Townsend's New York observer: grapefruit seed extract: effective? Safe?
Subject: Grapefruit seed extract (Health aspects)
Author: Cohen, Marcus A.
Pub Date: 02/01/2012
Publication: Name: Townsend Letter Publisher: The Townsend Letter Group Audience: General; Professional Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2012 The Townsend Letter Group ISSN: 1940-5464
Issue: Date: Feb-March, 2012 Source Issue: 343-344
Geographic: Geographic Scope: United States Geographic Code: 1USA United States
Accession Number: 282825236
Full Text: What is Grapefruit Seed Extract (GSE)? Grapefruit seed extract is described as a liquid derived from the pulp, seeds, and white membranes of grapefruit. Biochemical analysis reveals that the constituents of GSE include ascorbic acid (vitamin C), citric acid, flavonoids, limonoids, certain minerals, tocopherols, and sterols - as well as high concentrations of synthetic disinfectants. (1)

GSE prepared commercially for sale to consumers is made from glycerin, grapefruit pulp, grapefruit seed, and synthetic preservatives - all blended together. (Pure GSE is processed by grinding the pulp and seed without solvents, then adding glycerin.)

Note: People sensitive to synthetic preservatives should take commercial GSE at any dilution with caution.

Widespread Use. GSE has become a major ingredient of cosmetics, dietary supplements, and pesticides. Use is now virtually worldwide. Antibacterial, antifungal, and antioxidant claims abound for it. Conditions treated by GSE include acne, allergies, athlete's foot, body odor, Candida, colds (and cold sores), eczema, gastritis, GI infections, gingivitis, impetigo, parasitic diseases, sinusitis, sore throat, thrush, and ulcers. (2) There are even claims of beneficial GSE therapy for HIV infections. (3)

Recently, GSE has been advertised as a natural, environmentally friendly pesticide in ecofarming (especially in Europe). (3) And spraying fruits (tangerines) and vegetables (garlic, onion, and soybean sprouts) with GSE appears to prolong their shelf lives markedly. (4)

Studies Claiming GSE Effective and Safe. Several studies have been done on GSE after testimonials reported effectiveness against more than 800 strains of bacteria and viruses, 100 strains of fungus, and numerous single and multicelled parasites. (4)

A study in the journal of Alternative and Complementary Medicine in 2002 specifically investigated GSE at varying concentrations to learn whether a concentration existed that was both antimicrobial and nontoxic (and in what period of time). The investigators found that from concentrations 1:1 through 1:256, GSE was bactericidal but also toxic. At a 1:512 dilution, GSE "remained bactericidal, but completely nontoxic/'4 Note: This is a narrow safety margin and only two types oi bacteria were affected at this dilution.

Regardless, this study concluded that "the initial data shows GSE to have antimicrobial properties against a wide range of gram-negative and gram-positive organisms at dilutions found to be safe." Further, STEM (scanning transmission electron microscopy) disclosed that "GSE disrupts the bacterial membrane and liberates the cytoplasmic contents within 15 minutes after contact even at more dilute concentrations." (4) The same effect was seen in human cells at most dilutions.

A later study in the journal Infection revealed that GSE is a strong in vitro agent against Lyme disease bacteria. (5) This study proposed that studies in vivo be conducted on GSE, particularly "to test the hypothesis that a combination of GSE and antibiotics will be efficient in the treatment of resistant Lyme borreliosis." (5)

Studies Showing GSE Largely Ineffective by Itself, Unsafe. Many more studies in the scientific literature question the efficacy and safety of GSE. These studies indicate that the antimicrobial activity associated with GSE is due to adulteration or contamination of commercial GSE preparations with synthetic antimicrobials or preservatives.3

For example, a report issued by the Agricultural Research Service, US Department of Agriculture, published in the journal of Agriculture and Food Chemistry in 2005, offers an interpretive summary of the unfavorable studies, which specifies the chief contaminants:

"There is recent evidence that some commercial GSE samples are adulterated with synthetic preservatives and that these additives are solely responsible for the antimicrobial activity." [Emphasis added.] "Preservatives such as methyl 4-hydroxybezoate (methyl paraben) ... triclosan, and benzethonium chloride have been identified in commercial GSE samples. In this study we identified a new synthetic adulterant, benzalkonium chloride, in commercial GSE samples. This ingredient is a synthetic antimicrobial agent that is widely used in cleaning and disinfection agents. The presence of benzalkonium chloride in a commercial product designated for internal and external use by humans is troubling in light of its toxicity and allergenicity." (2) [Emphasis added.]

