How genes influence health
For most conditions, your genetic inheritance is only part of the story, and knowing which risks you've inherited can guide your health priorities. With that information in hand, there is much you can do to affect your health in the future.
Studies of identical twins — siblings who share the same genome — show that, for most inherited diseases, if one twin has the disease then the other is likely to have it too — but not always. The amount of difference between twins shows how much each condition depends on genetics, and how much it can be influenced by your behavior and environment.
Multiple genes each act on your risk of these complex disorders. Which versions of the genes you've inherited may push your risk slightly up or down. Your risks may be further modified by what you eat, what you drink, where you live, how you live, how active you are and factors not yet discovered.
Your genetic risk can't be changed. But the rest of your risks can. In some cases, the environmental risks carry much more weight than the genetic risks. Your overall risk of diabetes can be brought down by keeping your weight under control. Your overall risk of heart disease can be lowered if you get more exercise. And even if a condition is not preventable, knowing that you're at risk means you can pay closer attention to warning signs, detect the condition earlier and possibly lessen its effects.
