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Antimicrobials

Grapefruit seed extract

Also listed as GSE, citrus paradisi seed extract

Sold as a natural antimicrobial, but lab tests found the antimicrobial power of commercial extracts came from synthetic preservatives mixed in, not the grapefruit.

No real evidenceTypical strength: Small amounts; rarely disclosed

What it is

Grapefruit seed extract is marketed as a natural preservative and germ-fighter in toothpastes and skin products. Independent laboratory analyses of commercial extracts repeatedly found synthetic antimicrobials (benzethonium chloride, sometimes triclosan or methylparaben) at up to about 22%.

When researchers tested an uncontaminated commercial extract, and extracts they made themselves from grapefruit seed and pulp, they found no antimicrobial activity.

How strong is the evidence?

No real evidence

No clinical evidence supports an oral-health benefit. Laboratory studies indicate that genuine grapefruit seed extract has little or no antimicrobial effect and that commercial extracts' activity came from undeclared synthetic preservatives. Supply quality today may differ, but the burden of proof is on the product.

What it's used for, checked

Natural antibacterial for teeth and gums

Unproven

Antimicrobial activity traced to synthetic additives; pure extract showed none.

Natural preservative

Mixed

Can preserve a product if it contains undeclared synthetic preservatives, which defeats the 'natural' claim.

Who should be careful

  • Undeclared preservatives mean people allergic to them (for example quaternary ammonium compounds or parabens) cannot rule them out.
  • Choose toothpaste for its fluoride, not for this ingredient.

The studies

Every citation is checked against its PubMed record.

  1. Aspects of the antimicrobial efficacy of grapefruit seed extract and its relation to preservative substances contained.
    von Woedtke T, Schluter B, Pflegel P, Lindequist U, Julich WD · Pharmazie · 1999 · Laboratory analysis

    Five of six commercial grapefruit seed extracts killed a broad range of microbes, and every active one contained the synthetic preservative benzethonium chloride (some also triclosan and methylparaben). The one clean extract, and home-made extracts, had no antimicrobial activity.

  2. Simultaneous identification and quantification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract.
    Avula B, Dentali S, Khan IA · Pharmazie · 2007 · Laboratory analysis

    Commercial products labelled grapefruit seed extract contained benzethonium chloride at 0.29-21.84%, and two contained triclosan.