Date of Graduation

2007

Document Type

Thesis

Degree Type

MS

Committee Chair

Janet C. L. Tou

Abstract

Consumption of sugar-sweetened beverages has increased among adolescents. This may have health implication because sugar consumption has been suggested to lead to decreased calcium (Ca) intake and increased urinary Ca output and these effects on Ca balance may have a negative impact on bone. Also, the type of sugar added to beverages has also changed from sucrose to high fructose corn syrup resulting in higher fructose consumption. Although sugarsweetened beverage intake by adolescent has increased and the type of sugar consumed has changed; the effects of sugar-sweetened beverage consumption during the bone growth stage on skeletal acquisition and adult bone health are unknown. The objectives of this study were to determine the effect of feeding growing rats different sugar-sweetened beverages and its impact on bone and the possible mechanisms of action. Immature (28 days old) female Sprague-Dawley rats (n=8-9/group) were individually housed in metabolic cages and randomly assigned to be given a nonsugar beverage consisting of deionized distilled water (ddH2 O, Control), or ddH2 O containing 13% w/v common commercial caloric sweeteners of either: 1) glucose, 2) sucrose, 3) fructose or 4) high fructose corn syrup (HFCS-55). Assigned beverages were provided ad libitum throughout the 8 weeks study. Food intake, urine and fecal output were measured weekly. At the end of the study, the tibiae and femurs were collected. Bone mineral density (BMD) and Bone mineral content (BMC) were determined by dual x-ray absorptiometry (DEXA) and bone strength was measured using three-point bend testing. Bone turnover markers serum osteocalcin and urinary deoxypyrinoline (DPD) were determined using enzyme immunoassays. Urinary/fecal Ca and phosphorus (P) levels were determined using inductively coupled plasma mass spectrometry. There were no differences in BMC, BMD and bone strength between rats fed sugar-sweetened beverages and those fed non-sugar sweetened beverages. There were significant differences among rats fed the different sugar-sweetened beverages. Tibial and femoral BMD of rats fed glucose were reduced (p< 0.001) by 3-8% compared to rats fed the other sweetened beverages. Despite reduced BMD in glucose-fed rats, bone strength was not significantly reduced at the end of the study. There were no differences in serum osteocalcin and DPD levels among the treatment groups. However, calcium intake and retention was lower (p< 0.001) in glucose-fed rats compared to the other treatment groups which may explain their lower bone mass. Femoral and tibia total BMC and total BMD were significantly higher in fructose-fed animals compared to glucose-fed animals. . The higher BMD and BMC in fructose-fed animals may be due to higher Ca intake and retention compared to glucose-fed animals. Focus has been on the potential negative impact of higher fructose consumption. Based on our study results glucose rather than fructose appears to have the most deleterious effect on mineral balance and bone mass.

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