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Grapefruit Benefits (incl weight loss) + Side Effects

Written by Biljana Novkovic, PhD | Reviewed by Biljana Novkovic, PhD | Last updated:

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Grapefruit Juice

Grapefruit is recognized as a superfood with many health benefits, but has it been studied scientifically? Are these perceived health benefits real? Read on to discover 17 proven health benefits of including grapefruit in your diet.

What is Grapefruit?

Grapefruit is a citrus hybrid known for its bitter taste. It originated as a cross between sweet orange and pomelo, probably sometime in the 17th century.

Grapefruit is used in traditional (folk), Chinese, holistic, herbal, nutritional, and Ayurvedic medicine. You can take it as whole fruit, juice, seed extract, or essential oil.

It provides a wide range of health benefits, due to the antioxidant and detoxifying properties of its many flavonoid compounds (naringenin, narirutin, naringin, hesperidin, neohesperidin, didymin, and poncirin) [1, 2].

Grapefruit has been traditionally used for anorexia, enlarged prostate, cancers (breast, colon, prostate, lung, skin, and throat), candida, cold, diabetes, dysuria, high cholesterol, infection, insomnia, mycobacterium, mycosis, nervousness, pseudomonas, rheumatism, staphylococcus, and yeast [3].

Grapefruit juice has antioxidant, anticancer, antiseptic, detoxifying, and appetite stimulant properties. It is also a heart tonic, sedative, improves stomach activities, and lowers low-density cholesterol [3].

Grapefruit Components

The biologically active components of grapefruit include:

  • Flavonoids (e.g. naringenin, naringin, hesperidin)
  • Furanocoumarins (bergamottin, 6′,7′-dihydroxybergamottin -the CYP3A4 inhibitors responsible for ‘the grapefruit effect’)
  • Nootkatone

These components are unique to grapefruit and likely related to the effects of grapefruit, unlike quercetin or apigenin, which are flavonoids present in many plants, including grapefruit [3].

Flavonoids have antioxidant properties. Antioxidants are required to prevent the damage caused by ‘free radicals’ [4, 5].

The rich flavonoid content in grapefruit benefits degenerative diseases like diabetes and heart disease [6].

Grapefruit chemicals vary in concentration according to species, but also to handling methods [7].

Blending rather than squeezing produces higher levels of some beneficial chemicals (such as naringenin, limonene, citric acid, and bergamottin), whilst juicing and hand squeezing result in higher levels of others (ascorbic acid and dihydroxybergamottin, respectively) [7].

Therefore, consuming grapefruit juice processed by blending may provide more health benefits [7].

Other beneficial grapefruit components include [8, 3, 9]:

It is low in both sodium and cholesterol, and very low in calories and saturated fat.

Grapefruit Health Benefits

1) Grapefruit May Improve Weight Loss

Grapefruit may increase the rate of weight loss, but the mechanism is as yet unknown [10].

It is low in calories, so the substitution of higher calorie fruits may be one of the ways to improve weight loss.

A study (RCT) of 85 obese adults showed that consuming grapefruit (whole or juiced) before each meal, suppressed appetite by causing a feeling of fullness. This mechanism is termed ‘to preload’ (with low-calorie food) before meals [11, 12].

Three small trials, both cohort and double-blind, together with studying 185 people, show modest weight loss with grapefruit [1, 10, 13].

Nootkatone, found in grapefruit, activates AMPK in mice. AMPK increases energy metabolism and promotes weight loss [14].

One study suggests that consuming grapefruit daily for 6 weeks does not significantly decrease body weight, fats, or blood pressure as compared with controls. However, improvements in blood pressure and fats suggest that grapefruit should be further studied for obesity and heart disease prevention [1].

Grapefruit diets are not based on proper science and can be considered to be ‘fad’ at present [11, 15].

2) Grapefruit May Help Control Diabetes

Recent clinical studies indicate that grapefruit juice improves insulin resistance and reduces weight gain [16].

One study of 91 obese people shows that after 12 weeks of supplementation both grapefruit juice and grapefruit improved insulin sensitivity [R].

Rat studies suggest that grapefruit decreases high blood sugar levels [17, 18, 19].

In mice, grapefruit juice decreased blood sugar, similar to metformin [20].

In diabetic rats, grapefruit juice increased the activity of the enzyme glucokinase, which transformed glucose into glycogen in the liver and caused blood sugar levels to decrease [21].

The antidiabetic effects of grapefruit may be due to a blocking effect of flavonoids on liver enzymes such as AMPK, known as the ‘master energy sensor’ [22].

Another possible mechanism for whole or pulped grapefruit reducing fasting blood sugar is due to its fiber content. Increasing consumption of dietary fiber can reduce fasting glucose [23].

