Total n-6 Polyunsaturated Fatty Acid and Linoleic Acid Dietary Intakes Are Associated With Lower Serum Osteocalcin Among Postmenopausal Women

OBJECTIVES: Our research group has recently shown that plasma linoleic acid (LA), an essential n-6 polyunsaturated fatty acid (PUFA), was inversely associated with whole body bone mineral density (BMD) Z-score in a general US adult population. We aimed to determine whether dietary LA, arachidonic acid (AA) or total n-6 intake are likewise associated with serum bone turnover markers (BTMs) and BMD at sites prone to fracture, including total hip, lumbar spine, and femoral neck, among postmenopausal women without osteoporosis. METHODS: This was a cross-sectional study of healthy women (N = 34; 50–65 years) with onset of menopause < 5 years. Fasting serum samples were obtained, and BMD indexes were measured by dual X-ray absorptiometry (DXA) in the same visit. BMD values were converted to T-scores. Three-day food records were collected, and calorie-adjusted nutrient intakes calculated using Nutrition Data System for Research software. Serum concentrations of osteocalcin (OC, a bone formation biomarker) and C-terminal telopeptides of Type I collagen (CTX, a bone resorption biomarker) were measured by ELISA. Relationships between LA and each BMD T-score and serum BTM were assessed using linear regression adjusting for age, race, and body mass index. RESULTS: Total n-6 PUFA and LA intakes were not significantly associated with any BMD T-scores. AA intake was positively associated with lumbar spine BMD T-score [β = 10.4, (95% CI: 0.3, 20.5), P < 0.04]. For serum BTMs, total n-6 PUFA and LA intakes were inversely associated with serum osteocalcin [β = –6.8, 95% CI: (–13.2, –0.5) and β = –6.8, 95% CI: (–13.1, –0.5) respectively, both P < 0.05] but not significantly associated with serum CTX. AA intake was not significantly associated with either BTM. CONCLUSIONS: Dietary intake of total n-6 PUFAs and LA were inversely associated serum OC, while AA intake was positively associated with lumbar spine BMD. Cellular mechanistic and intervention studies in clinical populations are needed to confirm effects of total n-6 PUFA, LA, and AA intake on bone formation and BMD over time. FUNDING SOURCES: National Institutes of Health, John and Mary Brock Discovery Fund.