21 Things You Should Know About Grapefruit 

Grapefruit can seem like an acquired taste. Their bulbous size; bitter pith (the white stuff that surrounds the fruit); and tart taste can be off-putting to those who are more accustomed to their sweeter citrus cousins, like the orange. But consider adding this superfood to your regular rotation of healthy foods. It's among the 20 best foods to eat for breakfast. And you don't have to limit your intake to the early morning hours: Grapefruit are supremely portable and make a great snack (with very few calories) that fills you up while also relieving thirst due to its high water content.

But be a smart snacker: Grapefruit can inhibit an enzyme in the intestines called CYP3A4, (although some other fruits may do the same, grapefruit is the most documented) which plays a key role in breaking down certain medications in the body. The fruit, particularly the juice, has been shown to result in extra-high, even potentially dangerous levels of certain drugs in the body when consumed at the same time.

Read on to find to get more grapefruit nutrition facts, including the benefits and risks of this tangy superfruit.

Grapefruit is 92% water, giving it one of the highest water contents of any fruit. That makes it good for overall health. (It's one of our 15 foods that help you stay hydrated.)

"All of our body systems and process . . . require water," says Wesley Delbridge, RD, located in Phoenix, Arizona. "Proper hydration makes your body more efficient in everything you're doing."

About 20% of your daily fluid intake actually comes from food. So add some grapefruit to get closer to your daily H2O goal and choose the heavier of two fruits of equal size: It has more juice.

Several studies have shown that people who eat half a fresh grapefruit or drink grapefruit juice before each meal lose more weight than people who do not.

Not all studies have shown the same weight-loss benefit and scientists don't know if the effect seen in the studies was specifically due to grapefruit—or filling up on a low-calorie food in general—but fruits and vegetables should always be part of your strategy to lose or maintain weight.

What is 100% ironclad fact: Grapefruit delivers a lot of nutrition and water for very few calories. It's one of our 30 foods under 40 calories (39 calories in one half!) and 30 summer snacks under 100 calories (yes, we're fans). So it's a great choice if you want to boost your intake of high nutrient, low calorie foods.

When you peel away the outer layer of a grapefruit, you may be tempted to pick off the white flesh that is between you and the juicy fruit, and throw it away. This stuff is called pith. Don't do it.

"That [pith] is very rich in antioxidants and nutrients and also soluble fiber which is going to help you feel fuller and impact your glucose reactions," says Delbridge.

While the pith of grapefruit can have more of a bitter taste than say, oranges, it's worth eating along with the fruit (if you can). Fiber is a good thing, and can help lower blood sugar, cholesterol, and possibly even colon cancer risk.

A grapefruit a day may help lower "bad" LDL cholesterol levels by as much as 15.5%, according to a 2006 study in the Journal of Agricultural and Food Chemistry. In the study, researchers looked at 57 patients ages 39 to 72 who had high cholesterol and had undergone bypass surgery for heart trouble. For one month, some ate a grapefruit daily (either red or white) while others, the control group, did not. Grapefruit eaters, particularly those eating red, had a drop in bad cholesterol, while the control group did not.

This is great news for your heart. LDL cholesterol is a type of fat that can build up in your arteries and raise the risk for heart attack and stroke. But if you are taking a cholesterol-lowering drug, don't add a grapefruit for extra effect—the FDA issued a warning in 2012 about interactions with such medications.

That's because of the hefty dose of vitamins A and C in each serving. "Vitamin C and A are huge as far as immune boosting," says Delbridge.

Some research indicates that not having enough vitamin C (and other micronutrients) may actually hurt your immune system, especially if you're elderly.

Grapefruit may not prevent a cold but the vitamins inside may reduce your suffering or possibly the duration of a cold.

"There's nothing else you can do for a cold so why not?" says Ann Marie Chiasson, MD, assistant director of the Fellowship in Integrative Medicine at the University of Arizona College of Medicine in Tucson.

There's another reason grapefruit can be good for your heart: It reduces levels of triglycerides. Triglycerides are another type of fat—like "bad" LDL cholesterol—which can quickly clog up your arteries.

The same study that found that adding one grapefruit a day lowered cholesterol levels also found that this simple daily regimen lowered triglycerides—by as much as 27%. This was in patients who already had coronary artery disease and so were at high risk for heart attacks and other complications.

