The warming climate is hitting us right in the gut, as new research shows that rising temperatures are taking a toll on the health of our gastrointestinal systems and impacting the food we consume. As climate change exacerbates health conditions, it also increases inequality around the world — and it’s only going to get worse.
Heat stress is negatively affecting the human gut microbiome, according to a review published in Lancet Planetary Health. The microbiome is a complex ecosystem within the gastrointestinal tract that plays an important role in overall health. High external temperatures can “induce complex changes in the gut, including shifts in microbiota composition, increased oxygen levels and overproduction of stress hormones,” said a release about the review. The effects of this can be far-reaching.
When under stress, the body releases a “stress hormone” called cortisol, which can significantly affect the gut. The cells that line the gut all have cortisol receptors, and “all of them may become dysregulated if cortisol levels climb too high,” said Time. Cortisol can also “speed or slow the time it takes for food to transit through the intestines.” This leads to a condition called dysbiosis or an “imbalance in the number, type and distribution of the trillions of bacteria, viruses and fungi that make up the microbiome inhabiting the digestive tract.”
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Temperature also has a “direct effect on the intestines,” Desmond Leddin, a professor of medicine at Dalhousie University in Canada, said to Time. “One of the causes of heat stroke is thought to relate to intestinal permeability.” A decrease in intestinal permeability is called “leaky gut,” and it allows “organisms that make up the intestinal microbiome — which are supposed to remain in the intestines — to migrate into the bloodstream and spread infection,” said Time. “The microbes that remain behind, meantime, can be thrown entirely out of balance.”
While heat directly affects our bodies, it also affects what goes into our bodies. Air temperatures above 30°C or 86°F can “reduce the levels of antioxidants” in some plants that both humans and livestock consume, said the review. High temperatures are also “associated with increased water consumption, which might contain enteric pathogens or other toxin-producing microbes.” And increased consumption of water with “environmental pollutants, such as arsenic and other heavy metals, can also increase gut dysbiosis, especially early in life.”
A gut feeling
The gut is not the only area under attack by climate change. “A warming world leads to all manner of health problems, including increased risk of cardiovascular disease, exacerbation of pulmonary conditions like asthma and COPD, and mental health problems, including depression and anxiety,” said Time. High temperatures can additionally make certain crops harder to plant, decreasing food access, especially for lower-income countries; these countries are less equipped to handle a larger spread of pathogens and food insecurity. Unfortunately, global microbiome research “remains heavily skewed toward high-income countries,” Elena Litchman, a microbial ecologist at Michigan State University and the lead author of the review, said to Asian Scientist
The gut microbiome could “serve as a sensitive biosensor for climate-related health vulnerability,” but broader data, especially from middle and low-income nations, is still required to see how “climate change is truly reshaping human biology,” said Litchman. Further research is essential as “shifts in gut microbial composition might offer early warning signs of climate stress in human populations, helping guide targeted interventions.”
