By Ari LeVaux
Different diets work for different people. That is one of the primary takeaways from a fascinating new study at Cornell University, which showed how human genetics customize to specific diets over generations, optimizing the body for the metabolism of certain foods. Unfortunately, that message didn’t reach as many people as it could have, thanks to how many media outlets handled it.
“A Vegetarian Diet Might not be as Healthy as you Think,” ran one headline. “Being Vegetarian Could Kill You, Science Warns,” screeched another.
Meat lovers rejoiced. Animal lovers panicked. The researchers that conducted the study wondered how a press release titled “Eating Green Could be in Your Genes,” which was given to the media days ahead of its official release, could have gotten the story so wrong.
After the initial flare-up, and predictable backlash, most responses to the study were either “OMG vegetarian diet causes cancer,” or “OMG that is so much BS.”
The study, published in the journal Molecular Biology and Evolution, compared the genes of people who come from vegetarian societies with those from non-vegetarian and primarily meat-eating societies. And while the paper didn’t make specific dietary recommendations, the authors do extrapolate that a diet appropriate for someone with meat-eating genes might not work for someone with the so-called “vegetarian gene” [aka the “vegetarian allele,” or form of a gene] that the researchers were studying.
The story begins with genes that code for an enzyme, called FADS2, which helps the body process the omega-6 and omega-3 fatty acids we consume from dietary sources. We need both of these types of oil, and it is becoming increasingly clear that the two fats should be present in the body in roughly equal parts. Omega-3 is anti-inflammatory, while Omega-6 is pro-inflammatory. Inflammation is key to our bodies’ defense mechanisms, but too much or chronic inflammation can help cause many types of disease.
The FADS2 gene has a mutant, or “allele” form, dubbed the vegetarian allele because it helps people regulate their bodies’ balance of omega-3 and omega-6 oils when the precursors are consumed specifically from plant-based sources. The team found that, as expected, this allele is most common in predominantly vegetarian populations like India.
They also suspected that the vegetarian gene would be problematic among people who eat primarily meat, because omega-3 and 6 oils from animal products are metabolized differently. Indeed, the vegetarian allele is quite infrequent in Greenland, and actually seems to have been deleted from genes where, generations ago, it existed.
“Our genetic heritage, to some degree, tailors our genes to specific foods, and when that changes dramatically for whatever reason, there may be a mismatch,” explained the study’s lead author Tom Brenna of Cornell, in a recorded presentation sent to me by his lab.
This mismatch between diet and genes is the underlying premise behind the concepts of precision medicine and precision nutrition. “[Precision nutrition/medicine] means making recommendations on a person by person basis rather than on global means, which is what dietary guidelines do.”