Red grapefruit, in particular, surpassed its "blond" cousins in lowering triglycerides.

"Grapefruit has got some data that it decreases systolic blood pressure, not by a lot—it's usually about five points—but there's definitely good data," says Chiasson.

For the 70 million Americans who have hypertension, any drop in blood pressure is a good drop.

The effect on blood pressure may be due to grapefruit's high potassium levels. Potassium neutralizes the negative effects of sodium. (Here are 15 foods that are high in potassium.)

But again, don't eat grapefruit if you are already taking a blood-pressure lowering drug. Certain ones, such as Procardia and Adalat CC (both are from the generic nifedipine), can be dangerous when combined with grapefruit, according to the FDA.

All the grapefruit colors are packed with goodness, vitamins, and nutrients but the red and pink ones come with a little extra.

"They have a higher antioxidant level, specifically beta carotene," says Delbridge. "They also have lycopene, another antioxidant."

Lycopene is one of a group of carotenoids or pigments that gives hued grapefruit (and other fruits and vegetables) their color. Eating diets rich in carotenoids may lower the risk of heart disease and some cancers.

Antioxidants in general may play a key role in preventing cancer.

Grapefruits contain natural chemicals called furanocoumarin, which affect how your liver metabolizes certain drugs.

The presence of these compounds means that if you consume grapefruit and certain allergy medications, such as Claritin (loratadine) or Allegra (fexofenadine), you could end up with higher-than-recommended levels of the drugs in your blood stream.

"That can mean poisoning," says Ally Dering-Anderson, Pharm.D., clinical assistant professor of pharmacy at the University of Nebraska College of Pharmacy in Omaha.

Avoid grapefruit or its juice when taking these meds, or talk to your pharmacist about possible substitutes. Benadryl may be one, although it can make you sleepy.

Grapefruit also has a low glycemic index (GI), around 25, which means it doesn't raise blood sugar as quickly or as much as high-GI foods like white bagel (72) or even a banana (48) or watermelon (72). (The highest GI score is 100.)

A 2006 study published in the Journal of Medicinal Food, found that people who ate grapefruit (juice or half a fruit) before a meal had a lower spike in insulin two hours later than those taking a placebo, and fresh grapefruit was associated with less insulin resistance. All 91 patients in the 12-week study were obese, but they did not necessarily have type 2 diabetes.

While the results are promising in those without diabetes, blood-sugar reactions to food can vary widely, so if you have been diagnosed with type 2 diabetes, test your blood sugar after eating grapefruit to make sure it can be part of your healthy eating plan.

Grapefruit juice has plenty of benefits, but the traditional fruit itself is going to give you more bang for your buck when it comes to nutrition and health benefits.

"When you take juice, you're getting some of the nutrients but you're losing all the fiber," says Delbridge. "Grapefruit juice is great but at the end of the day, the entire fruit has pectin and rind and all the parts of it."

Grapefruit juice can also spike your blood sugar more than the fruit itself. If you opt for juice of any kind, Delbridge recommends not drinking more than 6 ounces a day and going only for 100% juice products that don't have added sugar.

Vitamin C helps form healthy scar tissue and new blood vessels, both of which help return your body to a healthy state. A grapefruit contains about 72 mg of vitamin C, which is 120% of the daily value.

"Vitamin C speeds up wound healing post surgically," says Chiasson. "I tell people to take 500 milligrams of vitamin C before they go into surgery."

Always ask your doctor before adding vitamins, minerals, or any herbal supplements to your daily regimen, especially if you're about to have surgery. In this case, that goes for grapefruit too, given its ability to affect the metabolism of certain drugs.

A large study conducted in Japan found that people who ate citrus (including grapefruit) throughout the week had a lower risk of developing cancer, especially prostate and pancreatic, compared with the total group of participants.

The effect was amplified among those who also drank a lot green tea.

The authors speculate that compounds in citrus fruits reduce inflammation and stop cancer cells from multiplying. They may also help repair damaged DNA, which contributes to the development of tumors.

The fiber in grapefruit may also help prevent colorectal cancer while fruits high in vitamin C and beta-carotene, which is in pink and red grapefruit, may lower the risk of esophageal cancer.

Grapefruit can be stored in your fridge for as long as three weeks but they release their best flavor when kept at room temperature. If you plan to eat them within a week, leave them on a counter or table.

There's an added advantage to keeping them in plain view.

