In the hot summer season, some people are accustomed to drinking pre-chilled cold tea, while others freeze tea, thinking it both quenches thirst and preserves the tea's nutrients. In reality, cold tea does not relieve heat but instead causes stagnation and phlegm. In fact, drinking hot tea in summer is the most effective way to quench thirst.

Although a cold drink provides an instant cooling sensation, this is only a short-term effect. The cooling mechanism of cold drinks relies on low temperature to counteract heat, but the amount of heat offset by a single cold drink is limited. After drinking cold beverages, the "cold" stimulus triggers a reflex in the body, causing skin capillaries to constrict, pores to close, and sweat secretion to decrease. As a result, the heat produced afterward cannot be efficiently expelled, making people feel even more stifled.

Of course, drinking a small amount of cold beverages occasionally is harmless. However, consuming large quantities of cold drinks over an extended period can disrupt digestive function and reduce appetite. Moreover, under the blazing sun, the heart beats faster, and blood flows more quickly to dissipate heat. Drinking a large amount of cold beverages suddenly slows down the heart rate and blood flow, akin to applying a "brake" to the heart.

Frequent "braking" can wear out the organs. At the same time, slower blood flow reduces oxygen supply, causing discomfort. On the other hand, although hot tea feels warm when consumed, the heat is soon expelled through sweat, providing long-lasting coolness. In summer, when the ambient temperature approaches or exceeds body temperature, heat can only be dissipated through sweat evaporation. When hot tea enters the body, the "heat" stimulates the body's temperature receptors—central thermosensitive neurons. Through a series of neural reflex adjustments, skin capillaries dilate rapidly, blood flow increases significantly, sweat glands secrete more actively, and sweat production rises, carrying heat from the body's core to the surface and dissipating it.

Experiments show that after drinking a cup of hot tea, each gram of sweat expelled carries away 0.58 calories of heat, reducing body temperature in about nine minutes. Drinking hot tea does not stimulate heart rate or alter blood flow speed, while the nutrients in the tea are absorbed by the body.