One of the last remaining hunter-gatherer tribes on earth confirm that our gut microbes were meant to change seasonally!
If you are a regular reader here at LifeSpa.com, this may be old news… you are probably already eating seasonally, enjoying the monthly recipes, utilizing the grocery and superfoods lists we publish for free each month as part of the yearlong 3-Season Diet Challenge. Or you may have read my book, The 3-Season Diet.
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What the Hunter-Gatherer Diet Does To the Body
In a new Stanford University study published in the Science journal, researchers found that the microbes in the members of the Hadza tribe in Tanzania change dramatically with each season, in sync with seasonal changes made to their diet.
The study showed that certain gut microbes that reside within the gut in one season may almost disappear in the next – suggesting there are dramatic changes taking place in the microbiome from one season to the next. The researchers concluded that the Hadza tribe’s gut microbes and their digestion is cyclical, and in sync with the precise bio-rhythm of nature. (1,2)
In addition to their microbiome making dramatic seasonal shifts, the Hadza microbiome is significantly more diverse than that of a western-cultured microbiome. They carry a powerful stable of gut microbes that are extremely skilled at breaking down fiber.
The Hadza microbiome had more enzymes for breaking down animal-made carbohydrates during the dry season, and more enzymes to target plant-based carbohydrates in the wet season.
Microbes in the digestive system manufacture enzymes that change seasonally. They do so to help in the digestion of seasonal foods, as well as boost immunity when needed in the winter, decongest the body in the spring, and dissipate heat during the long, hot summer.
For the Hadza, the combination of a higher fiber diet along with one that is seasonally changing from dry-season hunting to wet-season foraging has left them seemingly free of colon cancer, colitis or Crohn’s disease. (1,2)
How the Body Adapts to Seasonal Shifts
In my book, Eat Wheat, I cite research that shows how the starch-digesting enzyme, amylase, naturally increases in the body during the fall and winter. This is aligned with when more starchy tubers, wheat grasses and grains are in abundance and harvested.
The amylase enzyme decreases in the summer – when the diet was made to shift to be more vegetable-based.
Another way the human body responds to the change of seasons is that the parasympathetic nervous system (often referred to as the “rest-and-digest” nervous system) increases the body’s digestive potential in the fall and winter. It does this in order to more effectively break down the more dense and concentrated fall- and winter-harvested foods, such as root vegetables. (3)
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The Seasonal Microbe Symphony
The microbes that occupy the body’s microbiome come from the soil that nourishes the plants we eat.
Each plant seasonally attracts certain beneficial microbes from the soil, creating a symbiotic relationship. Plants seem to benefit from certain microbes, and certain microbes seem to benefit from the nutrients of certain plants.
With each seasonal shift, the microbiology of the soil changes, the chemistry of the plants change and the microbes that attach themselves to the roots, stems and leaves of each plant shift like a changing of the guard.
When we eat these plants in season, we consume the nutrients in the plant as well as the microbes that are attracted to and attached to that plant. We are also ingesting the foods that the microbes, who are attached to these plants, love.
These microbes create a microbial community within us. In fact, microbes make up 90% of the nucleated cells in the human body.
The Dangers of Eating out of Season
When we do not eat seasonally, our microbiome is quickly disconnected to the intelligence of nature, and much of our genetic dependence on seasonal microbes is lost.
Let me share a quote from the book, The Forest Unseen, to illustrate this point: (4)
Sudden changes in the diet can disrupt this elegant molding of the rumen community and its environment. If a deer is fed corn or leafy greens in the middle of winter, its rumen will be knocked off balance, acidity will rise uncontrollably, and gases will bloat the rumen. Indigestion of this kind can be lethal.
In other words, when an herbivore eats foods that are not in season, it causes a drastic shift in its microbiology, leading to severe indigestion that can actually kill the herbivore. Cows, for example, when taken from pastures and fed grain instead of seasonal grasses, have to be medicated to settle their stomachs.
I realize that we are omnivores and not herbivores but, clearly, this is food for thought! We are as connected to the cycles of nature as are the herbivores, albeit in a different way. If eating foods that are not in season can kill a deer, then is this a message for us begin to respect the diet that has been right in front of us for all these years?
There is no doubt that the microbes in our intestinal tract change according to diet and seasonal influences. Perhaps we are more resilient to these changes, but are we immune to them?
Without a diet rich in seasonally-changing microbes, our intestines are often populated by space-occupying microbes that, while not necessarily bad, are not beneficial either. They take up real estate in the intestines and can affect the gut, its immunity, and many other adaptive processes to function less than optimally.
Without the influx of seasonal microbes to boost our digestive strength and support a diverse community of essential and beneficial bacteria, we can become extremely vulnerable and often hyper-sensitive to our environment and foods.