Overview

Grapefruit is a natural cross of sweet orange and pomelo. It originated in the 18th century in Barbados. It is popular for its flavour, high nutrients, bioactive compounds, and health benefits. Grapefruits of different flesh and peel colours are available from natural or induced mutations. It includes nutrients like vitamin C, carbs, potassium, magnesium, calcium, phosphorus, fibre, organic acids, fatty acids, and amino acids.^1,2

They also have secondary metabolites like flavonoids (narirutin, naringin, hesperidin, neohesperidin, didimin, poncerin), ascorbic and citric acid, furanocoumarins (bergamottin, epoxy bergamottin, 6',7'-dihydroxybergamottin), phenolic compounds, carotenoids (lycopene and β-carotene).³

Studies have shown the antioxidant properties, inhibition of hypolipidemic activity, tumour growth, oxidative stress, and atherosclerosis from grapefruits.² Despite these health benefits, consuming grapefruits still raises concerns due to their interaction with medications. Furanocoumarins, present in grapefruit juice, interact with a number of prescription medications in the human body and cause adverse side effects.¹

Pros of grapefruit juice cleanse

Nutritional Profile of a 123 g (4.34 oz) grapefruit with pink or red flesh. 

As seen in the above table, grapefruit is rich in various essential nutrients. This article will further discuss how these nutrients and secondary metabolites present in grapefruits provide health benefits. 

Vitamin C: Citrus fruits, which also include grapefruits, are known for their high vitamin C content. The human body cannot make its own vitamin C, and it should be obtained through food to fulfil the requirement. It works as an antioxidant and protects cells against the damaging effects of free radicals that can play a role in causing cancer. It prevents cardiovascular diseases. It also helps in immunological function. Our body produces collagen which forms the skin, ligaments, tendons and blood vessels. Collagen cannot be made if vitamin C is not available. This also helps in the wound healing process.⁴

Fibre: Grapefruits contain low calories and high fibre. Research studies show that increased intake of fibre has several health benefits, including improved glycemic status, lower risk of type 2 diabetes, improved lipid profiles, improved insulin sensitivity, weight loss, decreased abdominal fat, decreased cardiovascular risk, improved gut health, and prevention of colorectal cancer.⁵

Potassium: Grapefruits are rich in potassium, which improves heart health and prevents heart diseases. The Food and Drugs Administration (FDA) has acknowledged the health claim that consuming a potassium and low sodium diet lowers the risk of high blood pressure by increasing vasodilation and urine sodium excretion. Overall, eating higher levels of potassium may not only benefit against high blood pressure but also help to prevent other kinds of heart diseases. Moreover, as indicated by observational research, increasing dietary potassium intake is associated with improvement in bone health and blood glucose levels.⁶

Grapefruits also have other nutrients like calcium, magnesium, zinc, phosphorus, iron, and folate, which are a part of different physiological functions and have their own health benefits. 

Role of secondary metabolites (phytochemicals)

Flavonoids are present in the grapefruit peels in high amounts. They are used for their anticancer, antibacterial, antiviral, antiangiogenic, antimalarial, antioxidant, neuroprotective, anti-diabetic, antitumor, and anti-proliferative properties. They have antioxidants that help our body in the natural immune protection from the toxins we contact on an everyday basis.

They inhibit cell growth and act as anticancer drugs. They help to prevent neurodegenerative disorders like dementia, Parkinson's disease, Alzheimer's disease, and age-related cognitive disorders. Several studies have shown that people who have high amounts of flavonoids in their diet have an 18% lower risk of suffering from cardiovascular conditions.⁷

Carotenoids, namely lycopene and beta carotene, are present in grapefruit. Lycopene is an effective antioxidant that protects from heart disease, cancer, and macular degeneration, reduces oxidative stress, and improves bone health.¹ Meanwhile, beta carotene provides antioxidant and anti-inflammatory benefits and helps with vision.

Furanocoumarins are one of the many secondary metabolites in grapefruit, which provide antioxidative, anti-inflammatory, and bone health-promoting properties.

