The George Mateljan Foundation
Grapefruit
Tart and tangy with an underlying sweetness, grapefruit has a juiciness that rivals that of the ever popular orange and sparkles with many of the same health promoting benefits. Although available throughout the year, they are in season and at their best from winter through early spring.
Grapefruits usually range in diameter from four to six inches and include both seed and seedless and pink and white varieties. The wonderful flavor of a grapefruit is like paradise as is expressed by its Latin name, Citrus paradisi.
Rich in the Nutritional Powerhouse Vitamin C
Grapefruit is an excellent source of vitamin C, a vitamin that helps to support the immune system. Vitamin C-rich foods like grapefruit may help reduce cold symptoms or severity of cold symptoms; over 20 scientific studies have suggested that vitamin C is a cold-fighter. Vitamin C also prevents the free radical damage that triggers the inflammatory cascade, and is therefore also associated with reduced severity of inflammatory conditions, such as asthma, osteoarthritis, and rheumatoid arthritis. As free radicals can oxidize cholesterol and lead to plaques that may rupture causing heart attacks or stroke, vitamin C is beneficial to promoting cardiovascular health. Owing to the multitude of vitamin C's health benefits, it is not surprising that research has shown that consumption of vegetables and fruits high in this nutrient is associated with a reduced risk of death from all causes including heart disease, stroke and cancer.Enjoy Benefits from the Antioxidant Lycopene
The rich pink and red colors of grapefruit are due to lycopene, a carotenoid phytonutrient. Lycopene appears to have anti-tumor activity. Among the common dietary carotenoids, lycopene has the highest capacity to help fight oxygen free radicals, which are compounds that can damage cells.Limonoids Promote Optimal Health
Phytonutrients in grapefruit called limonoids inhibit tumor formation by promoting the formation of glutathione-S-transferase, a detoxifying enzyme. This enzyme sparks a reaction in the liver that helps to make toxic compounds more water soluble for excretion from the body. Pulp of citrus fruits like grapefruit contain glucarates, compounds that may help prevent breast cancer.
In animal studies and laboratory tests with human cells, limonoids have been shown to help fight cancers of the mouth, skin, lung, breast, stomach and colon. Now, scientists from the US Agricultural Research Service (ARS) have shown that our bodies can readily absorb and utilize a very long-acting limonoid called limonin that is present is citrus fruits in about the same amount as vitamin C.
In citrus fruits, limonin is present in the form of limonin glucoside, in which limonin is attached to a sugar (glucose) molecule. Our bodies easily digest this compound, cleaving off the sugar and releasing limonin.
In the ARS study, 16 volunteers were given a dose of limonin glucoside in amounts ranging from those that would be found in from 1 to 7 glasses of orange juice. Blood tests showed that limonin was present in the plasma of all except one of the subjects, with concentrations highest within 6 hours after consumption. Traces of limonin were still present in 5 of the volunteers 24 hours after consumption!
Limonin's bioavailability and persistence may help explain why citrus limonoids are potent anti-carcinogens that may prevent cancerous cells from proliferating. Other natural anti-carcinogens are available for much less time; for example, the phenols in green tea and chocolate remain active in the body for just 4 to 6 hours. The ARS team is now investigating the potential cholesterol-lowering effects of limonin. Lab tests indicate that human liver cells produce less apo B when exposed to limonin. Apo B is a structural protein that is part of the LDL cholesterol molecule and is needed for LDL production, transport and binding, so higher levels of apo B translate to higher levels of LDL cholesterol.
Grapefruit Lowers Cholesterol
Grapefruit contains pectin, a form of soluble fiber that has been shown in animal studies to slow down the progression of atherosclerosis. In one study, animals fed a high-cholesterol diet plus grapefruit pectin had 24% narrowing of their arteries, while animals fed the high-cholesterol diet without grapefruit pectin had 45% narrowing.
Both blond and red grapefruit can reduce blood levels of LDL ("bad") cholesterol, and red grapefruit lowers triglycerides as well, shows a study published in the Journal of Agricultural and Food Chemistry.
Israeli researchers from the Hebrew University in Jerusalem first tested the antioxidant potential of blond and red grapefruits and then their cholesterol-lowering potential in humans. The test tube research showed that red grapefruit contains more bioactive compounds and total polyphenols than blond, but both grapefruits are comparable in their content of fiber, phenolic and ascorbic acids, and the flavonoid, naringinen, although red grapefruit contains slightly more flavonoids and anthocyanins.
In this recent study, participants added either red grapefruit, blond grapefruit or no grapefruit to their daily diet. The results indicated that both types of grapefruit appeared to lower LDL cholesterol in just 30 days: total cholesterol by 15.5% in those eating red grapefruit and 7.6% in those eating blond grapefruit; LDL cholesterol by 20.3% and 10.7% respectively; and triglycerides by 17.2% and 5.6% respectively. No changes were seen in the control group (those that didn't eat any grapefruit).
