Planet UltraMarathon

News Author: Laurie Barclay, MD
CME Author: Charles Vega, MD, FAAFP

Complete author affiliations and disclosures, and other CME information, are available at the end of this activity.

Release Date: October 11, 2006; Valid for credit through October 11, 2007

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October 11, 2006 — Regular consumption of carbonated cola drinks may increase risk for low bone mineral density (BMD) in women, according to the results of the Framingham Osteoporosis Study reported in the October issue of the American Journal of Clinical Nutrition.

"Soft drink consumption may have adverse effects on bone mineral density (BMD), but studies have shown mixed results," write Katherine L. Tucker, MD, from Tufts University in Boston, Massachusetts, and colleagues. "In addition to displacing healthier beverages, colas contain caffeine and phosphoric acid (H₃PO₄), which may adversely affect bone."

Using dual-energy x-ray absorptiometry, the investigators measured BMD at the spine and at 3 hip sites in 1413 women and in 1125 men in the Framingham Osteoporosis Study. Dietary intake was evaluated with a food frequency questionnaire. Each BMD measure was regressed on the frequency of soft drink consumption after adjustment for body mass index, height, age, energy intake, physical activity score, smoking, alcohol use, total calcium intake, total vitamin D intake, caffeine from noncola sources, season of measurement, and, for women, menopausal status and estrogen use.

Cola intake was associated with lower BMD at each hip site in women but not in men (P < .001 - .05). However, it was not linked with lower BMD at the spine for women or men. Compared with those who consumed less than 1 serving of cola per month, those with daily cola intake had a mean BMD 3.7% lower at the femoral neck and 5.4% lower at Ward's area. These results were similar with diet cola and to a lesser extent with decaffeinated cola.

There were no significant relationships between noncola carbonated beverage consumption and BMD. Although total phosphorus intake was not significantly higher in daily cola consumers than in nonconsumers, the calcium-to-phosphorus ratios were lower.

Study limitations include possibly incomplete control of confounding.

"Intake of cola, but not of other carbonated soft drinks, is associated with low BMD in women," the authors write. "Additional research is needed to confirm these findings.... Unless additional evidence rules out an effect, women who are concerned about osteoporosis may want to avoid the regular use of cola beverages."

The United States Department of Agriculture and the National Institutes of Health supported this study. The authors have disclosed no relevant financial relationships.

Am J Clin Nutr. 2006;84:936-942.

Learning Objectives for This Educational Activity

Upon completion of this activity, participants will be able to:

• Describe possible mechanisms for a negative effect of cola on BMD.
• Identify the risk for reduced BMD associated with cola intake among men and women.

Clinical Context

Increased cola intake has been demonstrated to reduce BMD in children, and several mechanisms may be responsible for this association. Caffeine is a defined risk factor for osteoporosis, and high fructose corn syrup may reduce bone density. In addition, colas contain phosphoric acid, which can reduce serum calcium levels and promote higher levels of parathyroid hormone. This hormone, in turn, can increase bone turnover and lead to osteoporosis.

The current cohort study examines the BMD in relation to cola intake among men and women.

Study Highlights

• The study population was drawn from the Framingham Offspring Cohort. 5124 participants comprised the study cohort and were evaluated every 4 years with an extensive health history, physical examination, and laboratory evaluation. Dietary intake was evaluated with a validated 126-item questionnaire. Subjects also underwent dual-energy x-ray absorptiometry at the lumbar spine and hip between 1996 and 2001. The current analysis excluded subjects using medications, which could increase BMD, and those at the extremes of daily caloric intake.
• The main study outcome was the relationship between BMD and intake of cola beverages. Results were adjusted for age, body mass index, height, smoking, and average daily consumption of alcohol, caffeine, and calcium. The authors also adjusted results for total energy intake and physical activity in both men and women as well as the presence of menopause and treatment with estrogen in women.
• 2538 subjects had data for analysis. The mean age of participants was 59 years, and the mean body mass index was 28 kg/m². Generally, participants tended to be overweight, ex-smokers, and moderate consumers of alcohol. Mean consumption of carbonated beverages was 6 servings per week among men and 5 servings per week among women. Average noncola carbonated beverage consumption was 1.5 servings per week, and diet cola intake accounted for approximately half of total cola consumption.
• Noncola carbonated beverage intake did not affect BMD. Cola intake did not significantly affect the BMD of men.
• While spine BMD was unaffected by cola intake among women, hip BMD was reduced in linear fashion with higher degrees of cola consumption. BMD was 3.8% lower when researchers compared women who consumed cola daily vs those who did not drink cola. Caffeinated cola had a greater effect in reducing hip BMD vs decaffeinated cola, although both types of beverage had significant effects. While sugared decaffeinated cola failed to achieve a significant effect at the hip, this cola was the least popular, and the association was probably underpowered.
• Cola intake did not affect levels of milk consumption, although there was a negative relationship between cola intake and consumption of fruit juice and calcium. Reduced consumption of milk or fruit juice failed to fully explain the negative effects of cola on the hip BMD in women.

Pearls for Practice

• Cola may reduce BMD through higher intake of caffeine, high fructose corn syrup, phosphoric acid, or some combination of these effects.
• The current study demonstrates that higher degrees of cola consumption may be associated with reduced hip BMD among women. However, cola consumption did not affect BMD among men, and it failed to significantly reduce BMD in the lumbar spine in either sex.

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Target Audience

This article is intended for primary care clinicians, endocrinologists, orthopedists, and other specialists who care for patients at risk for osteoporosis.

Goal

The goal of this activity is to provide medical news to primary care clinicians and other healthcare professionals in order to enhance patient care.

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Authors and Disclosures

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News Author

Laurie Barclay, MD
is a freelance reviewer and writer for Medscape.

Disclosure: Laurie Barclay, MD, has disclosed no relevant financial relationships.

CME Author

Charles P Vega, MD
Associate Professor, Residency Director, Department of Family Medicine, University of California, Irvine

Disclosure: Charles Vega, MD, FAAFP, has disclosed that he has received grants for educational activities from Pfizer.

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