Recently, a patient asked about the effectiveness and safety of grapefruit seed extract in dealing with fungal candida. In my practice over the past 30 years, I have found undecenoic acid to be far more effective than grapefruit seed extract in treating fungal candida. Grapefruit seed extract (GSE) was a better antiparasitic choice than undecenoic acid, but lacked the better absorption found with another product, Agrisept-L, which contains grapefruit seed extract, along with lemon, lime, and tangerine seed extracts. Absorption and distribution of undecenoic acid throughout the body appears to be equal to that of Agrisept-L, but undecenoic acid was still by far a much better choice against fungus, and Agrisept-L a much better choice than GSE for parasites. Agrisept-L and GSE have strong antibacterial properties, in addition to their antiparasitic effectiveness, and research hasn’t determined whether or not there is an effect against beneficial strains of bacteria, as well as against the pathogenic strains.

One study showed that GSE had a strong antibacterial effect against more than 800 bacterial and viral strains, 100 strains of fungus, and a large number of single and multicelled parasites. Along with the antimicrobial effects of GSE, there was also found to be a toxic effect against certain tissues at concentrations as little as 1:128. Further dilution down to a level of 1:512 showed no more toxicity to the tissues, with strong antibacterial functions still remaining. The GSE was found to disrupt bacterial membranes within 15 minutes after contact, even at the lowest dilutions. This ability to disrupt bacterial cell walls makes it a much better choice than antibiotics, but still presents the problems encountered when destroying bacteria can lead to imbalances within the bacterial flora composition, increased levels of inflammation, immune system dysregulation, and direct stimulation of the conversion of candida from its normal yeast to problematic fungal form. This last aspect may account its lesser effect as an antifungal internally, as the release of petidoglycans from gram-positive bacterial cell walls is known to directly stimulate the conversion of candida from its yeast to fungal forms.

Other issues with grapefruit seed extract include its effect on enzymes involved in drug metabolism, specifically the CYP3A4 (cytochrome P450 isoenzyme). Like grapefruit, the GSE could block the enzymes responsible for breaking down certain drugs, leading to higher levels of these drugs in the body and increasing the risk for adverse events, side effects, and overdose.

Another concern with GSE lies in several studies that show that the natural grapefruit seed extract has no antimicrobial effect. The effect attributed to GSE is due to synthetic antimicrobial agents used in processing and creating GSE. The process of extracting GSE uses compounds commonly known as benzalkonium chloride, “a widely used synthetic antimicrobial ingredient used in cleaning and disinfection agents”. Benzethonium chloride, “a synthetic antimicrobial agent commonly used in cosmetics and other topical applications” is not the only added synthetic substance that has been repeatedly found in GSE products. Another study found that  “samples either contained benzethonium chloride (2.5-176.9 mg/mL) or benzalkonium chloride (138.2-236.3 mg/mL), together with smaller amounts of 4-hydroxybenzoic acid esters, benzoic acid, and salicylic acid.” Yet another study found that in “all of the antimicrobial active grapefruit seed extracts, the preservative benzethonium chloride was detected by thin layer chromatography. Additionally, three extracts contained the preserving substances triclosan and methyl parabene. In only one of the grapefruit seed extracts tested no preservative agent was found. However, with this extract as well as with several self-made extracts from seed and juiceless pulp of grapefruits (Citrus paradisi) no antimicrobial activity could be detected (standard serial broth dilution assay, agar diffusion test). Thus, it is concluded that the potent as well as nearly universal antimicrobial activity being attributed to grapefruit seed extract is merely due to the synthetic preservative agents contained within. Natural products with antimicrobial activity do not appear to be present.” These same findings were repeatedly demonstrated in other studies. One study even suggested that the effect against CYP3A4 and other enzymes was due to the “benzethonium chloride (BTC) in addition to glycerol and water.” In that particular study, “No authentic GSE extract was found in any of the three GSE products analysed. Furthermore, BTC was found to be a potent inhibitor of CYP3A4 and CYP2C9 activity in vitro.”

Given the findings of all of the studies above, it can be stated that there is truthfully no comparison between undecenoic acid and grapefruit seed extract. The comparison as it stands is really being made between undecenoic acid and benzethonium chloride. We can then extrapolate from these studies and results and focus on the antifungal effects of benzethonium chloride (BC). Some sites warn about its use in humans. Other sites only list a need for minor caution and state that it is relatively safe for short-term use. As with many chemicals, some people will be much more reactive to it than others. I was able to find 3 studies that demonstrated an antifungal effect of GSE/BC. The first study comes from Poland, the second from the Czech Republic, and the third study from Germany. The first two studies identified Candida albicans, while the third study noted an effect against Candida maltosa. An important consideration with these studies is that there wasn’t a clear distinction between BC’s effect against the yeast form or fungal form of candida. If it harms the yeast form, then other imbalances will be created. If it destroys the candida cell wall membrane, then an increase in inflammation will result and people with high levels of inflammation will need to be aware of a possible exacerbation of symptoms.

One study showed that the amount of benzethonium chloride present in GSE was just over 8%,with powdered forms containing more. While this doesn’t seem like a lot, the dosage will determine if there is a toxic effect against human tissues as well as against bacteria and other microbes.

I have recommended GSE when Agrisept-L isn’t available, and both make an excellent choice as a natural antibiotic. I have had many people use Agrisept-L instead of antibiotics for dental work and surgeries. These short-term applications can present with less risk than the many offerings of drugs, which in comparison carry with them an average of 392 side effects per drug. I have never had anyone fall sick to Montezuma’s Revenge when traveling to Mexico and taking Agrisept-L or GSE daily. Others who have traveled there have always come down with this travel malady when not taking Agrisept-L or GSE. While it seems like toxicity issues are minimal or non-existent, knowing exactly what is in each bottle of GSE is a good place to start. Those that have been found to contain triclosan and other contaminants are more likely to do more damage and harm.

The best ear drop product that I have seen on the market contains GSE and I find it to be more effective than antibiotics and much safer to use. If you have children, it’s a must to own. Since it’s not taken internally, that makes it a more attractive choice. I wouldn’t want to be without Agrisept-L, as it is the most effective anti-parasitic that I have ever seen, with an ability to eradicate parasites in the blood when medications couldn’t touch them. GSE/BC absorption issues limit it’s effectiveness in such cases. As far as fungal candida goes, I have never seen GSE/BC come close to being as effective as undecenoic acid, and obviously it’s not as safe.

I’m not a big fan of anything that purports to kill microbes in the body. Many practitioner’s like to imbue substances like these with magical properties as though they only kill the bad bugs and leave the good ones alone. GSE/BC’s ability to wipe out over 800 species of bacteria means that there will innocent casualties long the way. Such widespread destruction of bacteria will almost always lead to other imbalances of the bacterial flora. This will reduce the diversity of the bacterial flora and thus the overall levels of health. This may be managed somewhat by modifying and monitoring the effects of dosages. Anyone taking medication will want to know if GSE/BC will increase their risk of side effects and adverse events. Smaller dosages may be able to mitigate this effectively.

Anything that has the ability to affect a wide number of bacteria in the body can create shifts that initially appear to be beneficial as they eliminate some of the bad bugs that created the symptoms in the first place. The long-term effects however will be harder to define. If given the choice between antibiotics and GSE/BC, the latter is almost always going to be a better choice. When it comes to fungal candida however, I’ll always choose the safety and effectiveness of undecenoic acid.