Vitamins and minerals are essential nutrients for a person's growth and development. Because they need to be absorbed from the bloodstream to be effective, anything that hinders this process can result in your body getting insufficient nutrients. And because many people start their day with a cup of coffee, it’s important to know that caffeine can interfere with absorption of vitamin D and calcium, for example, both of which are important for bone health.
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Caffeine is a chemical in various substances, including coffee, tea, carbonated drinks, chocolate and even some medicines. It acts as a stimulant in the body, making you feel more alert, and this is why many people turn to caffeinated drinks to begin their day. Caffeine also has a diuretic effect on the body.
Caffeine Vs. Vitamin D
In a collaborative study at Creighton University in Nebraska and the University of Miami, Florida, researchers showed that caffeine may interfere with vitamin D absorption. The results, published in the "Journal of Steroid Biochemistry and Molecular Biology," demonstrated that the higher the level of caffeine, the more it interfered with vitamin D absorption. The study suggested that caffeine did this by reducing the expression of vitamin D receptors on osteoblasts in the body -- the cells responsible for producing bone.
Caffeine Vs. Calcium
Caffeine can also interfere with the absorption of calcium. A study published in the journal "Osteoporosis International" showed that just a cup of coffee can slightly reduce calcium absorption in the body and increase its loss in urine due to its diuretic effect. Additionally, bone loss has been shown in people with low milk or low total calcium intake who drink 2 or more cups of coffee per day, according to a study of 205 postmenopausal women published in the "American Journal of Clinical Nutrition." And the results of a study in Norway, in which almost 20,000 women participated, suggested that women who drink 9 or more cups of coffee per day may be at risk of bone fracture. Another study in the "American Journal of Clinical Nutrition" even showed that bone mineral density may be reduced in older women who drink cola every day, compared with those who drink it less than once every month.
Bottom Line for Bone Health
In otherwise healthy people, the negative effects of caffeine on vitamin and mineral absorption are probably insignificant. Nevertheless, anyone concerned about bone health, including women who are worried about osteoporosis, may prefer to avoid drinking too many caffeinated beverages.