Showing posts with label lycopene. Show all posts
Showing posts with label lycopene. Show all posts

Thursday, 1 May 2014

Watermelon

  • Alongside of tomatoes, watermelon has moved up to the front of the line in recent research studies on high-lycopene foods. Lycopene is a carotenoid phytonutrient that's especially important for our cardiovascular health, and an increasing number of scientists now believe that lycopene is important for bone health as well. Among whole, fresh fruits that are commonly eaten in the U.S., watermelon now accounts for more U.S. intake of lycopene (by weight of fruit eaten) than any other fruit. Pink grapefruit and guava are two other important fruit sources of lycopene, although in the U.S., these fruits are more often consumed in the form of juice.
  • Health scientists are becoming more and more interested in the citrulline content of watermelon. Citrulline is an amino acid that is commonly converted by our kidneys and other organ systems into arginine (another amino acid). The flesh of a watermelon contains about 250 millligrams of citrulline per cup. When our body absorbs this citrulline, one of the steps it can take is conversion of citrulline into arginine. Particularly if a person's body is not making enough arginine, higher levels of arginine can help improve blood flow and other aspects of our cardiovascular health. There's also some preliminary evidence from animal studies that greater conversion of citrulline into arginine may help prevent excess accumulation of fat in fat cells due to blocked activity of an enzyme called tissue-nonspecific alkaline phosphatase, or TNAP.
  • If you've gotten used to thinking about the juicy red flesh at the center of a watermelon as its only nutrient-rich area—and far more nutrient-rich than the more lightly-colored flesh that is farther out near the watermelon rind—it is time to change your thinking. In a recent study, food scientists compared the nutrient content of flesh from different parts of a watermelon: flesh from the center, the stem end, the blossom end (opposite from the stem), and the periphery (the part nearest to the rind). What they've discovered were impressive concentrations of phenolic antioxidants, flavonoids, lycopene, and vitamin C in all of these different areas. The exact distribution of nutrients was also highly dependent on the variety of watermelon. But there was no area in any of the watermelon varieties that came out badly in terms of nutrients, and in many of the watermelon varieties, the flesh's outer periphery contained impressive concentrations of most nutrients.
  • Recent studies have confirmed the nutritional importance of allowing a watermelon to fully ripen. For example, research has shown that the biggest jump in lycopene content occurs at the time when a watermelon's flesh turns from white-pink to pink. Yet when that flesh continues to ripen, resulting in a color change from pink to red, the lycopene content becomes even more concentrated. Prior to ripening, when the flesh of a watermelon is primarily white in color, its beta-carotene content is near zero. Even when allowed to ripen to the white-pink stage, a watermelon still contains very little of its eventual beta-carotene content. But as it moves from white-pink to pink to red, the beta-carotene content of a watermelon steadily increases. Like lycopene and beta-carotene, total phenolic antioxidants in a watermelon also increase consistently during ripening, all the way up until the appearance of fully red flesh. The bottom line: eating a fully ripe watermelon can really pay off in terms of nutrient benefits. Please see our section called "How to Select and Store" to learn about determining a watermelon's ripeness before you purchase it.

Watermelon, diced, fresh
1.00 cup
(152.00 grams)
Calories: 46
GI: medium
NutrientDRI/DV

 vitamin C16.4%


 copper6.6%

 biotin5%

 potassium4.8%

 vitamin A4.8%

 vitamin B14.1%

 vitamin B64.1%

 magnesium3.8%

This chart graphically details the %DV that a serving of Watermelon provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Watermelon can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Watermelon, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

