Curcumin, the principal bioactive substance in turmeric, protects the skeleton against degeneration once the natural secretion of bone-building hormones starts to decline. Researchers at Kyungpook National University in Korea draw this conclusion from an experiment they did with female rats that shouldn’t really have been able to produce estradiol any longer – but that somehow still managed to do so.
In 2008 Canadian radiologists published a study that showed that curcumin inhibited bone degeneration in female rats whose ovaries the researchers had surgically removed. [Phytomedicine. 2008 Dec;15(12):1069-78.] The effect was about half that of bisphosphonate etidronate.
Curcumin probably inhibits the effects of the catabolic protein complex NFKB [spatial formula shown below] in bone cells. [Mol Cells. 2008 Nov 30;26(5):486-9.] Curcumin also does this in muscle cells.
These and a couple of other studies were what motivated the Koreans to take another good look at the bone-saving effect of curcumin. They removed the ovaries in most of their female rats and did a fake operation on the rest [Sham].
The researchers divided the rats that had no ovaries into three groups. One group received 10 mg curcumin per kg bodyweight daily, administered orally [Low curcumin]. Another group was given five times as much [High curcumin]. A third group was given no active ingredients [OVX].
To their amazement the Koreans observed that the high dose of curcumin maintained the estradiol concentration in the body at the right level. After eight weeks the same amount of estradiol was still circulating in the body of the rats in the High curcumin group as they had had before the researchers removed their ovaries.
Perhaps curcumin stimulates the secretion of DHEA – and indirectly therefore of androstenedione and estradiol – by the adrenals. Or perhaps curcumin sabotages the test that the Koreans used to measure the estradiol concentration.
One marker of bone decay is type I collagen C-telopeptide [CTX-1]. The more there is in the blood, the faster the bones weaken. Removing the ovaries increased the concentration of type I collagen C-telopeptide; curcumin supplementation prevented this.
The bone mass density [BMD] declined after the operation, but the speed at which this happened was lower in the rats that had been given curcumin.
When the Koreans made scans of vertebrae, they saw that ovary removal led to a decline in bone structure in the vertebrae, and that curcumin partially removed the deterioration.
The bones were weakened by the intervention the researchers discovered when they placed pressure on one of the rats’ vertebrae. The high dose of curcumin reduced the decline in bone strength.
“Although bisphosphonates, potent antiresorptive agents, have been the most popular first-line drugs for the treatment of osteoporosis for some time, many side effects have become evident in recent years”, the Koreans write.
“Some reports suggested a link between bisphosphonates’ use and the development of atypical insufficiency fractures [...]. These are thought to be due to long term over-suppression of bone turnover leading to impaired bone remodeling, accumulation of microdamage in bone and increased skeletal fragility. Therefore, there is increasing interest in the discovery of natural substances that could favorably affect the skeletal system, which could be used in place of pharmacological treatment for osteoporosis.”
Curcumin might be such a natural substance, the Koreans think. The human equivalent of the low and high doses that they used are somewhere in the region of 130 and 650 mg curcumin per day respectively.
In countries where people ingest large amounts of turmeric via their food, the daily intake is about 100 mg per day. If the human trials are to be believed, then people can consume several grams of curcumin per day without problems. [Anticancer Res. 2001 Jul-Aug;21(4B):2895-900.]
Therapeutic advantages of treatment of high-dose curcumin in the ovariectomized rat.
Although curcumin has a protective effect on bone remodeling, appropriate therapeutic concentrations of curcumin are not well known as therapeutic drugs for osteoporosis. The purpose of this study was to compare the bone sparing effect of treatment of low-dose and high-dose curcumin after ovariectomy in rats.
Forty female Sprague-Dawley rats underwent either a sham operation (the sham group) or bilateral ovariectomy (OVX). The ovariectomized animals were randomly distributed among three groups; untreated OVX group, low-dose (10 mg/kg) curcumin administered group, and high-dose (50 mg/kg) curcumin group. At 4 and 8 weeks after surgery, serum biochemical markers of bone turnover were analyzed. Bone histomorphometric parameters of the 4th lumbar vertebrae were determined by micro-computed tomography (CT). In addition, mechanical strength was determined by a three-point bending test.
High-dose curcumin group showed significantly lower osteocalcin, alkaline phosphatase, and the telopeptide fragment of type I collagen C-terminus concentration at 4 and 8 weeks compared with the untreated OVX group as well as low-dose curcumin group. In the analyses of micro-CT scans of 4th lumbar vertebrae, the high-dose curcumin treated group showed a significant increase in bone mineral densities (p=0.028) and cortical bone mineral densities (p=0.036) compared with the low-dose curcumin treated group. Only high-dose curcumin treated group had a significant increase of mechanical strength compared with the untreated OVX group (p=0.015).
The present study results demonstrat that a high-dose curcumin has therapeutic advantages over a low-dose curcumin of an antiresorptive effect on bone remodeling and improving bone mechanical strength.
PMID: 24527187 [PubMed] PMCID: PMC3921272