It’s that wonderful time of year when the leaves start to change colors, the cool brisk breeze begins to pick up, and the pumpkin spice lattes make their first appearances. That’s right, it’s fall, that glorious season that marks the end of summer and the beginning of those colder months. There’s no doubt that a change of seasons brings with it other forms of change as well, but what does a change in season mean for our genes?
While it might seem absurd at first, recent research has actually proven that seasons have a massive effect on how our genes function within our bodies. Upon thinking on it further, it makes sense that there would be a deep molecular change within us that comes about with a change in season. After all, trees lose their leaves, many animals begin to grow their winter coats, birds prepare for a massive journey south. We all primal genetic code, so why wouldn’t our genes vary with the seasons?
In a study conducted at Cambridge University, more than 16,000 people from around the world were tested to see how their genes might vary season to season. Samples of blood and tissue were taken throughout the year and 22,000 genes were analyzed (that’s nearly all of the genes that we understand the function of). The results of the study found that nearly a quarter of those genes showed clear signs of seasonal variation, meaning that their function changed with the seasons. In specific, genes that had a connection with the immune system and inflammation showed a significant increase in function during colder months. This would make sense when thinking about the increase in viral infections that occur in concurrence with the cold winter months. Our genes would have evolved to increase immune function during these months in order to better fight illness like cold or flu.
And just to prove that the changes in our genes that mirror changes in the seasons aren’t flukes, the study showed that these changes in our genes vary based on where we live, because seasons vary location to location. Genes involved in immunity and inflammation are more active during December-February for people living in the northern hemisphere and more active from June-August for people living in the southern hemisphere. For people living in consistently warm or consistently cold climates, those patterns vary as well. Those living close to the equator where the climate tends to stay at a steady temperature year round exhibit gene variation around the rainy season when illness becomes more prevalent and mosquito born disease such as malaria becomes rampant. On the flip side, people living in cold environments like Iceland show little to no seasonal variation in gene function because they lack a seasonal variation in disease.
While this seasonal variation in gene function developed as a tool for survival, there is evidence that this increased function may also be contributing to seasonal flare ups of inflammatory diseases including heart disease, type-1 diabetes, and arthritis. In the UK especially, the medical community sees a significant increase in these diseases during colder months when the immune system kicks into over drive and has the potential to attack the body itself. Professor Tim Spector of King’s College London says that the gut micro biome could also play a huge role in these disease flare ups as the gut micro biome changes seasonally as well. Of course, it’s nearly impossible to single out any one cause for these diseases, but seasonal gene variation certainly plays a role.
Evolutionarily speaking, seasonal changes in gene function would have been an advantage to humans, helping them fight off disease in times of need, but also helping them to conserve energy by varying the function of genes that relate to metabolism in order conserve energy during colder months or times of limited food. Although some of these seasonal gene variations may no longer be relevant due to our ability to alter our climate with AC or our year round access to food, some seasonal changes are still greatly appreciated. You can remember to thank your genes the next time flu and cold season rolls around and you manage to stay healthy and make it through to Spring.