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What does a home DNA test tell you about your health?

Home DNA tests are more popular than ever. You can order a test kit online or pick one up at your local pharmacy for about $50 to $100, mail in a sample of your saliva or a swab of your cheek, and in a few weeks’ time learn about everything from paternity, to ethnic origin, to your risk of passing on genetic diseases to your children.

But our ability to use DNA mapping as a predictive tool for future health is still in its early stages, making these tests less like a crystal ball and more like a partially deciphered language.

We spoke with OhioHealth licensed genetic counselor Nichole Morman to get a better idea about what home DNA tests tell you about your health, what they don’t, and how you can use what you learn to live a healthier life.

First, here’s a quick refresher on DNA:

  • Our DNA (deoxyribonucleic acid) molecules carry all of the genetic information that makes us who we are.
  • In our body’s cells, these DNA molecules form chromosomes that replicate and divide as our cells divide, giving each cell with these chromosomes a complete set of our genetic information.
  • There are sections of DNA within these chromosomes that pass on specific characteristics from parent to child, like hair and eye color. These are called genes.
  • Genetic variations or mutations on or between our genes are known as SNPs (single nucleotide polymorphisms, pronounced “snips”). These SNPs can be used as markers in our DNA to identify genes that are associated with disease.

“I decided to take one of these home tests, just to see what the experience was like,” says Morman. “Mine was from 23andMe. The kit includes a tube that you spit into and send to a lab in the mail. After a few weeks, I got an email that said I could review my results online.”

Currently, home DNA tests like 23andMe examine genetic information that can be split into three categories:

  • Carrier status: signals for more than 40 health conditions you could potentially pass to your children.
  • Genetic health risk: whether you have recognized markers for diseases like macular degeneration, Alzheimer’s or Parkinson’s disease, blood clotting disorders, and inherited lung and liver diseases.
  • Traits and wellness: physical characteristics, ethnicity, body composition, and how likely you are to be overweight or have problems with things like caffeine, lactose and sleep.

“One important thing to keep in mind is that these home DNA tests are not calculating your risk of disease,” says Morman. “They are simply listing the presence or absence of SNPs associated with diseases, and only those SNPs that the test looks for, which are not all of the SNPs you have by far, and may not be all of the SNPs associated with a particular disease.”

Morman says that the carrier screening portion of the test can be helpful for people planning to have children, and the traits and wellness information could help you make some beneficial lifestyle changes, but the personal genetic health risk results are not as clear-cut.

“One SNP alone often presents an incomplete picture of risk. We each have millions of SNPs in our DNA. Most SNPs are normal and do not cause disease by themselves, but they can signal an increased risk for disease, or in some cases increased protection against disease,” says Morman. “Take Alzheimer’s disease, for example. A home DNA test may look at one SNP, but that may not be your only factor for the disease, so it doesn’t say for certain whether or not you will develop Alzheimer’s.”

Unlike the broad review of your DNA offered in a home DNA test, Morman says clinical genetic tests performed by medical specialists analyze an entire gene to look for any mutation that may be the cause of disease. But testing at that level is generally only used when disease is documented in a family history. “Family history is a very important component in calculating disease risk for patients,” says Morman. “A take-home test may show you do not have a particular SNP associated with colon cancer, but if you have a family history of colon cancer, the absence of that SNP doesn’t mean you’re free of risk. There are other factors to consider. Fortunately, many risk factors are manageable with lifestyle changes or medical intervention.”

All things considered, Morman says home DNA testing can be a valuable resource if you measure your expectations going in. “Genetics is so complex, and no genetic testing is comprehensive. It takes several sources of data to paint a clearer picture. If you take a home DNA test, I would encourage you to share the information you receive with your family doctor. They can help you make plans for the things you can control, like getting more exercise, making changes to your medication or diet, or maintaining a healthy weight. And if any results are cause for concern, they can connect you to genetic counselors like me who can help you and your family make informed decisions about your health.”


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