A 250 µg/week dose of vitamin D was as effective as a 50 µg/d dose in healthy adults, but a regimen of four weekly followed by monthly doses of 1250 µg raised the risk of hypercalciuria.

The risk of vitamin D insufficiency is increased in persons having limited sunlight exposure and dietary vitamin D. Supplementation compliance might be improved with larger doses taken less often, but this may increase the potential for side effects. The objective of the present study was to determine whether a weekly or weekly/monthly regimen of vitamin D supplementation is as effective as daily supplementation without increasing the risk of side effects. Participants were forty-eight healthy adults who were randomly assigned for 3 months to placebo or one of three supplementation regimens: 50 µg/d (2000 IU/d, analysed dose 70 µg/d), 250 µg/week (10 000 IU/week, analysed dose 331 µg/week) or 1250 µg/week (50 000 IU/week, analysed dose 1544 µg/week) for 4 weeks and then 1250 µg/ month for 2 months. Daily and weekly doses were equally effective at increasing serum 25-hydroxyvitamin D, which was significantly greater than baseline in all the supplemented groups after 30 d of treatment. Subjects in the 1250 µg treatment group, who had a BMI >26 kg/m2, had a steady increase in urinary Ca in the first 3 weeks of supplementation, and, overall, the relative risk of hypercalciuria was higher in the 1250 µg group than in the placebo group (P=0·01). Although vitamin D supplementation remains a controversial issue, these data document that supplementing with ≤ 250 mg/week (≤ 10 000 IU/week) can improve or maintain vitamin D status in healthy populations without the risk of hypercalciuria, but 24 h urinary Ca excretion should be evaluated in healthy persons receiving vitamin D3 supplementation in weekly single doses of 1250 µg (50 000 IU).

Visual side effects of scopolamine/ dextroamphetamine among parabolic fliers.

INTRODUCTION: Scopolamine/dextroamphetamine has been used to combat motion sickness generated aboard research aircraft for decades. While it has shown to be effective, previous studies differ as to the presence of visual side effects secondary to scopolamine's anticholinergic properties. This study sought to quantify any such effects in order to determine if they are operationally significant. METHODS: Fliers in NASA's Reduced Gravity Program received a weight-based dose of scopolamine/ dextroamphetamine prior to boarding the aircraft. Measurements of pupil size, visual acuity, and accommodation were taken in identical conditions using subjects' dominant eyes prior to medication administration and again after landing. We enrolled 131 subjects ages 18-48. Pre- and postflight measurements of pupil size and acuity were available for 125 subjects. RESULTS: Average pupil size increased by 1.1 mm (95% CI 0.9-1.2). Only 1.6% of subjects experienced a change in visual acuity of greater than 10 ft. The average near-point accommodation changed from 8.61 to 7.84 diopters, a difference of -0.77 (-1.01 to -0.53) diopters or 1.34 cm (0.87-1.81). Increasing age also correlated significantly with worsening change in accommodation. DISCUSSION: This study found statistically significant changes in pupil size and near point accommodation that do not appear to be clinically important. No significant decrement in acuity was noted. While direct effects on in-flight performance could not be assessed, the use of scopolamine/dextroamphetamine among fliers aboard research aircraft does not appear to yield visual side effects sufficient to compromise later ground operations.

Response to vitamin D supplementation during Antarctic winter is related to BMI, and supplementation can mitigate Epstein-Barr Virus Reactivation.

Maintaining vitamin D status without sunlight exposure is difficult without supplementation. This study was designed to better understand interrelationships between periodic vitamin D supplementation and immune function in Antarctic workers. The effect of 2 oral dosing regimens of vitamin D supplementation on vitamin D status and markers of immune function was evaluated in people in Antarctica with no UV light exposure for 6 mo. Participants were given a 2000-IU (50 µg) daily (n = 15) or 10,000-IU (250 µg) weekly (n = 14) vitamin D supplement for 6 mo during a winter in Antarctica. Biological samples were collected at baseline and at 3 and 6 mo. Vitamin D intake, markers of vitamin D and bone metabolism, and latent virus reactivation were determined. After 6 mo, the serum 25-hydroxyvitamin D concentration (mean ± SD) increased from 56 ± 17 to 79 ± 16 nmol/L and from 52 ± 10 to 69 ± 9 nmol/L in the 2000-IU/d and 10,000-IU/wk groups, respectively (main effect over time, P < 0.001). Participants with a greater BMI (participant BMI range = 19­43 g/m2) had a smaller increase in 25-hydroxyvitamin D after 6-mo supplementation (P < 0.05). Participants with high serum cortisol and higher serum 25-hydroxyvitamin D were less likely to shed Epstein-Barr virus in saliva (P < 0.05). The doses given raised vitamin D status in participants not exposed to sunlight for 6 mo, and the efficacy was influenced by baseline vitamin D status and BMI. The data also provide evidence that vitamin D, interacting with stress, can reduce risk of latent virus reactivation during the winter in Antarctica.

Gradient compression garments as a countermeasure to post-spaceflight orthostatic intolerance.

INTRODUCTION: Post-spaceflight orthostatic intolerance affects approximately 30% of short-duration and 80% of long-duration crewmembers. While the current NASA antigravity suit is effective during Space Shuttle re-entry, it is not designed to be worn postflight and has several drawbacks. The purpose of this study was to evaluate the use of commercially available, thigh-high, gradient compression garments to prevent post-spaceflight orthostatic intolerance. METHODS: Before spaceflight, five male Shuttle astronauts were fitted for compression garments. Postflight stand time, blood pressure, heart rate, stroke volume, cardiac output, and peripheral resistance during 10-min, 80 degrees head-up tilt test within 4 h of landing in these astronauts were retrospectively compared to a group of nine male astronauts not wearing the compression garments. RESULTS: On landing day, three of nine non-countermeasure astronauts developed presyncopal symptoms and could not complete the test, while no countermeasure subjects became presyncopal. Compared to the non-countermeasure subjects, the countermeasure subjects had higher systolic blood pressure (116 +/- 3 vs. 134 +/- 2 mmHg), stroke volume (42 +/- 5 vs. 57 +/- 6 ml), and cardiac output (3.1 +/- 0.3 vs. 4.6 +/- 0.4 L). Heart rate was not different between groups. CONCLUSIONS: In this small pilot study, the rate of presyncope in the non-countermeasure group was similar to that reported previously in subjects without a compression garment. In contrast, thigh-high graded compression garments mitigated the symptoms of orthostatic intolerance by improving stroke volume, cardiac output, and systolic blood pressure responses to standing.

Relative bioavailability of scopolamine dosage forms and interaction with dextroamphetamine.

The NASA Reduced Gravity Office (RGO) uses scopolamine (SCOP) alone and in combination with dextoamphetamine (DEX) to treat motion sickness symptoms during DC-9 parabolic flights. The medications are sometimes dispensed as custom dosage forms in gelatin capsules for convenience. Reports of treatment failure during flights by the flight surgeons suggest that these formulations may be less efficacious for the treatment of motion sickness due to unreliable and inadequate bioavailability. We estimated bioavailability of four different oral formulations used by the NASA RGO physicians for the treatment of motion sickness.