Nature Verus Nurture

Sixth in a series of Ten Habits for a Healthy Mom

By J. Ron Eaker, M.D.

The debate over nature versus nurture, especially as it relates to health, rages on like a California wildfire.  Almost daily, new discoveries are published detailing the impact of genetic makeup and one’s health.  Cancer, heart disease, Alzheimer’s  and a host of other maladies are clearly dependent on a variety of “nature” indices like genes and mutations.

In particular, breast and ovarian cancer have been intimately linked to a myriad of genes that can be passed along to family members.  Many of you are familiar with the BRCA genes, specifically BRCA 1 and BRCA 2 , that, if they exist in your genetic code, dramatically increase your risk of both breast and ovarian cancer.  Let’s put that risk into context.  Currently, about 12% of women will develop breast cancer during their lifetime. By contrast, a recent large study estimated that about 72% of women who inherit a harmful BRCA1 mutation and about 69% of women who inherit a harmful BRCA2 mutation will develop breast cancer by the age of 80.¹   About 1% of women will be diagnosed with ovarian cancer in their lifetime; however, with the BRCA mutation present, that risk jumps to 44% for BRCA 1 and 17% for BRCA 2.²

These risks are real, fixed and scary because they are totally out of your control.  It’s important to notice, however, that there are still a number of women who have these mutations that remain perfectly healthy.  Here arises much of the debate over nature versus nurture for these folks.  Are there behaviors that make one woman more or less susceptible to these mutations?  The answer is a resounding yes.

Behavior, what we do and how we do it, as it turns out can have a profound effect on everything from cancer risk to longevity.  For example, one of the greatest risk factors for cervical cancer is multiple sexual partners.  Women who have a number of different encounters are at greater risk for contracting the Human Papilloma Virus which is the number one cause of abnormal changes in cervical cells that potentially can lead to cancer.  It’s really a matter of statistics and behavior.

There is a fascinating branch of science broadly labeled Epigenetics. Simply stated it is the study biological mechanisms that will switch genes on and off.  Going back to the BRCA example, why some women develop cancer and others don’t may be due to the expression of that mutated gene.  This is the essence of epigenetics, how and why some genes are active and others aren’t.  What’s truly fascinating are some of the epigenetic influences.  Environmental factors such as food, drugs or exposure to toxins can cause epigenetic changes by altering the way molecules bind to DNA or changing the structure of proteins that DNA wraps around.  You change the expression of the gene, you change the risk of developing a cancer.

Maleness and femaleness can effect gene expression as well as certain drugs.  Even exposure to x-rays and sunlight can exert an epigenetic influence.  Some researchers suspect diet, exercise and even mood can influence how genes function, so behavior certainly matters.  For example, a 2014 study from the Karolinska Institute in Sweden asked 23 men and women to bicycle using only one leg for 45 minutes, four times a week over three months. In comparing muscle biopsies before and after the experiment, scientists found that, in the exercised muscle, new patterns had developed on genes associated with insulin response, inflammation and energy metabolism.³

All this may be interesting, but is it practical?  Can what we do influence something as simple as living to 100?  Dan Buettner thinks so.  The author of the best seller, The Blue Zones notes certain consistent behaviors in cultures with the highest rates of centenarians. (People over 100)  He lists several habits that seem to correlate with extreme longevity. They include:

1. Drink lots and lots of water (and the occasional red wine).

2. Eat less overall (total calorie reduction improves longevity in rats and humans).

3. Continue living with purpose (staying mentally engaged).

4. Be in community (people who were alone or isolated died earlier).

5. Stay active (walking regularly is best).

6. Be optimistic (those who were more positive tended to live longer).

It’s easy to see that these characteristics are all choices available to anyone regardless of their genetic makeup.  We are learning more and more that genetics loads the gun but often behavior pulls the trigger.  You are not always and forever a captive of your family history but can exert remarkable influence on your health by making good choices.