Grapefruit is a popular citrus fruit that is a terrific source of vitamins, fiber and other nutrients. Grapefruit is known for its antioxidant- and immunity-boosting capabilities as well as its digestive and cholesterol-lowering benefits.
Grapefruit provides vitamins A and C, folate (B9), fiber, choline, limonins and lycopene, according to Alissa Rumsey, a New York City-based registered dietitian, certified strength and conditioning specialist and spokesperson for the Academy of Nutrition and Dietetics.
"Grapefruit has been hailed as a popular diet food for many years because it is widely believed to boost weight loss," said Rumsey. "While a grapefruit diet is far too extreme, the fruit can be added to one's diet for a healthy weight loss plan."
Grapefruit gets its name from the way it grows. Grapefruits grow on tree branches in grape-like clusters, according to the Library of Congress.
Grapefruit is an accidental hybrid between the orange and the pomelo, but no one is sure when it was first grown. It was first documented in 1750 by a Welshman in Barbados who described it as a "forbidden fruit," according to the Purdue University horticulture department. Until the 19th century, it was also called the shaddock, named after a sea captain who is said to have brought the seeds of a pomelo to Jamaica. It has also been called paradise fruit. It was given the scientific name, Citrus paradisi, but in the 1940s when research confirmed that it was hybrid, the name was changed to Citrus x paradisi — the x indicates that it is a hybrid.
Grapefruit grows in warm climates; Florida and southern areas of China are the world's top producers. There are several varieties of grapefruit, including white, ruby red and pink, which have varying levels of sourness and sweetness. "Try topping it with savory seasonings, like cilantro or chili powder, to offset the tangy flavor," Rumsey suggested. She noted that grapefruits go well with seafood dishes, too.
Here are the nutrition facts for grapefruit, according to the U.S. Food and Drug Administration, which regulates food labeling through the National Labeling and Education Act:
According to the George Mateljan Foundation's World’s Healthiest Foods website, half a medium-size grapefruit provides 59 percent of your daily vitamin C needs.
"Vitamin C is plays a role in immunity and helps neutralize free radicals in our body," said Rumsey. According to the Linus Pauling Institute at Oregon State University, vitamin C stimulates the production of white blood cells and may protect the integrity of immune cells. Vitamin C helps also protect leukocytes, which produces antiviral substances.
Vitamin C is linked to a reduced risk of cardiovascular disease, said Rumsey. A 2015 study published in The American Journal of Clinical Nutrition looked at more than 100,000 people and found that those who ate the most fruits and vegetables had a 15 percent lower risk of developing heart disease. Those with the highest vitamin C levels in their plasma had even more reduced rates of heart disease.
According to University of Wisconsin Health, citric acid, which is found in grapefruit, may deter stone formation and also break up small stones that are forming. The more citric acid in your urine, the more protected you may be from forming new kidney stones. A study published in theBritish Journal of Nutrition found that women who drank one-half to one liter of grapefruit, orange or apple juice each day saw their urinary pH value and citric acid excretion increase, which significantly lowered their risk of forming kidney stones.
According to Rumsey, vitamin C and beta-carotene may lead to a reduced risk of esophageal cancer. A study published in the Journal of Chemotherapy found that vitamin C supplementation exerted a chemotherapy-like effect on esophageal cancer cells. The researchers suggested that vitamin C might improve the efficacy of chemotherapy.
According to the Physician’s Committee for Responsible Medicine, red and pink grapefruit is one of the best sources for lycopene after tomatoes."Lycopene has been linked to a decreased risk of prostate cancer," said Rumsey. A large-scale study of nearly 50,000 men published in the Journal of the National Cancer Institute found an inverse relationship between lycopene (in this study, the lycopene was from tomatoes) and prostate cancer risk. Men with the highest levels of lycopene were 21 percent less likely to develop prostate cancer than those with the lowest lycopene levels.
The lycopene in grapefruits may also contribute to reducing risk of stomach cancer, according to a review in the Journal of Cancer Prevention. Researchers looked primarily at participants who smoked, suffered from chronic inflammation or had elevated levels of stomach bacteria Helicobacter pylori, though they noted that poor diet and family history could also be risk factors lessened by lycopene.
