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Grapefruit

The grapefruit is a citrus fruit. The fruit itself, the oil from the peel and extracts of the seeds are used as medicine. Grapefruit seed extract is made from grapefruit seeds and pulp, which is a by-product of grapefruit juice production. Vegetable glycerine is added to the final product to reduce the acidity and bitter taste. Grapefruit juice is used to treat high cholesterol levels, arteriosclerosis, cancer and psoriasis, as well as to support weight loss.

Grapefruit seed extract is taken orally for bacterial, viral and fungal infections, including yeast infections.

Grapefruit oil is applied to the skin for muscle fatigue, acne and oily skin, as well as to promote hair growth and to tone the skin. It is also used for colds and flu.

Grapefruit seed extract is applied to the skin as a skin cleanser and as a remedy for mild skin irritations and is used as a vaginal douche for vaginal yeast infections. It is also used as an ear or nasal rinse to prevent and treat infections, as a gargle for sore throats and as a mud rinse to prevent gingivitis, promote healthy gums and freshen breath. Some people inhale grapefruit vapors for headaches, stress and depression and to help the body retain water. Grapefruit seed extract vapors are also inhaled to treat lung infections. In food and beverages, grapefruit is used as a fruit, in the form of juice and as a flavoring component. In industrial production, grapefruit oil and grapefruit seed extract are used as an odor component in soap and cosmetics and as a household cleaner.

In agriculture, grapefruit seed extract is used to kill bacteria and fungi, to combat mold, to kill parasites in animal feed, as a preservative and to disinfect water. The interactions of grapefruit juice with medications are well documented. The chemistry of grapefruit varies depending on the species, growing conditions and extraction method used to produce juice. Before adding grapefruit to your diet or using it as a natural medicine, you should consult your doctor if you are taking medication.

How does grapefruit work?

Grapefruit is a source of vitamin C, fiber, potassium, pectin and other nutrients. Some components may have antioxidant properties that could help protect cells from damage or lower cholesterol levels. It is not known exactly how grapefruit oil might work in medicinal applications.

How effective is grapefruit?

There is not enough scientific data to make a statement about the effectiveness of grapefruit in the following applications:

  • Asthma: There is evidence that consumption of citrus fruits rich in vitamin C, including grapefruit, may improve lung function in asthmatics. These benefits have been observed in some studies, but not in others.
  • Eczema (atopic dermatitis): New research suggests that citrus fruit seed extract may reduce constipation, bloating and stomach discomfort in people suffering from atopic dermatitis, possibly due to changes in gut bacteria.

There is also not enough scientific data on the effectiveness of grapefruit for atherosclerosis, high cholesterol levels, psoriasis, muscle fatigue, headaches, stress, depression, infections, and yeast infections, as well as its use to prevent cancer, aid weight loss, promote hair growth, tone the skin, and reduce acne and oily skin.

Further scientific research is needed to evaluate the effectiveness of grapefruit in these applications.

Safety and side effects

Grapefruit is safe and harmless in the quantities in which it is normally consumed as a food and also appears to be safe and harmless when used appropriately for medicinal purposes.

However, if you are taking medication, you should consult your doctor before including grapefruit in your diet or using it as a medicine. Grapefruit interacts with a long list of medications.

Precautions and warnings

Pregnancy and lactation: Not enough is known about the use of grapefruit during pregnancy and lactation. For this reason, pregnant and breastfeeding women are advised to avoid grapefruit.

Breast cancer: There are concerns about the safety of consuming excessive amounts of grapefruit juice. Some research suggests that postmenopausal women who drink more than one liter of grapefruit juice per day have a 25 to 30% higher risk of breast cancer. Grapefruit juice reduces the breakdown of oestrogen in the body and could therefore increase oestrogen levels. Further research is needed to confirm these findings. Until more is known on this topic, women should avoid excessive amounts of grapefruit juice, especially women who have breast cancer or are at increased risk of developing breast cancer.

Interactions

Grapefruit products should not be used in combination with the following medications:

Artemether

The body breaks down artemether in order to excrete it. Grapefruit juice can reduce the rate at which the body breaks down artemether. Drinking grapefruit juice in combination with artemether can increase the effects and side effects of artemether. For this reason, you should not drink grapefruit juice when taking artemether.

