Nurture vs. Nature: How Much Control Do You Really Have Over Your Health?

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Many people—including many health practitioners—believe that our susceptibility to disease is built into our genes and thus we have little control over what happens to us.  The thinking, and a fairly robust body of evidence, suggests that if your parents and grandparents suffered from a particular disease, the probabilities are high that you will acquire it also.  Cancer, heart disease, diabetes, stroke, multiple sclerosis, arthritis, celiac disease, Parkinson’s, Alzheimer’s—the list goes on with the type of diseases thought to be mostly inherited. This fatalistic belief even extends into the mental health arena, where psychiatrists (and some psychologists) label just about anyone exhibiting dysfunctional behaviour as having a ‘mental illness’, traced in your medical history to one side or another of your family tree.  If your uncle or great-grandfather exhibited similar symptoms, it is dismissively concluded that the condition ‘runs in the family’.

But exciting research is shedding new light on this subject, revealing surprising data that empowers us in both preventing and reversing diseases long thought out of our control.  Recently, a Scandinavian study used a unique method to ferret out the genetic vs. environmental source for 28 different kinds of cancer.  The researchers compared the incidence rate of cancer among 89,576 identical and fraternal twins.  Recognizing that identical twins share the exact same genetic makeup whereas fraternal twins only share 50% of their genes, the difference in incidence rates between the two groups measured the degree to which genes were responsible for each kind of cancer.  The findings were shocking—revealing that environmental factors account for 60-80% of most cancers.

Proportion of Cancer Risk Attributed to Genetics vs. Environment (Source: New England Journal of Medicine, Vol 343, No 2, p78-85)
Proportion of Cancer Risk Attributed to Genetics vs. Environment (Source: New England Journal of Medicine, Vol 343, No 2, p78-85)

But even this study may be overstating the significance of the remaining 20-40% genetic causes of disease.  The rapidly evolving field of epigenetics is showing that many genes require an environmental trigger to determine when, how—or if—they will activate.  For instance, cervical cancer expression is largely dependent upon exposure to human papillomavirus, lung cancer is dependent upon exposure to carcinogens from cigarette smoke and other sources, bowel cancer is triggered by changes in our diet, etc.  In fact, it is now estimated that these epigenetic mechanisms account for one-third to one-half of all genetic alterations leading to disease.  Even our behaviour can alter our genes: one study showed that chronic stress produces steroid hormones called glucocorticoids, causing changes in gene expression in the brains of mice.

Between direct environmental effects and the interaction effect of the environment upon our gene expression, it is now widely recognized that external factors are the primarily determinant in our susceptibility to most diseases.  This has profound implications on our ability to prevent and reverse many disorders.  We can’t change our genes, but epigenetics suggests we have a high degree of control over how and whether our genes express themselves in a negative manner.  What are the main environmental factors that affect disease expression?  They can be boiled down to four main areas:

  1. Diet
  2. Exercise
  3. Stress
  4. Exposure to toxins

The direct link between diet and disease has been studied extensively.  Longitudinal studies of people that adopt new eating habits when they move from one culture to another show a strong and clear connection to increased rates of cancer and other diseases.  The epidemic of autoimmune disorders (lupus, IBS, MS, arthritis, Hashimoto’s, Graves, psoriasis, etc.) sweeping the developed nations of the world can be largely traced to the modern western diet.  New advances in genetically modified organisms (GMOs) and food processing have led to a dramatic change in the chemical composition of basic food crops such as wheat, corn, and soy, leading to widespread gluten and other food allergiesDiabetes is now widely accepted to be caused by obesity and high sugar intake.  Even heart disease, the number one killer of Americans, is shown to have a stronger dietary connection rather than a genetic link.

Exercise, specifically a deficiency of exercise, is another factor strongly linked to the development of a wide range of diseases.  Bone demineralization from lack of weight-bearing physical activity has been shown to lead to osteoporosis, osteoarthritis, broken hips, joint replacements, and the formation and painful passage of kidney stones.  Lung diseases such as chronic obstructive pulmonary disease (COPD) and emphysema are negatively correlated with aerobic exercise activity.  Even excessive loss of muscle is associated with poor prognosis in several diseases including diabetes, cancer, sepsis, and heart failure.  (See my article: What Happens to Your Body if You Don’t Exercise for a fuller explanation of the link between exercise and disease prevention.)

The third environmental factor, stress, is no longer the ‘silent killer.’  Heart attacks are widely known to be far more prevalent on Mondays than any other day of the week. Stress weakens the body’s natural immune mechanism to ward off pathogens, dramatically raising our susceptibility to a wide range of diseases.  Research shows that chronic psychological stress is associated with the body losing its ability to regulate the inflammatory response, implicated in a range of autoimmune disorders including fibromyalgia.  And of course, stress plays a primary role in the formation of many modern-day psychological disorders, including OCD, bipolar disorder, schizophrenia, and even autism.

Exposure to toxins is the other key contributor to illness and disease.  Toxins take many forms, from relatively benign to highly carcinogenic, and appear in many places.  Radiation from cell phones, mold in your wet basement, coliform bacteria in bagged salad, poisonous venom from spiders and ticks, plant toxins in peanuts and certain mushrooms, benzene in automobile exhaust, formaldehyde preservatives in cosmetics, pesticides/herbicides/fungicides used in agriculture—disease-promoting toxins are everywhere.  My own experience from analyzing hundreds of health cases across a broad spectrum of disorders suggests up to 50% of illnesses can be directly traced to exposure to a single environmental toxin.  (Many of these cases are described in other posts on this blog and in my book Be Your Own Health Detective.)

The good news is that understanding the environmental source and cause of these diseases equips us with the ability to both prevent (by avoiding exposure to the environmental source) and reverse (by removing the exposure from our environment) most diseases.  Depending on the stage of development, certain types of cancer have been shown to be fully reversible.  One cancer patient given six months to live completely reversed his symptoms and outlived all of his doctors simply by returning to his homeland in Europe and living a simple, stress-free life.  In my own practice, many if not most diseases routinely treated with medication by doctors have been quickly and permanently cured simply by identifying and removing the (usually environmental) source of the illness.

It’s time to stop blaming your genes and temporarily managing your symptoms with medication—take back control over your health with permanent drug-free cures by managing your environment instead.  Live long, and live naturally!

By Reid Jenner


  1. Rachel Cordova

    Thank you for this amazing information. I suffer from chronic pain and fibromyalgia, among other pain issues and have been extremely discouraged with the healthcare I’ve received the past 10 years. Reading this article gave me hope. Something that is very rare in my world.

    1. Rachel,

      Thanks for sharing your experience. Your condition sounds like many others insofar as having a strong possibility of an external cause, which means if you find the triggering factor(s) you’ll have a good chance of turning this around without any further need for drugs. Feel free to use the free downloadable health problem analysis worksheets at my site to assist with your analysis. My book walks you through the process with lots of relevant examples. Feel free also to send me a private note if you’d like a free phone consult to assist in your successful diagnosis and resolution. Please let me know how it goes!

      Reid Jenner

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