From the National Osteoporosis Foundation <a class="break-all" href="//www.nof.org/faq/588" rel="nofollow" target="_blank">www.nof.org/faq/588
Can soft drinks cause a problem for my bones?
People with osteoporosis should not drink more than five cola drinks a week.
Phosphorous in the form of phosphate or phosphoric acid is often added to processed foods and soft drinks. As a result, concern has been expressed that Americans may be getting too much phosphorous. Some studies suggest that too much phosphorous can reduce the amount of calcium that the body absorbs. However, there is no scientific agreement about whether the current level of phosphorus in the American diet is harmful to the bones. For people with normal kidney function, getting more phosphorus is believed to be safe as long as they get enough calcium
Caffeine: Caffeine is found naturally in coffee and tea, and it is often added to soft drinks. Caffeine in high amounts can cause bone loss. It interferes with calcium absorption and causes a slight increase in the amount of calcium in the urine. One study suggests that drinking 330 mg of caffeine, or about four cups of coffee every day, increases the risk of broken bones. If you enjoy drinks that have caffeine, you can make up for any calcium loss by getting enough calcium to meet your body’s needs. You can get calcium by eating calcium-rich foods and taking calcium supplements if you need them.
Be careful not to substitute caffeinated drinks for milk and calcium-fortified juices. When drinks that have caffeine take the place of milk and other sources of calcium, bone health may be affected. For coffee drinkers, the addition of milk can help make up for the loss of calcium caused by caffeine.
Carbonation: There is no connection between the carbonation in soft drinks and bone loss. In fact, certain carbonated mineral waters have been shown to improve bone health.
Summary: For bone health, it is best not to drink too many soft drinks or cups of coffee every day. To maintain bone health, NOF recommends that adults under age 50 get 1,000 mg of calcium every day, and adults age 50 and older get 1,200 mg of calcium every day.