New clinical trial documents plasma response and bone health benefits of Pure Encapsulations Vitamin D3

By Kelly C. Heim, Ph.D

The importance of vitamin D in bone physiology has been widely acknowledged for over 80 years. Through genomic and endocrine mechanisms that scientists continue to unravel, vitamin D3 maintains calcium uptake, mineral deposition and bone remodeling.1 While the positive influence of vitamin D3 on bone density is clear, few studies have dually monitored serum levels and bone density in response to different doses. These investigations are complicated by the influence of sunlight exposure and the lengthy time periods required to show changes in bone.

In a recent clinical study published in The Journal of Bone Mineral Research, a group of researchers led by Dr. Helen Macdonald at the University of Aberdeen in Scotland evaluated Pure Encapsulations’ Vitamin D3 in post-menopausal women.2 The double-blind, placebo-controlled trial recruited women between 60 and 70 years of age residing in Northeast Scotland, a region where low serum vitamin D levels are highly prevalent. The women were randomized to receive placebo, 400 IU, or 1000 IU of vitamin D3 daily for 1 year. The serum form of vitamin D3, 25-dihydroxyvitamin D (25(OH)D), was assessed every 2 months. At the end of the study, bone mineral density (BMD) was measured. By assigning UV sensing badges to the participants, the researchers excluded sunlight as a confounding source of vitamin D.

Serum 25(OH)D levels, which were low in all groups at baseline, increased by nearly 2-fold within two months of supplementation (Figure 1). Consistent with normal changes in bone after menopause, a significant decline in BMD at the hip was evident over the 1-year period in the placebo group (Figure 2). 400 IU of vitamin D3 failed to attenuate this loss. However, 1000 IU provided complete protection. These results corroborate existing evidence that 400 IU is insufficient to maintain bone health after menopause, particularly in patients with existing deficiencies.3

NewsCapsFigure 1. Mean serum vitamin D levels over the 1-year study. All groups began with low levels (12-15 ng/ml). 400 and 1000 IU of Pure Encapsulations’ Vitamin D3 elevated serum levels by up to 2- and 2.4-fold, respectively. The mid-year increase with placebo was due to summer sun exposure.
NewsCapsFigure 2. Bone mineral density at the hip declined over one year without supplementation. A daily dose of 400 IU vitamin D3 was not protective.  However, 1,000 IU maintained BMD, with a negligible change of -0.05 g/cm2.


Importantly, the data offer proof of the supplement bioavailability and effective accumulation in plasma. For each IU of the supplement, the increase in serum vitamin D was higher than in other studies. “This may be because our starting 25OHD was low,” commented Dr. Macdonald. “The lower the status you have at the start, the greater the increase.” Dose-response studies have reported similar findings.4

For optimal health, experts recommend a serum range of 30-60 ng/ml, and daily doses of 2000 IU or higher are often required to achieve these levels.4 Pure Encapsulations offers Vitamin D3 in a range of potencies to meet individual requirements. As part of a comprehensive approach to bone health, a small capsule may make a big difference.


  1. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
  2. Macdonald HM, Wood AD, Aucott LS, Black AJ, Fraser WD, Mavroeidi A, Reid DM, Secombes KR, Simpson WG and Thies F.  Hip bone loss is attenuated with 1000 IU but not 400 IU daily vitamin D3: a 1 year double-blind RCT in postmenopausal women. J Bone Mineral Res 2013, in press.
  3. Bischoff-Ferrari HA. Optimal serum 25-hydroxyvitamin D levels for multiple health outcomes. Adv Exp Med Biol. 2008;624:55-71.
  4. Gallagher JC, Sai A, Templin T 2nd, Smith L. Dose response to vitamin D supplementation in postmenopausal women: a randomized trial. Ann Intern Med 2012, 156(6):425-37.