Date: Feb. 11, 2004
Contacts: Christine Stencel, Media
Relations Officer
Chris Dobbins, Media Relations
Assistant
Office of News and Public
Information
202-334-2138; e-mail news@nas.edu
http://www4.nationalacademies.org/news.nsf/isbn/0309091691?OpenDocument
FOR IMMEDIATE RELEASE
Report Sets Dietary Intake Levels for Water, Salt, and
Potassium
To Maintain Health and Reduce Chronic Disease
Risk
WASHINGTON -- The vast majority of healthy people
adequately meet their daily hydration needs by letting thirst be their guide,
says the newest report on nutrient recommendations from the Institute of
Medicine of the National Academies. The report set general recommendations for
water intake based on detailed national data, which showed that women who appear
to be adequately hydrated consume an average of approximately 2.7 liters (91
ounces) of total water -- from all beverages and foods -- each day, and men
average approximately 3.7 liters (125
ounces) daily. These values represent adequate
intake levels, the panel said; those who are very physically active or who live
in hot climates may need to consume more water. About 80 percent of people's
total water comes from drinking water and beverages -- including caffeinated
beverages -- and the other 20 percent is derived from food.
"We don't offer any rule of thumb based on how many glasses of water
people should drink each day because our hydration needs can be met through a
variety of sources in addition to drinking water," said Lawrence Appel, chair of
the panel that wrote the report and professor of medicine, epidemiology, and
international health, Johns Hopkins University, Baltimore. "While drinking water
is a frequent choice for hydration, people also get water from juice, milk,
coffee, tea, soda, fruits, vegetables, and other foods and beverages as well.
Moreover, we concluded that on a daily basis, people get adequate amounts of
water from normal drinking behavior -- consumption of beverages at meals and in
other social situations -- and by letting their thirst guide them."
Regarding salt, healthy 19- to 50-year-old
adults should consume 1.5 grams of sodium and 2.3 grams of chloride each day --
or 3.8 grams of salt -- to replace the amount lost daily on average through
perspiration and to achieve a diet that provides sufficient amounts of other
essential nutrients. Elevated blood pressure, which may lead to stroke, coronary
heart disease, and kidney disease, is associated with sodium intake. On average,
blood pressure rises progressively as salt intake increases. A tolerable upper
intake level (UL) -- a maximum amount that people should not exceed -- is set at
5.8 grams of salt (2.3 grams of sodium) per day. Older individuals, African
Americans, and people with chronic diseases including hypertension, diabetes,
and kidney disease are especially sensitive to the blood pressure-raising
effects of salt and should consume less than the UL. More than 95 percent of
American men and 90 percent of Canadian men ages 31 to 50, and 75 percent of
American women and 50 percent of Canadian women in this age range regularly
consume salt in excess of the UL.
To lower blood
pressure, blunt the effects of salt, and reduce the risk of kidney stones and
bone loss, adults should consume 4.7 grams of potassium per day. However, most
American women 31 to 50 years old consume no more than half of the recommended
amount of potassium, and men's intake is only moderately higher. Canadians
typically eat more potassium than their American counterparts. African Americans
in the United States generally get less potassium than non-Hispanic whites, and
because they have a higher prevalence of elevated blood pressure, increased
potassium intake may have particularly significant benefits for them.
The typical Western diet is high in salt and low
in potassium -- the opposite of what evidence shows is optimal for good health
and reducing the risks of chronic disease, the report says. "Research is needed
to find ways to help people select better food choices to reduce their salt
intake and boost their potassium consumption," Appel said. In addition, because
Americans and Canadians get the majority of their salt -- 77 percent, according
to one study -- from prepared and processed foods, research should be done to
help food processors develop alternative technologies that can reduce the amount
of salt added during processing without impairing taste, shelf-life, or product
qualities at an affordable cost.
Additional
Findings on Water
This report refers to
total water, which
includes the water contained in beverages and the moisture in foods, to avoid
confusion with drinking water only.
Total water
intake at the reference level of 3.7 liters for adult men and 2.7 liters for
adult women per day covers the expected needs of healthy, sedentary people in
temperate climates. Temporary underconsumption of water can occur due to heat
exposure, high levels of physical activity, or decreased food and fluid intake.
However, on a daily basis, fluid intake driven by thirst and the habitual
consumption of beverages at meals is sufficient for the average person to
maintain adequate hydration.
Prolonged physical
activity and heat exposure will increase water losses and therefore may raise
daily fluid needs. Very active individuals who are continually exposed to hot
weather often have daily total water needs of six liters or more, according to
several studies.
While concerns have been raised
that caffeine has a diuretic effect, available evidence indicates that this
effect may be transient, and there is no convincing evidence that caffeine leads
to cumulative total body water deficits. Therefore, the panel concluded that
when it comes to meeting daily hydration needs, caffeinated beverages can
contribute as much as noncaffeinated options.
