, some low-risk and a smattering of people in between.

What I found interesting was, the pattern for the caffeine gene subtypes was replicated almost identically when we looked at hypertension (high blood pressure) or heart disease (myocardial infarction or heart attacks) once we broke down the people by gene type.

Researchers looked at different ethnic groups and guess what? The identical pattern emerged. This is because people with different gene subtypes metabolise nutrients differently and this makes them at a higher, or lower, risk of a specific disease. You may think of an uncle who smoked a lot who never developed lung cancer, or someone who didn’t smoke and ended up with the deadly disease. The same can be said for salt and high blood pressure etc.

The reasons different medical studies have come up with variable results (you can pretty much find a study to say a food group is good or bad for health -- my mother is always reading reports of how bad soymilk is, because she worries that I drink soymilk as I am somewhat lactose intolerant) is because the studies have been narrow and not wide-ranging enough, and have not taken genetic subtypes into calculation when it comes to nutritional metabolism.

The moment you insert the gene type into the graph (as I’ve done above) it makes perfect sense – some people have a higher risk due to their metabolism that is influenced by their gene subtype.

Another example is vitamin C (that I looked at next). Population studies have also shown variances in the metabolism of vitamin C. Those that had a non-functional “del” variant of GSTT-1, the gene that metabolises vitamin C, showed a higher risk of heart disease, blood pressure and obesity – and scarily these were studies in people in their 20s and 30s! Knowing what gene-type you have allows you to simply make a slight modification to your diet -- for these people eating an extra orange a day may keep the doctor away!

As I say in my book, I’ve always tried to differentiate health and medicine. Medicine, like Law is an old-fashioned guild, full of restricted access, rules and regulations. Health is something we need to take personal responsibility for. And part of that is controlling our environment – internal and external. The internal (diet and lifestyle), we have more control over; so, what are we waiting for?

In developing the Rxevolution 21-gene test, I took time to deliberate over what genes we would test for. I decided against testing for diseases (as many other companies do) because the science can get it wrong and cause unnecessary anxiety. I specifically chose ones that had good research evidence, and that would be meaningful i.e. that would give us information or allow us to take specific actions to improve our health.

Last year, I was awarded the Ko Awatea International Excellence Award for Leading Health Improvement on a Global Scale. It was at the Asia Pacific Forum (APAC), the largest medical gathering in this region. I felt deeply humbled when the citation said it was for “practicing patient-centred medicine” on a global scale.” My philosophy is simple – I never prescribe anything that I will not take myself. The first person to take the 21-gene test was me (followed by my daughter).