Many people are deficient in magnesium, due to over exploitation of our soils. This also makes a lot of the meat we consume lower in magnesium (unless it's meat from regenerative ranching).

So it's something I recommend for those starting a low carb diet, and the formulations I recommend depend on a few factors but they're:

-Magnesium citrate

-Magnesium glycinate

-Ionic magnesium

Most people don't need supplements, especially if on a low carb diet for some time.