Feel healthier during the summer? Thank genetics

Do you feel healthier in the summer than the winter? Are you stronger, fitter and less likely to get ill in the warmer months?

It’s not just your imagination. A new study from Cambridge University suggests the reason may be genetic.

The study, recently published in the journal Nature Communications, suggests that over 5,000 human genes – almost a quarter of the more than 22,000 we all carry – show some form of differing seasonal performance level. Many that are crucial to keeping us healthy do their best work come summer.

“In some ways, it's obvious,” Cambridge professor John Todd, director of the JDRF/Wellcome Trust Diabetes and Inflammation Laboratory, told ScienceDaily.com.

“It helps explain why so many diseases – from heart disease to mental illness – are much worse in the winter months. No one had appreciated the extent to which this actually occurred.”

"Given that our immune systems appear to put us at greater risk of disease related to excessive inflammation in colder, darker months, and given the benefits we already understand from vitamin D [in sunlight], it is perhaps understandable that people want to head off for some ‘winter sun’ to improve their health and well-being," Dr. Todd said.

But this isn’t just a warm-weather story. The study found genetic health benefits in wintertime as well. One set of genes, useful in maximizing the effectiveness of vaccinations, was found to function more efficiently in winter. This suggests a specific seasonal timing of vaccine administration might help boost their benefits.

“The implications for how we treat a disease like type 1 diabetes, and even how we plan our research studies, could be profound,” Dr. Todd said.

“This is a really surprising – and serendipitous – discovery.”

“We have long known there are more diagnoses of type 1 diabetes in winter,” said Karen Addington, CEO of the Juvenile Diabetes Research Foundation in the UK.

“This study begins to reveal why. It identifies a biological mechanism we didn't previously know of, which leaves the body seasonally more prone to the autoimmune attack seen in type 1 diabetes.”

Researchers concede that the actual mechanisms which cause these seasonal variations have not yet been identified. Daylight, temperature and other factors that shift throughout the year are thought to be the leading candidates.