Everyone talks about calcium, but what about the other side of the coin? Magnesium is the fourth most abundant mineral in the body and is involved in over 300 biochemical reactions in the body.* The problem as a paleo/primal/meat,veggies,nuts etc. eater is that good sources of magnesium are found in things we try to avoid: grains like cereal, bread, etc.** As a supplement, it will help relax the muscles and systems in your body, boost your immune system, maintain heart rhythms, and get better sleep.
Although there are many magnesium supplements out there, I personally take Natural Calm. It is touted as an anti-stress powder, but I like it to help me sleep better. Sometimes it can be hard to tell if a supplement is working, but when I take 1-2 tsp. of this powder mixed with water before bed, I am definitely more alert the next morning and sometimes even jump out of bed because of how well rested I am. Essentially, it makes my sleep more efficient.
Be sure to read up on side effects, follow directions to ramp up the dosage over time, and of course talk to your doctor if you have any conditions to see if you can take this. Magnesium supplements can be found anywhere (CVS, Whole Foods, Vitamin Shoppe, etc). You will probably discover that there are Magnesium + Calcium supplements out there. I don't see a reason not to get this if you want, but if you're eating enough green veggies and getting Vitamin D, you should be fine in retaining calcium.