Carbonated beverages and urinary calcium excretion - Minerals - Brief Article

Nutrition Research Newsletter, Oct, 2001

Intake of carbonated beverages has been associated with increased fracture risk, both later in life and in children in adolescence, in observational studies. The usual explanation given is that one or more of the beverage constituents increase urinary calcium. The issue is especially important today because calcium intakes in North America fall short of current recommendations. Per capita carbonated beverage consumption has risen dramatically, and carbonated sodas are now the preferred beverage of 20- to 40-yr-old women. The current study assessed the short-term effects on urinary calcium excretion of carbonated beverages of various compositions.

An incomplete random block design was used to study 20- to 40-yr-old women who customarily consume [greater than or equal to] 680 mL carbonated beverages daily. Four carbonated beverages were tested: two with caffeine and two without. Two contained phosphoric acid as the acidulant and two contained citric acid. The study included water as a neutral control, and skim or chocolate milk as a positive control. Beverage size was 567 mL for the carbonated beverages and water and 340 mL for the milks. Beverages were consumed with a light breakfast after an overnight fast; no other foods were ingested until urine collection was complete.

Relative to water, urinary calcium rose significantly only with the milk and the two caffeine-containing beverages. The excess calciuria was ~0.25 [micro]mol, about the same as previously reported for caffeine alone. Phosphoric acid without caffeine produced no excess calciuria; nor did it augment the calciuria of caffeine. The excess calciuria associated with consumption of carbonated beverages is confined to caffeinated beverages. Acidulant type has no acute effect. Because the caffeine effect is known to be compensated for by reduced calciuria later in the day, the researchers concluded that the net effect of carbonated beverage constituents on calcium economy is negligible. Until evidence of other mechanisms of action can be brought forth, the most sensible explanation for the association of carbonated beverage intake with poor bone status is likely primary milk displacement.

R. Heaney, K. Rafferty. Carbonated beverages and urinary calcium excretion. AJCN 74(3):343-347 (September 2001) [Correspondence: R.P. Heaney, Creighton University Osteoporosis Research Center, 601 North 30th St., Omaha, NE 68131. E-mail: rheaney@creighton.edu].