Hang on before opening that second diet soda. A survey has found significant reductions in blood filtering capabilities in the kidneys of older women who drank two or more artificially sweetened sodas a day. The study doesn't show a definitive link, but the lead researcher tells NPR that she avoids diet soda. "They're likely not good for you," she said. Surveyed soda-drinkers were white and at least 56, but other demographic groups should take heed, she warns.