Journal of the American College of Cardiology (JACC): Published on Feb 2021

Calcium and Vitamin D supplements are commonly used, often together, to optimize bone health. Multiple observational studies have linked low serum 25-hydroxyvitamin D concentrations with increased cardiovascular risk.

Given their widespread availability, low cost, and escalating use, the cardiovascular effects of such supplements are of great clinical and public health interest from the standpoints of both cardiovascular safety and cardiovascular health promotion.

In this review, the authors examine the currently available evidence investigating whether vitamin D and calcium supplements are helpful, harmful, or neutral for cardiovascular health.

TAKE HOME MESSAGE:

In observational studies, low blood levels of 25-hydroxyvitamin D have been associated with elevated cardiovascular risk.

In randomized trials, however, vitamin D supplementation has not reduced cardiovascular risk.

Vitamin D supplementation can be considered for those who are unable to achieve recommended vitamin D intake daily through diet.

Some studies have found increased risk with calcium supplementation.

Available data suggest that calcium intake should derive largely from dietary sources.

Calcium supplements are widely used for optimizing bone health; however, studies have emerged that suggest potential for cardiovascular harm. Therefore, calcium supplementation should be used cautiously and judiciously, and achievement of recommended daily allowances of calcium from dietary food sources should be encouraged.

Persons at risk for inadequate calcium intake including those with lactose intolerance or cow milk’s allergy, those with osteopenia or osteoporosis, and women who are amenorrheic or postmenopausal.

In such persons who are unable to obtain sufficient calcium supply through food sources, oral calcium supplementation might be needed on top of diet to achieve recommended daily allowances.

The National Academy of Medicine (NAM) has modified recommendations for treating vitamin D deficiency:

• Deficiency: ≤12 ng/mL
• Inadequacy: 12–20 ng/mL
• Adequate: 20–50 ng/mL
• Risk of adverse effects: ≥50 ng/mL

These data suggest avoiding supplementation unless 25-hydroxy vitamin D levels are ≤20 ng/dL, with better evidence for benefit when levels are <12 ng/mL.

Calcium Supplements: Implications for Clinical Practice

There is some concern (inconclusive) related to calcium use and increased CVD risk.

For calcium, smaller doses (approximately 500 mg) are better absorbed than larger doses. For someone who is at high risk for osteoporosis, calcium with vitamin D is better than calcium alone.

Certain subgroups, particularly those with very low calcium dietary intake and persons with increased calcium needs, may indeed benefit from supplementation. For example, among pregnant women with low calcium diets, calcium supplementation may reduce the risk for pre-eclampsia.

It may be best to reserve supplemental calcium only for those with low-calcium diets (<800 mg/day) who are unable to achieve greater calcium intake through foods. The recommended dose is 1000–1200 mg a day in divided doses.

In persons at risk for osteoporosis, moderate calcium intake (1,000 to 1,200 mg/day) in combination with vitamin D can reduce the risk for fractures; thus calcium supplementation may be considered to make up any gaps in intake not achieved from food sources.

Nevertheless, the potential for harm with calcium supplements, particularly at higher doses, should give practitioners pause before prescribing, and benefits should be carefully considered against risks.

Vitamin D: Implications for Clinical Practice

Although vitamin D does not appear to be harmful to cardiovascular health, the lack of a demonstrable benefit of supplementation in RCTs should discourage its use for this purpose, favoring optimizing vitamin D status through dietary intake and modest sunlight exposure instead and reserving vitamin D supplements only for documented 25(OH)D deficiency.

Based on a conservative benefit-risk management approach, vitamin D doses beyond the nutritionally recommended amounts of 600 to 800 IE daily currently cannot be advised for the prevention of CVD events.

Vitamin D supplementation can be considered for those who are unable to achieve NAM-recommended vitamin D intake daily through diet. Higher doses of vitamin D supplementation should be reserved for those at risk for deficiency (<12 ng/ml) with monitoring of laboratory values.

Overall, these findings do not provide conclusive evidence for preventive benefit of supplements when the nutrient is sufficient.