Some people can get away with eating red meat their whole lives and stay fit as a fiddle. For others, their carnivorous ways may end up contributing to heart disease, cancer or even Alzheimer's.
A new study in the journal Molecular Biology and Evolution suggests our different responses to diet may stem from where our ancestors lived. That's because the food available to our forebears resulted in differences in DNA that still linger today.
In some ways, this isn’t surprising. In the past, if there were mostly vegetables available in a certain geographical area, the people who do best eating vegetables would have thrived. Over the generations, those people would be healthier, have more kids and more frequently pass their genes on. Sooner than you may think, most people in the group would have a set of genes more conducive to eating vegetables and less tolerant of red meat.
You Are What Your Ancestors Ate
This is exactly what these researchers found when they looked at the DNA of over 1,000 people. Those whose ancestors ate very little red meat have a key variation in the FADS2 gene that allows them to flourish on a mostly plant-based diet. The variation boosts their ability to make long-chain polyunsaturated fatty acids (LCPUFA), critical for brain development and the control of inflammation. Thus, when these vegetarian-inclined people eat red meat, they may become more susceptible to inflammation, leading to disease.
The researchers first compared a group of 234 primarily vegetarian people of Indian origin to 311 people from the U.S., who presumably ate a more Western diet with lots of meat and processed food. Sixty-eight percent of the Indian vegetarian group had the genetic difference that optimized their bodies for a plant-based diet while only 18 percent of the group from the U.S. did.
The researchers then expanded the study, using the DNA available in the 1000 Genomes Project. This public database contains the DNA from people all over the world. The results were similar to what they found with the smaller group. For example, around 70 percent of South Asians had the “vegetarian” DNA difference while only 17 percent of Europeans did.
This suggests that what our ancestors ate might affect what our optimal diet is today. People with a “vegetarian” version of this gene might want to eat more veggies and less red meat to stay healthy, while those who lack this variation may be able to tolerate more red meat. There may be no one-size-fits-all diet that works best for everyone.
Of course, this calls into question diets like the paleo diet, which recommends we eat like our ancestors did because that is what our bodies have been configured for. But as this study shows, not everyone's body is the same.
Keep in mind, of course, that the genetic difference looked at in this study is one of many bits of DNA that affect how well our bodies process food. There are probably people with the "vegetarian" genetic variation who have other DNA that makes them better able to process red meat, and vice versa.
We do not yet understand our genetics well enough to predict from our DNA what our ideal diet maybe. This finding is one piece in that puzzle, but we still have a long way to go.
When we do get there, we will be able to go to our doctor and find out what diet is best for us. But we'll have to see if our future selves are any better at listening to nutritional advice.