Whether or not outcomes such as osteoporosis ( or low bone mass ) and specific types of cancer may be prevented by ' generous ' vitamin D supplementation is unclear and mostly based on indirect epidemiologic data not clearly substantiated by r and omized controlled trials SUMMARY The dose of daily vitamin D supplements needed to prevent rickets is probably much lower than that recommended by most expert committees .
PURPOSE OF REVIEW To underst and the basis for current recommendations for  vitamin D supplementation in childhood and the differences between the recommendations published by major expert committees , using the Medline engine of the US National Library of Medicine and the National Institutes of Health .
Most trials have examined the question of whether a specific daily vitamin D dose is capable or not to prevent rickets ( by study ing surrogate markers of rickets ) .
Calcium plus vitamin D supplementation and the risk of breast cancer.
BACKGROUND Although some observational studies have associated higher calcium intake and especially higher vitamin D intake and 25-hydroxyvitamin D levels with lower breast cancer risk , no r and omized trial has evaluated these relationships . METHODS Postmenopausal women ( N = 36 282 ) who were enrolled in a Women 's Health Initiative clinical trial were r and omly assigned to 1000 mg of elemental calcium with 400 IU of vitamin D(3 ) daily or placebo for a mean of 7.0 years to determine the effects of supplement use on incidence of hip fracture . Mammograms and breast exams were serially conducted . Invasive breast cancer was a secondary outcome . Baseline serum 25-hydroxyvitamin D levels were assessed in a nested case-control study of 1067 case patients and 1067 control subjects . A Cox proportional hazards model was used to estimate the risk of breast cancer associated with r and om assignment to calcium with vitamin D(3 ) . Associations between 25-hydroxyvitamin D serum levels and total vitamin D intake , body mass index ( BMI ) , recreational physical activity , and breast cancer risks were evaluated using logistic regression models . Statistical tests were two-sided . RESULTS Invasive breast cancer incidence was similar in the two groups ( 528 supplement vs 546 placebo ; hazard ratio = 0.96 ; 95 % confidence interval = 0.85 to 1.09 ) . In the nested case-control study , no effect of supplement group assignment on breast cancer risk was seen . Baseline 25-hydroxyvitamin D levels were modestly correlated with total vitamin D intake ( diet and supplements ) ( r = 0.19 , P < .001 ) and were higher among women with lower BMI and higher recreational physical activity ( both P < .001 ) . Baseline 25-hydroxyvitamin D levels were not associated with breast cancer risk in analyses that were adjusted for BMI and physical activity ( P(trend ) = .20 ) . CONCLUSIONS Calcium and vitamin D supplementation did not reduce invasive breast  cancer incidence in postmenopausal women . In addition , 25-hydroxyvitamin D levels were not associated with subsequent breast cancer risk . These findings do not support a relationship between total vitamin D intake and 25-hydroxyvitamin D levels with breast cancer risk
Whether or not outcomes such as osteoporosis ( or low bone mass ) and specific types of cancer may be prevented by ' generous ' vitamin D supplementation is unclear and mostly based on indirect epidemiologic data not clearly substantiated by r and omized controlled trials SUMMARY The dose of daily vitamin D supplements needed to prevent rickets is probably much lower than that recommended by most expert committees .
PURPOSE OF REVIEW To underst and the basis for current recommendations for  vitamin D supplementation in childhood and the differences between the recommendations published by major expert committees , using the Medline engine of the US National Library of Medicine and the National Institutes of Health .
Most trials have examined the question of whether a specific daily vitamin D dose is capable or not to prevent rickets ( by study ing surrogate markers of rickets ) .