How much adults need
The NIH Office of Dietary Supplements sets the adult RDA at 310–420 mg/day, varying by age and sex [1]. Magnesium intakes fall a bit short for many people, largely because refined grains lose magnesium during processing.
Best food sources
Magnesium is widespread in minimally processed plant foods [1]:
- Nuts and seeds: pumpkin seeds, chia, almonds, cashews.
- Legumes: black beans, edamame, lentils.
- Whole grains: brown rice, whole wheat, oats.
- Leafy greens: spinach and Swiss chard.
- Plus some fish, yogurt, and dark chocolate.
Choosing whole grains over refined ones is one of the simplest ways to raise magnesium.
Why diets run low
Refining grains removes the magnesium-rich bran and germ, so a diet heavy in white bread, white rice, and processed foods provides less. Shifting toward whole, plant-based foods closes most of the gap without a supplement.
When a supplement helps
If food can't get you there, a modest magnesium supplement can help — but note the supplemental upper limit is 350 mg/day (the limit applies to supplements, not food magnesium) [1]. Going above it commonly causes diarrhea, and forms differ in tolerability (see magnesium types compared). Food magnesium has no such limit because the kidneys clear dietary excess.
A note on absorption and medications
Magnesium supplements can interfere with some antibiotics if taken together, and long-term acid reducers can lower magnesium (see acid reducers). Food magnesium avoids the timing issues.
Practical guidance
- Favor whole grains, nuts, seeds, legumes, and greens to raise magnesium from food.
- Keep supplemental magnesium at or below 350 mg/day unless a clinician advises otherwise.
- If supplementing, choose a well-tolerated form and watch for loose stools.