Michael Snyder is the Stanford W. Ascherman Professor of Genetics at Stanford University. He speaks with Srijana Mitra Das at TE about ways —and whys — seasons impact our physiology:
So says Stanford genomicist Michael Snyder, who led a team studying molecular data spread over four years from 105 participants in California, aged 25 to 75, seeing how their systems corresponded to weather transitions. Forget festive sales, syrupy sweets or silken sweaters — the very molecules inside your body, those tiny collections of atoms bonded together, indicate when the seasons are changing and how you are going to like the shift. Further, your body may not always react to the widely understood ‘spring/summer/ autumn/winter’ quartet — you may simply respond to transitional periods, the seasonal portals of late spring-early summer and late autumn-early winter.
Thus, Snyder’s study found the latespring period came with increases in inflammatory biomarkers involving allergies — there is also a rise in molecules involved in rheumatoid arthritis and osteoarthritis and spikes in HbA1c, a form of hemoglobin and a protein that signals risk for Type 2 diabetes rise. Because of new foods people eat, there are different exposures in these two phases, from temperature shifts to microbes and even your gut microbiome, which changes possibly. Because people are coming out of a long, relatively inactive winter and they suddenly go out and find sun, pollen, etc., and many immunological things happen, snyder muses and adds, ‘We really did expect the late fall-early winter phase to show more biological changes — it was surprising to find these instead in spring but it’s.
Another interesting finding comes from winter when Snyder says higher depression can be experienced owing to reduced sunlight. As he says, ‘Mental conditions are deeply influenced by seasons. It’s quite likely, says Snyder, that these findings could vary in India which has several seasonal shifts and possibly more biological responses.
Snyder, who gestures, gets up and moves energetically several times as we speak, describes his research. ‘We use big data to study human health. We do deep profiling on people and track them over time, so we can catch disease before it appears. A lot of my work is to do with wearables. He holds up his arms, covered in biosensors that look chunky, yet slim, black and Matrix-like, tracking variables from blood pressure to glucose. Why does the human body react to two seasons, instead of four? Snyder explains, ‘Well, first, this study was based in California. So, the seasonal extremes are a little less. Second, if you think about it, ‘four seasons’ is just an arbitrary designation that humans made up, right? It’s not set in stone, so we went into this study agnostically, saying, let the biology tell us how many seasons there are. As it turned out, we found the body responding to two bursts when a lot of stuff happens. Alongside, a lot of metabolic differences occur while people’s activity level also differs significantly between warmer and cooler days. All these factors trigger changes in the body. Snyder’s team linked the latter to indulgent eating through winter — put down that pie and just eat an apple — and a waning of vigorous exercise in colder months. Further, the gene PER1, which works to regulate the circadian sleep-wake cycle, was also at its highest then. Following the data into winter, the study found an increase in immune molecules which fight viral infection alongside rises in molecules that contribute to acne. Further, molecular developments leading to hypertension or high blood pressure intensified in winter. The study also found differences in the microbiomes of people who processed glucose normally versus those who were insulin-resistant, which were around half the participants. Veillonella, a bacteria involved in lactic acid fermentation and glucose processing, was higher in insulin-resistant people through the year, except in mid-March through late June. What he does highlight is climate change now altering all these reactions — ‘Climate change is really going to affect our exposures, the amount of time we’re out in the sun, etc. It is concerning how this could impact the human system, which has evolved over millions of years to respond to seasonal transitions. We have to be on the alert for this.’
