It’s easy to get into a routine: eating, working, and exercising in the same ways day after day. But did you know that microbes in the air change from one season to the next? Did you know that microbes in your gut should be changing from one season to the next? Did you know that receptors in your brain for mood hormones also change seasonally?
Yup, it’s all true! We are seasonal circadian beings and we MUST live in sync and in harmony with nature’s rhythms to survive, thrive, and enjoy life on this planet. Ayurveda has been making the case for thousands of years and today this knowledge has been repackaged in what is now called Circadian Medicine (based on Nobel Prize-winning science).1
The Air is Changing You
In one study, airborne bacteria we breathe every day were measured for seven years and were found to have non-random seasonal shifts. In high elevation samples of rain and snow, consistent microbial patterns were found to be highly different in the summer and winter. More specifically, freshwater croplands and urban environments had more abundant bacteria in summer, while marine and forest environments had more in winter.2
These findings support health benefits reported when “forest bathing” or hiking in the wild or sitting by a lake or river. Learn more about the health benefits of nature here.
We RecommendThe Life-Changing Benefits of Forest Bathing
You Are What You Eat
In a study measuring seasonal variation of the human gut microbiome, diet and gut bacteria of a group of volunteers were evaluated over the course of a year. During summer, when a higher concentration of produce and complex carbohydrates was in the diet, there was a surge in complex carbohydrate-digesting bacteria called bacteriodetes, along with a decrease in actinobacteria, which have been negatively correlated to fiber content.3,4
The more carb-digesting bacteroidetes you have compared to firmicutes, the higher the risk for obesity. It was also found that actinobacteria increase in winter. Actinobacteria increase with the amount of fat consumed and decrease with fiber, suggesting a higher-fat diet in winter is supported by a related seasonal eating shift in the microbiome.3,4
More and more research suggests that receptors for food, digestive enzymes, nutrients, and even neurotransmitters change seasonally.9,10
Amylase, for example, a starch-digesting enzyme, has been found to wax and wane seasonally. During the season when starches are harvested, the body’s amylase enzyme surges.10
If you eat a high-carb high-starch diet 24/7, 365 days a year, instead of only during late summer months when carbs and starches are naturally available, carbohydrate-digesting bacteria such as bacteroidetes can overpopulate the gut and drive excess glucose (sugar) into the bloodstream, possibly contributing to today’s current epidemic of prediabetes.11,12
These and other studies documenting measurable seasonal changes in the microbiome beg the question: Why this is so important?
Food, like everything else in nature, is delicately balanced. Eating seasonally may be the most powerful way to keep circadian rhythms in check.
Now that Circadian Medicine won the Noble Prize, we may start paying attention to the simple logic and ancient wisdom of seasonal eating.
Brain Receptors Shift Seasonally
Every summer, sunlight turns on genes that drive brain chemicals to support greater energy, activity, and mood. This makes sense since, with winter coming, there is always much to do during the long summer months.
Come winter, when sunlight wanes, receptors in the brain for serotonin and brain-derived neurotrophic factors (BDNF) also wane. This helps explain why many folks have a more difficult time staying happy during winter. Seasonal Affective Disorder, for example, is linked to these changes.5,6
Fortunately, fall-harvested foods like nuts, seeds, beans (including chickpeas), cheese, and fish all boost serotonin levels, while fall-harvested herbal roots like bacopa, ashwagandha, and turmeric all boost BDNF in winter.
Learn how to boost BDNF here.
Learn how to boost serotonin with food here.
Horizontal Gene Transfer
Genetic information can pass from microbes on our food to genetic material on microbes inside our intestinal tract and then across the intestinal wall and modify the body’s genetic code. This is a process called horizontal gene transfer (HGT). If we ingest a microbe living on a lettuce leaf that was sprayed by an insecticide that mutated its genes, that mutated genetic material can be horizontally transferred to genetic material of microbes in your gut. This mutation can then be passed through the intestinal barrier to impact how the human genome is expressed.7,8
This process seems like a good design to let our genes know when something harmful or damaging is mounting in the environment. Horizontal gene transfer is our way to prepare genetically for an ever-changing environment.
It is thought that gene transfers take place seasonally, as the microbes in the soil and food dramatically shift from one season to the next. Horizontal gene transfer is thought to be part of our very intimate connection to the circadian rhythms of nature.
Eating seasonal foods may be the missing link that could help re-connect us to circadian rhythms and offer the genetic shift we need to stay healthy from one season to the next. This makes seasonal eating a new area of dietary research—although Ayurveda has been discussing it for thousands of years.
New research shows that stress from non-organic, highly processed refined foods as well as seasonal changes in diet, lifestyle, and many other factors are forcing the body to adapt genetically.
In addition, recent studies have gone further. Not just microbes on the food, but genetic information of the food itself has been shown to horizontally transfer into our genetic code—to negate any genetic surprises down the road that could take the species out.7,8
In this regard, GMO food is implicated in its ability to make changes to us on a genetic level—logic would tell us that this can’t be good! More on this in future articles . . . In the meantime, enjoy your healthy, organic, seasonal food and stay in tune with the cycles of nature!
Receive my free monthly seasonal eating guide, the 3-Season Diet Challenge, here.