A Refresher On Water for Long Life and Health

Overview

Nothing refreshes like an ice-cold glass of water on a hot summer day.
Water replenishes the body's cooling system, enabling it to survive sweltering heat or elevated body temperatures due to exercise. Sweating cools the body by evaporating water on the surface of the skin and dispersing excess heat.
But until the tap runs dry, most people take water for granted. Recent contamination of municipal water systems in the Midwest due to flooding, as well as a disease-borne outbreak in Milwaukee last (month), devastated millions of people.

Water's Lifeline

Although deficiencies of other nutrients can be sustained for months or even years, a person can survive only a few days without water. Indeed, experts rank water second only to oxygen as essential for life.
In addition to offering true refreshment for the thirsty, water plays a vital role in all bodily processes. It supplies the universal medium in which various chemical changes of the body occur, aiding in digestion, absorption, circulation and lubrication of body joints.
For example, as a major component of blood, water helps deliver nutrients to body cells and removes waste to the kidneys for excretion. Enzymes essential to digestion are also primarily water, working to break down food so that nutrients can be absorbed in the intestine.
Water comprises about 50 to 70 percent of body weight in humans. Males on average have a higher percentage of body water than females, because they tend to have less body fat. The more body fat in individuals, the less water therein. A decrease of as little as 10 percent of adult body water due to excessive vomiting or diarrhea is considered serious, and in a young child, could be fatal.
Average adults need about 64 ounces (eight cups) of fluid each day for optimal health. Although experts generally advise drinking several glasses of water a day, the need for fluid can also be met by consuming a variety of foods and beverages.
Milk is about 87 percent water; meat ranges from 40 to 75 percent water; and vegetables are as much as 95 percent water. Even foods normally considered "dry" such as cereal and bread contain about eight to 35 percent water.
Water supplies small amounts of many minerals vital for life, such as sodium, potassium, calcium, copper and magnesium. Minerals such as calcium are essential to bone formation and blood clotting, while magnesium is needed to produce energy and conduct nerve impulses. Different concentrations of these minerals determine whether water is considered hard or soft.
Hard water contains high concentrations of calcium and magnesium and is often associated with residues or crystals in the teapot over time. The principal mineral of soft water, on the other hand, is sodium. Soft water dissolves soap better, leaving fewer mineral deposits, and is therefore often viewed as more desirable.
But it's been suggested that sodium in soft water contributes to increased incidence of high blood pressure and heart disease in some populations. According to Jennifer Orme-Zaveleta, chief of the Environmental Protection Agency's (EPA) drinking water health assessment section, "Drinking water is not a significant source of sodium in the diet. You get much more sodium from salty foods, even in areas with a relatively high sodium concentration in the water, than from water itself"

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Water Safety

Given the indispensable nature of water to human life, it's no wonder water safety is considered a top public health priority. Chlorination of drinking water, which began in the early 1900s to control microbial contamination, has been hailed by EPA as one of the most effective public health measures of the century.
Prior to chlorination, microbial contamination of the water supply was a major source of cholera and typhoid fever in the United States. Today, more than 90 percent of community water supplies receive chlorinated water.
But as fewer outbreaks of waterborne infectious diseases have occurred, concern has shifted to the presence of lead and other compounds in water. Lead pipes and solder in older homes and buildings are major sources of lead exposure in some populations, causing neurological and other serious health problems.
The safety of chlorine residuals and the minor chemical byproducts in water that directly result from the chlorination process also have come under scrutiny.
One such byproduct, trihalomethanes (THMs), forms when chlorine reacts with organic materials such as the remains of leaves or soil in water. Some epidemiological studies have suggested a possible link between THMs and an increased risk for bladder and colorectal cancer.
According to Richard J. Bull, Ph.D., professor of pharmacology and toxicology at Washington State University, however, these findings need additional confirmation. "The studies do not clearly define whether cancer risks are linked to the chlorination process or to other contaminants in surface water," said Bull. "Since the reported risk varies according to geographic location, it's also unclear whether the health problems are due to chlorination or some other variable."

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When the Well Runs Dry

Thirst signals the body's need for fluid. But some experts believe the thirst mechanism cannot be considered entirely reliable, and that slight dehydration has already occurred by the time a person becomes thirsty. For this reason, athletes and other active persons must be sure to consume adequate water for optimal performance.
"Drinking enough fluid is certainly key to maximum athletic performance," said Nancy Clark, M.S., R.D., of Sports Medicine Brookline, one of the largest athletic injury clinics in the Boston area. "But it's even more basic than that. It can make the difference between feeling great or drained after exercise."
At one time, athletes were advised to take salt tablets to avoid salt depletion. However, experts now recommend consuming salty foods or sports drinks formulated to provide sodium as well as other nutrients. Sodium naturally present in water also helps to replace that lost through perspiration.

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Risk vs. Benefit

While disease from untreated water is virtually nonexistent in the United States today, other countries continue to be plagued by devastating epidemics related to contaminated water.
In a little more than a year, the current Peruvian epidemic spread to 16 other countries in Latin America, causing about 600,000 cases of cholera and 5,000 deaths. The failure to disinfect water supplies has been repeatedly implicated as a major contributing factor to the spread of disease.
Pan American Health Organization's Carlyle Guerra de Macedo, M.D., sums up the risk/benefit of chlorination in this way: "Accurate models still need to be developed to compare the risks of chlorination byproducts with the microbial risks of not chlorinating or otherwise disinfecting water. But it is obvious from the health statistics of Latin America that the microbial risk is several orders of magnitude greater."
Still scientists are examining various alternatives to chlorination. Some municipalities are using ozonation to disinfect their drinking water, which can be costly and cannot do the job alone. "Ozone is a good disinfectant, but it tends to break down quickly," said Orme-Zaveleta. "Therefore, additional disinfectants such as chlorine still must be used to protect against bacterial formation in water as it moves through the municipal system."
EPA is working to ensure that permissible levels of chlorination byproducts in drinking water adequately protect public health and is expected to release new regulations by the end of the year.
"For now, we must keep in mind that we're dealing with known benefits and only theoretical risks from the use of chlorine," Orme-Zaveleta concluded.

Reprinted from the International Food Information Council Foundation, 1993