Energy value (calories per serving): Low
Saturated fat: Low Cholesterol: None Carbohydrates: High Fiber: Moderate Sodium: Low
Major vitamin contribution: Vitamin A, vitamin C
Major mineral contribution: Potassium
About the Nutrients in This Food
Grapefruit and ugli fruit (a cross between the grapefruit and the tangerine) have moderate amounts of dietary fiber and, like all citrus fruits, are most prized for their vitamin C. Pink or red grapefruits have moderate amounts of vitamin A.
One-half medium (four-inch diameter) pink grapefruit has 1.4 g dietary fiber, 1,187 IU vitamin A (51 percent of the R DA for a woman, 40 percent of the R DA for a man), and 44 mg vitamin C (59 percent of the R DA for a woman, 49 percent of the R DA for a man). One half medium (3.75-inch diameter) white grapefruit has 1.3 g dietary fiber, 39 IU vitamin A (2 percent of the R DA for a woman, 1 percent of the R DA for a man), and 39 mg vitamin C (52 percent of the R DA for a woman, 43 percent of the R DA for a man).
Pink and red grapefruits also contain lycopene, a red carotenoid (plant pigment), a strong antioxidant that appears to lower the risk of cancer of the prostate. The richest source of lycopene is cooked tom atoes.
The Most Nutritious Way to Serve This Food
Fresh fruit or fresh-squeezed juice.
Buying This Food
Look for: Firm fruit that is heavy for its size, which means that it will be juicy. The skin should be thin, smooth, and fine-grained. Most grapefruit have yellow skin that, depending on the variety, may be tinged with red or green. In fact, a slight greenish tint may mean that the grapefruit is high in sugar. Ugli fruit, which looks like misshapen, splotched grapefruit, is yellow with green patches and bumpy skin.
Avoid: Grapefruit or ugli fruit with puff y skin or those that feel light for their size; the flesh inside is probably dry and juiceless.
Storing This Food
Store grapefruit either at room temperature (for a few days) or in the refrigerator.
Refrigerate grapefruit juice in a tightly closed glass bottle with very little air space at the top. As you use up the juice, transfer it to a smaller bottle, again with very little air space at the top. The aim is to prevent the juice from coming into contact with oxygen, which destroys vitamin C. (Most plastic juice bottles are oxygen-permeable.) Properly stored and protected from oxygen, fresh grapefruit juice can hold its vitamin C for several weeks.
Preparing This Food
Grapefruit are most flavorful at room temperature, which liberates the aromatic molecules that give them their characteristic scent and taste.
Before cutting into the grapefruit, rinse it under cool running water to flush debris off the peel.
To section grapefruit, cut a slice from the top, then cut off the peel in strips—starting at the top and going down—or peel it in a spiral fashion. You can remove the bitter white membrane, but some of the vitamin C will go with it. Finally, slice the sections apart. Or you can simply cut the grapefruit in half and scoop out the sections with a curved, serrated grapefruit knife.
What Happens When You Cook This Food
Broiling a half grapefruit or poaching grapefruit sections reduces the fruit’s supply of vitamin C, which is heat-sensitive.
How Other Kinds of Processing Affect This Food
Commercially prepared juices. How well a commercially prepared juice retains its vitamin C depends on how it is prepared, stored, and packaged. Commercial flash-freezing preserves as much as 95 percent of the vitamin C in fresh grapefruit juices. Canned juice stored in the refrigerator may lose only 2 percent of its vitamin C in three months. Prepared, pasteurized “fresh” juices lose vitamin C because they are sold in plastic bottles or waxed-paper cartons that let oxygen in.
Commercially prepared juices are pasteurized to stop the natural enzyme action that would otherwise turn sugars to alcohols. Pasteurization also protects juices from potentially harmful bacterial and mold contamination. Following several deaths attributed to unpas- teurized apple juices containing E. coli O157:H7, the FDA ruled that all fruit and vegetable juices must carry a warning label telling you whether the juice has been pasteurized. Around the year 2000, all juices must be processed to remove or inactivate harmful bacteria.
Medical Uses and/or Benefits
Antiscorbutic. All citrus fruits are superb sources of vitamin C, the vitamin that prevents or cures scurvy, the vitamin C-deficiency disease.
Increased absorption of supplemental or dietary iron. If you eat foods rich in vitamin C along with iron supplements or foods rich in iron, the vitamin C will enhance your body’s ability to absorb the iron.
Wound healing. Your body needs vitamin C in order to convert the amino acid proline into hydroxyproline, an essential ingredient in collagen, the protein needed to form skin, ten- dons, and bones. As a result people with scurvy do not heal quickly, a condition that can be remedied with vitamin C, which cures the scurvy and speeds healing. Whether taking extra vitamin C speeds healing in healthy people remains to be proved.
Possible inhibition of virus that causes chronic hepatitis C infection. In Januar y 2008, research- ers at Massachusetts General Hospital Center for Engineering in Medicine (Boston) published a report in the medical journal Hepatology detailing the effect of naringenin, a compound in grapefruit, on the behavior of hepatitis viruses in liver cells. In laborator y studies, naringenin appeared to inhibit the ability of the virus to multiply and/or pass out from the liver cells. To date, there are no studies detailing the effect of naringenin in human beings with hepatitis C.
Adverse Effects Associated with This Food
Contact dermatitis. The essential oils in the peel of citrus fruits may cause skin irritation in sensitive people.
Aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen, naproxen and others. Taking aspirin or NSAIDs with acidic foods such as grapefruit may intensif y the drug’s ability to irritate your stomach and cause gastric bleeding.
Antihistamines, anticoagulants, benzodiazepines (tranquilizers or sleep medications), calcium channel blockers (blood pressure medication), cyclosporine (immunosuppressant drug used in organ transplants), theophylline (asthma drug). Drinking grapefruit juice with a wide variety of drugs ranging from antihistamines to blood pressure medication appears to reduce the amount of the drug your body metabolizes and eliminates. The “grapefruit effect” was first identified among people taking the antihypertensive drugs felodipine (Plendil) and nifedip- ine (Adalat, Procardia). It is not yet known for certain exactly what the active substance in the juice is. One possibility, however, is bergamottin, a naturally occurring chemical in grapefruit juice known to inactivate cytochrome P450 3A4, a digestive enzyme needed to convert many drugs to water-soluble substances you can flush out of your body. Without an effective supply of cytochrome P450 3A4, the amount of a drug circulating in your body may rise to dangerous levels. Reported side effects include lower blood pressure, increased heart rate, headache, flushing, and lightheadedness.
Some Drugs Known to Interact with Grapefruit Juice*
Drug Class Generic (Brand name) Antianxiety drug Diazepam ( Valium) Antiarrhythmics Amiodarone (Cordarone) Blood-pressure drugs Felodipine (Plendil), nicardipine (Cardene), nimodipine (Nimotop), nisoldipine (Sular), verapamil ( Verelan) Cholesterol-lowering drugs Atorvastatin (Lipitor), lovastatin (Mevacor), simvastatin (Zocor), simvastatin/ezetimibe ( Vytorin) Immune Suppressants Cyclosporine (Neoral), tacrolimus (Prograf ) Impotence Drug Sildenafil ( Viagra) Pain Medication Methadone (Dolophine, Methadose)
* This list may grow as new research appears.