Living, Eating & Mating With The Seasons: A Functional Medicine Perspective
Chemical Messengers of Light
For the modern human, the seasons are mostly recognised for weather changes, a favourite holiday period or perhaps a particular recreational sport.
For our ancestors, they meant so much more: adjusting life according to the seasons was essential for survival. They played a key role in the evolution of culture and of important behaviours, such as sleep patterns, agricultural practices and the availability of different foods. Our survival depended upon seasonal practices that supported specific physiological functions, and these are still relevant today.
But how are seasonal biological rhythms orchestrated?
Just as flowers only bloom in response to particular hours of darkness, humans too have a cascade of chemical messengers inside the body that impact how our organ systems respond to sunlight hitting our eyes and skin. Summer days welcome longer hours of daylight, translating to higher levels of serotonin being synthesized in the gut and increased Vitamin D being produced in the skin.
Conversely, darkness regulates the hormone melatonin via the pineal gland. Melatonin then instructs how genes are translated (DNA transcription) to influence circadian rhythm and hormone cascades. For example, melatonin regulates thyroid and pituitary activity - these glands are master controllers of circadian rhythm, hormone and energy production. Higher levels of melatonin in the body during darker seasons causes thyroid activity to increase in order to allow the body to regulate its metabolism in response to energy (food) scarcity. Melatonin also exhibits protective gastrointestinal effects, powerful antioxidant properties as well as inhibiting cancer cell viability.
Seasonal Nutrition
The ‘Airborne’ Microbiome
There are many environmental factors that impact nutrition, and they shift dramatically throughout the year. For example, many people don’t realise that the microbiomes of our guts, skin and lungs are heavily influenced by microbes in the air, which change seasonally and in different environments. Just one cubic metre of "empty" air contains 10,000 bacteria or more, and recent research has been able to show differences of airborne bacteria in different seasons!
Other environmental factors, such as sun exposure, temperature, humidity, foods consumed and time spent outdoors also impact bacterial composition.
Nutrient Density
When produce is picked at peak ripeness (in season), key nutrients are found at higher concentrations. Additionally, seasonal foods provide nutrients that benefit a variety of corresponding physiological needs.
Summer and Autumn provides the greatest abundance of complex carbohydrates, to be stored as fat for the Winter. These include:
Pumpkin
Potatoes
Squash
Winter produce tends to be full of bioflavonoids and Vitamin C, and are supportive of the immune system:
Radish
Lemons
Tangerines
Spring offers many green leafy vegetables which naturally support liver detoxification pathways:
Mustard Greens
Asparagus
Dandelion
Tis’ the Mating Season
Seasons also elicit corresponding hormone changes that influence social and reproductive behaviours. Many mammals (including humans) experience physiological changes that encourage mating in order to increase the chances of survival for their offspring - it quite literally can mean life or death.
Female humans have a 28-day reproductive cycle, thus, we are able to reproduce during any month of the year. Yet, interestingly, June through August tend to have the highest birth rates. This coincides with higher conception rates in the Autumn and early Winter, and warmth and food abundance for mum and newborn baby in the summer.
Could this be the work of hormonal changes? We know melatonin can increase feelings of lethargy, tiredness and the desire to sleep more (i.e. spend more time in bed), but it also appears to increase certain sex hormones that drive mating, such as testosterone.
In fact, a recent study from the Weizmann Institute of Science reveals that many of our key hormones also follow a seasonal pattern. By analyzing millions of blood tests, the researchers discovered that all 11 key behaviour-driving hormones they looked at peaked at different times throughout the year.
Interestingly, they found that hormone-producing glands grow and shrink in continuous, self-regulating annual cycles. Theory follows that each maximum or minimum causes hormone levels to rise or fall by several percent—small but significant—though often several months later. These cycles are evident in hormones released by the thyroid, liver, adrenal cortex and gonads, directed by the pituitary gland in the brain. The results support a growing body of work that shows that fertility tends to be higher in midwinter, kids grow faster in spring and moodiness peaks in winter. So, as the lead author stated, the fact that more children are conceived in certain seasons may have more to do with hormone balances than the blooming of flowers in the fields.
Light, Electronics & Serotonin - Oh My!
There has been a lot of press recently about the impact of blue light on melatonin secretion. But what else can we do to support healthy seasonal hormone levels?
Eating foods that contain melatonin or support the melatonin synthesis pathway can help. These include:
Melatonin-rich foods such as tomatoes, olives, rice and walnuts
Tryptophan-rich foods such as tuna, chicken, oats, nuts, seeds and fruit
Co-factors that support melatonin synthesis, such as vitamins B6, B12, folate, magnesium, zinc, omega-3 fats.
Serotonin is the precursor to melatonin, so doing activities that support serotonin can also support melatonin production. This could include sun exposure, walking in nature and surrounding yourself with healthy social connections. Regular exercise and healthy, adequate sleep are also foundational.
Try to avoid alcohol and caffeine, as they are not supportive of seasonal hormone fluctuations or retaining B-vitamins. In general, limit exposure to artificial light - especially harsh fluorescent lighting - and screens, particularly in the evening. (Although orange-tinted glasses help, try not to rely on them by avoiding screens and turning off bright lights or installing red light bulbs in areas where you spend time before bed).
So, think about watching that film a little earlier and creating a low-light setting in your home. Your hormones will thank you for it.
References:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5886313/
https://extension.unh.edu/blog/2022/05/health-benefits-eating-locally
https://pubmed.ncbi.nlm.nih.gov/30772579/
https://www.news-medical.net/news/20221216/First-ever-atlas-of-global-airborne-microbiome-provides-a-wealth-of-insights-into-microbial-communities.aspx
https://onlinelibrary.wiley.com/doi/full/10.1111/j.1600-079X.2011.00963.x
https://onlinelibrary.wiley.com/doi/10.1111/cen.13351
https://www.afdil.com/blog/melatonin-and-testosterone-the-connection-explained/#:~:text=Studies%20have%20shown%20that%20melatonin,an%20increase%20in%20the%20other.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7575238/
https://www.popsci.com/birth-seasonality/
https://cmbl.biomedcentral.com/articles/10.1186/s11658-022-00375-z
https://pubmed.ncbi.nlm.nih.gov/23051584/