Animal studies have suggested that grapefruit may have a reduction effect on colon cancer cells. A study published in the journal Carcinogensis found that grapefruit increased the death of cancer cells in rats whose colons had been injected with carcinogens.
"There are numerous studies being conducted to understand the role folate plays in cancer reduction," Rumsey said. A 2007 article in the American Journal of Clinical Nutrition noted that folate's possible cancer-reducing properties are likely linked to its role in the production of substances that silence cancer DNA.
Limonins have also been linked to a decrease in cancer risk, said Rumsey. A 2012 article in the Journal of Nurtigenetics and Nutrigenomics looked at limonins in breast cancer cells and found that they could be a helpful aid to chemotherapy.
"Folate is essential for pregnant women in order to prevent neural tube defects," said Rumsey. While folate is present in prenatal vitamins, consuming it through whole foods is an excellent way to make sure the body absorbs it.
An article in the Journal of Agricultural and Food Chemistry evaluated the phenolic compounds in 13 fruit juices. Grapefruit juice ranked among the best juices. Phenolic compounds act as antioxidants, which are molecules that safely interact with free radicals to stop the condition of oxidative stress, according to an article in Pharmacognosy Review. Free radicals cause cell damage and disruption that can contribute to diseases. Vitamin C is also a potent antioxidant.
"Grapefruit is 91 percent water, so can help with hydration," said Rumsey.
The fiber and water in grapefruit can aid digestion and help relieve or prevent constipation, according to the Mayo Clinic.
"Grapefruit is naturally high in fiber, which contributes to feelings of satiation which can prevent overeating," said Rumsey. "Fiber also helps stabilize blood sugar levels, preventing spikes that contribute to hunger."
A study published in the Journal of Medicinal Food looked at 91 obese patients who took either grapefruit capsules, grapefruit juice, half of a fresh grapefruit or placebo capsules. All grapefruit-taking patients lost more weight than the placebo group, with those eating fresh grapefruit losing the most and those drinking grapefruit juice losing nearly as much. The grapefruit groups also saw improved insulin resistance and metabolic syndrome.
"Grapefruit contains pectin, a fiber that is can reduce LDL cholesterol levels and decrease triglycerides," said Rumsey. A study published in the Journal of Agricultural and Food Chemistry looked at 57 hyperlipidemic patients after coronary bypass surgery and found that supplementing their diets with either white or red grapefruit every day for 30 days lowered LDL cholesterol levels. Eating red grapefruit lowered LDL cholesterol levels more, and also lowered triglycerides.
Skin, hair and wound healing
According to a study published in the British Journal of Community Nursing, vitamin C is essential throughout the wound-healing process, largely because it contributes toward collagen synthesis and development. Collagen is also essential for healthy skin and hair. Furthermore, vitamin A is known to promote healthy tissue growth, including in skin, and the high water content in cantaloupes helps keep skin moisturized and supple.
Vitamin A, of which grapefruit is a good source, is essential for good vision. Through a complicated process in the eye, vitamin A (also called retinol) triggers an electrical signal in the optic nerve, causing the perception of colors and vision in dim light, according to the Linus Pauling Institute at Oregon State University. Vitamin A (acquired through phytonutrient beta-carotene, also found in grapefruit) is associated with a reduced risk of macular degeneration.
Risks of eating grapefruit
Some drugs become more potent when combined with grapefruit juice. These drugs include the immunosuppressent cyclosporine (Restasis, Neoral, Sandimmune), calcium-channel blockers (Norvasc, Cardizem, Procardia and others), the antihistamine terfenadine (Seldane), the antiviral agent saquinavir (Invirase) and the hormone estradiol, according to World's Healthiest Foods.
People taking statins may want to avoid grapefruit. Grapefruit causes a higher amount of statins to enter the circulatory system than would normally. This causes a build up of statins that can be dangerous and lead to a rare, serious disease called rhabdomyolysis.
Individuals taking pharmaceutical drugs, particularly statins, should consult a doctor before eating grapefruit.
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Jessie Szalay is a contributing writer to FSR Magazine. Prior to writing for Live Science, she was an editor at Living Social. She holds an MFA in nonfiction writing from George Mason University and a bachelor's degree in sociology from Kenyon College.