No dose-dependent increase in fracture risk after long-term exposure to high doses of retinol or beta-carotene.

UNLABELLED: Uncertainty remains over whether or not high intakes of retinol or vitamin A consumed through food or supplements may increase fracture risk. This intervention study found no increase in fracture risk among 2,322 adults who took a controlled, high-dose retinol supplement (25,000 IU retinyl palmitate/day) for as long as 16 years. There was some evidence that beta-carotene supplementation decreased fracture risk in men. INTRODUCTION: There is conflicting epidemiological evidence regarding high intakes of dietary or supplemental retinol and an increased risk for bone fracture. We examined fracture risk in a study administering high doses of retinol and beta-carotene (BC) between 1990 and 2007. METHODS: The Vitamin A Program was designed to test the efficacy of retinol and BC supplements in preventing malignancies in persons previously exposed to blue asbestos. Participants were initially randomised to 7.5 mg retinol equivalents (RE)/day as retinyl palmitate, 30 mg/day BC or 0.75 mg/day BC from 1990 to 1996; after which, all participants received 7.5 mg RE/day. Fractures were identified by questionnaire and hospital admission data up until 2006. Risk of any fracture or osteoporotic fracture according to cumulative dose of retinol and BC supplementation was examined using conditional logistic regression models adjusting for age, sex, smoking, body mass index, medication use and previous fracture. RESULTS: Supplementation periods ranged from 1 to 16 years. Of the 2,322 (664 females and 1,658 males) participants, 187 experienced 237 fractures. No associations were observed between cumulative dose of retinol and risk for any fracture (OR per 10 g RE=0.83; 95% CI, 0.63-1.08) or osteoporotic fracture (OR per 10 g RE=0.95; 95% CI 0.64-1.40). Among men, cumulative dose of BC was associated with a slightly reduced risk of any fracture (OR per 10 g=0.89; 95% CI 0.81-0.98) and osteoporotic fracture (OR per 10 g=0.84; 95% CI 0.72-0.97). CONCLUSIONS: This study observed no increases in fracture risk after long-term supplementation with high doses of retinol and/or beta-carotene.

Assessing the risk of stroke from neck manipulation: a systematic review.

BACKGROUND: Strokes, typically involving vertebral artery dissection, can follow cervical spinal manipulative therapy, and these types of stroke occur rarely. There is disagreement about whether a strong association between neck manipulation and stroke exists. An earlier systematic review found two relevant studies of association that used controls, which also discussed the limitations of the two papers. Our systematic review updates the earlier review, and aims to determine whether conclusive evidence of a strong association exists. METHODS: PRISMA guidelines for systematic reviews were followed, and the literature was searched using a strategy that included the terms 'neck manipulation' and 'stroke' from the PubMed, Embase, CINAHL Plus and AMED databases. Citations were included if they met criteria such as being case-control studies, and dealt with neck manipulation and/or neck movement/positioning. Papers were scored for their quality, using similar criteria to the earlier review. For individual criteria, each study was assigned a full positive score if the criterion was satisfied completely. RESULTS: Four case-control studies and one case-control study, which included a case- crossover design, met the selection criteria, but all of them had at least three items in the quality assessment that failed to be completely positive. Two studies were assessed to be the most robustly designed, one indicating a strong association between stroke and various intensities of neck movement, including manipulation, and the other suggesting a much reduced relative association when using primary care practitioners' visits as controls. However, potential biases and confounders render the results inconclusive. CONCLUSION: Conclusive evidence is lacking for a strong association between neck manipulation and stroke, but is also absent for no association. Future studies of association will need to minimise potential biases and confounders, and ideally have sufficient numbers of cases to allow subgroup analysis for different types of neck manipulation and neck movement.

Polyunsaturated fatty acid intake and blood pressure in adolescents.

Evidence that intake of polyunsaturated fatty acids (PUFAs) may modify blood pressure (BP) is generally limited to middle-aged or hypertensive populations. This study examined cross-sectional associations between BP and dietary intake of PUFAs in 814 adolescents aged 13-15 years participating in the Western Australian Pregnancy Cohort (Raine) Study. Fatty acid intakes were assessed using 3-day diet records and resting BP was determined using multiple oscillometric readings. In multivariate regression models, systolic BP was inversely associated with intakes of polyunsaturated (b=-0.436, P<0.01), omega-3 (b=-2.47, P=0.02), omega-6 (b=-0.362, P=0.04) and long chain omega-3 fatty acids (b=-4.37, P=0.04) in boys. Diastolic BP and mean arterial pressure were inversely associated with intakes of long chain omega-3 fatty acids in boys (b=-3.93, P=0.01, b=-4.05, P=0.01, respectively). For specific long-chain omega-3s, significant inverse associations were observed between eicosapentaenoic acid (EPA) and docosahexaenoic acid, such as systolic BP decreasing by 4.7 mm Hg (95% CI -9.3 to -0.1) for a quarter gram increase in EPA, but no significant associations were observed with docosapentaenoic acid. No significant associations were observed in girls, or with the omega-6 to omega-3 ratio. Our results suggest that gender may moderate relationships between fatty acid intake and BP in adolescence.