Does Caffeine Affect The Absorption Of Vitamins Or Minerals?

Caffeine is a bitter-tasting substance which occurs naturally in coffee beans, tea leaves, chocolate and kola nuts. Caffeinated beverages have a stimulant effect. The caffeine in these drinks also may affect absorption of some nutrients.

Caffeine and Calcium

Some evidence suggests that caffeine affects calcium absorption. The National Office of Dietary Supplements notes that one cup of coffee causes a loss of 2 mg to 3 mg of calcium. R.P. Heaney, writing in the September 2002 issue of "Food Chemistry and Toxicology," noted that calcium has a clear but small depressant effect on absorption of calcium from the intestine, but no effect on excretion of calcium in the urine. Caffeine has been implicated in bone fractures in postmenopausal women, as noted in the Iowa Women's Health Study. Researchers reported in the September 2000 journal "Public Health Nutrition" a modest increase in fracture risk is associated with the highest caffeine intake.

Caffeine and Vitamin D

Vitamin D is a hormone that humans manufacture through exposure of skin to sunlight. Vitamin D is crucial for absorption of calcium, and a deficiency can lead to rickets in children, or osteomalacia -- bone softening -- in adults. B. Prema, et. al., noted in the November 2006 "Journal of Steroid Biochemistry & Molecular Biology" that some women have a genetic variant that can make them more susceptible to problems with vitamin D metabolism if they drink caffeinated beverages. Called the Vitamin D receptor variant, or VDR, this receptor is found in cells that form new bone. While the researchers were not able to determine exactly how caffeine affects the VDR, their research did show that women who had an intake above 300 mg of caffeine a day had higher bone loss, and women with the VDR variant were at greater risk of developing the problem.

Other Considerations

While caffeine definitely has an effect on vitamin D and calcium, the National Office of Dietary Supplements notes that there may be other problems with vitamin and mineral absorption related to caffeine-containing beverages. In addition to caffeine, tea and coffee contain polyphenols and tannins, which can affect absorption of iron.

The Bottom Line

While caffeine and caffeine-containing beverages such as tea and coffee can affect vitamin and mineral absorption, the risk for most people seems low. According to Medline Plus, two to four cups a day is not harmful for most people. If you have concerns about caffeine's effect on a particular health condition, discuss them with your doctor.