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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Food for Thought, Watching Your Intake Food for Thought, Watching Your Intake

Tap Water Or Bottled: Which Is Better?

July 10, 2013

By Stephanie Vangsness, M.S., R.D., L.D.N., C.N.S.D.
Brigham and Women's Hospital

Nutritionists are often asked, "Which is better: tap water or bottled water?" Surprisingly, very little objective, credible research exists to answer this question. This means that deciding which water to drink, be it tap or bottled, involves personal principle and an effort to find out what’s in your water.

Water-Quality Regulation

Two different groups govern the quality of drinking water in the United States. The U.S. Food and Drug Administration sets standards for bottled water, while the Environmental Protection Agency sets standards for tap water. Side-by-side there are very few differences between these two sets of guidelines. However, proponents of both bottled water and tap water would have you believe otherwise.

The International Bottled Water Association (IBWA) is a consortium of bottled-water companies that joined forces to promote and help regulate the bottled-water industry. They created a policy called "The Model Bottled Water Regulation," (available online at All companies in the IBWA abide by these regulations and claim that bottled water is subject to certain standards that are more aggressive than those governing tap water. No third-party investigations have demonstrated that bottled water passes more safety and health checks before reaching the consumer.

In 1999, The National Resources Defense Council (NRDC) conducted a four-year study looking at the difference between safety standards for bottled water versus tap water. They tested over 1,000 bottles of 103 different brands of bottled water and concluded, “There is no assurance that just because water comes out of a bottle it is any cleaner or safer than water from the tap.”

Certain concerns also exist about levels of contaminants in tap water. Levels of bacteria and contaminants in tap water differ depending on where you live. The cleanliness and quality of tap water is subject to issues of environmental politics.

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An Individual Choice

For some, the decision to buy bottled water or drink tap water is as simple as considering the cost differential. The NRDC reports that a five-year supply of bottled water costs more than $1,000, whereas the same amount of tap water costs $1.65. For others, concern about the environmental impact of the 1.5 million tons of plastic used each year to bottle water encourages them to choose tap water. Still others prefer the convenience of bottled water and choose it as a healthier alternative to soda, especially when dining out or grabbing a beverage on the go.

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The Bottom Line

Choosing bottled water or tap water is an individual choice. One is not necessarily better than the other. People who may have a weakened immune system, (such as cancer patients who have undergone a stem-cell or bone-marrow transplant and people with HIV/AIDS) should consult their health care professional to discuss whether filtered tap water or bottled water is best.

Whether you choose tap water or bottled water, here are a few things you can do to increase your awareness of the safety and health concerns in the water you consume.

  • If you decide to filter your tap water, make sure to choose a filter that is certified by the NSF, formerly known as the National Sanitation Foundation, to remove the type of contaminants thought to be in your water. Be sure to change the filter according to manufacturer's directions.
  • If you choose bottled water you may want to identify the source of that water as well as learn more about how the bottling company tests for quality and lack of contaminants. This information is not usually listed on the bottle, but can be tracked down by calling or writing the bottler or the bottled-water program in the state where the water was packaged.
  • Despite the urban legend, plastic bottles do not leach harmful levels of carcinogens (cancer-causing substances) into bottled water. At the same time, it seems prudent to avoid repeatedly reusing plastic water bottles meant for single use.

Additional educational information on bottled water and tap water is available at NSF International (, a nonprofit, nongovernmental agency addressing public health issues.

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Stephanie Vangsness, M.S., R.D., L.D.N., C.N.S.D., received her master’s degree in nutrition and health promotion from Simmons College, Boston. She is a senior clinical nutritionist at Dana-Farber Cancer Institute and Brigham and Women's Hospital.


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