Nature versus nurture: It’s an age-old dilemma. How much of our health and well-being do we owe to nature (our genes) and what role does nurture (the environment) play?
Throughout the late twentieth century when scientists were mapping the human genome, they believed that genes would be the determining predictor of future illness. However, that isn’t the case. Recent research indicates that genes explain only 5 to 10 percent of your risk for developing any chronic disease.
In genetic terms scientists describe most chronic diseases as “multifactorial.” That means the risk is spread across many genes and that each plays only a small part in whether you develop a condition. Thanks to the science of epigenetics we know that your genes are not static: They are constantly engaged with the environment. Interactions like diet and stress change how they are expressed, influencing the likelihood that you will develop a disease.
Take stroke, for instance. If either of your parents had a stroke, you’re probably afraid that you will have one, too. However, the American Stroke Association states that 80 percent of strokes are preventable, largely through lifestyle modifications. Epigenetics explains why this is the case.
A Nutritious Diet Reduces the Risk of Stroke
Numerous studies have linked good nutrition with lowering the risk of stroke. The Mediterranean Dietary Pattern (MD) has been investigated in depth and those studies indicate that a diet built around whole foods, like fruits, vegetables, whole grains and fish, shrinks your chances of having a stroke. For instance, the MD muzzles inflammation and provides an abundance of antioxidant compounds, benefits that have been shown to improve gene expression in ways that reduce stroke risk.
Gut Health Plays a Role
The MD has also been shown to increase the quantity of certain types of beneficial bacteria in your gut. Among their advantages, these bacteria can help your body battle inflammation. A 2012 study published in the journal Nature Communications found that some also produce carotenoids, a type of antioxidant that may protect against stroke. When these researchers compared healthy subjects with people who had experienced stroke, they found higher levels of carotenoid-producing bacteria in the guts of the healthy subjects, as well as higher levels of a specific carotenoid in their blood.
Nutrients Can Trump Your Genes
Some people have genetic variations that predispose them to forming blood clots, which increases the likelihood of stroke. Some of these variants may set the stage for higher levels of homocysteine. This amino acid is linked with inflammation and also raises the risk of blood clots. If your homocysteine is high, a vitamin deficiency may be to blame. Vitamins B12, B6, B2 (ribolflavin) and folate all help to metabolize homocysteine. Research has shown that nutritional supplementation may lower homocysteine levels, in part by supporting DNA methylation, an epigenetic process.
It’s worth noting that consuming nutrients as part of a healthy diet is preferable to taking them as supplements. Nature doesn’t provide nutrients in isolated form as they appear in supplements, but rather in combinations that work together to promote health and prevent disease. Consuming nutrients from a variety of whole foods has been shown to create synergy, boosting their benefit as individual foods.
If, like many people, you spend a big chunk of your day seated, here are two words of advice: Get moving. Sedentary behavior increases the risk of stroke and regular exercise has been shown to reduce that risk by about 25 percent. One study showed that committing to an exercise program for 6 months improved the expression of numerous genes involved in DNA methylation, which as noted above has been associated with stroke.
Smoking cigarettes has also been linked with an increased risk of stroke. Basically, smoking promotes the buildup of plaque in your arteries. It also thickens your blood, making you more vulnerable to clots. Recent research suggests that these negative outcomes result from changes in how several genes are expressed.
The American Heart Association recommends mindfulness training as one component of a package of positive lifestyle modifications directed at preventing stroke. Studies suggest that meditation can lower blood pressure, thereby reducing the likelihood of stroke. Meditation has also been shown to blunt the expression of genes that promote inflammation.
Returning to the question of nature versus nurture, if you’re old enough to remember when photographs were shot on film, think of your genome as the negative. It’s the raw material that processing can tweak to produce desired results. The curious case of identical twins provides a powerful case in point. Born with identical genomes, over time their lives diverge and research shows that twins rarely die of the same disease.
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Karisson, F. et al. Symptomatic athersclerosis is associated with an altered gut metagenome. Nature Communications 2012.
Liu, R.H., Health benefits of fruit and vegetables are from additive and synergistic combinations of phytochemicals. The American Journal of Clinical Nutrition. 2003
Rönn T, et al.A Six Months Exercise Intervention Influences the Genome-wide DNA Methylation Pattern in Human Adipose Tissue.” PLoS Genet2013.
Cheng, X. Smoking affects gene expression in blood of patients with ischemic stroke. Annals of Clinical and Translational Neurology 2019.
Kaliman, P. et al. Rapid changes in histone deacetylases and inflammatory gene expression in expert meditators. Physchoneuroendocrinology 2014.
Judith Finlayson is the author of You Are What Your Grandparents Ate: What You Need to Know About Nutrition, Experience, Epigenetics, and the Origins of Chronic Disease. Visit her at www.judithfinlayson.com.