• 1What is Hydration? (VIDEO)
  • 2Your Body of Water
  • 3Water, Water Everywhere
  • 4Water At Work
  • 5A Walking, Talking Water Balloon
  • 6Staying Afloat
  • 7How We Acquire & Lose Water
  • 8The Thirst Cycle
  • 9Why So Thirsty?
  • 10Electrolytes
  • 11Balancing Act
  • 12Dehydration
  • 13Water Fun Facts
CHAPTER 9

Why So Thirsty?

PART 1

The Thirst Signal

Talking the Talk
Intravascular Volume Status
From the day we’re born our brain and body knows how to detect and resolve a need for fluids. A fantastic series of internal signals are relayed to convey the sensation of thirst. READ MORE

How Thirst Works

Because water is a major component of blood, lack of water decreases overall blood volume. It also destabilizes the body’s water:salt balance. The changes don’t go undetected: the drop in blood volume is picked up by pressure receptors in the cardiovascular system, and special cells in the brain’s hypothalamus note the increased salt concentration.

The pituitary gland — master controller of homeostasis — stores and releases hormones produced by the hypothalamus. In response to the water and salt signals, it sends antidiuretic hormone (ADH) to the kidneys, conveying a message to retain water and produce less urine. The kidneys also release an enzyme into the bloodstream which leads to the formation of another hormone, angiotensin II.

Coming full circle, angiotensin II signals the brain’s subfornical organ to stimulate the hypothalamus to release more ADH — producing the sensation of thirst, and prompting you to take a drink. LESS
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PART 2

A Bevy Of Bottled Water

It Adds Up
Er, Where’s the Loo?
On the Shelves

The FDA is responsible for regulating bottled water (the EPA regulates tap water), and has established a number of manufacturing requirements to ensure the bacteriological and chemical safety of bottled drinking water in every phase of processing. While carbonated waters, club soda, tonic, and seltzer are categorized as soft drinks, plenty of players still flood the field. Labels prominently featuring any of the words below are regulated by the FDA as “bottled water”: READ MORE

  • Bottled water: Regulated by the FDA as a packaged food product

  • Drinking water: Potable water that meets state and federal standards

  • Artesian water: Groundwater that has risen above an aquifer as a result of being pressurized between layers of impermeable rock

  • Mineral water: Has increased volume of mineral solutes (minimum 250 parts per million). Minerals are not added but occur naturally in the water at its source.

  • Sparkling bottled water: Treated with pressurized carbon dioxide gas to become effervescent. Club soda, soda water, and seltzer are all sparkling waters.

  • Spring water: Collected where water naturally flows to the surface from underground, or tapped from the source of a spring

  • Purified water: Water that has been distilled, demineralized, deionized, or undergone other processing such as reverse-osmosis to remove impurities

  • Flavored and nutrient-added water: Includes additives but must meet federal bottled-water standards if the term “water” is prominent on the label. All flavorings and nutrients must be identified on the label’s ingredient list.

The Decay of Progress

The American Dental Association has an issue with bottled water. Noting that the prevalence of tooth decay had been in decline for years following the fluoridation of community water supplies, the ADA says the slowing of that trend may be due in part to drinking water from a bottle rather than a tap. According to the dentists, the majority of bottled waters on the market do not contain optimal levels of fluoride. LESS
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PART 3

Washing Away The Hype

Key Word
Antidiuretic hormone (ADH)
Cold Truth

In the search for zero-effort weight-loss techniques, no stone is left unturned. It’s been claimed by a handful of hopefuls that drinking beverages at a cold temperature helps burn calories, the logic being that the body has to expend energy to warm the drink as it is digested and absorbed. READ MORE

Well, no such luck. In a 2006 Swiss study published in The Journal of Clinical Endocrinology and Metabolism, researchers measured the energy expenditure of subjects and compared data after cool and room-temperature drinks had been consumed. The study found negligible disparity and concluded that their results “cast doubt on water as a thermogenic agent for the management of obesity.”

Vitamin Water: Help or Hype?

Enriched drinking water seems like a good idea, but major beverage manufacturers have yet to get it right. Targeting the consumer’s sweet tooth, the makers add so much sugar that any nutritional benefit from so-called vitamin water is eclipsed. Moreover, you’re not likely to derive much benefit from fat-soluble vitamins (A, D, E, K) that come in a bottle since the body does not absorb them well in isolation. Natural, whole foods remain your best sources of vitamins and minerals because they’re packaged up the way nature intended your body to use them.

In 2010, a federal judge allowed a suit against Vitaminwater (a Coca-Cola product), citing misleading health claims on the label in violation of FDA policy. His decision also noted that the product name referenced two but not all three key ingredients — the omitted ingredient being sugar. LESS
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