Bone mineral density, polyphenols and caffeine: a reassessment

Abstract

Several studies have shown beneficial associations between tea consumption and bone mineral density (BMD) and fracture risk. Current investigations into potential mechanisms of benefit are focused upon the F and polyphenol components of tea. However, previous studies have pointed towards caffeine consumption as a potential risk factor for low BMD and high fracture risk. Tea, therefore, represents an interesting paradox as a mildly caffeinated beverage that may enhance bone health. Fruit and vegetable intake has also been associated with BMD, and it is now apparent that several fruit and vegetable components, including polyphenols, may contribute positively to bone health. Evidence surrounding the function(s) of polyphenol-rich foods in bone health is examined, along with more recent studies challenging the relevance of caffeine consumption to in vivo Ca balance. Plant foods rich in polyphenols such as tea, fruit and vegetables, as significant factors in a healthy diet and lifestyle, may have positive roles in bone health, and the negative role of caffeine may have been overestimated. The present review covers evidence of dietary mediation in positive and negative aspects of bone health, in particular the roles of tea, fruit and vegetables, and of caffeine, flavonoids and polyphenols as components of these foods. Since the deleterious effects of caffeine appear to have been overstated, especially in respect of the positive effects of flavonoids, it is concluded that a reassessment of the role of caffeinated beverages may be necessary.

Effects of Yerba Mate (IIex paraguariensis) on Histomorphometry, Biomechanics, and Densitometry on Bones in the Rat

“…It is important to consider not only the differences in the concentration of caffeine between coffee and yerba mate, but also the concentration of flavonoids and other organic compounds which have favorable effects on bone [32]. The presence of polyphenols [1,33,34] with favorable effect on bone tissue can mitigate the negative effect of caffeine.…”

Tea consumption didn’t modify the risk of fracture: a dose–response meta-analysis of observational studies

“…In animal models, high doses of caffeine could induce calcium loss and influence the normal development of bone [36]. Nowadays tea, regarded as a beverage with multiple nutrients and caffeine, is a positive factors in the bone health [37]. …”

Cardiovascular calcification and bone: a comparison of the effects of dietary and serum antioxidants

“…Although tea contains caffeine, levels are relatively low. 109 alcoholism has often been associated with osteoporosis but other studies have shown a protective effect, with a J-shaped dose/response curve with 1-2 drinks per day correlating with improved BMd in postmenopausal women; when stratified by type of alcohol, wine gave the greatest benefit in women and beer in men, while spirits gave the lowest BMd 110 . In vitro studies have also shown that resveratrol is active in osteoblastic MC3t3-e1 cells and may have a synergistic effect with vitamin D in promoting bone health 111 .…”

“…Bone tea consumption was associated with reduced fracture risk among older women in southern europe; the fact that most subjects drank black tea suggests that the benefit is independent of any added milk 103 . Both black tea 104 and green tea 105 were generally associated with increased BMd among older women but Vestergaard et al suggest that the benefit from tea may be due to lower coffee consumption 106 , which was found in some studies to result in lower BMC and higher fracture risk in those drinking more than two cups a day 107,108 , although others have found no effect 109 . to the extent that caffeine is detrimental, it may be due to its potential to reduce calcium absorption and increase its urinary excretion, although this has been contradicted in other studies; provided calcium intake exceeds 800mg/d, moderate caffeine is unlikely to be detrimental to bone.…”