A three-year study has analyzed the link between high doses of vitamin D and bone mineral density. It has found that taking high doses of Vit D provides no benefit. And there is a need for more research to check if Vit D in high dose can worsen the bone health. The journal “JAMA” has published this research.
Vitamin D is necessary for bone health
A person’s skin makes Vit D when exposed to sunlight. Vitamin D leads to the absorption of calcium. And as a result, it ensures healthy and strong bones. In Canada, there is no exposure to sunlight in long winter months. So, many people turn to supplements to fulfill their daily needs of vitamin D.
For healthy and normal adults, Health Canada has suggested a daily intake of 600 IU up to age 70 and 800 IU after this age. This dose may prevent many bone diseases. On the contrary, Osteoporosis Canada suggests that people at high risk of osteoporosis should take a dose of 400 – 2000 IU daily.
The research team has followed 300 people with age between 55 and 70. And has tested the hypothesis that an increase in the dose of vitamin D will lead to a dose-related increase in bone mineral density. The team gave 400 IU of vitamin D per day to 1/3rd of the study participants.
While among the remaining people, 1/3rd received 4000 IU, and 1/3rd got 10,000 IU per day. Later, the team analyzed bone mineral density (BMD) of these people. That was done by using a high-resolution CT scan (XtremeCT) of bone at the ankle and wrist.
Bone mineral density tells about the amount of calcium and other minerals in a part of the bone. The team has also performed standard DXA bone density. And has collected fasting blood samples and urine samples to check calcium and Vit D levels.
Higher doses of vitamin D may not lead to an increase in BMD
The results of the DEXA has shown a moderate decrease in BMD over time. While there was no variation among the three groups. But the values of BMD with XtremeCT showed notable differences in the bone loss in these groups. During this study, BMD decreased by 1.4% in 400 IU group, 2.6% in the 4000 IU group, and 3.6% in 10000 IU group.
The results have suggested that higher doses of Vit D can’t increase bone mineral density or bone strength. On the contrary, the XtremeCT has shown a dose-related decrease in BMD. Where the largest reduction was in the group taking 10,000 IU per day. The bone loss in this group isn’t enough to increase the risk of fracture in the three years.
The study has also found a safety concern linked with high levels of Vit D. The groups with higher doses (4000 IU AND 10,000 IU) had a greater risk of hypercalciuria than the group receiving a lower daily dose. The team detected hypercalciuria in 87 people. While the incidence was 17% in 400 IU, 22% in 4000 IU, and 31% in 10,000 IU study groups.
Though not common, this condition can enhance the risk of kidney stones, and impair kidney function. Overall, the results of the study have shown that Vitamin D doses (400-2000 IU) suggested by Osteoporosis Canada are enough for healthy bones. And the doses above 4000 IU aren’t suggested to the majority of the people.