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15 January 2015

23andMe: Why bother with predictions about yourself when you are almost certainly average?

Want to understand your genes? Call your parents.

By Michael Brooks

Why bother with predictions about yourself when you are almost certainly average? Alongside the columns packed with advice for creating a healthy new you, you will have seen at least one account of “everything that will matter in 2015”. You shouldn’t take either too seriously. Remember that the news predictions you read at the start of 2014 failed to foresee, say, a Russian invasion of Ukraine, the ebola epidemic, or the rise of Ukip.

It’s a truism to say that prediction is difficult. What is interesting is just how compelling human beings find any kind of window on the future. It’s a trait that the genetic analysis service 23andMe depends on.

The company offers an analysis of the DNA in your saliva. For £125, you can find out information about yourself such as whether you are a carrier of certain inherited conditions and your risk of developing particular kinds of disease. The company says that its reports are “for informational purposes only and do not diagnose disease or illness”, but that they will help you “make better lifestyle choices and appropriately monitor your health”.

Experts are divided on the value of 23andMe’s services. In November 2013 the US Food and Drug Administration ordered the firm to “immediately discontinue” marketing, though ancestry and raw genetic data tests are still available. Ahead of the UK launch, the Science Media Centre gathered the opinions of various UK geneticists. Shirley Hodgson, professor of cancer genetics at St George’s Hospital in London, said 23andMe’s tests were “very open to misunderstanding” and could lead to wasted NHS time.

According to the Cambridge geneticist Eric Miska, 23andMe can give us “a glimpse of the fun, excitement and risks associated with human genome data” but we ought to discuss how our personal genome should be accessed and shared. As Google is one of 23andMe’s financial backers, that’s a conversation we need to have sooner rather than later.

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Privacy issues aside, 23andMe has very limited powers when it comes to drawing conclusions from your genetic information. Accurate predictions rely on accurate information. Where genes are concerned, certainty is rare and surprises are common.

Take a study published at the end of last year in the Proceedings of the National Academy of Sciences. The study looked at data collected over a 30-year period and found a strong correlation between possession of a particular gene variant (the rs993609 variant of the FTO gene, to be precise) and a higher-than-desirable body-mass index.

That was expected: it is what we have seen in recent studies. What wasn’t expected was the absence of this correlation in subjects born before 1942. Only when we began to do less manual work, rely more on technology and have better access to food resources did the genes have something to work with.

So, even with a genetic predisposition, obesity was far from inevitable in the pre-war years. For most health conditions, environment and lifestyle matter far more than the details of your genome.

What’s more, most of 23andMe’s customers will surely find themselves devoid of any meaningful predisposition: the odds are that you are decidedly average. So, whatever your genetic destiny, wherever and whenever you happen to be living, a life of moderate consumption and moderate exercise is probably the best prescription. If that’s too banal and you really want to harness technology to predict the impact of your genes on your future health, pick up your miracle smartphone. Use it to call your parents and ask them how they are. No one knows more than they do about the troubles coming your way. 

Editor’s note, 20 January 2015: The FDA has ordered 23andMe to cease trading its health tests. Ancestry and raw genetic data tests are still available in the US. A change to the text was made to reflect this.