thumb|Statue drinking from a traditional [[waterskin|alt=Statue of a man drinking|upright=1.2]]

thumb|upright|A person drinking a glass of milk

Drinking is the act of ingesting water or other liquids into the body through the mouth, proboscis, or elsewhere. Humans drink by swallowing, completed by peristalsis in the esophagus. The physiological processes of drinking vary widely among other animals.

Most animals drink water to maintain bodily hydration, although many can survive on the water gained from their food. Water is required for many physiological processes. Both inadequate and (less commonly) excessive water intake are associated with health problems.

Methods of drinking

In humans

When a liquid enters a human mouth, the swallowing process is completed by peristalsis which delivers the liquid through the esophagus to the stomach; much of the activity is assisted by gravity. The liquid may be poured from the hands or drinkware may be used as vessels. Drinking can also be by sipping or sucking, typically when imbibing hot liquids or drinking from a spoon. Infants employ a method of suction wherein the lips are pressed tight around a source, as in breastfeeding: a combination of breath and tongue movement creates a vacuum which draws in liquid.

In other land mammals

thumb|Cat lapping water in slow motion|alt=refer to caption

thumb|[[Jack Russell Terrier laps in water with its tongue. |upright]]

By necessity, terrestrial animals in captivity become accustomed to drinking water, but most free-roaming animals stay hydrated through the fluids and moisture in fresh food, and learn to actively seek foods with high fluid content. When conditions impel them to drink from bodies of water, the methods and motions differ greatly among species.

Cats, canines, and ruminants all lower the neck and lap in water with their powerful tongues. Canines lap water by scooping it into their mouth with a tongue which has taken the shape of a ladle. However, with cats, only the tip of their tongue (which is smooth) touches the water, and then the cat quickly pulls its tongue back into its mouth which soon closes; this results in a column of liquid being pulled into the cat's mouth, which is then secured by its mouth closing. Ruminants and most other herbivores partially submerge the tip of the mouth in order to draw in water by means of a plunging action with the tongue held straight. Cats drink at a significantly slower pace than ruminants, who face greater natural predation hazards. In savannas, the drinking method of giraffes has been a source of speculation for its apparent defiance of gravity; the most recent theory contemplates the animal's long neck functions like a plunger pump. Uniquely, elephants draw water into their trunks and squirt it into their mouths. Additionally, all terrestrial insects constantly absorb a certain amount of the air's humidity through their cuticles. Saltwater fish, however, drink through the mouth as they swim, and purge the excess salt through the gills.

Human water requirements

thumb|Astronaut [[Thomas Reiter during Expedition 14 drinking water on the International Space Station|alt=refer to caption]]

A daily intake of water is required for the normal physiological functioning of the human body. The USDA recommends a daily intake of total water: not necessarily by drinking but by consumption of water contained in other beverages and foods. The recommended intake is 3.7 liters (appx. 1 gallon) per day for an adult male, and 2.7 liters (appx. 0.75 gallon) for an adult female.

Other sources, however, claim that a high intake of fresh drinking water, separate and distinct from other sources of moisture, is necessary for good health – eight servings per day of eight fluid ounces (1.8 liters, or 0.5 gallon) is the amount recommended by many nutritionists, although there is no scientific evidence supporting this recommendation.

Evidence-based hydration experts say that the amount of drinking water needed depends on ambient temperature, activity level, body size, and sweat rate. Research shows drinking when thirsty will maintain hydration to within about 2% of the needed level. Evidence of fermented drinks in human culture goes back as early as the Neolithic Period, and the first pictorial evidence can be found in Egypt around 4,000 BC.

Alcohol consumption has developed into a variety of well-established drinking cultures around the world. Despite its popularity, alcohol consumption poses significant health risks. Alcohol abuse and the addiction of alcoholism are common maladies in developed countries worldwide. A high rate of consumption can also lead to cirrhosis, gastritis, gout, pancreatitis, hypertension, various forms of cancer, and numerous other illnesses.

See also

  • Eating
  • Hydration (disambiguation)

References

Bibliography

  • "Are You Drinking Enough?", recommendations by the European Hydration Institute (Madrid)