Grapefruits are healthy and refreshing, but their seeds may pack even greater benefits. Grapefruit seed extract fights candida and all kinds of microbial infections. It may boost your health in many ways but also inflict damage in some cases. This article breaks down the pros and cons of grapefruit seed extract.

What is Grapefruit Seed Extract?

Grapefruit seed extract is a substance derived from the seeds and pulp of grapefruit. This tropical fruit is a concentrated source of citrus flavonoids and other healthy nutrients [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

PROS

  • Fights Candida and other microbes
  • May help with UTIs
  • Boosts oral health
  • May prevent heart disease and diabetes
  • May support weight loss
  • May protect the liver and skin

CONS

  • Not well studied in humans
  • May cause dangerous drug interactions
  • Often contaminated with toxic chemicals

Grapefruit Seed Extract Health Benefits

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 can support your health by [6, 7, 8, 1, 9]:

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

1) Fights Candida and Other Microbial Infections

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), but clinical trials haven’t confirmed this effect.

Grapefruit seed extract inhibited over 60 types 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) Improves Oral Health

Many types of mouthwash contain grapefruit seed extract. It supports oral health by killing germs and relieving oxidative stress [24].

In a clinical trial on 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, 3 times daily for 2 weeks [26].

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

In beef samples, grapefruit seed extract cut the levels of E. coli, a major cause of UTIs [27].

4) May Combat Diabetes

In diabetic rats, grapefruit seed extract was able to boost insulin function and lower the levels of glucose, LDL, total cholesterol, and triglycerides [2].

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 [28, 29, 30, 31, 32].

Naringenin and naringin may prevent a host of diabetes complications. They were able to shield diabetic rats against:

  • Retinopathy (eye damage) [33, 34]
  • Heart disease [35, 36, 37]
  • Bone loss [38]
  • Kidney damage [39]

5) May Prevent Heart Disease

Naringenin, hesperidin, and other flavonoids found in grapefruit seed extract support the heart and blood vessels. They may lower the risk of heart disease by [40, 41, 42, 43, 44, 45, 46]:

  • Fighting oxidative stress and inflammation
  • Cutting 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. This may help lower LDL in the blood [47, 48, 49].

6) May Support Weight Loss

Grapefruit seed extract enhanced weight loss in rats; it also cut their risk of heart disease and diabetes. Naringenin showed the same results in obese rats [50, 51].

In a cell study, naringenin enhanced fat burning, energy production, and insulin sensitivity. This effect is vital for everyone looking to shed extra pounds [52].

7) May Protect the Liver

The liver is your master detox organ–it helps you get rid of nasty chemicals and metabolites. These toxins can expose the liver to oxidative stress and impair its function [53].

A flavonoid from grapefruit seed extract, naringenin, protected the liver in different animal trials. It was able to [28, 54, 55, 56]:

  • Prevent oxidative damage
  • Shield the liver against toxins
  • Reduce fat buildup

Another grapefruit flavonoid, hesperidin, relieved liver scarring in rats [57, 58].

In test tubes, hesperidin lowered the levels of enzymes that point to liver damage (AST and ALT) [59].

8) 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 [60, 61]:

In cell experiments, grapefruit seed extract inhibited the growth of Helicobacter pylori, the top cause of stomach ulcers [62, 63].

9) May Boost Skin Health

Some natural sunscreen products contain naringenin because it blocks UV rays and provides antioxidant support [64].

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) [65, 66, 67, 68].

In a study on rats, naringenin enhanced the healing of skin burns via the same mechanisms [69].

Limitations and Caveats

The above trials indicate versatile health potentials of grapefruit seed extract, but clinical evidence is scarce. Most verified uses and benefits 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
  • Conflict of interest

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

Dosage

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

In the other clinical trial, UTI patients consumed whole seeds, not the extract. They took 5 – 6 seeds, 3x daily for 2 weeks [26].

Grapefruit Seed Extract Side Effects and Dangers

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 [70].

Theres 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

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 [71]:

  • 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 seed extract, atorvastatin and some other statins may cause severe muscle damage. Besides calcium channel blockers, grapefruit seed extract has minor interactions with other drugs for the heart and blood vessels including [72, 73]:

  • 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 danger of grapefruit seed extract [74].

Product Contamination

Most grapefruit seed extract products are contaminated with antiseptic agents such as triclosan, benzethonium chloride, or benzalkonium chloride [75, 76, 77, 78, 79, 80].

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

Health Risks

You will find triclosan in many personal care and household products. Its widespread use is a major environmental issue but also has detrimental health effects. Triclosan exposure may raise the risk of miscarriage, asthma, allergies, hormonal disturbance and more [81].

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 [82, 83, 84].

In other words, you should avoid getting in contact with the above chemicals, let alone ingesting them. The fact that some people treat infants with grapefruit seed extract makes the contamination issue even worse.

Grapefruit Seed Extract Supplements

Despite their potential health dangers and the limited evidence for their efficacy, 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 nasal sprays, toothpaste, mouthwashes, and cosmetics.

When it comes to choosing the best grapefruit seed extract supplement, pay extra attention to the ingredients list. Go with verified brands that test their products and don’t add harmful chemicals. Beware: some products are for external use only!

Reviews and User Experiences

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.

Buy Grapefruit Seed Extract

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Take-Away:

Grapefruit seed extract is a potent antimicrobial, antioxidant, and anti-inflammatory supplement. It may fight an array of microbes, including candida. Plus, it helps prevent heart disease and diabetes while protecting your liver and skin. However, there’s no clinical evidence for these benefits.

Due to the risk of dangerous drug interactions and toxic contaminants, you may want to avoid oral supplements. Whether you plan to use it orally or on the skin, be sure to choose verified lab-tested products (free of triclosan, benzalkonium chloride, and other chemicals).

About the Author

Aleksa Ristic, MSc (Pharmacy)

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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