Are you dehydrated?

Nutrition Notes on the dangers of not drinking enough fluids By Karen Collins, R.D. SPECIAL TO MSNBC

April 30 — Many Americans may be in chronic states of mild dehydration, according to a recent review of fluid needs in the Journal of the American Dietetic Association. Among those most at risk are older adults, because age seems to blunt thirst.

A STUDY OF healthy retirees found 8 percent with moderate dehydration and one-third likely to have chronic mild dehydration. Age alone is not the problem, though. Research involving medical interns reported that 27 percent were mildly dehydrated.

Why worry? One of the strongest concerns about low fluid intake is the risk it poses for kidney stones. Consuming too little fluid limits the amount of urine produced, which is thus very concentrated, increasing the tendency for stones to form. According to the dietetic association journal, drinking less than two cups of fluid per day increases the risk of stones, while getting at least eight cups of fluid per day can prevent most stones, even in people prone to the condition.

Strength and endurance in athletic activities are hurt by the mild dehydration of losing just 1 or 2 percent of body fluid. That is why experts encourage loading up on fluid before, after and possibly during physical activity.

Some reports link adequate fluid with a lower risk of some cancers, but for now there is not really enough research to warrant such statements. Claims that fluid helps prevent urinary tract cancer by keeping a dilute urine to prevent concentrated levels of any cancer-promoting waste products sound good, but have not been proven.

Reports suggesting ways in which dehydrated cells may lose some of their abilities to detoxify and remove carcinogens are also just conjecture at this time.

And researchers face difficulties in separating any effects of total fluid consumption from any positive or negative effects of particular beverages such as alcohol, coffee, tea, milk and juice.


The National Research Council’s fluid recommendations are individualized based on how many calories are burned each day. Adult women, who may expend 1,600 to 2,200 calories each day, would need six-and-a-half to nine cups of fluid; while men, who often need 2,200 to 2,800 calories each day, are advised to drink nine to 12 cups. If all that counting seems too much, studies show that adequate fluid consumption is indicated by a pale yellow or straw-colored urine; dark urine suggests dehydration.

While the general formula is a good starting point, people on high-fiber diets or who lose more fluid, as in exercise, would need additional fluid. Alcohol and caffeine also increase losses and thus fluid needs. Some reports suggest that only non-alcoholic, caffeine-free drinks and soups be counted as liquids for meeting fluid needs. One study found that six cups of coffee per day left subjects mildly dehydrated and yet not necessarily thirsty.

While not all of the claims about the benefits of drinking enough water are proven, it is clear that a healthy diet is not just about good food choices, but also about getting the fluid we need.

Karen Collins is a registered dietitian with the American Institute for Cancer Research in Washington, D.C.