Feb. 11, 2004 -- A new report urges Americans to drastically cut back on salt in their diet but eases the rules on water intake by saying most people can simply let "thirst be their guide."
But don't drop that water bottle or saltshaker yet.
The report, issued today by the Institute of Medicine of the National Academies, says that most healthy Americans meet their daily hydration needs by letting thirst be their guide, rather than by following the old "eight to nine glasses a day" rule.
On salt, the report calls for healthy 19-to 50-year olds to limit themselves to 1.5 grams of sodium and 2.3 grams of chloride each day, which is the equivalent of 3.8 grams of salt. Previous government guidelines set the recommended sodium amount at 2.4 grams of sodium. Most sodium in the diet is consumed in the form of sodium chloride (salt).
This recommend intake does not apply to highly active people such as endurance athletes who lose large amounts of sweat on a daily basis. For older adults and the elderly, the limits are 1.3 grams/day for men and women aged 50-70 years and 1.2 grams for those 71 years and older.
The report is the sixth in a series from the Institute of Medicine and contains nutrient recommendations for water, potassium, sodium, chloride, and sulfate. Researchers say the study highlights the fact that the typical American diet is too high in sodium and too low in potassium, which increases the risk of chronic diseases, such as heart disease.
Fulfilling Your Thirst
The report doesn't specify exact requirements for water intake, but it does make general recommendations of 91 ounces per day for women and 125 ounces for men of total water per day, which actually translates to a few glasses more than eight glasses a day.
But in a change from the past, the panel loosened the requirements on how people can meet those recommendations, allowing caffeinated beverages, such as soda and coffee, and food to count toward total water intake. Although caffeine has been thought to have a diuretic effect, researchers say studies show that effect is only temporary.
They say that although low intake of water has been associated with some chronic diseases, there is not enough evidence to establish water intake recommendations as a means to reduce the risks of chronic disease.
"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," says panel chairman Lawrence Appel, MD, MPH, in a news release. "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," says Appel, who is also professor of medicine, epidemiology, and international health at Johns Hopkins University in Baltimore.
Following your thirst may work for healthy, sedentary adults, but experts say there are also important exceptions to that rule.
"If you're active, participating in exercise, living in an environment that's a little bit warmer or drier, then I think you'll have to look at more physiological signs as opposed to looking at thirst," says Jackie Berning, PhD, RD, spokeswoman for the American Dietetic Association.
"You have to look at the color of your urine," says Berning, who is associate professor of nutrition at the University of Colorado at Colorado Springs. "If it's that dark apple juice color, then despite the fact that you're not thirsty, you've got to put more fluids in."
Berning says that among active people, dehydration is the No. 1 danger she sees. If someone is not optimally hydrated, any type of stress, such as a change in altitude, activity, or temperature, could put their health at risk.
Pass on Salt, Reach for Potassium
The report sets a maximum upper limit on salt at 5.8 grams (5,800 mg) per day. But researchers say more than 95% of Canadian men aged 31 to 50 and 75% of American women in that age group regularly consume more salt than that.
But it's not the saltshaker's fault. More than three-quarters of that salt comes from eating processed or prepackaged foods. A one-cup serving of most commercial canned soups contains about 1,000 mg of sodium, which is only 500 mg shy of the recommended daily amount.
Berning says that aside from reading the label on packaged foods, the best way to cut back on salt is to make dinner yourself rather they buying it in a box or a can so you can control the amount of salt that goes in.
In addition to reducing salt intake, the report calls for Americans to get more potassium in their diet to help lower the risk of high blood pressure, kidney stones, osteoporosis, and stroke. It recommends at least 4.7 grams of the nutrient per day for all adults. Potassium helps blunt the effects of salt on blood pressure.
Researchers found most American women consume only about half of the daily recommended amount of potassium, and men only fare slightly better. Foods rich in potassium include spinach, cantaloupes, almonds, mushrooms, bananas, oranges, grapefruits, and potatoes.