Evidence Based
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Grapefruit Seed Extract for Candida + Benefits & Side Effects

Written by Aleksa Ristic, MS (Pharmacy) | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Aleksa Ristic, MS (Pharmacy) | Reviewed by Ana Aleksic, MSc (Pharmacy) | Last updated:

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Grapefruit

Grapefruit seed extract is promoted to fight candida and other infections and provide antioxidant support. However, the available research is limited and points to some important drawbacks. This article breaks down the potential benefits and dangers of grapefruit seed extract.

What is Grapefruit Seed Extract?

Grapefruit seed extract is a substance derived from the seeds and pulp of grapefruit. It’s a concentrated source of citrus flavonoids and other healthy nutrients from this tropical fruit [1].

Alternative medicine practitioners use grapefruit seed extract to treat microbial infections and gut disorders. In Africa, its traditional uses include diabetes, obesity, and anemia [2].

Thanks to its antiseptic properties, you will find grapefruit seed extract in various personal care products and household cleaners.

American immunologist Jacob Harich discovered grapefruit seed extract in 1980. The intense bitterness of grapefruit seeds and their resistance to contamination inspired him to process the seeds and pulp into a liquid antimicrobial extract.

Don’t confuse grapefruit seed extract with:

  • Grapefruit seed oil – pressed from the seeds, lacks other nutrients
  • Grapefruit essential oil – aromatic compounds from the peel
  • Grape seed extract or oil – come from grapes, not grapefruit

Snapshot

Proponents:

  • Fights Candida and other microbes
  • May help with UTIs and stomach ulcers
  • Improves oral health
  • May prevent heart disease and diabetes
  • May protect the skin

Skeptics:

  • Clinical research is lacking
  • May cause dangerous drug interactions
  • Often contaminated with toxic chemicals

Grapefruit Seed Extract Health Benefits

Insufficient Evidence:

How It Works

Grapefruit seeds are rich in flavonoids naringin, naringenin, and hesperidin, which are responsible for their bitterness and distinct health benefits. The seeds also contain citric acid, vitamin C, and vitamin E [3, 4, 5].

Active ingredients from grapefruit seed extract may support your health by [6, 7, 8, 1, 9]:

  • Fighting bacteria, viruses, and fungi
  • Boosting antioxidant support
  • Reducing inflammation

1) May Fight Candida and Other Infections

Grapefruit seed extract is often promoted as a universal cure for all kinds of infections. However, despite the promising cell-based research, current clinical evidence to support such claims is scant.

Grapefruit seed extract (450 mg daily for 4 weeks) suppressed gut microbes such as Candida, Geotrichum, and E. coli in 15 patients with skin issues. All of them experienced improvement of constipation, bloating, and other digestive symptoms [10].

This study had a tiny sample and other notable limitations we’ll discuss in “Limitations and Caveats” below.

In test tubes, grapefruit seed extract stopped the growth of different Candida strains taken from infected patients. It can also prevent the contamination of pharmaceuticals with Candida and other microbes [11, 12].

Some people use grapefruit seed extract for thrush (oral candida infection) and vaginal yeast infections, but clinical trials haven’t confirmed its beneficial effects.

Grapefruit seed extract inhibited over 60 strains of bacteria and yeasts in cell-based studies. It was efficient against both gram+ and gram- bacteria, especially foodborne pathogens such as Salmonella [1, 13, 9, 14].

Viral Infections

Mosquitos in tropical areas can transmit malicious viruses. One of them is the dengue virus, which causes dengue – the world’s leading mosquito-transmitted disease [15].

Grapefruit seed extract can prevent the growth of dengue virus, as well as some stomach viruses [16, 17].

Antimicrobial Uses

Due to its potent antiseptic properties, grapefruit seed extract is a vital ingredient in [18, 19, 20, 21, 22, 12]:

  • Food packaging and storing
  • Beekeeping
  • Laundry and house cleaning
  • Farming
  • Pharmaceutical industry

However, the extract partly owes its germ-killing potential to chemical contaminants found in some products. Find more details in “Side Effects and Dangers” below [23].

2) May Improve Oral Health

Many mouthwashes contain grapefruit seed extract. It supports oral health by killing germs and combating oxidative stress [24].

In a clinical trial of 20 patients, a mouthwash with grapefruit seed extract reduced plaque buildup (47%), gum bleeding and inflammation (78%), and bad breath (35%) [25].

3) May Help With UTIs

In a tiny clinical trial (4 patients), eating grapefruit seeds relieved the symptoms of urinary tract infections (UTIs) caused by different germs. The patients experienced a definite improvement after consuming 5-6 seeds, three times daily for two weeks [26].

