Low serum 25-hydroxyvitamin D (25(OH)D) has been shown to correlate with increased risk of type 2 diabetes. Small, observational studies suggest an action for vitamin D in improving insulin sensitivity and/or insulin secretion. The objective of the present study was to investigate the effect of improved vitamin D status on insulin resistance (IR), utilising randomised, controlled, double-blind intervention administering 100 mg (4000 IU) vitamin D 3 (n 42) or placebo (n 39) daily for 6 months to South Asian women, aged 23-68 years, living in Auckland, New Zealand. Subjects were insulin resistant -homeostasis model assessment 1 (HOMA1) . 1·93 and had serum 25(OH)D concentration , 50 nmol/l. Exclusion criteria included diabetes medication and vitamin D supplementation . 25 mg (1000 IU)/d. The HOMA2 computer model was used to calculate outcomes. Median (25th, 75th percentiles) serum 25(OH)D 3 increased significantly from 21 (11, 40) to 75 (55, 84) nmol/l with supplementation. Significant improvements were seen in insulin sensitivity and IR (P¼0·003 and 0·02, respectively), and fasting insulin decreased (P¼ 0·02) with supplementation compared with placebo. There was no change in C-peptide with supplementation. IR was most improved when endpoint serum 25(OH)D reached $80 nmol/l. Secondary outcome variables (lipid profile and high sensitivity C-reactive protein) were not affected by supplementation. In conclusion, improving vitamin D status in insulin resistant women resulted in improved IR and sensitivity, but no change in insulin secretion. Optimal vitamin D concentrations for reducing IR were shown to be 80 -119 nmol/l, providing further evidence for an increase in the recommended adequate levels. Registered Trial No. ACTRN12607000642482. Vitamin D: Type 2 diabetes: Insulin resistanceThere is mounting interest in the role of vitamin D in the aetiology of type 2 diabetes, and the most commonly preceding conditions, reduced insulin sensitivity and compromised b-cell function.Low serum 25-hydroxyvitamin D (25(OH)D) concentrations have been shown to correlate with impaired glucose tolerance and an increased risk of type 2 diabetes (1 -5) , while a correlation between hypovitaminosis D and insulin resistance (IR) has been identified in pregnant women and obese adolescents (6,7) . A 10-year prospective study identified an inverse relationship between baseline serum 25(OH)D concentrations and later risk of IR (8)

Sun exposure is the main source of vitamin D. Due to many lifestyle risk factors vitamin D deficiency/insufficiency is becoming a worldwide health problem. Low 25(OH)D concentration is associated with adverse musculoskeletal and non-musculoskeletal health outcomes. Vitamin D supplementation is currently the best approach to treat deficiency and to maintain adequacy. In response to a given dose of vitamin D, the effect on 25(OH)D concentration differs between individuals, and it is imperative that factors affecting this response be identified. For this review, a comprehensive literature search was conducted to identify those factors and to explore their significance in relation to circulating 25(OH)D response to vitamin D supplementation. The effect of several demographic/biological factors such as baseline 25(OH)D, aging, body mass index(BMI)/body fat percentage, ethnicity, calcium intake, genetics, oestrogen use, dietary fat content and composition, and some diseases and medications has been addressed. Furthermore, strategies employed by researchers or health care providers (type, dose and duration of vitamin D supplementation) and environment (season) are other contributing factors. With the exception of baseline 25(OH)D, BMI/body fat percentage, dose and type of vitamin D, the relative importance of other factors and the mechanisms by which these factors may affect the response remains to be determined.

A number of factors contribute to success in sport, and diet is a key component. An athlete’s dietary requirements depend on several aspects, including the sport, the athlete’s goals, the environment, and practical issues. The importance of individualized dietary advice has been increasingly recognized, including day-to-day dietary advice and specific advice before, during, and after training and/or competition. Athletes use a range of dietary strategies to improve performance, with maximizing glycogen stores a key strategy for many. Carbohydrate intake during exercise maintains high levels of carbohydrate oxidation, prevents hypoglycemia, and has a positive effect on the central nervous system. Recent research has focused on athletes training with low carbohydrate availability to enhance metabolic adaptations, but whether this leads to an improvement in performance is unclear. The benefits of protein intake throughout the day following exercise are now well recognized. Athletes should aim to maintain adequate levels of hydration, and they should minimize fluid losses during exercise to no more than 2% of their body weight. Supplement use is widespread in athletes, with recent interest in the beneficial effects of nitrate, beta-alanine, and vitamin D on performance. However, an unregulated supplement industry and inadvertent contamination of supplements with banned substances increases the risk of a positive doping result. Although the availability of nutrition information for athletes varies, athletes will benefit from the advice of a registered dietician or nutritionist.

Objectives: The purpose of this study was to investigate the knowledge and health beliefs regarding osteoporosis risk factors of New Zealand women aged 20-49 years. Design: A descriptive, web-based survey. Subjects: An opportunistic sample of 622 women aged between 20 and 49 years living in Auckland, New Zealand was recruited by email. Results: There was a moderate level of knowledge about osteoporosis risk factors among the women surveyed, with a mean total score for all subjects of 16.4 (standard deviation (SD) 4.0) out of a possible 26 correct responses. Mean scores for osteoporosis knowledge were statistically different by age group, with women aged 40 -49 years scoring higher than those aged 30 -39 years and 20-29 years (17.3 (SD 4.0), 16.4 (SD 4.1) and 15.8 (SD 3.9), respectively, P , 0.001). Overall, about a third of the women perceived that they were likely to develop osteoporosis and 22% believed the disease to be potentially crippling. Most women were aware of the benefits of exercise and optimal calcium nutrition in preventing osteoporosis. Few women perceived barriers to exercise participation and eating calcium-rich foods. Older women (40-49 years) were more motivated to take care of their health than younger women (P , 0.001). A large percentage of subjects (77%) thought that calcium-rich foods contained too much cholesterol. Conclusions: Despite reporting higher than average educational attainment and health consciousness, these women demonstrated average levels of knowledge about osteoporosis risk factors. They had low feelings of susceptibility towards development of osteoporosis, but most considered it to be a serious disease.

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