Both red and blond grapefruits both positively influenced cholesterol levels, but red grapefruit was more than twice as effective, especially in lowering triglycerides. In addition, both grapefruits significantly improved blood levels of protective antioxidants. Red grapefruit's better performance may be due to an as yet unknown antioxidant compound or the synergistic effects of its phytonutrients, including lycopene.
In response to this rapid and very positive outcome, the researchers concluded that adding fresh red grapefruit to the diet could be beneficial for persons with high cholesterol, especially those who also have high triglycerides. One caveat, however: Compounds in grapefruit are known to increase circulating levels of several prescription drugs including statins. For this reason, the risk of muscle toxicity associated with statins may increase when grapefruit is consumed. (See our Safety section for more information.)
Prevent Kidney Stones
Want to reduce your risk of calcium oxalate kidney stones? Drink grapefruit juice. A study published in the British Journal of Nutrition found that when women drank ½ to 1 liter of grapefruit, apple or orange juice daily, their urinary pH value and citric acid excretion increased, significantly dropping their risk of forming calcium oxalate stones.Promotes Optimal Health
Not only are grapefruit rich in vitamin C, but new research presented at the 228th National Meeting of the American Chemical Society provides two more reasons to drink grapefruit juice: protection against lung and colon cancer.
In humans, drinking three 6-ounce glasses of grapefruit juice a day was shown to reduce the activity of an enzyme that activates cancer-causing chemicals found in tobacco smoke. In rats whose colons were injected with carcinogens, grapefruit and its isolated active compounds (apigenin, hesperidin, limonin, naringin, naringenin, nobiletin) not only increased the suicide (apoptosis) of cancer cells, but also the production of normal colon cells. Researchers also confirmed that grapefruit may help prevent weight gain by lowering insulin levels.
Grapefruit Boosts Liver Enzymes that Clear Out Carcinogens
Grapefruit juice significantly increases the production and activity of liver detoxification enzymes responsible for preparing toxic compounds for elimination from the body.
The liver clears out toxins, including carcinogens, using a two step process called Phase I and Phase II detoxification. In the first part of this process, Phase I, enzymes belonging to the cytochrome P450 family, work on the toxin to make it more attractive to enzymes involved in the second part of the process, Phase II. Unfortunately, the action of Phase I enzymes often renders the toxin not only more attractive to Phase II enzymes, but even more dangerous, and some foods contain compounds that only increase the activity of Phase I without also turning up Phase II.
Grapefruit increases the activity not only of the Phase I enzyme CYP1A1, but also that of NAD(P)H:quinone reductase 1, a Phase II detoxification enzyme that protects cells against oxidative stress and toxic quinones. The end result: grapefruit works in both Phase I and Phase II to enhance the liver's ability to remove cancer-causing toxins.
Grapefruit's Naringenin Repairs DNA
Naringenin, a flavonoid concentrated in grapefruit, helps repair damaged DNA in human prostate cancer cells (cell line LNCaP), reports a lab study published in the Journal of Nutritional Biochemistry.
The risk of prostate cancer, the most commonly diagnosed cancer in men in the U.S, increases with age since the older we become, the more times our cells have divided and the greater the chance for DNA mutations to occur. DNA repair is one of the body's primary defense mechanisms against the development of cancer since it removes potentially cancer-causing mutations in cells.
Naringenin helps restore health to damaged DNA by inducing two enzymes that repair DNA during the replication stage. These enzymes, 8-oxoguanine-DNA glycosylase 1 (hOGG1), and DNA polymerase beta (DNA poly beta), are both involved in the DNA base excision repair (BER) pathway.
The scientists in this study exposed cell cultures to 80 micromoles per liter, an amount we cannot achieve by consuming grapefruit since research indicates that only between 2 and 15% flavonoids in the food we consume are absorbed in the GI tract, and plasma concentrations after eating flavonoid-rich foods range from 0.5 to 1 micromole per liter.
Fortunately, however, the researchers also demonstrated that the concentration of naringenin inside the cells that was needed for its beneficial effects was only 5% of the amount in the medium, and this amount is physiologically achievable in our tissues. Unlike many other cancers, prostate cancer is slow growing initially and often remains undetectable for a long time. Enjoying grapefruit regularly may be one way to prevent its progression by promoting the repair of damaged DNA in prostate cells, thus preventing them from becoming cancerous.
The grapefruit is a large citrus fruit related to the orange, lemon and pomelo. Grapefruits are categorized as white (blond), pink or ruby. However, this terminology doesn't reflect their skin color, which is either yellow or pinkish-yellow, but rather describes the color of their flesh.
Grapefruits usually range in diameter from four to six inches, with some varieties featuring seeds while others are seedless. The wonderful flavor of a grapefruit is like paradise, just as its Latin name Citrus paradisi connotes. It is juicy, tart and tangy with an underlying sweetness that weaves throughout.
Grapefruits have a rather recent history, having been discovered in Barbados in the 18th century. Many botanists think the grapefruit was actually the result of a natural cross breeding which occurred between the orange and the pomelo, a citrus fruit that was brought from Indonesia to Barbados in the 17th century.