Naringin, a grapefruit flavonoid, didn’t decrease blood sugar in rats but reduced the effects of ketoacidosis and oxidative stress. Thus, naringin supplements could alleviate the complications of diabetes [18, 10].

However, a meta-analysis of 12 RCTs showed that grapefruit juice may have no overall effect on fasting glucose and insulin concentrations [24].

Note: Grapefruit may interact negatively with metformin. One study showed that grapefruit juice increases metformin-induced lactic acidosis in rats by increasing metformin uptake by liver cells [25].

3) Grapefruit Improves Immunity

Vitamin C, beta-carotene, lycopene, and the flavonoids (narirutin, naringin, hesperidin, neohesperidin, didymin, and poncirin) present in grapefruit all help boost the immune system [26].

Grapefruit can boost the immune system due to its high vitamin C content. Vitamin C stimulates the immune system and is also anti-inflammatory, antiviral, and antibacterial [27].

4) Grapefruit Helps Fight Infections

Grapefruit components (naringin and hesperidin) have antibacterial and antifungal properties [28].

In a study of 4 adults with urinary tract infections, grapefruit seed extract was as effective as the antibiotic drugs usually given [29].

A wide range of microbes is sensitive to grapefruit seed extract and grapefruit pulp. The seed extract contains naringin, hesperidin, and polyphenols, which are antiseptic [30, 28, 31, 28].

Grapefruit seed extracts (oils) may be used to treat antibiotic-resistant UTIs.

Studies showed the potential of essential oils and their vapors as antibacterial agents and to treat methicillin-resistant Staphylococcus aureus (MRSA) infection [32].

5) Grapefruit May Reduce the Risk of Heart Disease

Grapefruit May Prevent Blood Clots

The flavonoids hesperidin and naringin, and other compounds in grapefruit can prevent blocked arteries, relax tension in blood vessel walls, and reduce the formation of blood clots [25].

The action of nootkatone inhibits platelet clumping. This reduced the risk of clots in rats [33].

However, one double-blind study of 10 people showed that grapefruit juice taken for 7 to 10 days didn’t change their blood clotting test results [34].

Grapefruit May Lower Blood Pressure

Consumption of half of a small grapefruit 3 times daily for 6 weeks is associated with a moderate drop in systolic blood pressure with no influence on diastolic blood pressure or heart rate [35, 11].

The polyphenol flavonoids present in grapefruit increase nitric oxide (NO) in the blood. NO widens blood vessels reducing blood pressure[36, 1, 37].

Grapefruit Decreases Bad and Increases Good Cholesterol

A study of 74 overweight adults showed that grapefruit lowered LDL-cholesterol, which, when high, may cause obesity and heart disease [1].

A double-blind study of 27 people showed that grapefruit pectin decreased cholesterol levels in people at risk of heart disease [38].

In another study of 57 adults with high cholesterol, grapefruit lowered total and LDL-cholesterol, particularly the triglycerides, which are implicated in hardening of the arteries. Red grapefruit proved to be more effective than white [39].

A study of 85 obese adults showed an increase in good cholesterol (HDL) in groups taking grapefruit or grapefruit juice before meals [12].

Grapefruit May Prevent Hardening of the Arteries

Grapefruit stops plaques build up. Plaque formation leads to hardening of the arteries (atherosclerotic plaque formation) [3, 40, 41].

Naringin decreases a protein (apolipoprotein). Increased levels of apolipoprotein increase the risk of hardening of the arteries, which can lead to heart problems [42, 43].

However, naringin may induce arrhythmia and block the effect of antiarrhythmic drugs [22].

6) Grapefruit May Protect Against Cancer

  • The antioxidant properties of grapefruit may be beneficial in reducing the risk of cancer by improving the immune system and reducing cancer cell growth [44].
  • Limonoids in grapefruit inhibit the growth of colon, lung, mouth, stomach, and breast cancer in animal and cell studies [45, 46, 47].
  • Lycopene, a powerful antioxidant found in grapefruit, protects against prostate cancer. Lycopene was not associated with a reduced risk of advanced prostate cancer. Pink and red grapefruit are rich in lycopene, which reduces the risk of cancer and slows tumor growth [48, 49].
    Animal and cell studies show that lycopene also protects against the negative effects of radiotherapy [49].
  • The flavonoids hesperetin and naringenin inhibit breast cancer cell formation and growth [50, 51].
    Naringenin helps repair DNA in prostate cancer cells in humans [48, 52, 53].
    Naringenin assists with repair of DNA damage caused by chemotherapy [54, 55].
  • Another flavonoid, kaempferol, inhibited pancreatic cancer and lung cancer in laboratory cell lines and caused cell death in ovarian cancer [56, 56].
    Bergamottin and kaempferol cause cell death in some cancer cells [57, 56].
  • Apigenin protected against lung and colon cancer by slowing cancer cell growth [58].

