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What DNA Can Tell You About How You'll Die

©iStock.com / Marilyn Nieves

Genetic testing can't tell you everything about your future health, but it can be revealing.

If you've ever wondered when the sci-fi-tinged future will arrive, the answer seems to be that it's already here… or, at least, the genetic testing part of it is.

The human genome, an inscrutable mystery just a few decades ago, has been fully mapped. In practical terms, that means scientists can take a sample of your DNA – from a cheek swab or a bit of saliva – and use it to learn about the genes that make you who you are. Stated in such simple terms, it may not seem like the massive advance into the future it is, but remember that this technology can both reveal our ancient ancestors and predict what diseases might affect us in our future – and by doing so, it can help us understand how to live the healthiest and longest lives we can.

Genetic testing certainly can't tell you everything about your future health. Our genes can't reveal whether we might one day contract pneumonia, the flu, or other bacterial or viral illnesses. But if a disease is transmitted hereditarily, genetic testing can tell us if it's something that may affect us in the future. As Douglas Brutlag Ph.D. explains, "The percentage of our health dictated by our genetics and the faction by behavior and environment depends on individual diseases. ...Diseases such as Huntington's disease, cystic fibrosis, sickle cell anemia, Tay-Sachs disease and Downs syndrome are purely genetic. Other, more complex diseases such as Type 2 diabetes or rheumatoid arthritis have a significant behavioral component. That means that even if a person has a genetic predisposition towards the disease there is a lot one can do behaviorally to prevent it."

In some cases, we can work to prevent a disease we might contract in the future via our lifestyle choices – if we're genetically predisposed toward Type 2 diabetes, we can be sure to eat right and get plenty of exercise. But some people take a more radical approach to preventing hereditary diseases. Angelina Jolie made headlines when she elected to have a double mastectomy due to her incredibly high predisposition toward breast cancer – and the headlines were back later, when she had her ovaries removed in order to prevent the ovarian cancer that killed her mother. She learned through genetic testing that her risk to contract ovarian cancer was 50 percent, and it skyrocketed to 67 percent for breast cancer. Her decision was to endure surgeries that came with far less risk than cancer itself would bring.

Jolie isn't the only person making health decisions based on genetic testing results, though she may be the highest-profile face of this new dilemma. One mother shared her story about the life-saving decision she and her husband were able to make for their baby after he received a genetic test at birth. Without genetic testing, they probably would not have known about his phenylketonuria until it was too late to treat – but since they were aware of the genetic predisposition at birth, they were able to adjust their son's diet to prevent the devastating effects of the condition. Another writer had her genome sequenced and chose not to worry about what it showed her: the elevated risk of stroke in her future, a predisposition toward rheumatoid arthritis, a potential for a bad reaction to the flucloxacillin strain of antibiotics… though it's certainly possible that the knowledge she received will affect her future health decisions.

It's our choice what we do with the results of genetic testing, if we even choose to have it done, but studies show that most people who undergo the tests use the results as catalysts toward positive, proactive changes in their lifestyles. Rather than sticking their heads in the sand or taking a "we're all going to die someday" approach to the news they receive, most people make adjustments in order to extend their healthy lives. Some adjustments are big, like Jolie's preventative surgery. Others are much smaller – cutting certain foods out of the diet, adding others, exercising both the body and the mind to keep them in top defensive shape. The more we know about what's in store for our bodies as we age, the better able we are to prepare ourselves for long, healthy lives – and even pass that knowledge and preparation along to our children and grandchildren.