The resulting fruit was given the name "grapefruit" in 1814 in Jamaica, a name which reflects the way it's arranged when it grows-hanging in clusters just like grapes.
Grapefruit trees were planted in Florida in the early 19th century, although they did not become a viable commercial crop until later that century. Florida is still a major producer of grapefruits, as is California, Arizona and Texas. Other countries that produce grapefruits commercially include Israel, South Africa and Brazil.
A good grapefruit doesn't have to be perfect in color. Skin discoloration, scratches or scales may affect the appearance of a grapefruit, but they do not impact the taste or texture quality.
Signs of decay include an overly soft spot at the stem end of the fruit and areas that appear watersoaked. These forms of decay usually translate into poor taste-a flavor that is less vibrant and more bitter than a good quality grapefruit.
The fruits should be heavy for their size as this usually indicates that they feature thin skins and therefore a higher concentration of juicier flesh. Those that have overly rough or wrinkled skin usually tend to be thick skinned and should be avoided.
Grapefruits should be firm, yet slightly springy when gentle pressure is applied. While chilled grapefruits do not have an apparent fragrance, those kept at room temperature should have a subtly sweet aroma. Grapefruits can be purchased throughout the year although the height of the season ranges from winter through early spring.
Since grapefruits are juicier when they're slightly warm rather than cool, store them at room temperature if you are planning on consuming them within a week of purchase. If you will not be using them within this time period, store them in the refrigerator crisper where they will keep fresh for two to three weeks.
Tips for preparing grapefruit:
Grapefruits should be rinsed under cool water before consuming, even though you will probably not be eating the peel, since cutting into an unwashed fruit may transfer dirt or bacteria that may reside on the skin's surface to the edible flesh.
Grapefruits are usually eaten fresh by slicing the fruit horizontally and scooping out sections of the halves with a spoon. To separate the flesh from the membrane you can either cut it with a sharp knife, a special curved-blade grapefruit knife, or a serrated grapefruit spoon. If there are seeds, you can remove them with your spoon before you eat the grapefruit.
Grapefruits can also be eaten like oranges. You can peel them with your hands or with a knife. If choosing the latter method, starting at the top, make a vertical incision that runs downward and then back up to the top on the other side and then repeat so that there will be four sections of similar size.
Be careful to only cut through skin and not into the membrane. The skin can then be peeled back with your hands or with the knife. The membranes can be separated, as you would do to an orange eaten in this manner.
Another way to serve grapefruit is to peel and slice them.
A few quick serving ideas:
Grapefruit sections add a tangy spark to green salads.
Instead of your morning glass of OJ, have a glass of grapefruit juice.
Combine diced grapefruit with cilantro and chili peppers to make a unique salsa.
To enjoy a salad with a tropical flair, combine chopped grapefruit pieces, cooked shrimp and avocadoes and serve on a bed of romaine lettuce.
Grapefruit and Drug Interactions
Check with your healthcare practitioner about consuming grapefruit juice if you're taking pharmaceutical drugs. Certain pharmaceutical drugs combined with grapefruit juice become more potent. Compounds in grapefruit juice, including naringenin, slow the normal detoxification and metabolism processes in the intestines and liver, which hinders the body's ability to breakdown and eliminate these drugs.
These interactive drugs include the immunosuppressent cyclosporine and calcium channel blocker drugs, such as felodipine, nifedipine and verapamil. Other drugs whose bioavailability is enhanced by grapefruit juice are the antihistamine terfenadine, the hormone estradiol and the antiviral agent saquinavir.
Research also indicates that individuals taking statin drugs should avoid grapefruit. Grapefruit increases the amount of statin drug that reaches the general circulation in two ways. First, grapefruit contains a compound called naringenin, which inactivates an enzyme (cytochrome P450 3A4) in the small intestine that metabolizes statin drugs. Secondly, grapefruit also inhibits P-glycoprotein, a carrier molecule produced in the intestinal wall that would normally transport the statin drug back to the gut. The end result of these two mechanisms is that much more of the statin drug enters the systemic circulation than would normally be the case, leading to a build up in statin levels that can be quite dangerous, and may trigger a rare but serious statin-associated disease called rhabdomyolysis. Rhaddomyolysis affects muscle tissue, usually causing temporary paralysis or weakness, unless the muscle is severely injured.
Grapefruit is an excellent source of vitamin C. It is also a good source of dietary fiber, vitamin A, potassium, folate, and vitamin B5. Grapefruit also contains phytochemicals including liminoids and lycopene.
For an in-depth nutritional profile click here: Grapefruit.
In-Depth Nutritional Profile
In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Grapefruit is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.Introduction to Food Rating System Chart
The following chart shows the nutrients for which this food is either an excellent, very good or good source. Next to the nutrient name you will find the following information: the amount of the nutrient that is included in the noted serving of this food; the %Daily Value (DV) that that amount represents; the nutrient density rating; and the food's World's Healthiest Foods Rating. Underneath the chart is a table that summarizes how the ratings were devised. Read detailed information on our Food and Recipe Rating System.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
No comments:
Post a Comment