“Cold water does not block digestion, but if it is too cold it can make it slower and less comfortable”

With the arrival of the heat, something that many people may want is to grab a bottle of very cold water and start drinking as if there were no tomorrow. But along with this common practice, a classic phrase also arises under the myth that drinking ice water can “block” digestion.

The idea in mind. The claim has a physiologically plausible basis, since cold induces transient gastric vasoconstriction. However, when crossing these claims with the primary scientific literature, we discovered that the line between proven biological mechanism and exaggerated myth is extremely fine.

To break this line, Silvia Gómez, specialist in the digestive system, in statements to La Vanguardia pointed that “cold water does not block digestion, but if it is too cold it can make it slower and less comfortable.” And this last part is where the key to this issue is found.

The physiology of cold. To understand what happens when we drink ice water, we must know that our digestive system operates optimally at the body’s core temperature, which is approximately 37ºC. In this way, when we introduce a liquid at temperatures close to 0ºC the body reacts and the cold causes the blood vessels to constrict to conserve heat.

The consequence is simply a temporary alteration in the contraction patterns of all the muscles in the stomach and, therefore, affects the ability to digest.

It is studied. The most direct and recent proof of this is found in a work published in 2020. In this crossover experimental trial, researchers followed 11 healthy men after ingesting 500 mL of water at three different temperatures: 2°C, 37°C, and 60°C.

Gastric ultrasound results made it clear that 2°C water significantly reduced the frequency of gastric contractions compared to body temperature or hot water during the hour after a meal. But curiously, this modulation of gastric motility showed that the subjects who drank the ice water experienced earlier satiety, reducing their energy intake in the subsequent meal by between 19% and 26%.

It is not a block. The fact that it is proven that the stomach reduces its contraction work does not mean that digestion is “blocked” or “cut off.” We must keep in mind that the human body has an enormous thermoregulatory capacity that means that, when we drink a cold liquid, it reaches body temperature in a matter of minutes, restoring normal gastric activity.

Many myths. There are many phrases around drinking cold water that are very mythical in our society, such as, for example, that it “solidifies fats.” And, although thermodynamics dictates that cold hardens fats, in the human gastric environment this has no clinical relevance, since the thermal effect is so ephemeral and the combined action of hydrochloric acid, enzymes and subsequent mechanical agitation is so powerful, that the body compensates for the thermal impact quickly.

Another quite important myth is related to the effect that cold water has on the intestinal microbiota, but so far there is no solid evidence that demonstrates damage to our bacteria.

We are not all the same. That the effect is harmless to the general population does not mean that all digestive systems react the same. In clinical practice, the temperature of beverages becomes important in patients with important functional pathologies such as, for example, functional dyspepsia, gastroesophageal reflux, gastritis or irritable bowel syndrome.

In these cases, sudden thermal stimuli that modify gastric motility can increase the symptoms, and here the gastric slowing of cold water can be a problem. Although we are talking about specific cases that should follow the recommendations of your specialist doctor.

Images | Nigel Msipa

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