Grapefruit 101: A Complete Guide

Next to the orange, grapefruit is one of the most popular citrus fruits in the United States. Known for its combination of bitterness and slight sweetness, this large citrus fruit is versatile in salads, fruit medleys, and other recipes. Perhaps more important is its nutritional profile, which includes antioxidants, which may play a role in fending off chronic disease.

Get the lowdown on grapefruit in this complete guide, which has information on its nutrition facts, health benefits, side effects, and more.

Whether you eat grapefruit for breakfast or turn to it for a refreshing snack, this bittersweet citrus fruit is a staple in many American households. It belongs to the Rutaceae family, known for edible fruit and aromatic leaves, according to Encyclopaedia Britannica. The grapefruit goes by the scientific name Citrus paradisi, per Purdue University.

Grapefruit, like other citrus fruits, grows on trees. They tend to flourish in more tropical climates and when planted in sandy soil. The trees have dark green leaves and can grow up to 20 feet tall. The fruit they yield looks nothing like a grape: It has a yellow or blush rind with pulp that may be yellow, a very light pink, or a darker, deeper red. Each cluster on the tree produces 12 to 20 grapefruits at a time, Purdue notes.

Grapefruit trees are now grown in many parts of the United States, but the modern grapefruit we know today may have evolved from a hybrid that originated in Jamaica. It was originally popularized in the West Indies before making its way to the United States, per Purdue. It’s thought that the first U.S. commercial grapefruit was grown in Florida after enjoying a brief period as a novelty plant. Today, it can be found in other subtropical warm climates, including Texas, Arizona, and California.

More people began consuming grapefruit the 1970s largely because of its status as a “diet food.” As a result, grapefruit grew exponentially in popularity across the country. According to Purdue, some reports found that grapefruit was the fourth most popular fruit or vegetable among metropolitan New Yorkers in the 1980s.

The pulp of the grapefruit varies in color from yellow to pink and red, Encyclopaedia Britannica notes. Generally, the darker the pulp, the more antioxidants the grapefruit contains.

According to Purdue, there are at least 10 known varieties of grapefruit, including:

• Ruby Red
• Redblush
• Sweetie
• Triumph
• Duncan
• Thompson
• Foster
• Paradise Navel
• Marsh
• Oroblanco

Grapefruit is also a popular fruit for juicing because it’s high in water, per Encyclopaedia Britannica. Grapefruit juice may be a more convenient way to obtain some of the nutrients from the fruit without having to deal with the rind and pulp. Be aware, though, that some types of commercialized grapefruit juice may contain added sugars. And keep in mind that if you're drinking the juice, you're not getting the beneficial fiber of the whole fruit.

Per the U.S. Department of Agriculture, a 1 cup serving of whole pink and red grapefruit sections with juice contains:

• Calories: 69
• Total fat: 0.2 grams (g)
• Carbohydrates: 17 g
• Dietary fiber: 2.5 g
• Protein: 1.3 g
• Calcium: 34.5 mg
• Iron: 0.3 mg
• Magnesium: 18.4 mg
• Phosphorus: 20.7 mg
• Potassium: 292 mg
• Zinc: 0.2 mg
• Vitamin C: 85.1 mg (an excellent source)

Nutritionally speaking, grapefruit is popular because of its vitamin C content, and is on the list of healthy fruits recommended by the U.S. Department of Agriculture (USDA) MyPlate guidelines. Ounce for ounce, it ranks third behind oranges and lemons among the highest fruit sources of vitamin C. Like other fruits, this large citrus fruit also provides some dietary fiber.

Like many fruits and veggies, grapefruit is also rich in water, with 211 g per cup, the USDA notes.

Like other citrus fruits, such as oranges and tangerines, grapefruit is an excellent source of vitamin C. As the National Institutes of Health notes, this water-soluble nutrient is important for:

• Effective protein metabolism
• Wound healing
• Collagen maintenance to reduce signs of premature aging
• Nerve communication and muscle movement
• Promoting heart health

In considering these basic body functions, the NIH recommends most adults get between 75 and 90 mg of vitamin C per day. Pregnant and breastfeeding women need even more than nonpregnant women, but not more than 90 mg. Because vitamin C is water soluble, any excess C in the body is removed in the urine, and this can occur after just one grapefruit.

Adequate vitamin C is also important to help prevent long-term health issues. Research has shown vitamin C plays a role in fending off chronic diseases, including certain types of cancer, cataracts, and heart disease. It may also help support your immune system and reduce the likelihood of a cold, per the NIH.

The high antioxidant content of grapefruit has made it a popular ingredient in beauty products. Research suggests antioxidants help your skin by reducing free radical damage that can lead to premature aging, which shows up on the skin as wrinkles, sagging, or dullness.

Grapefruit is also used in the farming industry, primarily for pigs and cattle. Some people also use the wood from grapefruit trees for firewood, furniture, and flooring, per Purdue.

As far as other health claims around grapefruit go, some people use grapefruit seed extracts and essential oils with the hope of treating medical ailments. For example, grapefruit flower extract is sometimes used for insomnia, while grapefruit leaf essential oils are used for antibiotic benefits, notes Purdue. But research backing these claims is limited. Also, essential oils are stronger and more processed than extracts. Health experts generally don’t recommend ingesting essential oils, Poison Control notes.

During the 1970s, the “grapefruit diet” began making headlines in the United States and gained a reputation as a good way to lose weight. While health experts widely regard it as an ineffective type of fasting diet, people who have tried this eating approach use it for the purpose of losing 10 pounds or more in a short amount of time, according to Purdue. On the grapefruit diet, you consume large quantities of grapefruit and grapefruit juices in an effort to burn more fat, the Cleveland Clinic notes.

