Vitamin D status of Australian women

This is an observational study which will require one visit to the IHMRI clinical trials area/building 41, at the University of Wollongong. The visit will take place in winter 2020 and winter 2021 (June-August). The duration of the visit will last approximately 2 hours, and the total duration of involvement in the study will last 4 days, to include the time wearing the dosimeter and filling in the 4 day food diary. Of these 4 days, one day will be a weekend day. Recruited participants will come to IHMRI clinical trials area/building 41 fasted. The following measurements will be taken: 1. Consent taking Consent will be taken by the trained investigators at the beginning of the session. The participants will be given ample time to read and understand each point within the consent form and be giving time to ask any questions before initialling and signing off. Participants will be made aware that they do not have to take part, and that there will be no adverse consequences if they do not participate. 2. Anthropometric measurements The following anthropometrical measurements will be taken from each participant: Weight, height, waist to hip ratio, waist circumference, waist to height ratio and body composition. Weight and body composition will be measured to the nearest 0.1kg. This will be achieved using a Tanita Body Composition Analyser BC-418. Standing height will be measured using a wall stadiometer, to the nearest 0.1cm. Waist and hip circumference will be measured using a non-extendable standard measure tape, at the narrowest point of the torso for waist measurement (if this cannot be estimated, the level of the belly button will be used as a reference point), and the widest part of the hips for the hip measurement, to the nearest 0.1cm. Waist to hip ratio will be calculated by dividing the waist measurement by the hip measurement (waist ÷ hip) and the waist to height ratio will be calculated by dividing the waist measurement by the height measurement (waist ÷ height) 3. Dual energy X-ray absorptiometry (DEXA) scan Two DEXA scans will be taken. One scan to assess whole body bone mineral density and body composition, and the other to specifically assess fracture risk by scanning the femoral the hip and femoral head. Effective exposure doses for these scans are approximately 9 uSv and 8 uSv respectively. Total research protocol dose is approximately 18 uSv, this is equivalent to approximately 3 days of natural background radiation. Prior to the DEXA scan, participants will take a pre-scan questionnaire, which includes declaring they are not pregnant. Participants will be given the option to take a pregnancy test before the DEXA scans. 4. Blood sample An 8 hour-fasted blood sample will be taken by a trained phlebotomist. The following collection tubes will be used: • 2 x 10ml BD Vacutainer® SSTTM (red top) tube: serum 25OHD, calcium and albumin, P1NP, CTX, lipid profile, micronutrient status • 6ml BD Vacutainer® EDTA (purple) tube: PTH plasma, blood glucose level Blood sampling will occur once, with approximately 30ml of blood taken. Serum 25(OH)D for the analyses of vitamin D status will be sent to the University of Sao Paulo, Brazil for analysis. The remaining analytes will be analysed in laboratories in Australia. Calcium and P1NP and CTX (bone markers) are directly related to vitamin D status due to the role of vitamin D in calcium homeostasis, and this bone health. We are including these measures in order to assess the effect of vitamin D status on musculoskeletal health. Because vitamin D is a fat-soluble vitamin and is stored in adipocytes, it is necessary to have an indication of participants’ lipid status. Regarding micronutrient status, we will investigate those micronutrients known to impact on vitamin D status, namely the minerals serum calcium and phosphorus. Blood samples will be stored at -80°C at the University of Wollongong. 5. International Physical Activity Questionnaire (IPAQ) short form A physical activity questionnaire will be undertaken to obtain data on physical activity in everyday lives. 6. Sun exposure questionnaire The sun exposure questionnaire measures how often participants spend in the sun across different seasons, what body parts were exposed and if they have been on a recent summer holiday. This questionnaire was designed specifically for this study. 7. Lifestyle questionnaire The lifestyle questionnaire measures a range of factors including skin type, medical history, education, behaviours and attitudes towards sun exposure and knowledge and consumption of vitamin D. This questionnaire was designed specifically for this study. 8. Sit-to-stand test The 30 second Sit to Stand Test is used to measure leg strength and endurance. A chair without arms will be placed against a wall to prevent slipping. The participant will sit in the chair with their back straight, feet shoulder width apart on floor, with their arms crossed at their wrists and held against the chest. If the participant uses their arms to stand up they are scored 0. The participant will complete as many full stands as possible within 30 seconds. 9. Grip strength test The purpose of this test is to measure the maximum isometric strength of the hand and forearm muscles. Placing their arm at a right angle with the elbow at the side of the body, the participant will use their non-dominant hand to hold the hand grip dynamometer. The participant will squeeze the dynamometer with maximum effort for 5 seconds. An average of three tests will be taken, to the nearest 0.1kg. 10. Instruction on how to complete a 4-day food diary 4-day food diaries will be kept to measure dietary intake, in particular, intake of vitamin D. These will be used at home for four days, one of which days will be a weekend day. The participants are asked to record the time, what they eat, method of cooking and the amount eaten. They will be instructed to send these back to the investigators using the freepost envelopes provided. The researchers may phone or email the participants if any further information of their diet is required. Data will be analysed using Foodworks® nutritional analysis software. This diary was designed specifically for this study. 11. Instructions on how to wear a dosimeter to measure UVB exposure Participants will be asked to wear a dosimeter polysulphone film badge to measure UVB exposure. The dosimeters are clipped to the outer clothing with a pin, worn on the upper chest/shoulder region. Individuals are asked to wear the badge on from sunrise to sunset, for 4 days, one of which will be a weekend day. They are instructed to store the dosimeter in the supplied envelope (of thick and dark material to prevent further UVB exposure during storage) until returning. Data will be read pre and post use at the University of Southern Queensland. A x Spectophotometer (CV <1%) will be used at 330nm to detect a change in absorbency. Results of individual badge doses are reported in standard erythema dose (SED) units (1 SED = 100 J/m2).