This study confirms the antibacterial properties of grapefruit seeds but doesn’t allow for any reliable conclusions about the extract.

In test tubes, grapefruit seed extract and grapefruit juice were able to inhibit bacteria associated with UTIs in people wearing catheters. The extract lowered the levels of E. coli, a major cause of UTIs, in beef samples [27, 28].

Animal Research (Lacking Evidence)

4) May Help With Diabetes and Heart Disease

In diabetic rats, grapefruit seed extract was able to boost insulin function and lower the levels of glucose, LDL, total cholesterol, and triglycerides. The effects were comparable to those of an antidiabetic drug, metformin [2].

One-month supplementation with the extract yielded similar results in another study on rats and also caused moderate weight loss [29].

Flavonoids found in grapefruit seeds – naringenin, naringin, and hesperidin – enhanced glucose metabolism and blocked oxidative damage in many studies on rats with diabetes and insulin resistance [30, 31, 32, 33, 34].

Additionally, they were able to prevent a host of diabetes complications, such as:

  • Retinopathy (eye damage) [35, 36]
  • Heart disease [37, 38, 39]
  • Bone loss [40]
  • Nephropathy (kidney damage) [41]

Grapefruit seed extract flavonoids support the heart and blood vessels. According to different clinical reviews, they may protect against heart disease by [42, 43, 44, 45, 46, 47, 48]:

  • Fighting oxidative stress and inflammation
  • Cutting the blood lipid levels
  • Preventing plaque buildup in blood vessels (atherosclerosis)
  • Protecting the heart cells against damage

In test tubes, naringenin and hesperidin boosted cholesterol metabolism by raising the number of LDL receptors 4-7 times [49, 50, 51].

Truth be told, the potential benefits of isolated flavonoids and their dietary sources might not translate to grapefruit seed extract.

5) Weight Loss

Many supplements are promoted to stimulate weight loss, but valid clinical research has debunked most of those claims. A healthy, calorie-controlled diet and increased physical activity remain your best allies in weight control.

Grapefruit seed extract enhanced weight loss in rats and cut their risk of heart disease and diabetes. Naringenin showed the same results in obese rats [29, 52].

In a cell study, naringenin enhanced fat burning, energy production, and insulin sensitivity [53].

Without clinical evidence to back them up, these findings are far from conclusive.

6) May Prevent Stomach Ulcers

Grapefruit seed extract protected rats against stomach ulcers caused by alcohol and stress. The extract caused a 50% reduction in ulcers by [54, 55]:

In cell experiments, grapefruit seed extract inhibited the growth of Helicobacter pylori, the leading cause of stomach ulcers [56, 57].

7) May Protect the Skin

Some natural sunscreen products contain naringenin because it blocks UV rays and provides antioxidant support [58].

Three major flavonoids from grapefruit seed extract – naringenin, naringin, and hesperidin – protected mice against UV-induced skin lesions. They relieved oxidative stress and cut the levels of inflammatory molecules (TNF-a, IL-1B, IL-6, and IL-10) [59, 60, 61, 62].

In a study on rats, naringenin enhanced the healing of skin burns via the same mechanisms [63].

Limitations and Caveats

The above findings indicate versatile health potentials of grapefruit seed extract, but clinical evidence is scarce. Most verified uses are industrial, and they exclude human consumption.

Flavonoids from grapefruit seeds have a range of beneficial effects, but that doesn’t grant the same benefits to grapefruit seed extract.

The only clinical trial with grapefruit seed extract comes from a low-impact journal and has massive limitations such as [10]:

  • Small sample size
  • Lack of placebo control
  • Possible conflict of interest

In addition to that, the use of grapefruit seed extract comes with certain health risks we’ll discuss below.

Grapefruit Seed Extract Side Effects and Dangers

Keep in mind that the safety profile of grapefruit seed extract is relatively unknown, given the lack of well-designed clinical studies. Consult your doctor about potential side effects, based on your health condition and other factors.

In the only clinical trial, grapefruit seed extract caused no significant side effects [10].

The US Food and Drug Agency (FDA) classified one product with grapefruit seed extract as safe for human consumption [64].

There’s not enough evidence to proclaim grapefruit seed extract safe for children and pregnant women. Due to the potential dangers discussed below, these sensitive groups should steer clear of grapefruit seed extract supplements.

Drug Interactions

Supplement/Herb/Nutrient-drug interactions can be dangerous and, in rare cases, even life-threatening. Grapefruit juice can interact with many medications, but this might not be the case with the extract. Still, you should discuss its use with your doctor and tell him about all drugs and supplements you are using or considering.