Buspirone

Grapefruit juice may increase the amount of buspirone absorbed by the body. Drinking grapefruit juice in combination with buspirone could increase the effects and side effects of buspirone.

Carbamazepine

Grapefruit juice may increase the amount of carbamazepine absorbed by the body. The consumption of grapefruit juice in combination with carbamazepine could increase the effects and side effects of carbamazepine.

Carvedilol

The body breaks down carvedilol in order to excrete it. Grapefruit juice can reduce the rate at which the body breaks down carvedilol. The consumption of grapefruit juice in combination with carvedilol may increase the effects and side effects of carvedilol.

Cisapride

The body breaks down cisapride in order to excrete it. Grapefruit juice can reduce the rate at which the body breaks down cisapride. The consumption of grapefruit juice in combination with cisapride can increase the effects and side effects of cisapride.

Clomipramine

The body breaks down clomipramine in order to be able to excrete it. Grapefruit juice can reduce the rate at which the body breaks down clomipramine. The consumption of grapefruit juice in combination with clomipramine can increase the effects and side effects of clomipramine.

Cyclosporine

Grapefruit juice may increase the amount of cyclosporine absorbed by the body. The consumption of grapefruit juice in combination with cyclosporine could increase the effects and side effects of cyclosporine.

Dextromethorphan

The body breaks down dextromethorphan in order to be able to excrete it. Grapefruit juice can reduce the rate at which the body breaks down dextromethorphan. Consuming grapefruit juice in combination with dextromethorphan may increase the effects and side effects of dextromethorphan.

Oestrogens

The body breaks down oestrogens in order to be able to excrete them. Grapefruit juice can reduce the rate at which the body breaks down oestrogens. Consuming grapefruit juice in combination with taking estrogens could increase estrogen levels in the body and increase the risk of estrogen-related side effects such as breast cancer.

Etoposide

Grapefruit juice may reduce the amount of etoposide absorbed by the body. Consuming grapefruit juice in combination with etoposide could reduce the effectiveness of etoposide.

Itraconazole

Itraconazole is used to treat fungal infections. Grapefruit juice could reduce the amount of itraconazole absorbed by the body. The consumption of grapefruit juice in combination with etoposide could reduce the effectiveness of etoposide. For this reason, you should not drink grapefruit juice when taking itraconazole.

Drugs that are broken down by the liver (cytochrome P450 3A4 (CYP3A4) substrates)

Some drugs are broken down by the liver. Grapefruit juice can affect the rate at which the liver breaks down certain drugs. Consuming grapefruit juice in conjunction with medications that are broken down by the liver may increase the side effects of some medications. For this reason, you should consult your doctor before drinking grapefruit juice if you are taking medication that is broken down by the liver.

Blood pressure medication

Grapefruit juice may increase the amount of high blood pressure medication absorbed by the body. Drinking grapefruit juice in combination with high blood pressure medication could result in an excessive drop in blood pressure.

Medication to lower cholesterol levels (statins)

The body breaks down some drugs used to lower high cholesterol levels in order to be able to excrete them. Grapefruit juice can reduce the rate at which the body breaks down these drugs. Drinking grapefruit juice in combination with high cholesterol medications may increase the effects and side effects of these medications.

However, grapefruit juice does not appear to influence the effect of pravastatin.

Methylprednisolone

The body breaks down methylprednisolone in order to excrete it. Grapefruit juice can reduce the rate at which the body breaks down methylprednisolone. The consumption of grapefruit juice in combination with methylprednisolone can increase the effects and side effects of methylprednisolone.

Praziquantel

The body breaks down praziquantel in order to excrete it. Grapefruit juice can reduce the rate at which the body breaks down praziquantel. The consumption of grapefruit juice in combination with praziquantel can increase the effects and side effects of praziquantel.

Quinidine

The body breaks down quinidine in order to be able to excrete it. Grapefruit juice can reduce the rate at which the body breaks down quinidine. The consumption of grapefruit juice in combination with quinidine may increase the effects and side effects of quinidine.

