Writing in the October issue of the American Journal of Clinical Nutrition, Amanda Devine and co-workers from the University of Western Australia report that bone mineral density levels were 2.8 per cent greater in tea drinkers than non-tea drinkers, suggesting the beverage has the potential to aid in the prevention of osteoporosis.
The condition is currently second only to cardiovascular disease in terms of global healthcare burden, according to the World Health Organisation, affecting some 200 million people today but the number of sufferers is set to increase steadily with growing numbers of elderly living longer, and obesity adding extra strain on bones.
The new study involved 1500 elderly women (age range 70 to 85) taking part in a five year prospective trial looking at the effects of oral calcium supplements on osteoporotic fractures. Tea consumption data were collected using 24 hour dietary recall in a subset of 275 subjects, while all the subjects completed a self-administered food frequency questionnaire on beverage consumption at the end of the trial.
Devine and co-workers report that total bone mineral density (BMD) was 2.8 per cent higher in tea drinkers, compared to non-tea drinkers. Over the course of four years, the researchers add that tea drinkers lost an average of 1.6 per cent of their total hip BMD, while non-tea drinkers lost significantly more (4.0 per cent).
"Tea drinking is associated with preservation of hip structure in elderly women. This finding provides further evidence of the beneficial effects of tea consumption on the skeleton," they concluded.
The results add to an ever-growing body of science linking consumption to a wide range of health benefits, including lower risk of certain cancers, weight loss, heart health, and protection against Alzheimer's.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
Indeed, it is these polyphenols that were identified by Devine and co-workers as the potential bioactives in the beverage.
"Tea-derived flavonoids and lignans may be important in maintaining BMD, particularly in older women, who have low concentrations of endogenous oestrogen," wrote Devine. "A recent review suggests that flavonoids from green tea may be associated with increases in BMD via a potent stimulatory effect on osteoblast function."
"A major tea flavonoid, (-)-epigallocatechin-3-gallate, has been shown to increase the expressions of osteogenic genes, elevate bone marker activity, and augment mineralization in a murine bone marrow mesenchymal stem cell line.
"These findings suggest a stimulatory effect of the compound as a possible mechanism for the associated higher BMD seen in tea drinkers," she said.
Source: American Journal of Clinical Nutrition
October 2007, Volume 86, Pages 1243-1247.
"Tea drinking is associated with benefits on bone density in older women"
Authors: Amanda Devine, J.M. Hodgson, I.M. Dick, and R.L. Prince
