If you are among the many sweaty runners who wonder what to drink to quench your thirst, you may feel confused by the abundant choices of fluids. There is plain ol' water, sports drinks, soft drinks (sugar-sweetened or diet), 100% fruit juices, juice drinks, milk (skim, low fat, or whole), beer, wine, and the list goes on. As a sports dietitian, I get lots of questions about what is best (or worst) to drink. Here are my answers to just a few commonly asked questions about liquids with calories.

Q. Should I stop drinking orange juice because it is loaded with (fattening) carbs and sugar?

A. No! To start, carbs are not fattening, but rather an important fuel for your muscles. Please do not knock OJ out of your breakfast (and then, gulp, replace it with a Coffee Coolatta). OJ offers a strong dose of vitamin C, potassium, folate, and other health protective nutrients. Yes, eating the whole orange is slightly better because solid foods are more satiating than liquids, but you can simply balance the OJ- calories into your daily calorie budget.

Q. After a hard run, I really like having a Coke or Pepsi. How bad is this -- for recovery and for my health?

A. Many tired runners welcome the combination of sugar + caffeine + water to refuel, rehydrate, and revive themselves. While juice would offer far more vitamins and minerals, dietary guidelines indicate that 10% of calories can appropriately come from refined sugar. Hence, most runners can enjoy, if desired, 200 to 300 calories of daily sugar--a can or two of soft drink. Would spending those calories on "premium nutrition" contribute to greater health benefits in the long run? Unclear.

Q. Are soft drinks causing the obesity epidemic? A. In 1942, the average person drank 90 eight-ounce sodas per year. By the year 2000, this jumped to 600 sodas per year. America's obesity problem mirrors this increase in soft drink consumption. The beverage industry states many other changes have occurred in this time-span, specifically, an increasingly sedentary lifestyle, so soda is not solely to blame.

Independent studies (not funded by the beverage industry) suggest people who drink sugary beverages tend to be heavier than those who do not. This might be because fluid calories fail to "register" (that is, they may not satiate one's appetite), so soda drinkers consume more calories per day. Other studies report soda might trigger the desire to eat more food. Hence, if soda drinking culminates in consuming more calories than you burn off, the result is indeed weight gain.

You, as a runner, can likely enjoy a daily soda without fat gain if you keep the soda-calories within your daily calorie budget. (And please, choose wholesome foods for the rest of your sports diet!)

Note: If you are concerned about soft drinks being fattening, also pay attention to sports drinks. Many thirsty runners overlook the fact that chugging a quart of sports drink after a workout (or during lunch, for that matter) contributes 200 to 300 sugar calories--and these calories quickly erase what you burned during two or three miles of running!

Q. Soft drinks are sweetened with high fructose corn syrup (HFCS). Is this really bad for our health?

A. Animal research suggests consuming pure fructose can lead to weight gain due to changes in insulin and leptin, two hormones that influence appetite. In humans, whether or not HFCS (comprised of about 55% fructose, 45% glucose) promotes obesity requires more study. Food industry research leads us to believe HFCS is not fattening. However, other research hints that fructose is digested, absorbed, and metabolized differently than glucose in ways that favor fat production. Your best bet? Eliminate the concern by drinking less soda.

Q. Which is the healthier choice: regular soft drinks (sweetened with HFCS) or diet soft drinks?

A. That's a personal choice; I prefer water myself! Regular soda is filled with empty calories of sugar; diet soda has artificial sweeteners--"unnatural" substances that are rumored to cause cancer. Two recent studies show no link between artificial sweeteners and cancer. Pick your choice of beverage.

Q. Is green tea health protective? A. Green tea is made from fresh tea leaves and, compared to black or oolong teas, has a higher concentration of compounds that may protect against heart disease and cancer, particularly cancer of the breast, stomach, and skin. Many of the green tea studies have been done on animals or in research labs. To date, the FDA says there is not enough scientific evidence with human studies to prove that green tea reduces the risk of cancer. Stay tuned.

I have clients who have started drinking Starbucks green tea latte. This is a questionable way to invest in good health. Starbucks' 16-ounce Tazo Green Tea Latte offers 230 calories, of which 60 are from fat and 140 from sugar. This likely wipes out the possible health benefits of the green tea.

Q. What about Enviga and other green tea beverages that claim to burn calories?

A. Drinking Enviga is unlikely to solve your weight concerns. While the CocaCola Company claims the caffeine plus green tea extracts in three cans of Enviga a day (@ $116 a month) will result in burning 60 to 100 additional calories, you could just as easily create that calorie deficit by drinking less sports drink or eating one less cookie. Yet, desperate dieters will try any gimmick. Green tea-enhanced Celsius, another "calorie- burning soda," saw more than $1.5 million in revenue in 2006 and expects to blow past that figure this year. Do you really want to fatten them up with your efforts to slim down? I hope not.

Nancy Clark, MS, RD, CSSD (Board Certified Specialist in Sports Dietetics) counsels both casual and competitive athletes in her private practice at Healthworks, the premier fitness center in Chestnut Hill MA (617-383-6100). Her Sports Nutrition Guidebook, Food Guide for Marathoners, and Cyclist's Food Guide are available via www.nancyclarkrd.com. See also sportsnutritionworkshop.com.