Although it is no longer necessary to demonstrate the benefits of calcium and vitamin D in preventing osteoporosis, those of a diet containing high levels of plant products have only been suggested by a few epidemiological studies. Thus scientists have been working recently on this new concept concerning the role of non-calcium factors, and particularly plant nutrients. Experiments have been performed on ovariectomized rats as a model of menopausal women.
The role of polyphenols in preventing osteoporosis
Working on the growing female rat, INRA scientists have demonstrated the efficacy of a 3-month diet containing 0.5% hesperidin – a citrus polyphenol – not only in protecting bone mass but also acquiring peak bone mass. The same diet prevented the bone disorders characteristic of ovariectomized animals during growth and adulthood. Clinical studies are currently under way in humans.
The researchers have also demonstrated in animals the bone-protectant properties of oleuropein, a major polyphenol in olive products, under conditions of senile osteoporosis, because of its anti-inflammatory properties. Indeed, the consumption of oleuropein at a dose of 0.015% in the diet helped to protect the skeleton from ageing mimicked by castration coupled with an inflammatory process. These findings help to explain, at least in part, the benefits of a Mediterranean-type diet containing high levels of olive oil (lower incidence of the pathology in southern European countries). Clinical studies are planned in the short term in order to validate the properties of oleuropein in man.
These two polyphenols with specific properties open very interesting perspectives regarding the prevention of osteoporosis, of both the postmenopausal and senile types. They thus constitute two novel and complementary nutritional strategies to manage the pathology. These results have been the subject of patent applications, with exclusive licenses taken out by INRA Transfert on behalf of INRA.
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Effects of consuming oleuropein for 3 months on femur quality in ovariectomized rats presenting with inflammation (experimental model of senile osteoporosis)
Control
Rarefaction of bone trabeculae
Osteoporotic animal (castrated)
Partial prevention of bone los
Osteoporotic animal (castrated) but having received oleuropein-enriched diet
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Role of phytoestrogens in preventing osteoporosis
Prospective studies have estimated that in 25 years' time, nearly 50% of French women will be menopausal. But the authorities recommend that hormone replacement therapy should be considered with parsimony in view of its potential risks to health. In the first instance, the INRA scientists used model animals to study the impact of the period of exposure to phytoestrogens on the efficacy of bone protection. Female rats were thus exposed or not via their mother's diet during the perinatal period to soy isoflavones. At weaning, these animals then received either a standard diet or an isoflavone-enriched diet. The results showed that exposure to phytoestrogens had no impact during the period of growth on the acquisition of bone mass. However, bone mass was shown to be superior in all animals at the end of their life, i.e. whatever the diet attributed after weaning, and fracture resistance was greater in all females.
In conclusion, although animal experiments have provided some proof as to efficacy in preventing bone loss, further research is still necessary in humans.
References :
Coxam V, Skalstounis AL, Puel C & Mazur A (2003). Brevet P954PCT. Composition nutritionnelle ou thérapeutique contenant le composé oleuropéine ou l’un de ses dérivés.
Horcajada MN, Coxam V, Morand C & Davicco MJ (2003). Brevet FR0208171, WOFR2003002005, 2004 : Composition nutritionnelle contenant le composé hespéridine ou l’un de ses dérivés.
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