By: Nancy Monson: Health Writer for Health Central

Image Credit: iStock

It’s hard to turn on a TV today without seeing an ad hawking direct-to-consumer DNA ancestry tests, and I was as curious as anyone about what my results might be. But can you trust them to be accurate? To find out, I contacted three of the major providers today: Ancestry.comMyHeritage.com, and 23andme.

The first two gave me complimentary tests as a journalist but sell for $99 each; I spent $199 for the 23andme ancestry plus health test.

For Ancestry.com and 23andme, I sent in plastic vials of my saliva; for MyHeritage.com I sent in cotton swabs that I used to scrape the inside lining of my cheeks. Your saliva and your cheek cells contain DNA, which carries the genetic information the companies require for their analyses. I got the results of the tests in 6 to 8 weeks via regular mail, though the companies promise results faster if you go online.

It turns out that all three DNA ancestry test kits produced fairly uniform results: I found out I am largely Northern and Western European (Scandinavian, Finnish and Irish) and a quarter Ashkenazi Jewish. That all makes sense from what I know of my grandparents, who hailed from Norway and Finland on my father’s side and Germany and Ireland on my mother’s side.

A DNA primer

We each receive half of our DNA from our mothers (called mitochondrial DNA) and half from our fathers (called Y-chromosome DNA). Most of our DNA, 99.5 percent of it, is identical from person to person, but there are small differences, called variants, that make each person unique.

The direct-to-consumer DNA ancestry test kits use a process called genotyping to find variants in specific areas of the DNA, which in turn can be linked to certain ancestral groups and ethnic regions, physical traits, and health conditions.

Research suggests that there is a 4 to 9 percent genetic variance among major continental groups, so your ancestry is determined by comparing your variants to reference populations around the world. It is difficult to draw absolute conclusions about ancestry, however, from the tests, given how much humans have migrated and populations have mixed together over the course of history.

I asked the president-elect of the National Society of Genetic Counselors, Erica Ramos, for some clarifications about the accuracy of the DNA ancestry test kits. “This type of testing is very accurate for medical and ancestry testing if the companies follow quality controls,” she explains. But the technology is only one piece of the puzzle, and the estimates of your genealogy are another and are based on the way each company chooses to interpret the data.

The bottom line: The DNA ancestry test kit results are best guesses (although my little experiment showed that the three companies I chose are all playing in the same ballpark).

More than you bargained for

While your goal may be to learn more about your heritage by purchasing one of those DNA ancestry test kits, you should be prepared for the chance that you may uncover some disturbing findings about your health risks.

In the past, test kits like these relayed relatively frivolous health information, like whether your urine was likely to smell after you ate asparagus or how likely you were to be lactose intolerant.

In April 2017, however, 23andme received approval from the U.S. Food and Drug Administration to test for genetic variants for certain diseases, such as late-onset Alzheimer’s disease, Parkinson’s disease, blood clots, and celiac disease.

More tests will undoubtedly follow, and physicians are concerned about the accuracy of the testing, how to counsel patients about their DNA reports, and how well people will understand the results.

Moreover, knowing you have “DNA variants associated with certain health conditions is no guarantee that a person will indeed develop these conditions,” stated Mayo Clinic medical researcher Michael Joyner, M.D.

Some people may be scared by the results they find with direct-to-consumer genetic testing, he continued, while others may become cavalier about their risks.

Either way, if you decide to opt for health tests and have questions about the results, consult with a physician or a genetic counselor for a fuller picture of your medical future. “You don’t want to start modifying your behavior in a way that could be harmful, such as taking an aspirin a day if you find out you have a variant for blood clots,” Ramos says. “It’s important to have education and context for your risks.”

Just for fun?

Given how complex genetics can be, DNA ancestry tests today should mostly be done for curiosity’s sake rather than for definitive results. To learn the most about where you came from, you need to supplement the DNA findings with searches of historical records and discussions with family members. “Ancestry is an accumulation of a lot of different pieces of information,” Ramos says.

Even though I was fairly certain of my immediate ancestry, I still found the DNA test results to be worthwhile. As a bonus, both Ancestry.com and MyHeritage.com offer in-depth reports and extras like help in building a family tree, searching historical records, and linking customers with similar DNA to one another.

Testing sites

  • Ancestry.com: $99 for autosomal (maternal and paternal) DNA saliva test
  • MyHeritage.com: $99 for autosomal (maternal and paternal) DNA cheek swab test
  • 23andme.com: $99 for autosomal (maternal and paternal) ancestry DNA saliva test or $199 for health and ancestry DNA saliva test