Thirsty? If you're concerned about your health and weight, reach for water instead of soda, says M. Eric Gershwin, allergist/ immunologist and professor at the UC Davis School of Medicine. Colas, uncolas and soda pops are usually a mixture of carbonated water, sugar, flavorings, dyes, preservatives and caffeine, he says, and many are nutritional disasters. "A standard sugar-sweetened, 12-ounce container of soda gives you about 200 empty calories and, if you are susceptible to any of the freight of chemicals it carries, a chance to wheeze or break out in hives," he writes in a new book titled "Living Allergy Free." The dyes, sweeteners and preservatives are all capable of causing adverse reactions, Gershwin says. In addition, some concerns have been expressed that drinking colas increases the risk of osteoporosis because the phosphate-rich drink removes calcium from your body. The result can be thinning of bones over time and easy fractures in old age.