But like most other fad diets that focus on a low calorie intake, the grapefruit diet hasn't been proven to be safe or effective. While grapefruit is a healthy food choice, eating too much of any one food — even fresh fruits — won’t provide your body with the variety of nutrients it needs. Too much grapefruit can also cause gastrointestinal reactions, such as diarrhea or nausea, due to its high vitamin C content, per the NIH.

While grapefruit consumption alone won’t help you burn more fat, research does show that including grapefruit in your diet can help you shed excess pounds. For example, researchers behind one small randomized controlled trial found that participants with obesity who ate half a fresh grapefruit before each meal for 12 weeks lost an average of 1.6 kilograms (kg), or about 3.5 pounds (lb), compared with a control group who lost 0.3 kg, which is less than 1 lb.

According to one theory, this may be thanks to an ingredient in grapefruit called nootkatone. Results from a past study noted that nootkatone stimulated energy metabolism in a mouse model. Metabolism is the group of processes by which the body uses energy or burns calories; the faster your metabolism, the more calories you’ll burn both during rest and while exercising, per Harvard Health Publishing. These findings show the potential weight loss effect of grapefruit, and how this fruit can complement a healthy diet. (Keep in mind, though, that this is just a theory, and further research is needed to determine exactly how grapefruit may lead to weight loss.)

Also, a 1 cup serving of red or pink grapefruit with juice has 2.5 g of fiber, making it a good source of the nutrient, notes the aforementioned USDA data. Fiber-rich, low-calorie foods like grapefruit and other fruits can help promote weight loss efforts by keeping you feeling full longer, compared with empty-calorie foods like sodas and cookies, which can leave you hungry, according to the Mayo Clinic.

Not all grapefruits are equal. Here’s how to pick and maintain the freshest fruit.

Selection

Select fully ripe, heavy grapefruit that’s free of bruises and cuts. A yellow (or pinkish) rind indicates that your grapefruit is fully ripe, according to Encyclopaedia Britannica.

Storage

You can keep the fruit at room temperature for up to a week. Refrigeration can help extend the life by an additional week or two, per Purdue.

Grapefruit is a typical breakfast food; the fruit is cut in half and the pulp is eaten with a spoon, according to Purdue. Some people sprinkle sugar on top to balance the sourness, but this addition can reduce the health factor of your fruit. If you must sweeten your grapefruit, try no-calorie stevia instead of sugar. Grapefruit is also sometimes used to make jellies, marmalades, and syrups, Purdue notes.

If you’re tired of your normal grapefruit routine, or are looking for other ways to incorporate it into your diet, try topping your salad or tacos with grapefruit slices, incorporating grapefruit into a fruit salsa, your favorite smoothie, or as an ingredient in a mocktail. The opportunities for cooking with grapefruit are limited only by your imagination!

While grapefruit itself isn’t a risky food, it may pose health risks in certain circumstances, for example if you’re eating too much of it.

• Tissue damage Vitamin C, a key nutrient in grapefruit, isn’t typically toxic in large amounts. But exceeding the recommended intake on a daily basis for a long period of time may be associated with tissue damage, according to the NIH. As mentioned, high levels of vitamin C can lead to diarrhea, nausea, cramps, and other minor gut health issues.
• Tooth damage This is another possible side effect of eating too much grapefruit or drinking grapefruit juice. The acid in citrus fruits may damage your enamel. To help protect your teeth, the American Dental Association (ADA) recommends rinsing your mouth with water immediately after consuming acidic foods like citrus fruits. The ADA suggests you wait an hour after eating acidic foods before you brush your teeth, because your saliva has a protective effect.
• Medication interactions Grapefruit, grapefruit juice, and related oils and extracts sometimes interact with certain medications. Grapefruit has a natural ability to block an enzyme called CYP3A4, which is important to the absorption of medications. When you drink grapefruit juice with your medication, for example, the medication won’t work as it ought to, according to the U.S. Food and Drug Administration (FDA).

Here are some of the grapefruit and drug interactions of concern you might wish to discuss with your doctor, per the FDA:

• Anticoagulants/blood thinners (including warfarin)
• Antihistamines
• Anxiety medications
• Cholesterol-lowering statins
• Heart rhythm drugs
• High blood pressure medications
• Organ transplant drugs
• Some corticosteroids

Talk to your doctor if you take any medications or supplements, or if you have any related underlying health conditions, before you consume grapefruit or grapefruit juice. It’s also possible for grapefruit to interact with birth control: While it doesn’t make birth control less effective, it can increase your risk of side effects like nausea and breast tenderness, according to Drugs.com.

Is It Possible to Be Allergic to Grapefruit?

Yes, and a grapefruit allergy is more likely to happen in someone who has an allergy to pollen, trees, or grass, research suggests.

According to the Cleveland Clinic, this type of allergy can be considered oral allergy syndrome, and symptoms include swelling in and around the mouth. Some less common symptoms are nausea, vomiting, and skin rashes.

Avoiding grapefruit is one way to keep symptoms at bay; but you might consider allergy shots, the Cleveland Clinic notes.

Grapefruit is a popular fruit in the United States that has a sterling nutritional profile with some fiber and lots of vitamin C, a nutrient that may help support immunity and play a role in preventing various chronic diseases. Grapefruit is a generally healthy food, but it is not a magic bullet for any one result, such as weight loss, despite the so-called grapefruit diet having been en vogue for a period. People on certain medications should be mindful about grapefruit consumption, because the fruit can interact with some prescription drugs. If grapefruit is safe for you to consume, cut it in half and scoop out the flesh to enjoy the possible health perks, or try it as a refreshing addition to a variety of recipes, from smoothies to salads.

Additional reporting by Laura McArdle.