7) Grapefruit Is Anti-Inflammatory

Grapefruit decreased inflammation in obese rats with increased production of inflammatory markers [59].

Quercetin, found in grapefruit, had an anti-inflammatory effect in mice with allergic asthma [60].

8) Grapefruit and Parkinson’s

Grapefruit may be effective in the treatment of Parkinson’s disease. In mice, naringin causes dopamine-releasing nerve cells to produce GDNF, which improves Parkinson’s disease [61].

In mammal cells affected by nervous system diseases (e.g. Parkinson’s), naringin decreased a specific protein (EGFP-polyQ97) from clumping. This protein can initiate cell death (apoptosis) [62].

9) Grapefruit and Depression

Hesperidin, present in grapefruit, has antidepressant-like properties in mice. The mechanism involves nerve endings that release and are stimulated by serotonin (serotonergic) at the 5-HT1A receptors [63].

10) Grapefruit and Skin Aging

The high concentrations of antioxidants and vitamin C may be beneficial to aging skin [64].

11) Grapefruit and Stroke

A prospective study of 69,622 women showed that those taking higher levels of flavonoids (from sources including grapefruit) had a lower risk of ischemic stroke [65].

12) Grapefruit and Kidneys

A small study of 7 patients showed that drinks containing grapefruit juice increased urinary flow and increased urinary excretion of citrate. Grapefruit juice drinks could be used as a natural alternative to potassium citrate in the management of kidney disease (nephrolithiasis) [66].

14) Grapefruit and Wound Healing

Grapefruit contains about 72 mg of vitamin C, which helps form healthy scar tissue and new blood vessels. This promotes rapid wound and post-surgery healing [67].

15) Grapefruit for Energy

Mice studies show that nootkatone, found in grapefruit, activates AMPK. This significantly increases energy metabolism, prevents obesity caused by diet, and increases endurance [14].

16) Grapefruit and Cortisol

Grapefruit juice increases the effect of cortisone when taken soon after. People with Addison’s disease may benefit from supplementing with grapefruit juice [68].

17) Grapefruit and Digestion

Grapefruit’s high-fiber content improves digestion, bulky stools, and reduces constipation and flatulence [8].

Grapefruit Supplements

Other than consuming the whole fruit or juice, you can purchase grapefruit and grapefruit seed extracts in a wide range of commercially available products: tablets, capsules, powders, oils, creams, and syrups.

If taking the liquid concentrate, 10 drops in a cup of water is a typical dose, to be taken 3 times a day.

In tablet form, 100 to 200 mg 1 to 3 times a day should be sufficient.

Creams and oils are used topically to treat acne, tighten skin, help diminish dark circles around the eyes, moisturize, reduce scars, restore collagen, and fight aging. These uses reflect the high levels of antioxidants in grapefruit, particularly vitamin C, which is known to benefit aging skin [69, 70]

Risks and Side Effects

Grapefruit compounds are not toxic as such, only when taken in conjunction with any of a large number of popular medications (this is the so-called “grapefruit effect”) [71].

More than 50% of drugs that interact with grapefruit are used to treat heart conditions [25, 3, 72].

Side effects may include flushing (from the widening of veins), fast heart rate, or low blood pressure [25].

Melanoma (Skin Cancer)

Two 25-year prospective studies of large groups of adults showed that grapefruit consumption may be associated with an increased risk of malignant melanoma (skin cancer). Citrus products are high in psoralen, which absorbs ultraviolet light. Animal studies and long-term use of the drugs in people have shown it may increase the risk of melanoma [73].

User Reviews

Users are generally positive about grapefruit’s effects
on appetite;
“The grapefruit essential oil was exactly as I was hoping it would be. I definitely feel like it helps curb my appetite.”

and energy whilst losing weight;
“I lost 6 pounds in 1 week when taking grapefruit juice daily before meals, and it was easy. The diet gave me a lot of energy.”

One user stated that, “… grapefruit pectin seems to have gotten rid of the thumping heartbeat when I lie down at night. It is supposed to keep arteries clear & I feel that it is doing its job in a very short period of time.”

There are also positive reports on its effectiveness against infections;

“I was diagnosed with Entamoeba histolytica – an amoeba. One small study online suggesting GSE could kill this. I took 6 drops 2 or 3 times a day for 10 days or so and I also did 2 enemas in that time with 30 drops in a quart of warm water. I was re-tested and was clear of the amoeba”.

“Got rid of non-eczema skin problem that has been intractable for over 30 years.!”

“I used Grapefruit Seed Extract to treat thrush in my mouth. I followed the directions on the bottle, diluting 10 drops in water. Within 3 days my tongue was cleaner than ever!.”

Buy Grapefruit Supplements

About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.

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