“Some people perspire after drinking cold liquids,” says Mark Mattar MD, a clinician and assistant professor of medicine at MedStar Georgetown University Hospital, Washington, D.C. The body likes to keep its core temperature steady at about 100° F., which is when the best digestion occurs. If cold temperatures — such as ice water or cold food in the diet — enter the stomach, the body works quickly to warm it.
A Centuries-Old Science
Temperature — of the body, weather, or the foods you eat — and its effects on digestion has intrigued physicians and scientists for at least 100 years. A well-regarded professor of several New York hospitals at the turn of the last century, the late William Gilman Thompson MD, included a chapter on the topic in his 1905 book, Practical Dietetics With Special Reference to Diet in Disease. In it, he writes: “One may begin a dinner with iced raw oysters, then take hot soup, and later conclude the meal with ice cream, followed by hot coffee,” he said of a proposed diet. “And yet throughout, the temperature of the stomach contents does not vary so much as half a degree.” Dr. Thompson came to his conclusions based on the outcomes of “many experiments which I have made upon patients…to whom I have given fluids at different temperatures, which were immediately siphoned out of the stomach and tested for heat loss or gain.”
Warm Is Better
Even on a hot day, warm liquids generally soothe the system, Mattar said. Colonoscopy patients find warm liquids infused in the colon help alleviate pain or spasms. And anecdotally, he said, the wisdom from our grandmothers was to drink warm liquids — the belief being that warmth caused the muscles to relax — even the minuscule muscles that support the blood vessels. It’s also likely that the body’s preference for warmth has to do with the latest frontier in biology, the microbiome — those trillions of microscopic bugs that live in the gut, he said. In the lab, these microorganisms thrive in incubation. Although these bugs like a warm host, even they have their limit. While hot cocoa on a hot day probably would be fine, Mattar said, “if it’s hotter than 100 degrees, your body will try to cool it down.”
Air Temperature
In warm climates, the blood vessels open and more hormones circulate to aid in all systems, including digestion, Mattar said. In cold climates, everything slows down, but not too much. In fact, the change is so subtle, the effects of air temperature on digestion usually goes unnoticed — except in extreme cases when the core temperature drops and hypothermia sets in. Treatment generally includes blankets and possibly intravenous fluids that are a little warmer than room temperature. “You don’t want to shock the system,” he said.
Illness and Diseases
In the opposite extreme, when hotter becomes the new normal, there is no real consensus on treatment, Mattar said. Some people recommend blankets and warm drinks, despite the discomfort, while others report the body should be kept cool to let the fever take its course. Thompson added that while “cooling drinks have long been used [to treat] fevers…to this day one occasionally meets with opposition from mothers to giving a child with high fever anything really cold.” Ice also can be effective in relieving nausea, and hot liquids aid in “cleansing the mucous membrane,” Thompson said. Likewise “hot-air baths…are of undoubted service” in treating kidney disease. And despite the body’s quick response to cold drinks, the cold still can irritate the bowel, possibly causing diarrhea, constipation or abdominal pain, Mattar said, but that’s not true for everyone. “I myself love freezing cold water,” he said. “But if my wife drinks it, her stomach will hurt.”
