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    Ingredient guide · Ingredient reference

    Magnesium in peanut butter: about 54 mg in a reference 32 g portion

    Plain smooth peanut butter contributes magnesium. Fortified products can differ substantially, so the exact entry and serving size matter.

    Read the evidence ↓

    Supplement Science Insights Editorial Team

    Published September 23, 2026

    The unfortified reference

    USDA SR Legacy lists smooth peanut butter without salt at 168 mg magnesium per 100 g. A hypothetical 32 g serving supplies 53.76 mg. That is a useful contribution, but it should not be treated as a complete daily magnesium intake or a deficiency treatment. [1]

    Fortification changes the comparison

    The historical vitamin-and-mineral-fortified smooth peanut-butter entry contains 355 mg magnesium per 100 g, giving 113.6 mg in 32 g. This does not mean every brand is fortified. Check the specific formulation instead of selecting the higher database value for ordinary peanut butter. Neither record is an independent test of a current jar. [1]

    A hypothetical spread portion

    For the unfortified reference, 16 g provides 26.88 mg and 32 g provides 53.76 mg. A heaped spoon is not a precise weight, so weighing the amount can improve a food-log estimate. Composition still varies, and peanut butter remains unsuitable for someone with a peanut allergy regardless of its magnesium content. [1]

    Hypothetical example — apply reference composition to specified hypothetical portions
    Unfortified smooth peanut butterMagnesium estimate
    16 g26.88 mg
    32 g53.76 mg
    Magnesium in peanut butter: about 54 mg in a reference 32 g portion — original article outline diagram
    Original editorial diagram of this article’s sections; no product photograph or clinical finding is depicted.

    Sources for this article

    1. USDA FoodData Central — SR Legacy April 2018 composition and portion tables
      Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.