Cons of grapefruit juice cleanse

Studies have already shown that grapefruit juice has the potential to interact with many prescription medications in such a way that it causes an increase in the drug’s bioavailability. This can, eventually, cause toxicity or adverse effects in human beings. These drug interactions are caused by furanocoumarins, present in grapefruit, that stop the action of CYP3A4 enzyme and P-glycoprotein transporter in our body.

CYP3A4 is one of the many intestinal enzymes in our body that metabolises (breaks down) some medications. When the action of the CYP3A4 enzyme is blocked, the drug metabolism stops, which leads to an increase in the plasma concentration of the medication and may result in adverse reactions. On the other hand, an efflux pump known as P-glycoprotein found in the small intestine among the liver, kidney, and blood-brain barrier can reduce the effect of medicine by decreasing medicine absorption in the intestines. When the P-glycoprotein action is blocked, it fails to lower the bioavailability, leading to increased plasma concentration.⁸ The amount of enzymes that break down the drugs may differ for every individual. Therefore, grapefruit juice may affect people differently. 

Grapefruit juice can interact with over 85 different medications; 43 of these medications have interactions that have the potential to cause severe adverse side effects. From 2008 to 2012, the number of medications with the ability to interact with grapefruit and have severe damaging effects (torsade de pointes, rhabdomyolysis, myelotoxicity, respiration despair, gastrointestinal bleeding, nephrotoxicity) have significantly increased from 17 to 43, representing an average annual increase of 6 tablets.¹⁰ Below is the list of some common medications known to interact with furanocoumarins when taken with grapefruit juice and their respective adverse effects.

The prevalence of vulnerability is not known, but as per studies older people are more likely to consume grapefruit and medications, making them more prone to adverse reactions.¹⁰

Consultation with healthcare professionals

As grapefruit juice is already known to interact with certain medications, which can reduce its effectiveness and cause side effects, it is highly recommended that you consult a healthcare professional if you are taking any medication and drinking grapefruit juice. They will review your medication history and the current medications you are taking. They will help identify interactions and make recommendations accordingly, ensuring medications are taken safely and effectively. It is also the person’s responsibility to notify a doctor if they are drinking grape juice.

FAQs

What is grapefruit juice good for?

Grapefruit is a good source of vitamin C, potassium, calcium, folate, fibre, magnesium, zinc, flavonoids, carotenoids, furanocoumarin, etc. These compounds help prevent acute and chronic diseases and assist in bodily functions required for the human body to function properly. Not only do they provide health benefits, but also compensate for most of the Recommended Dietary Allowance (RDA) of essential nutrients.

Does grapefruit burn belly fat?

There is no evidence for the role of grape juice in burning belly fat. However, it is the most suitable food for weight loss due to its low-calorie content and high-fibre content. Eating more fibre will not only help you lose weight but also reduce belly fat and reduce your risk of cardiovascular diseases, type 2 diabetes and colorectal cancer.

Is grapefruit juice safe?

While grapefruit has many health benefits, it can cause serious side effects due to interactions with certain drugs. The prevalence of these interactions is seen in people taking statins, anti-cancer drugs, immunosuppressants, antipsychotics, calcium channel blockers, beta-blockers, antihistamines, urinary tract substances, etc., with grapefruit juice in their diet, so it is important to talk to your doctor if you are drinking grapefruit juice and taking any medication to prevent side effects.

Summary

Grapefruit juice is very popular among the general public due to its positive effects on health. Nutrients and secondary metabolites have anti-inflammatory, antiviral, antibacterial, antiangiogenic, anti-malarial, and neuroprotective benefits. It reduces the risk of cancer and heart disease and helps with gut and bone health.

However, the nature of drug interactions with furanocoumarins raises concerns about possible adverse effects from drinking grape juice. To date, grape-drug interactions have been identified in 85 drugs, 43 of which have serious side effects. It is very important that these people stay informed about these interactions and discuss them with a healthcare professional to prevent side effects.