Should You Get Personalized Genetic Risk Testing?
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
Today, you can get your DNA sequenced—the letters of your entire genetic code spelled out—for like a thousand bucks, a bargain compared to the 100 million or so it cost 20 years ago. And for around a hundred dollars, you can get partial DNA sequencing. It’s only a click away, direct-to-consumer genetic testing like 23andMe for ancestry, health, love—you name it. Unfortunately, many tests currently offered have not been appropriately validated, and consequently, the consumer may be paying for something that is ultimately useless. Or just flat out wrong.
There is an increasing demand from the public for direct-to-consumer genetic tests, but when put to the test, researchers found an alarmingly high false positive rate, meaning the analysis said you had some high-risk gene, but it simply wasn’t true. And this happened 40 percent of the time! Like they said you had the Angelina Jolie BRCA breast cancer genes, but it wasn’t true. And in addition to the 40 percent false positive rate, some variants they did identify correctly were misclassified as being high risk when in actuality they weren’t high risk at all. You can see how it’s in these companies’ best interest to give you scary outlier results, so you’ll think the money was worth it and pay for additional testing. But both false positive results and misclassification of variants can result in significant implications for an individual, including unnecessary stress and even unnecessary medical procedures. I mean, what if you got a preventive double mastectomy because you falsely thought you were at high risk when you didn’t even have the BRCA mutation?
Yes, these genome-wide association studies have now successfully identified thousands of common genetic variants that influence the risk of complex diseases, as I talked about in my video on personalized nutrition. But nevertheless, the discovered gene variants do not markedly expand our predictive ability, compared with what can be achieved by using only information from long-known traditional risk factors.
Take type 2 diabetes, for example. We’ve identified about 50 genes that are linked to increased diabetes risk, but even if you put them all together, “obese persons with the lowest genetic risk for diabetes were nearly 5 times more likely to develop the disease than normal-weight persons with the highest genetic risk.” In other words, this would send out the wrong message to someone who was obese, giving them a false sense of security. Knowledge about type 2 diabetes genetic susceptibility based on what we know so far has no implications for decisions about who should be targeted for intensive lifestyle interventions. Everyone with excessive body fat, regardless of genetics, needs to slim down to reduce the risk of diabetes.
What about this famous study that purported to show that personally tailored dietary interventions could improve blood sugar responses, to the extent that some commentators said it raised questions about the usefulness of universal dietary recommendations, period. But if you actually read the study, it turns out their results do not demonstrate high interpersonal variation in relative blood sugar responses; do not show that their model is superior to current methods of detecting high blood sugars; and do not show that personalized nutrition advice is superior to standard dietary advice to manage high blood sugar responses after meals.
But what about personalized genetic risk counseling just to at least motivate diabetes prevention? In a somewhat forlorn bid to regain credibility, ‘‘knowledge’’ of individual genetic risk proﬁles has been touted as effective in motivating people to commit more strenuously to relevant disease prevention efforts. Here again, however, available evidence does not support the claims. And indeed, it did not seem to help those at risk for diabetes.
Randomize people to get genetic tests worth hundreds or thousands of dollars profiling their subtle differences in risk for up to 40 different diseases. In this case, it was Navigenics who described their goal as empowering people with personal genetic insights to help motivate them to improve their health. Yet, it didn’t work. There were no measurable changes in diet or lifestyle, even in the short-term.
Randomize people to personalized nutrition insights is like determining who might genetically benefit particularly well from eating more greens or eating to lower their cholesterol, yet there were no significant changes in diet at month six compared to those who didn’t get that personalized info, or even at month three. So, it’s no surprise there were no differences in weight, belly fat, cholesterol, or any of the other biomarkers.
Put all of the studies together, and what do we find? No significant benefits for telling smokers who’s at particular risk for lung cancer, for instance, or who needs to eat particularly healthy, or move especially more. The bottom line is that expectations that communicating DNA-based risk estimates changes behavior are not supported by existing evidence. Yet that was the stated reason for the big presidential push for precision medicine: to empower individuals to take a more active role in their own health.
It is no surprise that the theme of personal empowerment is invoked. It’s great for marketing, but it’s not particularly empowering. In fact, if anything, it leaves patients even more reliant on authority, and it’s not even very personal, since the genetic contributions we know of are so small compared to how we actually live our lives. Why, then, is patient empowerment emphasized as its cardinal virtue? Because it exploits the appeal to generate political and public support for an increasingly industrialized medical-industrial-scientific complex, which moves literally trillions of dollars around the globe.
This isn’t some grand conspiracy theory; it’s just the way the system works. Healthy living directly threatens many powerful corporations. Eat less sugar? Eat less meat? And healthier populations do nothing but lower the demand for doctors and drugs. Seemingly willfully blind to this evidence, the United States continues to overwhelmingly spend its health dollars overwhelmingly on clinical care, cleaning up our lifestyle-induced messes. So, it’s not surprising that we far outspend other countries while at the same time have worse outcomes. While major new taxpayer gifts were being promised to high-tech medicine, the United States had already sunk to the bottom of the list of comparable countries in terms of disease experience and life expectancy. “Overrated ’precision medicine’ promises may be serving vested interests, …justifying the exorbitant healthcare expenditure in our finance-based medicine.” But in many ways, the American health care system is the most advanced in the world, yet all our whiz-bang technology just cannot fix what ails us. “Let’s start with the basics. Eat your broccoli, take the stairs, and don’t worry about whether you have a 5.6 percent or 7.7 percent lifetime risk for a grave disease because either way, a sensible lifestyle is the healthiest choice.”
Please consider volunteering to help out on the site.