High-Dose Vitamin D Does Not Affect Peripheral Arterial Calcification in People Without Deficiency

By Scott Baltic

July 27, 2020

NEW YORK (Reuters Health) - Daily vitamin D supplements of 400, 4,000, or 10,000 IU has no effect on tibial-artery calcification over a three-year period in adults without osteoporosis who have adequate vitamin levels at baseline, according to a secondary analysis of trial data.

Preclinical research had suggested that vitamin D deficiency, or, conversely, excess, might promote arterial calcification, Dr. Emma Billington of the Cumming School of Medicine at the University of Calgary and colleagues report in Osteoporosis International. Although more than a quarter of participants had calcifications of the tibial artery at baseline, no new cases were seen over the course of the study.

"Arterial calcification is a marker of risk for cardiovascular and peripheral vascular events, and appears to be a causative factor," Dr. Billington told Reuters Health by email. "The most established mechanism for this is stiffening the arteries and making them less responsive, which can impair delivery of blood to the heart and peripheral tissues."

To the authors' knowledge, this is the first study using serial high-resolution peripheral quantitative computed tomography (HR-pQCT) measurements to follow the progression of tibial-artery calcification.

The report notes that although there's "a lack of convincing evidence" for health benefits in adults with sufficient vitamin D, it's estimated that more than half of U.S. adults take a vitamin D supplement, of whom more than 7 million take 4,000 IU or more daily.

The new study used data from the Calgary Vitamin D Study, a double-blind, randomized controlled trial that evaluated whether increasing levels of vitamin D supplementation affected bone density and/or strength.

Participants were randomized to receive vitamin D3 400, 4,000, or 10,000 IU daily for three years. To be included, they had to have lumbar spine and total hip bone DEXA scores of greater than -2.5.

Tibial-artery calcification was identified in 85 (28%) of 302 participants at baseline. These individuals were significantly likelier than individuals without calcification to be male and on average had significantly lower systolic and diastolic blood pressure and lower 24-hour urine calcium excretion.

Among participants with existing calcification, this increased linearly throughout the study, but there was no evidence of a treatment-group effect (P=0.6 for interaction).

Dr. Billington said the study "provides an additional piece of evidence suggesting that supplementation with high-dose vitamin D does not appear to have significant non-skeletal effects, when administered to healthy adults who are not vitamin D deficient."

This study was funded by Pure North S'Energy Foundation.

SOURCE: https://bit.ly/3gbpVAg Osteoporosis International, online June 15, 2020.