"Our present findings indicate that CLA has the potential to be a safe and economically feasible dietary supplement that could serve as an alternative medical approach to preventing bone loss associated with inflammation during aging," wrote lead author Md Mizanur Rahman in the Journal of Nutritional Biochemistry (doi: doi:10.1016/j.jnutbio.2006.08.002).
Bone health is set to become a major segment of the supplements and functional foods market, as ageing populations and the additional strain from obesity swell the numbers affected by osteoporosis.
The new research, performed at the University of Texas Health Science Center at San Antonio, adds to previous studies into the potential benefits of CLA for bone health, with a study published in the Journal of the American College of Nutrition (Vol. 24, pp. 177-181) last year reporting a positive benefit for the acid in post-menopausal women.
Rahman and his colleagues used ten-month old C57BL/6 mice and fed them all a standard diet for two months before dividing them into two groups - one group consumed the standard diet with 10 per cent corn oil, and the other group consumed the standard diet with 9.5 per cent corn oil and 0.5 per cent CLA (Clarinol).
CLA are found predominantly in dairy products such as milk, cheese and meat, and are formed by bacteria in ruminants that take linoleic acids - fatty acids from plants - and convert them into conjugated linoleic acids, or CLA.
Clarinol, produced by Lipid Nutrition, is derived from safflower oil. It has two CLA isomers - known as cis-9 trans-11 and trans-10 cis-12.
After 10 weeks of either diet, it was found that the CLA-fed mice had higher bone mineral density (BMD) in specific bone regions than corn oil (CO)-fed mice. This increased BMD was tied to a reduced activity of pro-inflammatory cytokines (such as tumor necrosis factor alpha (TNF-alpha), and interleukin-6 (IL-6)).
In agreement with other studies looking at the effects of CLA on weight, Rahman reports that the CLA-fed mice also had significantly lower fat mass and increased muscle mass, compared to CO-fed mice.
"By inhibiting osteoclastogenic proinflammatory cytokines, CLA not only prevents bone loss due to excessive osteoclastogenesis but also prevents accretion of fat mass and loss of muscle mass during aging," said Rahman. Osteoclasts are multicentred cells that degrade and reabsorb bone, and thereby weaken the overall bone.
"Indeed, our data warrant a clinical trial to show the efficacy of CLA on bone loss protection in aging people," said the researchers.
Rahman and co-workers also called for more studies with different CLA isomers ratios to investigate the safety and the mechanisms of behind the observed effects.
"In conclusion, these findings suggest that CLA may prevent the loss of bone and muscle mass by modulating markers of inflammation and osteoclastogenic factors," they said.
Osteoporosis is estimated to affect about 75m people in Europe, the USA and Japan. According to the International Osteoporosis Foundation, the total direct cost of osteoporotic fractures is €31.7bn in Europe, and 17.5bn in the US (2002 figure). The total annual cost of osteoporosis in the UK alone is over £1.7bn (€2.5bn), equivalent to £5m (€7.3m) each day.