Vitamin D status and calcium intake in systemic inflammation, insulin resistance and the metabolic syndrome: An update on current evidence

•Systematic reviews of RCTs and observational studies were selected.•No support for vitamin D in systemic inflammation or insulin resistance from RCTs.•Vitamin D status and metabolic syndrome were inversely related in observational studies.•Data on calcium intake was meagre, but mechanistic pathways are strong.•Potential issues to address are discussed.