be associated with many weight-related diseases, including diabetes, metabolic syndrome, and cardiovascular risk factors. Dental decay Most soft drinks contain high concentrations of simple carbohydrates: glucose, fructose, sucrose and other simple sugars. If oral bacteria ferment carbohydrates and produce acids that may dissolve tooth enamel and induce dental decay, then sweetened drinks may increase the risk of dental caries. The risk would be greater if the frequency of consumption is high. A large number of soda pops are acidic as are many fruits, sauces, and other foods. Drinking acidic drinks over a long period and continuous sipping may erode the tooth enamel. A 2007 study determined that some flavored sparkling waters are as erosive or more so than orange juice. Using a drinking straw is often advised by dentists as the drink does not come into as much contact with the teeth. It has also been suggested that brushing teeth right after drinking soft drinks should be avoided as this can result in additional erosion to the teeth due to mechanical action of the toothbrush on weakened enamel. Bone density and bone loss A 2006 study of several thousand men and women, found that women who regularly drank cola-based sodas (three or more a day) had significantly lower bone mineral density (BMD) of about 4% in the hip compared to women who did not consume colas. The study found that the effect of regular consumption of cola sodas was not significant on men's BMD. Benzene In 2006, the United Kingdom Food Standards Agency published the results of its survey of benzene levels in soft drinks, which tested 150 products and found that four contained benzene levels above the World Health Organization (WHO) guidelines for drinking water. The United States Food and Drug Administration released its own test results of several soft drinks containing benzoates and ascorbic or erythorbic acid. Five tested drinks contained benzene levels above the Environmental Protection Agency's recommended standard of 5 ppb. As of 2006, the FDA stated its belief that "the levels of benzene found in soft drinks and other beverages to date do not pose a safety concern for consumers". Kidney stones A study published in the Clinical Journal of the American Society of Nephrology in 2013 concluded that consumption of soft drinks was associated with a 23% higher risk of developing kidney stones. Mortality, circulatory and digestive diseases In a 2019 study, 451,743 people