People with a family history of cancer face a higher risk of developing cancer themselves. That’s why each of us should become aware of cancer patterns in our families and tell our doctors about them. But for the vast majority of us, inherited genetic traits play only a very small role in determining whether or not we get cancer. In fact, about 85 percent of cancer patients don’t have any family history at all.

Cancer develops when abnormal genes – which can either be inherited or develop over the course of one’s lifetime – allow cells to overcome normal restraints on their growth and reproduction. According to the National Cancer Institute, most cancers result from an interaction between genetic and lifestyle factors. Some people may be so resistant to cancer that they never develop the disease no matter how unhealthy their lifestyle; others may be so susceptible that even the healthiest of lifestyles can’t protect them. But most people are in the middle: how we live greatly influences our odds of developing cancer.

There are two types of inherited abnormalities that play a role in cancer risk, genetic mutations and genetic polymorphisms. Inherited genetic mutations (the so-called “cancer genes”) occur in a tiny percentage of the population, but 50 to almost 100 percent of those who do inherit them eventually get cancer. Inherited genetic polymorphisms, on the other hand, are significantly more common, but raise an individual’s cancer risk by a much smaller degree.

Hereditary mutations of specific genes are so rare in the population that they are responsible for no more than one to five percent of any cancer. Examples of cancers inherited because of specific genetic mutations include familial adenomatous polyposis and hereditary nonpolyposis, both of which are forms of colon cancer. Specific mutations that occur on genes called BRCA1 and BRCA2 often make headlines because of their role in hereditary breast and ovarian cancers.

If you have a family history of cancer, it does not mean that you necessarily possess one of these rare “cancer genes.” You may instead have inherited a much more widespread type of inherited cancer risk involving what researchers call genetic polymorphisms. Polymorphisms are common abnormalities – possibly present in up to half the population – that occur in genes that control the elimination of carcinogens, damage repair to DNA, or cell growth.

Inheriting this second type of abnormal gene affects how vulnerable we are to cancer-causing influences around us every day. For example, some people inherit genetic polymorphisms that cause their bodies to quickly activate and form colon carcinogens from substances called heterocyclic amines (HCAs). HCAs are found in meat that is heavily browned or cooked at high temperatures.

People who inherit polymorphisms like this face two to four times the cancer risk of the general population. But being at higher risk doesn’t mean resigning oneself to a fate of cancer and giving up on the kind of lifestyle choices that have been shown to help lower cancer risk. Instead, people whose family history has placed them at higher risk should understand that a healthy diet and active lifestyle are even more important, not less.

The take-home message about inheriting cancer risk is two-fold. You should know your family history – who had what disease and at what age. Tell your doctor, since a family history may change how early or how often you should have cancer-screening tests. But remember that for most of us, lifestyle factors like healthy eating, regular exercise, weight control and avoiding tobacco have a much greater effect on our chances of developing cancer than our genes do.