 Osteoporosis is a major public health problem. One in two women and one in five men over age 50 will have a fracture. Fractures cause pain, disability and reduce life-expectancy. Women with below-average bone density around the time of the menopause might have previously taken hormone replacement HRT to prevent osteoporosis, but HRT is much less used now due to side effects. Therefore there is a need for safe, effective and inexpensive preventative interventions for women at risk of osteoporosis. 