Magnesium is involved in over 300 processes in the body — muscle function, sleep regulation, blood sugar control, and mood among them — yet most adults, and especially women over 40, fall short of recommended intake. Modern diets, certain medications, and age-related changes in absorption all contribute. Food sources (leafy greens, nuts, seeds, legumes) are the best starting point, with supplements as a reasonable next step if a deficiency is confirmed or strongly suspected.
Magnesium doesn't get the attention calcium or vitamin D do, despite touching an almost absurd number of things your body does every day — sleep, muscle function, blood sugar regulation, even mood.
It's also one of the more commonly under-consumed minerals in typical diets, which makes it worth understanding rather than overlooking.
Why is magnesium deficiency so common?
Several factors converge. Modern diets heavy in processed foods tend to be genuinely low in magnesium, since processing strips much of it from grains and other foods. Certain common medications (some diuretics, acid reflux medications, and others) can reduce magnesium absorption or increase how much the body excretes. And with age, the digestive system's efficiency at absorbing magnesium from food can decline somewhat, compounding the dietary gap.
What does magnesium actually affect?
Sleep: magnesium plays a role in regulating the nervous system and supporting the body's natural relaxation response, tying into the sleep picture covered in our sleep guide.
Muscle function: magnesium is directly involved in muscle contraction and relaxation, and deficiency is a documented, common cause of muscle cramps and twitches.
Blood sugar regulation: magnesium supports insulin function, and research links adequate magnesium intake with better blood sugar control.
Mood: magnesium interacts with neurotransmitter systems involved in mood regulation, adding another thread to the anxiety and stress picture covered in our anxiety guide and cortisol guide.
What foods are highest in magnesium?
- Leafy greens (spinach, Swiss chard)
- Nuts and seeds, particularly pumpkin seeds and almonds
- Legumes (black beans, chickpeas, lentils)
- Whole grains
- Dark chocolate (70% cacao or higher)
Building a few of these into regular meals is a more sustainable, food-first approach than reaching straight for a supplement.
If you do supplement, which type matters
Not all magnesium supplements are equal. Magnesium glycinate is well-absorbed and gentle on digestion, commonly chosen for sleep and relaxation. Magnesium citrate absorbs well too, but is more likely to have a laxative effect. Magnesium oxide is inexpensive but poorly absorbed, making it a less efficient choice despite being common on store shelves. Matching the form to your actual goal — sleep, general deficiency, or occasional constipation — makes a real difference.
When should you talk to a doctor about magnesium?
Worth a conversation if you have persistent muscle cramps, sleep issues, or fatigue without an obvious explanation, or before starting a supplement if you take other medications or have kidney issues, since magnesium can interact with certain drugs and isn't cleared as efficiently when kidney function is reduced.
Frequently asked questions
How do I know if I'm magnesium deficient?
Common signs include muscle cramps, trouble sleeping, fatigue, and headaches, though these overlap with other causes. A blood test can check levels, interpreted alongside your symptoms.
What foods are highest in magnesium?
Leafy greens, nuts and seeds, legumes, whole grains, and dark chocolate are among the richest sources — a better first step than supplementing directly.
Which type of magnesium supplement is best?
Depends on your goal — glycinate for sleep with minimal digestive effects, citrate for general use (more laxative effect), oxide is cheap but poorly absorbed.
Can you take too much magnesium?
Yes, from supplements — can cause diarrhea, nausea, and rarely more serious effects, especially with kidney problems. Stick to recommended doses and check with your doctor first.
Sources
- National Institutes of Health, Office of Dietary Supplements — magnesium fact sheet. ods.od.nih.gov
- Harvard T.H. Chan School of Public Health — magnesium and health. hsph.harvard.edu
Chris S. — Founder & Writer
Chris is 46 and living the same chapter she writes about. She started The Well Chapter to turn solid sources into calm, practical guidance for women navigating the changes that come after 40 — without hype, fear, or miracle promises.