For many years, vitamin D was solely recognized for its role in bone health. Now, thousands of studies have been published supporting the beneficial role of vitamin D in a wide range of health outcomes. In fact, to name a few, vitamin D has been shown to support physical and mental health, help regulate the immune system and manage inflammation in the body.
However, the relationship between vitamin D and bone health has recently been called into question. Vitamin D deficiency undoubtedly plays a causal role in the development of rickets (a weakening and softening of the bones) among infants and toddlers. In addition, a German study of bone biopsies in a large population of cadavers found that an incredible 25% of the general population had osteomalacia on bone biopsy, but it is almost never picked up on X-rays. Osteomalacia was directly related to 25(OH)D, meaning the prevalence of osteomalacia increased as 25(OH)D decreased. However, the impact of vitamin D status on osteoporosis outcome and among older individuals remains unclear.
Observational studies suggest that vitamin D deficiency is associated with an increased risk for bone fractures among those with poor bone mineral density, leading researchers to hypothesize that vitamin D supplementation may offer a protective effect against fractures in older adults. Unfortunately, clinical trials have yielded conflicting findings.
These contradictory findings led researchers to conduct a meta-analysis of randomized controlled trials in an effort to provide more clarity on the relationship between calcium, vitamin D supplementation and fracture risk among older adults.
Studies were included in the meta-analysis if they were randomized controlled trials (RCT) that compared calcium, vitamin D, or a combination of the two with a placebo or non-treatment group on fracture risk among individuals over the age of 50 years. Thirty-three studies with a total of 51,145 participants met these criteria, and thus were evaluated in the meta-analysis.
Here is what the researchers found:
- Neither calcium (RR: 1.53; 95% CI: 0.97 to 2.42) nor vitamin D (RR: 1.21; 95% CI: 0.99 to 1.47) significantly impacted hip fracture risk compared to a placebo or no treatment.
- The combination of vitamin D and calcium did not significantly impact hip fracture risk compared to placebo or no treatment (RR: 1.09; 95% CI: 0.85 to 1.39).
- Neither calcium or vitamin D, independent of each other or combined, significantly affected the incidence of non-vertebral, vertebral or total fractures.
The researchers concluded,
“In this meta-analysis of randomized clinical trials, the use of supplements that included calcium, vitamin D, or both compared with placebo or no treatment was not associated with a lower risk of fractures among community-dwelling older adults.”
When taking a closer look that the RCTs chosen for review, there appears to be a few significant limitations worth mentioning. Most of the studies supplied their participants with between 400-800 IU/day (10-20 mcg) of vitamin D. This dose in unlikely to enable the average adult to reach vitamin D sufficiency (40-80 ng/ml). When meta-analyses contain a large number of studies using insignificant doses, null findings are expected.
In addition, several studies offered bolus dosing of vitamin D, ranging between large doses every 1-3 months to a single dose of 300,000-500,000 per year. Research has shown that bolus dosing is not as effective as daily dosing at improving one’s vitamin D levels. In addition, the half-life of circulating vitamin D is about three weeks. This means that those who received doses of vitamin D greater than a few months apart would only experience an increase in vitamin D levels over a period of a few weeks before it would begin to decline again, making the relationship between vitamin D status and fracture risk over a period of time nearly impossible to determine.
Last, while reviewing the handful of studies that provided the equivalent of at least 1,000 IU vitamin D3 among at least 30 participants for a minimum of three months, I discovered bone health wasn’t the primary outcome of interest in several of these studies, and only three of the seven studies meeting these criteria directly evaluated fracture risk. Nevertheless, these studies were selected to weigh in on this relationship.
As the Vitamin D Council has stated several times before, there are a variety of factors that affect our bones, and vitamin D alone cannot prevent age-related bone loss, nor can vitamin D reverse this damage once it has occurred. Having said that, based off this meta-analysis, it may be premature to dismiss vitamin D for its role in bone health among elderly individuals.
Bone health is contingent not only on vitamin D and calcium but also on magnesium intake (which is deplorable in many Americans), zinc intake, vitamin K intake and even silica intake. Bio Tech Pharmacal makes an excellent bone health product, Osteo-Tech, which can be purchased through their website.
In addition, hundreds of studies that have observed a relationship between chronic vitamin D deficiency and age-related muscle loss, cognitive impairment, Alzheimer’s disease, impaired quality of life and decreased ability to carry out activities of daily living. The flippant statement by the authors of this study to discontinue routine supplementation among older adults frankly neglects the abundance of research that proves otherwise.
Therefore, the Vitamin D Council continues to recommend older individuals supplement with 5,000-10,000 IU (125-250 mcg) vitamin D per day to support its wide range of health benefits including but not limited to musculoskeletal health.
Are you over the age of 50 and supplement with vitamin D? If so, please consider sharing your experience with the Vitamin D Council team so that we may continue helping our community on their path to wellness.
Sturges, M. & Cannell, JJ. Meta-analysis questions relationship between vitamin D and bone health among the elderly. The Vitamin D Council Blog & Newsletter, January 23, 2018.