Beer is the latest plant-based food to be investigated for its ability to protect bones from osteoporosis because of its readily bioavailable silicon, writes Dominique Patton.
Osteoporosis, a disease where bone is lost more rapidly than it is replaced, leading to a predisposition to fractures, is a burgeoning health and economic issue. The World Health Organisation has defined it as the second leading health care problem after cardiovascular disease and researchers are seeking agents that promote bone formation in the search for methods of prevention.
A study in the February 2004 issue of the Journal of Bone and Mineral Research (19(2):297-307) found that silicon intake correlated positively with adjusted bone mineral density at four hip sites in men and premenopausal women, but not in postmenopausal women.
It led the UK researchers to suggest that higher dietary silicon intake in men and younger women may have salutary effects on skeletal health, especially cortical bone health, that has not been previously recognised.
While confirmation of these results is underway in a longitudinal study to assess the influence of silicon intake on bone markers, another team the from the University of London in the UK looked at the impact of silicon absorption from beer, known to have high levels of the mineral.
They examined the silicon content of 76 different beers and then estimated the silicon absorption from beer in 17 healthy volunteers - nine males and eight females with a mean age 25 years.
They found that the silicon content of beer varied from 9 to 39 mg per litre. Although the researchers say the reason for the variability is not clear, they suggest that the final beer silicon levels may be due to variations in the way the malted barley is processed.
No link was traced between the silicon content of beer and the type of beer - wheat beer, stout, ale, lager, bottled, canned or draught, the concentration of ethanol or country of origin.
Subjects' blood and urinary silicon levels were measured after consuming comparable amounts of beer, a soluble silicon solution, ethanol or water. The scientists report in the March issue of the British Journal of Nutrition that the subjects' blood and urinary silicon levels increased considerably and similarly following the ingestion of beer or the soluble silicon solution, but not with the ingestion of ethanol or water.
"We already knew that beer was likely to contain the highest source of silicon per serving because its manufacture uses the husk of the grain, where the silicon is contained," said lead researcher Dr Jonathan Powell. "Now we have confirmed that beer is a readily bioavailable source of silicon. Unlike some other high-silicon foods, the silicon in beer is readily absorbed because it exists as soluble silicate," he added.
Plant oestrogens have also been examined for their potential to protect against bone loss, particularly in postmenopausal women. A study in last month's American Journal of Clinical Nutrition on 177 women aged between 49 and 65, demonstrated that the isoflavone supplement Promensil reduce spinal bone loss after a year-long period. It is one of the largest and longest investigations of an isoflavone supplement to date but researchers still do not know if isoflavones can prevent fracturers caused by osteoporosis.
The search for further data on agents against bone loss will continue however, as the numbers of people with osteoporosis rise rapidly with ageing populations.