Scopolamine

The body breaks down scopolamine in order to be able to excrete it. Grapefruit juice can reduce the rate at which the body breaks down scopolamine. The consumption of grapefruit juice in combination with scopolamine can increase the effects and side effects of scopolamine.

Sedatives (benzodiazepines)

Sedatives can cause drowsiness and dizziness. The body breaks down sedatives in order to be able to excrete them. Grapefruit juice can reduce the rate at which the body breaks down sedatives. The consumption of grapefruit juice in combination with sedatives can increase the effects and side effects of sedatives.

Sildenafil (Viagra)

The body breaks down sildenafil in order to be able to excrete it. Grapefruit juice can reduce the rate at which the body breaks down sildenafil. The consumption of grapefruit juice in combination with sildenafil can increase the effects and side effects of sildenafil.

Terfenadine

Grapefruit juice may increase the amount of terfenadine absorbed by the body. The consumption of grapefruit juice in combination with terfenadine could increase the effects and side effects of terfenadine.

Care should be taken when combining grapefruit products with the following medications:

Caffeine

The body breaks down caffeine in order to be able to excrete it. Grapefruit juice can reduce the rate at which the body breaks down caffeine. Drinking grapefruit juice in combination with caffeine could increase the side effects of caffeine, including restlessness, headaches and rapid heartbeat.

Erythromycin

The body breaks down erythromycin in order to excrete it. Grapefruit juice can reduce the rate at which the body breaks down erythromycin. The consumption of grapefruit juice in combination with erythromycin may increase the effects and side effects of erythromycin.

Fexofenadine

Grapefruit juice may reduce the amount of fexofenadine absorbed by the body. The consumption of grapefruit juice in combination with fexofenadine could reduce the effectiveness of fexofenadine.

Losartan

The liver activates losartan to make it effective. Grapefruit juice may reduce the rate at which the liver activates losartan. Consuming grapefruit juice in combination with losartan could reduce the effectiveness of losartan.

Drugs that are broken down by the liver (cytochrome P450 1A2 (CYP1A2 substrates)

Some drugs are broken down by the liver. Grapefruit juice can affect the rate at which the liver breaks down certain drugs. Consuming grapefruit juice in conjunction with medications that are broken down by the liver may increase the side effects of some medications. For this reason, you should consult your doctor before drinking grapefruit juice if you are taking medication that is broken down by the liver.

Drugs that are broken down by the liver (cytochrome P450 2C19 (CYP2C19 substrates)

Some drugs are broken down by the liver. Grapefruit juice can affect the rate at which the liver breaks down certain drugs. The consumption of grapefruit juice in combination with medications that are broken down by the liver can increase the side effects of some medications. For this reason, you should consult your doctor before consuming grapefruit juice if you are taking medication that is broken down by the liver.

Drugs that are broken down by the liver (cytochrome P450 2C9 (CYP2C9 substrates)

Some drugs are broken down by the liver. Grapefruit juice can affect the rate at which the liver breaks down certain drugs. Consuming grapefruit juice in combination with medications that are broken down by the liver can increase the side effects of some medications. For this reason, you should consult your doctor before consuming grapefruit juice if you are taking medication that is broken down by the liver.

Saquinavir

Grapefruit juice could increase the amount of saquinavir absorbed by the body. Drinking grapefruit juice in combination with saquinavir could increase the effects and side effects of saquinavir.

Theophylline

The consumption of grapefruit juice could reduce the effects of theophylline. There is not enough information to assess whether this is a major cause for concern.

Warfarin

Warfarin is used to slow down blood clotting. Consuming grapefruit juice could increase the effects of warfarin and increase the risk of bruising and bleeding. For this reason, the blood should be checked regularly. It is possible that the warfarin dose may need to be adjusted.

Dosage

An appropriate dosage of grapefruit depends on various factors such as age, state of health and others. At the present time, there is insufficient scientific data to make a statement about appropriate dosage ranges for grapefruit. For this reason, you should follow the dosage instructions on the label and/or consult a doctor or pharmacist before use.

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