Some athletes who engage in strenuous activity and some individuals
with certain psychiatric disorders occasionally drink water in excessive amounts
that can be life-threatening. However, such occurrences are highly unusual.
Therefore, the panel did not set a UL for water.
Additional Findings on Salt and Potassium
The recommended intake levels for salt provide enough sodium to
balance losses from sweat by people who are exposed to temperatures higher than
what they are used to or who are moderately physically active. Endurance
athletes and other very active individuals may need more sodium because they
lose more in sweat from intense and prolonged physical activity.
High salt intake has been directly linked to
elevated blood pressure, also known as hypertension. About 25 percent of
American adults and more than half of those age 60 and older have hypertension.
American men's median intake of salt is between 7.8 and 11.8 grams per day, and
women consume between 5.8 and 7.8 grams every day. Canadian men and women
consume 7.1 to 9.7 grams and 5.1 to 6.4 grams per day respectively. Because
these figures do not include the salt that people add at the table, they are
probably underestimates.
Studies indicate that
reduced consumption of salt coupled with increased potassium intake can blunt
the age-related rise in blood pressure. American men consume just 2.8 to 3.3
grams of potassium daily on average, and women get an average of only 2.2 to 2.4
grams each day. Canadians consume slightly more, at 3.2 to 3.4 grams per day for
men and 2.4 to 2.6 grams per day for women. Fruits and vegetables are both low
in sodium and high in potassium. Among foods with the highest amounts of
potassium per calorie are spinach, cantaloupes, almonds, brussels sprouts,
mushrooms, bananas, oranges, grapefruits, and potatoes.
There was no evidence of chronic excess intakes in apparently healthy
individuals to compel establishing a UL for potassium. However, people who have
kidney dysfunctions that impair their ability to excrete potassium or who are on
certain types of drug therapies -- such as ACE inhibitors -- should be under the
supervision of a medical professional, who may recommend consuming less than the
recommended 4.7 grams per day.
This study was
sponsored by the U.S. Department of Health and Human Services' Office of Disease
Prevention and Health Promotion and the National Institutes of Health; Health
Canada; U.S. Environmental Protection Agency; U.S. Department of Agriculture;
Institute of Medicine; the Dietary Reference Intakes Private Foundation Fund,
including the Dannon Institute and the International Life Sciences
Institute-North America; and the Dietary Reference Intakes Corporate Donors'
Fund, contributors to which have included the Nabisco Food Group, Mead Johnson
Nutritionals, and M&M Mars.
This study is
one of a series undertaken by scientists from the United States and Canada under
the auspices of the Institute of Medicine's Food and Nutrition Board to develop
reference values for nutrients for use in both countries. The Institute of
Medicine is a private, nonprofit organization that provides health policy advice
under a congressional charter granted to the National Academy of
Sciences.
Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and
Sulfate is available on the Internet at
http://www.nap.edu. Copies of the
report will be available for purchase later this year from the National
Academies Press; tel. 202-334-3313 or 1-800-624-6242. Reporters may obtain a
pre-publication copy from the Office of News and Public Information (contacts
listed above).
[ This news release and report are
available at http://national-academies.org
]
INSTITUTE OF
MEDICINE
Food and Nutrition
Board
Panel on Dietary Reference Intakes for
Electrolytes and Water
Lawrence J. Appel,
M.D., M.P.H. (chair)
Professor
Departments of Medicine, Epidemiology, and International
Health
Johns Hopkins Medical
Institutions
Baltimore
David H. Baker, Ph.D.
Professor
Department of Animal Sciences,
and
Division of Nutritional Sciences
University of Illinois
Urbana-Champaign
Oded Bar-Or,
M.D.
Professor
Department of Pediatrics
McMaster
University
Hamilton, Ontario
Kenneth L. Minaker, M.D.
Chief
Geriatric Medicine
Unit
Massachusetts General Hospital
Boston
R. Curtis Morris Jr.,
M.D.
Professor
Departments of Medicine, Pediatrics, and Radiology
University of California
San
Francisco
Lawrence M. Resnick,
M.D. *
Attending Physician and Professor
Division
of Hypertension
New York Presbyterian
Hospital
Cornell University Medical
College
New York City
Michael N. Sawka, Ph.D.
Chief
Thermal and Mountain Medicine
Division
U.S. Army Research Institute of
Environmental Medicine
Natick,
Mass.
Stella L. Volpe, Ph.D. ,
R.D.
Associate Professor
School of Nursing
University of
Pennsylvania
Philadelphia
Myron H. Weinberger, M.D.
Professor
School of
Medicine
Indiana University
Indianapolis
Paul K. Whelton, M.D.,
M.Sc.
Senior Vice President for Health Sciences,
and
Professor of Epidemiology
Tulane University Health Sciences Center
New Orleans
INSTITUTE
STAFF
Allison A. Yates, Ph.D.,
R.D.
Study Director
* Active member through May 2003
