Animals fed L-carnitine supplements had a bone mineral density 6.3 per cent higher than control animals, according to results published in the journal Phytomedicine.
“Our preliminary findings suggest that dietary supplementation of carnitine may prevent the rapid and sustained reductions in the rate of bone loss associated with aging and other conditions in which individuals experience a rapid bone loss such as early postmenopausal women,” wrote lead author Shirin Hooshmand from Florida State University.
However, the researchers noted that many questions remain unanswered, particularly the nutrient’s metabolic role in bone. “How it suppresses bone turnover remains to be answered,” they wrote.
“Nonetheless, further studies are needed to elucidate the mechanism underlying the effect of carnitine on bone and evaluate the benefits of carnitine supplementation as an alternative/ adjunctive treatment to reduce bone turnover.”
L-Carnitine, a vitamin-like nutrient, occurs naturally in the human body and is essential for turning fat into energy. It is frequently used as a dietary supplement by physically active people to help with post-exercise recovery.
Lonza, which claims to be the world's largest manufacturer of L-Carnitine, has said that extensive scientific research shows the supplement promotes cardiovascular health and that other studies suggest the nutrient may be useful in weight management.
The new study was supported by Lonza, utilizing its Carnipure tartrate ingredient.
The researchers used female rats that had had their ovaries removed (ovariectomised) to model postmenopausal bone loss, which is associated with osteoporosis. This is characterized by low bone mass, which leads to an increase risk of fractures, especially the hips, spine and wrists. An estimated 75 million people suffer from osteoporosis in Europe, the USA and Japan.
Women are four times more likely to develop osteoporosis than men.
Rats were divided into two groups, with one fed the control diet, while the other fed the control diet and supplemented with 150 mg of carnitine per kg of diet for eight weeks.
At the end of the study, Hooshmand and co-workers report that, in addition to the higher bone mineral density, animals supplemented with L-carnitine also had lower levels of a substance called tartrate-resistant acid phosphatase (TRAP) by 73 per cent. TRAP is an indicator of bone resorption, or a weakening of the bones.
Moreover, levels of alkaline phosphatase (ALP) and collagen type-1 (COL) – substances associated with bone formation – were also decreased by 64 and 61 per cent, respectively.
“To our knowledge, the present study is the first to report that carnitine suppresses the expression of selected genes involved in both bone resorption and formation in aging rats under in vivo conditions,” wrote the researchers.
“Our data here showed that carnitine decreased […] levels of TRAP as well as ALP and COL, suggesting that carnitine may suppress bone turnover by decreasing the rates of both bone resorption and formation. decreasing two markers of bone formation by over 60 per cent, compared with the control group,” they added.
The researchers, affiliated with Florida State University, the University of Connecticut, and Lonza, called for further study to build on these promising results.
Source: Phytomedicine (Elsevier)1 August 2008, Volume 15, Issue 8, Pages 595-601“Dietary l-carnitine supplementation improves bone mineral density by suppressing bone turnover in aged ovariectomized rats”Authors: S. Hooshmand, A. Balakrishnan, R.M. Clark, K.Q. Owen, S.I. Koo, B.H. Arjmandi