At the end of this column, I've listed a number of studies that challenge claims of effectiveness and safety for GSE. Some of these studies detail the adverse effects of the main additives in GSE.


Is Elimination of Commercial GSE From Our Diet Sufficient Protection? Short answer: No! Commercially prepared GSE is being sprayed on fruits and vegetables before harvesting. It is sprayed on fruits and vegetables - even organic produce - after picking and sending them to markets because it extends their shelf life. My best advice on this: washing these foods thoroughly before eating them is a must!

Comments. As a columnist for a periodical that on its cover proclaims itself 'The Examiner of Alternative Medicine." I'd prefer to report agreement among expert sources on the effectiveness and safety of grapefruit seed extract - a product increasingly promoted as a natural, organic antibacterial, antifungal, and antiviral agent. But the amount and weight of the sources that say "ain't so!" are too numerous and heavy to dismiss or ignore.

In a world frequently clouded by conflicting or contradictory scientific findings, I turn to poetry as a personal refuge. Poetry doesn't resolve such differences for me. It can offer views that somehow make the differences more acceptable, bearable. (Sunnier, one may say.)

Jacques Prevert (1900-1977) was a French poet and writer of film scripts. In the years immediately following World War II, he spoke more directly to and for the French who had come of age under the German occupation of France than any other contemporary poet.. His poems have remained very popular in the French-speaking world. His film Les Enfants du Paradis (Children of Paradise) is still considered one of the greatest films of all time.

Here's a Prevert poem that seems to lighten the "yes-no" situation surrounding GSE.

The Dunce

He says no with his head

but he says yes with his heart

he says yes to what he loves

he says no to the teacher

he stands

he is questioned

and all the problems are posed

sudden laughter seizes him

and he erases all

the words and figures

names and dates

sentences and snares

and despite the teacher's threats

to the jeers of infant prodigies

with chalk of every color

on the blackboard of misfortune

he draws the face of happiness.


(1.) Grapefruit seed extract/Properties [Web page]. Wikipedia.

(2.) Takeoka G et al. Identification of benzalkonium chloride in commercial grapefruit seed extracts. J Agric Food Chem. 2005;53:7630-7036.

(3.) Ganzera M et al. Development and validation of an HPLC/UV/MS method for simultaneous determination of 18 preservatives in grapefruit seed extract. J Agric Food Chem. 2006;54:3768-3772.

(4.) Heggers JP et al. The effectiveness of processed grapefruit-seed extract as an antibacterial agent: II. Mechanism of action and in vitro toxicity. I Altera Complement Med. 2002;8(3):333-340.

(5.) Brorson 5 et al. Grapefruit seed extract is a powerful in vitro agent against motile and cystic forms of Borreiia burgdorferi sensu lato. infection. 2007;35:206-208.


Avula B et al. Simultaneous identification by liquid chromatography of benzethonium chloride, methyl paraben and triclosan in commercial products labeled as grapefruit seed extract. Pharmazie. 2007 Aug;62(8):593-596.

Bekiroglu S et al. Validation of a quantitative NMR method for suspected counterfeit products exemplified on determination of benzethonium chloride in grapefruit seed extracts. J Pharm BiomedAnal. 2008;47:958-961.

Brandin H et al. Adverse effects by artificial grapefruit seed extract products in patients on warfarin therapy. Eur J Clin Pharmacol. 2007;63:565-570.

Sugimoto N et al, Survey of synthetic disinfectants in grapefruit seed extract and its products. J Food Hygienic Soc Japan. 2008;49(1):56-62.

by Marcus A. Cohen
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