Grapefruit juice inhibits cytochrome P450 enzymes involved in drug metabolism. This may lead to adverse effects and a possible overdose with certain prescription drugs, especially [65]:

  • Immunosuppressants
  • Lipid-lowering drugs (statins)
  • Sedatives (benzodiazepines)
  • High blood pressure drugs (calcium channel blockers)
  • Antiepileptics (carbamazepine)

Other grapefruit products, including the seed extract, may cause these interactions, too.

When combined with grapefruit, atorvastatin and other statins may cause severe muscle damage. Grapefruit also has minor interactions with other drugs for the heart and blood vessels including [66, 67]:

  • Drugs for heart rhythm (verapamil, amiodarone, propafenone)
  • Antiplatelet drugs (clopidogrel)
  • Drugs for erectile dysfunction (sildenafil, tadalafil, vardenafil)

Doctors reported a case of bruising as a consequence of the interaction between grapefruit seed extract and blood thinner, warfarin. Lab tests revealed that a chemical contaminant triggered the interaction, which leads us to another potential danger of grapefruit seed extract discussed below [68].

Product Contamination

Most grapefruit seed extract products are contaminated with antiseptic agents such as triclosan, benzethonium chloride, or benzalkonium chloride [69, 70, 71, 72, 73, 74].

Since most people use the extract as a natural disinfectant, manufacturers probably add these chemicals to boost the effects.

You will find triclosan in many personal care and household products. Its widespread use is a major environmental issue but also has problematic health effects. Triclosan exposure may raise the risk of miscarriage, asthma, allergies, hormonal disturbance and more [75].

Benzalkonium chloride acts as a preservative in different pharmaceuticals for external application, but most manufacturers have started replacing it with safer alternatives. It can damage the eyes, nose, and lungs [76, 77, 78].

Grapefruit Seed Extract Supplements

Grapefruit seed extract supplements have not been approved by the FDA for medical use. In general, regulatory bodies aren’t assuring the quality, safety, and efficacy of supplements. Speak with your doctor before supplementing.

Various forms of grapefruit seed extract supplements are available on the market. They include:

  • Liquid grapefruit seed extract
  • Pills (125-400 mg)
  • Bulk powder

Some products are standardized to 45% polyphenols (flavonoids). Besides oral supplement forms, you will find grapefruit seed extract in nasal sprays, toothpaste, mouthwash, and cosmetics.

Pay extra attention to the ingredients list and go with verified brands that test their products and don’t add harmful chemicals. Beware: some products are for external use only!

Dosage & How to Use

The safe and effective dosage of grapefruit seed extract has not been established. If your doctor suggests using it, work with them to find the optimal dosage according to your health condition. Below suggestions are based on anecdotal evidence.

Grapefruit seed extract dosage that suppressed the growth of gut pathogens and relieved digestive symptoms in the only clinical trial was 150 mg, 3x daily for 4 weeks [10].

Thrush

Apply grapefruit seed extract to a cotton pad. Those with sensitive skin can dilute the extract in coconut oil, which also antifungal properties. Gently wipe the affected area and leave it to dry. You can do this twice daily.

Athlete’s Foot

Apply GSE directly to the affected area 2-3 times a day. Try to keep your feet dry and clean and change your socks regularly.

Reviews and User Experiences

The opinions expressed in this section are solely from the users who may or may not have medical background. Their reviews do not represent the opinions of SelfHacked. SelfHacked does not endorse any specific product, service, or treatment.

Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice from your doctor or another qualified healthcare provider because of something you have read on SelfHacked.

Mouthwashes and gargles with grapefruit seed extract are very popular. People report their benefits for thrush (oral candida infection), sore throat, and oral hygiene.

Some users complain about the unpleasant “chemical” taste (may indicate contamination!), lack of effect, and irritation.

Grapefruit seed extract nasal spray seems to help with chronic congestion and sinus inflammation but may also irritate mucous membranes.

User experiences with oral consumption are limited, though some report success with UTIs and digestive issues.

Takeaway

Grapefruit seed extract contains citrus flavonoids with potent antimicrobial, antioxidant, and anti-inflammatory properties. It acts as a natural disinfectant in personal care and cleaning products.

Despite some promising findings, there is insufficient evidence to support the use of grapefruit seed extract for candida, oral health, heart disease and diabetes, weight loss, and skin protection.

Users report positive experiences with grapefruit seed extract mouthwashes and nasal sprays for thrush, sore throat, and nasal congestion.

Due to the risk of dangerous drug interactions and toxic contaminants, you may want to avoid oral consumption. Either way, choose verified lab-tested products with no added chemicals, and make sure to consult your doctor before supplementing.

About the Author

Aleksa Ristic

Aleksa Ristic

MS (Pharmacy)
Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets. 
Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.

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