For all those harassed coffee and cola drinkers who've been told caffeine's a diuretic, there's good news. The 2nd of two studies reinforces the finding that all drinks without alcohol, including caffeinated beverages, are hydrating.
"People can enjoy a variety of their favorite beverages and feel confident they are staying hydrated," says Kristin Reimers, who co-authored the hydration study. Reimers serves as associate director of the Center for Human Nutrition, located at the University of Nebraska Medical Center, Omaha.
Reimers and her research team have shown that all beverages -- both non-caffeinated and caffeinated -- are hydrating, contrary to conventional wisdom. "We all understand that we get vitamins and minerals from a variety of foods. Water is a nutrient too. Like other nutrients, we get water from a variety of foods and fluids. It doesn't have to be plain water; all foods and fluids provide water."
Reimers says, "Most people don't realize the longstanding recommendation to drink six to eight glasses of water a day in addition to other beverages and foods has little scientific basis."
Sedentary people stay hydrated simply by consuming a variety of foods and drinking fluids when they are thirsty, according to Reimers. Many scientific questions exist about what constitutes normal hydration and the effect of foods and fluids on hydration status in healthy adults.
And that's what led Reimers and her colleagues to study the effect of varying beverages on hydration. In the most recent study, the research team found no differences in hydration between adults who consumed a variety of beverages and those who drank water.
The study, published in the April 2003 issue of the Journal of the American College of Nutrition, evaluated two diets, over three days, for their effects on several indicators of hydration status in 27 healthy male volunteers. One diet provided plain water to drink as part of the beverages served, while the second omitted plain water. The beverages chosen were designed to reflect those commonly consumed in the United States, with the exception of milk and alcohol. Thus, both caffeinated and non-caffeinated beverages were included.
"This research proves that people need not worry if they don't have access to plain water each day," says Reimers, a registered dietitian. "While it is not my intent to imply people don't need water, it's important for people to know that a variety of beverages will support hydration."
This is the second of Reimers' studies showing caffeinated beverages are hydrating for the normal, healthy adult who typically consumes them. Her earlier research, also published in the Journal of the American College of Nutrition showed that consumption of caffeinated beverages is not dehydrating.
Because people's lifestyles, food intake and physiological needs are vastly different, people's needs for hydration vary greatly, defying a "one size fits all" recommendation.
However, says Reimers, that variance doesn't have to lead to confusion, because, "The body is often smarter than we are." She says, "If average adults pay attention to thirst and monitor how often and how much they urinate, and respond to these signals, they will be hydrated."
According to Reimers, the bottom line is, "All people need to think about drinking enough fluids to stay hydrated, but people should feel comfortable knowing that part of their requirements are met through foods and the rest can be met by drinking a variety of beverages -- both caffeinated and non-caffeinated -- with or without water. Choosing the beverages you enjoy can have a positive impact on your hydration status."