Health Benefits

Anti-Inflammatory and Antioxidant Support

Phenolic compounds in watermelon—including flavonoids, carotenoids, and triterpenoids—make this fruit a choice for anti-inflammatory and antioxidant health benefits. If you had to pick a single nutrient from this anti-inflammatory and antioxidant category that has put watermelon on the map, that nutrient would be lycopene. Alongside of pink grapefruit and guava, watermelon is an unusually concentrated source of this carotenoid. Whereas most fruits get their reddish color from anthocyanin flavonoids, watermelon gets it reddish-pink shades primarily from lycopene. The lycopene content of watermelons increases along with ripening, so to get the best lycopene benefits from watermelon, make sure that your melon is optimally ripe. (See our section entitled, "How to Select and Store" for practical tips on selecting a fully ripe watermelon.) The lycopene in watermelon is a well-documented inhibitor of many inflammatory processes, including the production of pro-inflammatory messaging molecules, the expression of enzymes like cyclo-oxygenase and lipoxygenase that can lead to increased inflammatory response, and the activity of molecular signaling agents like nuclear factor kappa B (NFkB). Lycopene is also a well-known antioxidant, with the ability to neutralize free radical molecules.
Recent research has shown that the lycopene content of watermelon also remains very stable over time. When two-inch cubes of fresh-cut watermelon were stored in the refrigerator at 36°F (2°C) over 48 hours, researchers found virtually no deterioration in lycopene content. That deterioration did not start to become significant until about seven days of storage, when it decreased by about 6-11%. While we do not recommend waiting seven days before consuming fresh cut watermelon, we believe that the excellent stability of watermelon lycopene over a two-day period is great news for anyone wanting to enjoy fresh cut watermelon over the course of several days.
Cucurbitacin E is another unique anti-inflammatory phytonutrient (called a tripterpenoid) found in watermelon. Like the carotenoid lycopene, this anti-inflammatory nutrient has been shown to block activity of cyclo-oxygenase enzymes and neutralize reactive nitrogen-containing molecules. (Interestingly, cucurbitacin E does not appear to neutralize activity of reactive oxygen species—called ROS—but only activity of reactive nitrogen species, called RNS.)
Antioxidant carotenoids found in watermelon include significant amounts of beta-carotene. Like lycopene, the beta-carotene in watermelon also increases with ripening.
Red-pink fleshed watermelons typically contain far more lycopene and beta-carotene than yellow-white fleshed varieties. For example, one study we've seen showed red watermelon to contain over 600 micrograms of beta-carotene per 3.5 ounces of melon and over 6,500 micrograms of lycopene. By comparison, yellow-fleshed varieties were found to contain only 5-10 micrograms of beta-carotene and no measurable amount of lycopene. In red/pink-fleshed watermelons as a group, we've seen lycopene amounts that vary widely in a range of approximately 2,000–6,700 micrograms per 3.5 ounces of fresh melon. Beta-carotene in these red/pink-fleshed varieties also varies widely, in a range of approximately 5–325 micrograms. Because watermelon contains so many different phytonutrients—as well as key vitamins and minerals, as well as dietary fiber—your health is going to be improved by any watermelon variety that you choose. However, if you specifically want to maximize your lycopene and beta-carotene intake, you'll most likely want to stick with red/pink-fleshed varieties of watermelon.
It would be a mistake to ignore the important amount of vitamin C found in watermelon. In our Food Rating System, watermelon qualifies as very good source of vitamin C, even though the amount provided (about 12 milligrams per cup of fresh melon) is only 16% of the Dietary Reference Intake (DRI). However, due to its very high water content, the same amount of watermelon that provides us with 16% of the DRI for vitamin C only costs us about 46 calories, or about 2% of our total daily calories on a 1800-2000 calorie diet. That's excellent nutrient richness, and it makes watermelon a great choice for increasing vitamin C antioxidant protection.