"The increased visibility helps you remind yourself that you need to eat them," says Delbridge. "Studies show that when you put fruits and vegetables out in a bowl or common area of the house, you will eat more."

If you don't think you will eat the grapefruit for 2 or 3 weeks, tuck them in the fridge but make sure they're at room temperature before you actually dig in. This will give you maximum flavor.

Grapefruit also interacts with erectile dysfunction drugs. All of them. Such drugs include Viagra (sildenafil), Cialis (tadalafil), and Levitra (vardenafil).

These drugs, known as the phosphodiesterase inhibitors, already feature a warning about possible prolonged erections, a painful, serious, and potentially damaging side effect known as priapism. Grapefruit could make that worse and it could also cause headaches, flushing, and low blood pressure. One whole grapefruit or a 6- to 7-ounce glass of juice is enough for drug toxicity, according to a 2013 study.

"With grapefruit, you increase the chance of having an emergency visit," says Dering-Anderson. "My advice is, don't take grapefruit."

Grapefruit is most often associated with breakfast, but don't let that limit your imagination.

Grapefruit is also super in salads and with fish or chicken. In fact, it's best when paired with protein and a little fat, like a handful of walnuts.

"If it's paired with proteins and fats, it will delay your gastric emptying so you'll feel full longer," says Delbridge. The fiber, too, keeps you feeling fuller longer.

We suggest trying this Kale, Grapefruit, and Hazlenut Salad, Grapefruit & Avocado Salad with Seared Salmon, or Honey Grapefruit with Banana.

But you can keep it simple too, using grapefruit in a smoothie or drink. Try this Grapefruit Pomegranate Smoothie or Immune Booster drink.

There's more to add to the list of possible drug interactions. Grapefruit also causes cholesterol-lowering statin drugs to build up in your blood stream. Common statin drugs are Lipitor (atorvastatin) and Zocor (simvastatin).

Other dangerous grapefruit combinations you should be aware of: the painkilling, narcotic-based, fentanyl patch, and HIV/AIDS drugs (such as Invirase).

And the anti-anxiety drug Xanax (alprazolam) is a big one. "Alprazolam is one that just jumps off the page," says Dering-Anderson.

Ask your pharmacist if there's a problem and if there's a safe alternative if you would like to be able to consume grapefruit.

If you have a canker sore or cold sore—or if you've had recent dental work—the acid in grapefruit or grapefruit juice can boost your pain level.

"Grapefruit is really acidic and it really does burn," says Dering-Anderson. Citrus fruit can be one of the worst foods for your teeth, and can erode tooth enamel over time. But reducing the risk to your oral health could be as simple as rinsing the mouth with water, then brush and floss as you normally do.

Good dental hygiene such as brushing your teeth after meals and flossing once a day may also help prevent mouth sores.

One-half of one grapefruit contains 28% of your daily value of vitamin A (based on a 2000-calorie daily intake), or far more than the 4% in oranges, says Delbridge. This first vitamin in the alphabet is good for your eyes, not to mention your heart, lungs, kidneys and other organs.

What's more, you also get 64% of your vitamin C, 8% of your fiber, a bit of calcium (3%) and iron (1%), and you start to understand why it's called a superfood. (For more comparisons, read "12 Foods That Have More Vitamin C Than an Orange.") Why eat a half a grapefruit when you can eat a whole one?

If you find the fruit itself to be too tart, try a grapefruit-flavored beverage: There are a bevy of products—including grapefruit-flavored beer—that might be more palatable to you.

Because citrus pairs well with beer, there are plenty of orange and lemon flavored beers, but grapefruit is the a newer flavor in the brewing world: A few examples include Pink Fuzz, Grapefruit Shandy, and Turtle Power Grapefruit Pale Ale.

Citrus scents are becoming more popular in aromatherapy for a reason. "Citrus is really amazing for increased energy and vitality," says Chiasson. "It will wake people up."

Not all aromatherapy is inhaled. You can also rub an essential oil on your skin, which allows you to feel it and inhale it at the same time. Grapefruit aromatherapy may even act as a natural skin toner, says Chiasson.

While the options are endless, these are some popular grapefruit-themed products: NEST Fragrances Classic Candle in Grapefruit ($42), Aura Cacia Grapefruit Essential Oil ($9), and Kiehl's Grapefruit Bath and Body Wash ($20).