Nutrigenomics: Skinny Genes and the Effects of Food

A new science looks at how food shapes us

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Have you ever wondered how the foods you and your family eat actually affect your health? Or why some people can eat certain foods and stay slim, but those same foods cause you to gain weight?

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Nutrigenomics, a form of science that combines nutrition and genetics, seeks to answer these questions and many more. Below are some examples of the promise — and limitations — of this new field.

Q: Is there such a thing as a “skinny” or “fat” gene?

A: You might read in the news about newly discovered genes — “skinny” or “fat” genes, for example — that have a very specific role in the body. But in reality, many genes interact with our diet to affect our health. Scientists have identified more than 100 genes thought to play a role in obesity. For example, researchers have shown that individuals with a particular version of a gene called FTO had an increased abdominal circumference and higher body mass index (BMI) when eating a diet higher in saturated fat. But other individuals, with a different version of the gene than the first group, did not have a change in their measurements when eating the same diet. This study suggests that some people may benefit from slight changes to their diet, depending on their genetic make-up. But it’s important to remember that genetics isn’t everything — our lifestyle and environment play a big role in our health. There are many things we can control and changes ourselves.

Q: Can a genetic test help me decide what to eat?

A: Your food preferences and choices probably have a lot more to do with your culture and upbringing than what current science could recommend. There is a lot of interest in the ability of genetic testing to personalize your diet, but most scientists agree more work needs to be completed before this is a practical reality. Most of the genes that have been studied have only a very small effect on disease risk.

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Be very cautious of companies that offer “SNP,” a type of genetic testing, and provide dietary recommendations. Often their tailored reports use information from your demographics, lifestyle behaviors and present health conditions, not information directly from your genes! Also, these companies typically offer expensive nutritional supplements without enough research to back up their benefits. If you want to know your personal risk of common, chronic diseases, being aware of your family history and changing your lifestyle — exercising, quitting smoking and watching your alcohol intake — is likely more helpful.

Q: What are some examples of how our genes affect how our bodies use foods?

A: The rare genetic condition phenylketonuria is caused by a change, or mutation, in the group of genes that helps our body process protein. When there is a mutation, the body cannot break down one of the building blocks of protein. Build-up of this protein is toxic to the body and affects development of the brain, pigmentation of the skin, and other parts of the body. Individuals with this condition need special foods and supplemental formulas.

Celiac disease is another example. Celiac disease is a condition where the body has difficulty tolerating gluten, a protein found in most bread and wheat products. Individuals with Celiac must avoid gluten in their daily diet so they don’t get uncomfortable side effects from inflammation in the small intestine. Unlike phenylketonuria, the genetics of Celiac disease are not well understood yet. Instead of specific mutations, variations in genes may predispose certain people to Celiac. And not everyone with these variations will develop Celiac. Environment and other exposures may also be risk factors.

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Even with cautions about the current limits of nutrigenomics, the future is promising. A lot of great work is being done to understand how our genetic differences affect the way nutrition improves our health. By measuring the level of gene “expression,” scientists hope to discover targeted ways to reduce the risk of chronic disease through dietary intervention.

Keep on the lookout for more advances in this field, and be aware of the positive health choices you can make already.

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Kathryn Teng, MD

Kathryn Teng, MD, is Director of the Center for Personalized Healthcare and leads Cleveland Clinic’s efforts to integrate personalized healthcare into standard practice.
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