The choice between an ice-cold drink and a room-temperature beverage is often a matter of preference, especially on a hot day. Questions persist about whether the temperature of water affects the body’s internal processes, from digestion to metabolism. This inquiry involves two distinct concerns: the regular consumption of ice water and the less common, yet often compulsive, habit of chewing on the ice itself. Understanding the biological responses to cold intake helps clarify the health implications of these common practices.
Cold Water, Hydration, and Metabolism
The primary benefit of drinking water, regardless of its temperature, is maintaining proper hydration. For many people, cold water is significantly more palatable than warm water, which encourages greater fluid intake, especially during periods of high physical activity. This increased consumption is often the most valuable aspect of choosing a chilled drink.
The idea that drinking ice water can significantly boost metabolism is based on thermogenesis, where the body expends energy to warm ingested cold substances up to the core body temperature of about 98.6°F. This process does burn calories, but the effect is minimal. Estimates suggest only about five to ten calories are expended per glass of ice water compared to room-temperature water, making reliance on this negligible caloric expenditure for weight loss impractical.
During physical exertion, particularly in warm or humid environments, cold water offers a more tangible benefit by helping to regulate internal temperature. Studies show that ingesting cold water or an ice slurry can help delay or reduce the rise in core body temperature during a workout. This effect can improve comfort and may slightly enhance endurance by reducing the thermal strain on the body. The cooling sensation also encourages athletes to drink more, ensuring better rehydration and fluid balance.
Effects on the Digestive System
When very cold water reaches the stomach, it can trigger temporary vasoconstriction, causing the blood vessels in the stomach lining to narrow. This constriction reduces the blood supply to the organ, which can potentially slow down the muscular contractions of the stomach and intestines, a process called peristalsis.
A delay in peristalsis and gastric emptying can lead to food remaining in the stomach longer than usual. Some theories suggest this slowing of the digestive mechanism could also slightly impede the optimal breakdown of fats and carbohydrates by digestive enzymes. Individuals with pre-existing digestive sensitivities may notice more discomfort from this effect. Consuming beverages closer to room temperature minimizes the potential for temperature-induced vasoconstriction and digestive delay.
The Dangers of Chewing Ice and Ice Cravings
The habit of compulsively chewing ice, known medically as pagophagia, carries risks that far outweigh those associated with simply drinking cold water. The act of crushing the hard, frozen substance between the teeth places extreme pressure on the tooth enamel. Chewing ice can lead to chips, cracks, or even outright fractures in the enamel and the underlying tooth structure.
The rapid temperature change from the extreme cold of the ice to the body’s internal temperature causes the enamel to expand and contract, creating microscopic fissures over time. This process weakens the tooth structure, increasing the likelihood of sensitivity and making the teeth more vulnerable to decay. Moreover, existing dental work, such as fillings, crowns, and veneers, is particularly susceptible to damage or dislodgment from the force and temperature changes involved in chewing ice.
Beyond the mechanical damage to teeth, a persistent and intense craving for ice is often a sign of an underlying medical condition, most commonly iron deficiency anemia. Pagophagia is a specific subtype of pica, a disorder characterized by the compulsion to eat non-food items. Researchers hypothesize that the craving arises because chewing ice stimulates blood flow to the head and brain, providing a temporary boost of alertness. This boost may counteract the fatigue and reduced oxygen delivery caused by low iron levels. A persistent craving for ice should be considered a medical symptom and warrants a blood test to check for iron deficiency.