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The effect of conjugated linoleic acid (CLA) on postmenopausal bone metabolism has not been investigated. Therefore, fortythree adult ovariectomised (OVX) rats (8–9 rats per group) were fed either a control diet containing 40 g/kg soyabean oil (SBO diet) or the SBO diet with 0 (control OVX), 2.5, 5 or 10 g/kg of CLA (replacing soybean oil) for 9 weeks. A group of sham-operated (SH) rats were fed the SBO diet. OVX rats had significantly (Po0.05) lower femoral bone mineral density and macromineral concentration, and intestinal Ca absorption compared to SH rats. CLA supplementation had no effect on these parameters. Ex vivo PGE2 biosynthesis by bone and urinary Pyr and Dpyr (markers of bone resorption) were significantly higher (Po0.001) in control OVX rats compared with SH rats, and were significantly (Po0.001) lowered by CLA supplementation with 5 and 10, but not 2.5 g/ kg diet in OVX rats. In conclusion, CLA supplementation appeared to reduce the rate of bone resorption in adult OVX rats. r 2004 Elsevier Ltd. All rights reserved.

The effect of polyunsaturated fatty acids (PUFA), in particular conjugated linoleic acid (CLA), on Ca and bone metabolism is unclear. In a 2 × 2 factorial design study, forty male 4-week-old rats were fed a control diet containing 70 g added fat (soyabean oil (SBO;n–6 PUFA-rich diet) or menhaden oil–safflower oil (MSO;n−3 PUFA-rich diet))/kg diet with 0 or 10 g CLA/kg for 8 weeks.Ex vivoprostaglandin E2biosynthesis by bone organ culture was significantly higher (PPex vivoprostaglandin E2production. Neither PUFA type nor CLA altered circulating or femoral mRNA levels of osteocalcin (a marker of bone formation) or insulin-like growth factor-I (a mediator of bone metabolism). While urinary pyridinium crosslinks levels (markers of bone resorption) were unaffected by CLA irrespective of PUFA type, they were significantly higher (PPPn−3 PUFA-rich diet, whereas CLA had no effect in animals fed then–6 PUFA-rich diet. There was no effect of CLA supplementation on bone mineral mass. In conclusion, CLA supplementation over 8 weeks appeared to enhance Ca absorption in young growing rats fed ann−3 PUFA-rich diet, but had no measurable effect on bone metabolism or bone mass over this time frame.

The beneficial effect of bovine whey protein (WP) on bone metabolism has been shown in adult human subjects and ovariectomised rats. However, its effect on bone formation in earlier life, particularly during periods of bone mineral accrual, has not been investigated. Twenty-one male rats (4 weeks old, Wistar strain) were randomised by weight into three groups of seven rats each and fedad libitumon a semi-purified low-Ca diet (3·0 g Ca/kg diet) containing 0 (control), 10 (diet WP1) or 20 (diet WP2) g bovine WP/kg for 47 d. On day 34 of the dietary intervention, all rats had two gelatine capsules containing demineralised bone powder implanted subcutaneously in the thorax region (a well-establishedin vivomodel of ectopic bone formation). At 14 d after implantation, alkaline phosphatase activity (reflective of bone formation) in the bone implants from animals fed WP1 and -2 diets was almost 2-fold (PP