Our Genes are Not Our Fate
While it has become generally accepted that our lifestyles play
a role in health and disease, most people believe that the
ultimate determinant of longevity resides in their genes.
Whenever I have asked a patient how long he or she expects to
live, their first instinct is to say, "Well, my mother died at
age X, and my father..." This is another way of saying that my
genes are my fate.
The twenty-first century has been heralded as the age of the
genome, and medical genetics is widely touted as the future of
health care. Diseases will soon be diagnosed by identifying the
faulty gene; therapy will either fix or replace it. While genes
are undeniably important factors in causing disease, their roles
have been vastly overemphasized. For the most common diseases
such as cancer and atherosclerosis, genes are predispositions,
not inevitabilities.
Identical twins have the same genetic risk for disease, yet
several studies have shown substantial differences in their
health histories. This is because another crucial factor in
determining one's propensity for disease: an individual's
environment. According to Craig Venter, former CEO of the
company that first decoded the human genome, "The wonderful
diversity of the human species is not hard-wired in our genetic
code. Our environments are critical."
A recent report in the New England Journal studied 44,788 twins
to evaluate the comparative importance of genes and the
environment in causing the most common types of cancer. The
study concluded: "Inherited genetic factors make a minor
contribution to susceptibility in most types of cancer. The
overwhelming contributor to the causation of cancer is the
environment." It is now widely accepted that 80 to 90 percent of
human cancer is due to non-genetic factors.
The overriding importance of environmental elements is also
clear in the development of atherosclerosis, the number one
killer in the United States. Atherosclerosis is a multifactoral
disorder resulting from an interaction of several predisposing
abnormalities such as high cholesterol, hypertension and
diabetes. Research has conclusively shown that reducing these
risks substantially decreases the probability of having a heart
attack or stroke. For example, a loss of just 7 percent of body
weight in obese people reduces the incidence of diabetes by 58
percent, while shedding 10 pounds will normalize the blood
pressure of those with borderline hypertension, no matter what
their genetic propensity.
Genetic diseases generally fall into one of three categories.
The first, called "chromosomal disorders," are caused either by
excess or a deficient number of genes. Down's syndrome is an
example of this type of disorder. The second, referred to as
"simple inherited disorders," are primarily determined by a
single abnormally altered or mutant gene. An example is sickle
cell anemia, a disease affecting red blood cells.
The last and most common group is called "multifactoral
disorders" because they result from an interaction of multiple
genetic and environmental factors. Coronary artery disease and
most cancers fall into this category. Genetics experts agree
that the risk of inheriting a disease is substantially lower in
the multifactor group than it is in the first two groups.
Experience has convinced me that in addition to genes
themselves, our minds' conclusions about our genes--something I
call mental genetics--also has a major influence on our health
and longevity. When we conclude that our parents' medical
histories and their lifespans determine our own, that belief can
create its own reality.
Some time ago, I met a man named Jerry who wanted to talk about
his heart problem. He began by telling me not about himself, but
about his father. Years before, Jerry was with family and
friends in the woods near their cabin when suddenly a large
snake appeared. Jerry's father ran up an incline to the cabin,
ran back down with a rifle in his hands, shot the snake, and
then fell to the ground. He was dead of a massive heart attack
at age sixty-four. For jerry, who was thirty-seven at the time,
heart disease became "my bugaboo." As he entered his sixties, he
became filled with ominous thoughts and anxieties. His father's
death felt "like a shadow pursuing me." It culminated in a heart
condition when Jerry turned sixty-four. Fortunately, Jerry was
lead to a physician whom he respected and whose advice he took.
He began a program of exercise, stress reduction and a sensible
diet, and has done well since.
People with a strong will to live understand that when they take
life-enhancing measures, their health and longevity will be
favorably affected regardless of their genes. They take
responsibility for their lives instead of being at the mercy of
circumstances. Remember: at times, our thoughts about our genes
can have as much impact on our health and the genes themselves.