Recommend against calcium and vitamin D supplementation due to insufficient evidence that it reduces fractures.
B, USPSTF recommends; high certainty that net benefit is moderate, or moderate certainty that net benefit is moderate to substantial.
C, USPSTF selectively recommends based on professional judgment and patient preferences; at least moderate certainty that net benefit is small.
Grossman DC et al. JAMA. 2018;319(16):1696–1704.