National Institute of Health Recommendations:
Teens: 1300mg per day
Adults <50 y/o: 1000mg
Adults >50 y/o: 1,200mg
The main reason for the increased dosage in teens is due to the desire to help them avoid osteoporosis later in life. It is also important for Women to be mindful of their Calcium intake. Bones are made of calcium, and many females do not get the recommended dosage of calcium through their diets alone. This may lead to osteoporosis later in life which can lead to fractures, and pain.
Calcium is absorbed in the small intestine when we have an acidic gastric pH. This level of acidic pH is generated normally after meals. Interestingly enough, popular antacids claim to give you calcium in every dose. However, these antacids work by raising the pH in your stomach and small intestine, thereby limiting the amount of calcium you are able to absorb. The same is true of other antacids including the popular proton pump inhibitors containing omeprazole “Prilosec”, or lansoprazole “Prevacid®.” The Journal of The American Medical Association found “the risk of hip fracture was significantly increased among prescribed long term high dose proton pump inhibitors.” This study appears to reveal the link between proton pump inhibitors and osteoporosis later in life, so be careful with what you are giving to your children.
Adding a Calcium supplement to your diet may help lower the risk of osteoporosis later in life. If you or your children are not getting enough calcium through the foods you eat, you should consider taking a calcium supplement. I recommend the cheapest form of calcium available, which is calcium carbonate. Your body will only absorb about 500mg of calcium at one time, so depending on the amount of calcium you are getting from your diet, I advise taking about 500mg twice a day. Another important fact to remember is that Vitamin D is needed for proper calcium absorption. Sunlight produces Vitamin D naturally in your body, so I recommend getting 15 minutes of sunlight each day. Too much Calcium has been linked to the development of kidney stones; however, so limit your intake to 1000-1500mg/day.
Yang, Yu-Xiao, James Lewis, Solomon Epstein, and David Metz. "JAMA -- Long-term Proton Pump Inhibitor Therapy and Risk of Hip Fracture, December 27, 2006, Yang Et Al. 296 (24): 2947." JAMA, the Journal of the American Medical Association, a Weekly Peer-reviewed Medical Journal Published by AMA. Web. 10 June 2010. http://jama.ama-assn.org/cgi/content/full/296/24/2947.
Shaw, Gina. "Understanding Calcium: Supplements, Calcium Carbonate, Calcium Citrate, and More." WebMD - Better Information. Better Health. Web. 10 June 2010. http://www.webmd.com/osteoporosis/features/calcium-supplements-pills.