Magnesium is a common supplement and it can compete with calcium for absorption. On this page, we will discuss

• Role of Magnesium in our bodies
• Why people supplement with magnesium (including how much)
• Different forms of Magnesium supplement
• How to maximize absorption of both calcium and magnesium when taking both

Role of Magnesium in our bodies

• Muscle and nerve support: Helps muscles relax after contracting and eases cramps.

• Sleep and relaxation: Supports calming brain chemicals like GABA to promote rest.

• Digestion: Relieves occasional constipation.

• Blood sugar: helps move blood sugar out of your blood and into your muscles where the sugar can be used as fuel

• Blood pressure: Assists in keeping glucose and blood pressure levels steady

• Bone health: 50% to 60% of the total magnesium in the human body is found in bones. The magnesium is found on the surface of hydroxyapatite crystals in bone where it provides a structural role. It prevents the crystals from growing too large and becoming brittle. It also helps synthesize the collagen framework that calcium and phosphate bind to. As with calcium, it is also a reserve supply when serum levels dips too low.

Why people supplement with magnesium

There are two existing (and somewhat conflicting) goals for dietary magnesium.

• Recommended Dietary Allowance (RDA) - from a combination of food, drink and supplement
  • Adult men: 400 - 420 mg per day
  • Adult women: 310 - 320 mg per day
  • for other age groups and including pregnancy and breastfeeding, see Office of Dietary Supplements Fact Sheet
• Recommended Calcium to Magnesium ratio
  • 1989: original recommendation for a 2:1 ratio (by weight) of elemental Calcium to elemental Magnesium
    • Durlach J. Recommended dietary amounts of magnesium: Mg RDA. Magnesium Research. 1989 Sep;2(3):195-203. PMID: 2701269. (link is to abstract only)
  • 2021: Costello et al. Advances in Nutrition: 12: 291-297. Perspective: Characterization of Dietary Supplements Containing Calcium and Mgneisum and Their Respective Ration- Is a Rising Ratio a Cause for Concern

Many people find it difficult to reach the RDA for magnesium by diet alone - hence the supplementation. Food processing such as refining grains strips away the nutrient rich germ and bran which contains much of the inherent magnesium. Some good dietary sources:

• seeds and nuts
  • pumpkin seeds: 156 mg/ounce
  • chia seeds: 111 mg/ounce
  • almonds: 80 mg per ounce (but note they are also high in oxalates)
  • cashews: 74 mg per ounce
• Vegetables and legumes
  • spinach: 78 mg per 1/2 cup of boiled spinach - but note extremely high oxalate content
  • black beans: 60 mg per 1/2 cup of cooked beans
  • edamame: 50 mg per 1/2 of cooked, shelled beans
  • baked potato: 43 mg for a 3/5 ounce potato
• Whole grain
  • brown rice: 42 mg per 1/2 cup of cooked rice
  • plain yogurt (dairy): 42 mg per 8 ounces

Different forms of magnesium supplement

How to maximize absorption of both calcium and magnesium