High Coffee Consumption: Small Decrease Bone Density, No Increase Fracture Risk

Helena Hallström Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Surgical Sciences, OrthopaedicsMedicalResearch.com Interview with:
Helena Hallström Ph.D., M.Sc. (Toxicology)
Department of Surgical Sciences, Section of Orthopedics
Uppsala University, Uppsala, Sweden and
Risk and Benefit Assessment Department National Food Agency, Uppsala, Sweden.


MedicalResearch.com: What are the main findings of the study?

Answer: The aim of the study was to investigate whether high consumption of coffee is associated with osteoporosis and development of osteoporotic fractures, since results from previous fracture studies regarding potential associations between coffee drinking and fracture risk are inconsistent. The longitudinal population-based Swedish Mammography Cohort, including 61,433 women born between 1914 and 1948, was followed from 1987 through 2008. Coffee consumption was assessed with repeated food frequency questionnaires. During follow-up, 14,738 women experienced any type of fracture and of these 3,871 had a hip fracture. In a sub-cohort (n=5,022), bone density was measured and osteoporosis was determined (n=1,012). There was no evidence of a higher rate of any fracture or hip fracture with increasing coffee consumption. However, a high coffee intake (≥4 cups) in comparison with a low intake (<1 cup) was associated with a 2-4% reduction in bone mineral density (BMD), depending on site (p<0.001), but the odds ratio of osteoporosis was only 1.28 (95% confidence interval: 0.88, 1.87). Thus, high coffee consumption was associated with a small reduction in bone density that did not translate into an increased risk of fracture.

MedicalResearch.com: Were any of the findings unexpected?

Answer: Previous studies in women on consumption of coffee or intake of caffeine and fracture risk have shown discrepant results. Some studies have demonstrated increased risk of fractures with high intakes of coffee/caffeine, whereas others were unable to demonstrate such an association. In contrast to the present results, we have earlier observed an increased rate of osteoporotic fractures in women consuming at least four cups of coffee per day in a subset of the present cohort. Limitations in our previous analysis, some also shared with other studies, were a shorter maximum follow-up time, a lower number of fracture cases, and most importantly we had incomplete case ascertainment since we were only able to identify fractures occurring in the county where the study was performed. Further, we were previously not able to adequately control for lifestyle habits and comorbidity, which could potentially influence the association, although adjustments in our study did not confer major changes in estimates. In this subset of the present cohort, we found that the higher risk of fracture with high coffee intake was concentrated to women with a modest calcium intake. This effect modification was not confirmed in the present analysis.

In the majority of previously performed studies in women investigating associations between coffee/caffeine consumption or intake and BMD no association could be demonstrated, whereas some studies have observed such association. Several explanations for the lack of association in these studies are possible, including small study size, low consumption of coffee or not assessing tea and coffee consumption separately.


MedicalResearch.com: What should clinicians and patients take away from your report?

Answer: The small differences in BMD observed in the present study associated with coffee consumption do not seem to impact the risk of osteoporosis or incident fractures.

MedicalResearch.com: What recommendations do you have for future research as a result of this study?

Answer: Since this study, to our knowledge, is one of largest studies performed in this research area, with a long follow-up, a large number of fractures, BMD as a secondary outcome in a large sub-cohort and the use of repeated measurements of coffee consumption, we believe that this study ends a long running debate about coffee as a potential risk factor for osteoporotic fractures, at least in women. An interesting issue for future research would however be to clarify possible mechanisms of coffee and tea on bone mineral density.


Long-term Coffee Consumption in Relation to Fracture Risk and Bone Mineral Density in Women
American Journal of Epidemiology(ISSN 0002-9262)(EISSN 1476-6256)