Few people get sufficient magnesium through diet.
Calcium supplementation generally requires supplementation with magnesium.
What is it?
Magnesium is a trace mineral that is abundant in the body. The majority of the body’s magnesium is stored in bone, making it hard to measure.
What it does
Magnesium is a cofactor in over 300 enzyme systems that regulate a broad range of biochemical processes. These include protein synthesis, muscle and nerve function and blood glucose and blood pressure control. 
Calcium supplementation generally requires supplementation with magnesium
Best food sources for magnesium include tofu, legumes, seeds, nuts, whole grains and green leafy vegetables.3
Few Canadians eat enough of these to ensure an adequate magnesium intake.
Recommended Dietary Allowance (RDA)
Canada’s RDA can be found here.
Molecular Dosage Range
Orthomolecular practitioners often recommend dosages somewhat higher that the RDA. Vitamin D is required for absorption of magnesium.
, site reviewed August 2016