Advanced Doses of Vitamin D Are Required To Achieve Optimal Vitamin D Status
It is currently estimated that more than 1 billion people worldwide have vitamin D deficiency. Relatively small amounts of vitamin D are obtained through the diet and many lifestyle factors reduce endogenous vitamin D synthesis, therefore supplementation offers an important avenue for achieving and maintaining optimal vitamin D status.
Scientists at USANA Health Sciences and Linus Pauling Institute recently conducted a clinical study to evaluate the effectiveness of moderately high daily doses of vitamin D3 on increasing circulating levels of vitamin D during winter, spring, and summer seasons.
19 healthy volunteers, most using USANA’s HealthPakTM daily dietary supplement packs, BiOmegaTM and/or Active CalciumTM supplements, were randomly divided into the treatment or control (placebo) groups. The treatment group was given a daily supplement providing 4000 IU of vitamin D3 for three months from December 2008 to March 2009. The control group received a matching placebo tablet. Both the Vitamin D3 and matching placebo tablets were manufactured at USANA Health Sciences, Inc. (Salt Lake City, USA). Blood samples were drawn at baseline and after 4, 8, and 12 weeks of supplementation, to analyze circulating vitamin D levels (25-hydroxy vitamin D3).
The study found that:
* Treatment with 4000 IU/day significantly increased circulating vitamin D levels during the winter and maintained them in the optimal range above 50 mg/mL.
* Circulating vitamin D levels reached maximal levels after 4 weeks of supplementation and plateaued thereafter.
* Upon cessation of supplementation between weeks 12-16, vitamin D levels declined appreciably underscoring the need for continuous supplementation to maintain optimal levels throughout the winter and early spring.
* Supplementation of 2000 IU/day through the late spring and summer maintained vitamin D levels in the optimal range.
* At the conclusion of the study, vitamin D levels in all subjects that did NOT continue supplementation through the summer returned to the baseline values originally measured in December.
This study shows that continuous intakes of vitamin D are needed to obtain optimal circulating levels of vitamin D above 50 mg/mL throughout the entire year.
Source: Dixon B et al; 2009; USANA Clinical Research Poster; Accessed 21 Jun 2010.