Environmental Nutrition: Can your diet override genetic risk for disease?

The question of nature vs nurture usually refers to a person's personality and character and asks which one is most likely to determine who you will be as an adult. But the question of nature vs nurture is also relevant to your risk of developing certain diseases.

Your genetic makeup, passed onto you from your parents, determines everything from the color of your eyes and your curly hair to your predisposition to certain diseases. That's nature. Everyone knows that eating a healthy diet can reduce the risk of developing certain diseases, such as cardiovascular disease, Type 2 diabetes, and some cancers. That's nurture.

Your genetic makeup is beyond your control, but can what you eat throughout your lifetime override your genes and reduce your disease risk?

"Not exactly," says Debbie Petitpain, MBA, RDN, a spokesperson for the Academy of Nutrition and Dietetics. "Diet and lifestyle choices can greatly influence whether certain genes are turned on or off, so that even if someone has a genetic predisposition to a particular disease, healthy food choices and supplements can reduce the risk or delay the onset, but I wouldn't refer to this as an 'override.'"

Nutrigenomics

The study of diet's effect on genes is called "nutrigenomics," and it's a growing and constantly evolving research field. It's important to remember that not every gene is affected by diet. Your genetic makeup sets a baseline for some diseases that cannot be altered by diet. Diseases such as Huntington's disease or cystic fibrosis, for example, are determined by specific genetic mutations that exist at birth, and diet won't have a significant impact on the course of the disease. Diet may not completely control your genes, but what you eat does have the power to turn on or off genetic markers for some preventable diseases.

Your diet can affect the "on" or "off" switch for genes in a variety of ways. A recent study out of the UK of more than 350,000 adults found that a healthy lifestyle, which included a healthy diet, physical activity, and not smoking offset a genetic predisposition to disease by 60 percent and added an average five years to life for subjects. The effect of diet alone wasn't teased out, but the researchers concluded that, regardless of a person's genetic background, a healthy diet as part of a healthy lifestyle could reduce the risk for disease and extend life.

While diet can affect gene expression, the reverse is also true. Genes can affect the absorption and metabolism of certain nutrients that then affect the way in which those nutrients turn on or off specific disease-related genes. Several genes are known to influence how nutrients are metabolized. This area of study is called "nutrigenetics."

Diet, of course, affects the gut microbiome -- the 40 trillion bacteria, viruses, yeast, and fungi that reside in the intestinal tract. That teaming population of microorganisms can affect health for good or bad, depending on the balance of "good" and "bad" microorganisms. A high-fiber diet, probiotics, fermented foods, and yellow, green, and orange fruits and vegetables are all beneficial for the balance, which can in turn influence whether a gene is activated or remains dormant.

The future

The hope is that eventually, you will be able to get a blood test that would provide the information needed to know whether a Mediterranean diet might be better for reducing your disease risk than, say, a vegan diet. The goal is to eventually evolve from one-size-fits-all dietary recommendations to tailor-made recommendations based on an individual's genetic makeup.

While some companies currently offer genetic testing coupled with dietary advice, the ability to recommend "gene-based" diets specifically designed for individuals is an incredibly complicated endeavor, and we're just not there yet. But government-funded research and private companies are working to develop reliable methods that take into account as many factors as possible that could affect the "on/off switch" for genes that influence disease risk.

Developing a personalized diet recommendation will depend on that person's genetic makeup, microbiome balance, and their other lifestyle factors, such as physical activity, exposure to toxins in the environment, and smoking status. "The relationship between genes and diet is complex and not fully understood," says Peitipain. "The interaction between multiple genes and environmental factors can make it difficult to predict how someone will respond to a particular diet based on genetics alone."

Bottom line

Until accurate and reliable genetic testing to determine the specific diet that will reduce your disease risk is widely available, dietitian Petitpain says, "Absolutely we know the fundamentals of health-promoting diets -- eat plenty of plants (fruits, vegetables, whole grains), nuts, seeds, unprocessed foods low in salt and sugar, avoid solid fats and too much alcohol." She says following a balanced, plant-based diet fits the bill and has been linked to a decreased risk of several diseases.

(Environmental Nutrition is the award-winning independent newsletter written by nutrition experts dedicated to providing readers up-to-date, accurate information about health and nutrition in clear, concise English. For more information, visit www.environmentalnutrition.com.)

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