By Michael J. Critelli | MakeUsWell Newsletter, 

This summer, many parts of the world have experienced extreme heat, including places poorly equipped to deal with it. Americans have air-conditioned a high percentage of homes, offices, stores and public buildings. That is far less common in many other countries.

These heat waves raise an interesting question: How have societies that have lived for centuries in climates we find intolerable adapted to them?

One answer can be found at the dinner table:

For millennia, climate has helped shape human cuisine. It determines what crops can grow, how quickly food spoils, how much water is available, how long food must be stored, and how much energy people need. Along the way, humans also discovered foods and spices that affect our perception of heat, cold and comfort.

The result is that regional cuisines are, in part, records of human adaptation to the environment.

Consider chili peppers.

Capsaicin, the compound that gives chilies their heat, activates TRPV1 receptors, the same sensory pathways that respond to physical heat. The brain interprets the signal as heat and may trigger sweating. If that sweat evaporates, it can contribute modestly to cooling.

This does not mean chili peppers function as biological air conditioning. Their effect on core body temperature is limited, and scientists continue to debate why hot-climate cuisines often use more spices.

One long-standing theory is food preservation. Before refrigeration, meat and other foods spoiled rapidly in warm climates. Capsaicin and many other spices possess antimicrobial properties, which may have helped inhibit some foodborne organisms. More recent research, however, suggests that climate alone cannot explain spice use. Culture, trade, agriculture and culinary tradition matter enormously.

Mint illustrates another intriguing relationship between food chemistry and temperature.

Menthol activates TRPM8 receptors, which produce the sensation of cold. That is why mint can make the mouth feel cool even when the food or beverage itself is warm. A cup of hot mint tea in North Africa or the Middle East therefore produces an interesting combination: the hot liquid may encourage sweating while menthol creates a powerful perception of coolness.

Again, perception is not the same as lowering core body temperature. But in an oppressive climate, feeling cooler has value of its own.

Fermentation may represent an even more important climatic adaptation.

Warm, humid environments accelerate food spoilage. Long before anyone understood microbiology, human societies learned that fermentation could extend the useful life of food. Lactic-acid bacteria reduce pH, making conditions less hospitable to many undesirable organisms while also altering flavor, texture and digestibility.

Across India, fermented foods became integral parts of regional cuisines. Idli and dosa rely on fermented rice-and-lentil batters. In Odisha, Pakhala Bhata traditionally involves cooked rice soaked and sometimes fermented in water.

We should be careful about calling every fermented food “probiotic.” Cooking can destroy many of the organisms responsible for fermentation. Nevertheless, fermentation itself can improve preservation and change nutrient availability.

Cold climates created an almost opposite challenge.

People needed dense sources of energy and foods that could survive long periods when little could be grown. Ginger, black pepper and other pungent spices can produce sensations of warmth and may modestly affect metabolism, but their thermogenic effects are small. They certainly do not prevent frostbite or substitute for clothing, shelter or adequate calories.

The more important adaptation was agricultural.

In high-altitude regions such as Tibet and Ladakh, short growing seasons and harsh conditions favor hardy crops such as barley and buckwheat. Barley provides carbohydrates, protein and beta-glucan fiber while tolerating conditions in which many other grains struggle.

In Nepal and surrounding Himalayan regions, gundruk, fermented and dried leafy vegetables, allowed greens to be preserved for periods when fresh vegetables were unavailable.

In the hot, drought-prone regions of Rajasthan, another climate-adapted grain became important: bajra, or pearl millet. Pearl millet tolerates extreme heat and limited rainfall remarkably well while providing carbohydrates, fiber, minerals and other nutrients.

These examples point to a broader lesson: The foods that characterize regional cuisines are not simply accidents of taste. They reflect generations of experimentation with agriculture, preservation, water scarcity, spoilage, sensory comfort and human physiology.

Some foods alter how hot or cold we feel. Others help food remain edible when refrigeration is unavailable. Still others survive where more delicate crops cannot.

In that sense, cuisine really does function as a kind of culinary thermostat, not because food can override the body's temperature controls, but because human societies have continually redesigned what they eat to fit the climates in which they live.

Today, for the first time in history, many of us can eat foods from virtually every climate on earth.

That gives us an opportunity not merely to enjoy different cuisines, but to understand the environmental problems those cuisines evolved to solve.