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With Comments by Adriane Fugh-Berman, MD
April 2001; Volume 3; 32
Source: Hegarty VM, et al. Tea drinking and bone mineral density in older women. Am J Clin Nutr 2000;71:1003-1007.
Design/Setting/Subjects: Community-based study in 1,256 free-living women age 65-76 in Cambridge, United Kingdom.
Outcomes: Bone mineral density (BMD) was measured at lumber spine, femoral neck, greater trochanter, and Ward’s triangle. Tea drinking was assessed by questionnaire.
Results: 1,134 women were classified as tea drinkers and 122 classified as non-tea drinkers. Tea drinkers were classified by amounts of tea consumed (one to three cups, four to six cups, more than six cups/d), whether or not they added milk to tea, and whether or not they drank coffee. There was no difference between tea drinkers and non-tea drinkers in BMD measured at the femoral neck (0.477 g/cm2 vs. 0.452 g/cm2), but age and BMI-adjusted mean BMD at lumber spine (0.919 g/cm2 vs. 0.886 g/cm2), greater trochanter (0.614 vs. 0.586), and Ward’s triangle (0.477 vs. 0.452) were significantly higher in tea drinkers than in non-tea drinkers. There was not a dose-related effect. Adding milk to tea made no difference in mean BMD at any site except at the greater trochanter, where those who added milk to tea had higher BMD (0.614 g/cm2 vs. 0.604 g/cm2). Coffee drinking (n = 1,025) was not related to BMD; neither was smoking. Current hormone replacement therapy use was associated with increased BMD at all sites. Associations of BMD with tea drinking remained after exclusion of current smokers and current hormone replacement therapy users.
Comment: Several other studies have found a negative effect of caffeine intake on bone mineral density in older women, but as the authors of this study note, other studies were conducted in populations of coffee drinkers. Tea is a much more popular beverage than coffee in Britain. Additionally, when British women do drink coffee, they often drink instant coffee rather than brewed coffee and routinely add milk to coffee, thus supplementing the beverage with calcium. One study found that coffee drinkers who also consumed at least a cup of milk a day were protected from a deleterious effect of coffee on bone.1
The authors of this study theorize, possibly inaccurately, that a protective effect of drinking tea may be because of the fact that tea contains isoflavonoids. Tea contains isoflavones, but to my knowledge, tea does not contain the phytoestrogenic type presumed to help bone density. Nevertheless, the study is interesting.
1. Barrett-Connor E, et al. Coffee-associated osteoporosis offset by daily milk consumption. The Rancho Bernardo Study. JAMA 1994;271:280-283.