European guidelines on colorectal cancer screening and diagnosis

Should vitamin D (with or without calcium) supplementation in addition to the usual diet vs. usual diet alone be used for primary prevention of colorectal cancer in average risk adults?

The WG members acknowledged that the benefits of using vitamin D supplementation in addition to a usual diet are unknown, while harms are certain and at least small. The WG also considered that probably there is no important uncertainty or variability in how much people value the main outcomes and that, despite probably acceptable and feasible, using vitamin D supplementation would probably reduce equity.

The ECICC working group agreed on this recommendation by consensus.

Vitamin D deficient people and those who have other clinical indications for vitamin D supplementation are not included in this recommendation. 

The WG hypothesised likely differences in men and women and also geographical differences (resulting in different baseline vitamin D levels before supplementation), however there is limited evidence to make suggestions for such subgroups. There is ongoing debates how to define deficiency of vitamin D.

Some members noted that, given the widespread availability of vitamin D supplements, their accessibility may present challenges to the implementation of this conditional recommendation against their use. Also, members suggested referring to legislation on false claims of health benefits, particularly as there is not enough evidence on beneficial effects. Still, they noted this is a general remark that applies to other similar topics.

Quality indicators for monitoring the implementation of this recommendation are planned for development.

Despite this recommendation being supported by only very low certainty, it was considered that more research is not good use of resources.