9 August 2017

Warning over dubious diet genetic testing

Clinical Nutrition Obesity

Losing weight is hard work and it’s no secret that most diets fail to stick. But what if you could do a simple DNA test and discover the diet which was most likely to be successful for you?

That’s what a new product by genetics company myDNA is now offering consumers for $99, and it has healthcare professionals concerned.

“With a simple mouth swab, a DNA test can be carried out to learn more about our likelihood of gaining [weight], sense of feeling full and how we process and store fat,” the company says.

“General advice doesn’t work for everyone,” the promotional material says, and points to a case study of a woman who used her personalised diet plan to learn about foods that would make her feel fuller and reduce snacking.

In the two months since its launch, myDNA CEO Dr Lior Rauchberger said thousands had bought the test.

For their money, customers are given a 20-page report, split into three sections that include the test results, recommendations based on the results and a final section that includes technical details for healthcare professionals.

The decision on which tests are included was made by an independent scientific advisory committee which assessed the clinical literature. The evidence level supporting the tests was given a star rating system, with five stars having the greatest level of evidence, and anything less than three not included, Mr Rauchberger said.

But some health professionals are doubtful about the value of such genetic testing interpretations. When asked whether genetic tests could shed light on people’s likelihood of gaining weight, feelings of satiety and fat metabolism, obesity expert and academic GP Professor John Dixon just laughed.

“I’ve been in the game for 20 years in full-time research and … it’s made me sceptical,” the senior research fellow at the Baker Heart and Diabetes Institute said.

“When it comes to predicting who’s going to lose weight, or predicting a diet, we have an exceptionally low amount of information,” Professor Dixon said.

“In fact, when we try and look for things that will predict a result, we find almost nothing. Many, many, many studies have looked at that, [and] I’ve published numerous studies where we’ve looked at genes,” he said.

“We do not know of any specific genome testing that is going to tell you which diet is going to work best for you.”

Professor Ronald Trent, an Australian leader in the field of human molecular genetics, stressed that the six or so genes included in the test had only been shown to be associated with obesity.

“That is not as strong as saying the gene causes obesity,” Professor Trent said.

When looking at the specific genes in myDNA, the professor of molecular genetics at the University of Sydney said FTO seemed to have the strongest association with obesity, while the ADIPQ and PRAPR gene associations were thought to be more related to metabolic syndrome.

Overall, however, he said it was a huge leap to go from a population-based statistical association to making health recommendations for an individual based on these results.

“This is problematic, because it is likely that within the patients tested in an association study (based on hundreds to thousands of different people) there will be exceptions,” he said.

“When you test the individual, that association might not be so obvious or it might even be wrong because obesity in that individual is not caused by gene X which is what you tested with the association study but gene Y or gene Z which have not been yet detected or they work together to have their effect through some other mechanism,” he said. “So, while there may be an association with FTO for obesity, the association to the next related issue, such as dietary response, is even more tenuous.”

The myDNA company already offers genetic testing for pharmacodynamics and has plans to soon offer another panel of genetic tests for exercise and fitness.

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10 months 27 days ago
I used to laugh at all this until I read a book. That one happened to be on the human genome project. It said that the Basques are the aborinal population of Europe, and the have the highest incidence of O- blood in the world. It is now understood that Europe was settled in about four waves – some were existing agriculturalists and others were nomads. We know that the evolution of at least one dietary trait – lactose tolerance – has been very recent, about 7,000 years ago. We also know that Caucasians have a special relationship with alcohol,… Read more »