Female rats that no longer synthesise estradiol resemble women in the menopause. Their bone mass declines, so scientists like to use them for research on substances that may help fight osteoporosis. Among these are the Egyptian researchers at Ain Shams University, who wrote a few months ago in BMC Complementary and Alternative Medicine that supplementation with olive oil prevents breakdown of bone tissue once estradiol production has ceased.
The researchers did experiments with female rats aged between 12 and 14 months. Some of the animals were treated surgically so that they no longer produced estradiol [OVX].
Half of the rats were given 10 ml virgin olive oil per kg bodyweight every day [Olive-OVX]. That was 9 g in weight, and this amount contained about 20 mg phenols such as hydroxytyrosol , oleuropein  and oleocathal  [structural formulas shown below].
If you convert these doses conservatively to human equivalents, you arrive at about 200 mg olive phenols per day. And there are no doubt supplements available that contain this amount per capsule.
The rats were given the olive oil four weeks before the researchers operated on them, and continued for eight weeks afterwards. When the researchers examined the rats' bones at the end of the period they observed that the supplementation had prevented a decrease in both the thickness of the hard part of the bones [cortical bone thickness, CBT] and of the soft part [trabecular bone thickness TBT]. In addition, supplementation prevented an increase in the number of 'bone-breaking' cells [osteoclasts, OCL].
The researchers also discovered a possible explanation for the bone-building effect of olive oil in the rats' blood. They found that the blood contained lower levels of nitrates and malondialdehyde [MDA]. Both of these are markers for inflammatory processes. Olive oil apparently inhibits attacks by the immune system on the bone mass.
"Olive oil represents a promising therapeutic option for the prevention and/or treatment of postmenopausal osteoporosis", the Egyptians conclude.
BMC Complement Altern Med. 2011 Feb 4;11:10.