Citrulline, Arginine, and Nitric Oxide-Related Benefits

One of the more unusual aspects of watermelon is its rich supply of the amino acid, citrulline. Citrulline is an amino acid that is commonly converted by our kidneys and other organ systems (including cells that line our blood vessels) into arginine (another amino acid). The flesh of a watermelon contains about 250 millligrams of citrulline per cup. When our body absorbs citrulline, one of the steps it can take is conversion of citrulline into arginine.
An enzyme called nitric oxide synthase (NOS)—found in many of our body's cell types—is able to take the amino acid arginine and use it to help produce a very small molecule of gas called nitric oxide (NO), which is a muscle relaxant. For example, when NO tells the smooth muscles around our blood vessels to relax, the space inside our blood vessels can expand, allowing blood to flow more freely and creating a drop in blood pressure. The relaxing of muscle tension and increasing of blood flow is also the way that NO can change erectile function in men. (The prescription medication sildenafil or Viagra (TM) works in this way.)
The amount of citrulline found in fresh watermelon is not enough to make it a food that can automatically improve blood pressure or affect other problems like erectile dysfunction. But in animal studies, intake of watermelon has been shown to help support cardiovascular function, including improvement of blood flow (through relaxation of blood vessels, or what is technically called vasodilation). In humans, intake of watermelon has been shown to increase blood levels of arginine, but only when consumed in very large amounts. For example, in one study that we reviewed, participants consumed either three cups or six cups of fresh watermelon juice daily over the course of three weeks and experienced increases in their blood arginine levels of approximately 12-22%.
Another fascinating new area of research involving watermelon and its citrulline content relates to the deposition of body fat. In animal studies, high intake of amino acid citrulline—followed by conversion of citrulline into the amino acid arginine—can result in the formation of arginine-related molecules called polyarginine peptides. These polyarginine peptides are able to block activity of an enzyme called tissue-nonspecific alkaline phosphatase, or TNAP. When TNAP activity is shut down, our fat cells (adipocytes) tend to create less fat (adipogenesis). Researchers believe that the connection between citrulline in food, arginine production by nitric oxide synthase, and fat cell metabolism may eventually provide us with additional tools for helping prevent over-accumulation of body fat.
At present, however, the best we can conclude about watermelon and its unusual citrulline content is that it's likely to provide us with some cardiovascular benefits, especially if we don't consume many foods that are high in arginine. (Some of the WHFoods highest in arginine include shrimp, spinach, sea vegetables, turkey, sunflower seeds, and sesame seeds.)

Other Health Benefits

Watermelon seeds can provide us with small but helpful amounts of both iron and zinc. We're talking about several hundred seeds (the amount contained in a typical seeded watermelon, which is not an amount that we would anticipate or suggest eating at one time) to obtain 1–2 milligrams of either mineral. Still, regular consumption of whole, seeded watermelon would provide us with nutrient benefits in this area over time. Interestingly, we've seen one study showing that the iron and zinc in watermelon seeds is surprisingly bioavailable (85-90%), despite the oxalates and phytates that are contained in the seeds. (Oxalates and phytates can sometimes bind with minerals like iron and zinc to lessen their bioavailability.)
The amount of protein in watermelon seeds is approximately 1 gram per 24 seeds. At this rate, we're likely to get several grams of protein when we eat several slices of whole, seeded watermelon. While we would not want to depend on watermelon as a key protein food, this valuable amount of protein in its seeds should at least remind us that a fruit like watermelon does have something to offer us in the way of protein benefits.
At approximately two-thirds of one gram of dietary fiber per cup, watermelon does not rank as a good, very good, or excellent source of this nutrient in our ranking system. However, you'd be receiving about 3-4 grams of dietary fiber if you enjoyed 175–200 calories of fresh watermelon in the form of several large slices, and this dietary fiber would include a nice mix of soluble to insoluble fiber. (Insoluble fibers can provide special support to the digestive system, and soluble fibers can provide special support to the cardiovascular system.) So while watermelon is not a concentrated source of fiber, we often enjoy it in larger amounts that can provide us with great fiber benefits at a low calorie cost.

Description

If you have ever tasted a watermelon, it is probably no surprise to you why this juicy, refreshing fruit has this name. Watermelon has an extremely high water content, approximately 92%, giving its flesh a juicy and thirst-quenching texture while still also subtly crunchy. As a member of the Cucurbitaceae family, the watermelon is related to the cantaloupe, squash, pumpkin, cucumber, and gourd that grow on vines on the ground. Watermelons can be round, oblong, or spherical in shape and feature thick green rinds that are often spotted or striped. (Many people report, however, that they like the taste and predictable ripeness of a watermelon best if the watermelon is symmetrical in shape.) Watermelons range in size from a few pounds to upward of ninety pounds. Between 600–1,200 different varieties of watermelon exist worldwide, but all of these varieties belong to the same scientific genus and species of plant, called Citrullis lanatus.
While we often associate a deep red/pink color with watermelons, there are many varieties that feature orange, yellow, or white flesh. These varieties are typically lower in the carotenoid lycopene than red/pink varieties.
A good bit of controversy has arisen over the exact nature of seedless watermelons. Contrary to some information that you will find on various websites, seedless watermelons are not the result of genetic engineering. Seedless watermelons are the result of hybridization. By crossing a diploid watermelon (with two sets of chromosomes) and a tetraploid watermelon (with four sets of chromosomes), it is possible to produce a watermelon that contains triploid seeds (with three chromosomal sets). When planted, these triploid seeds will grow into seedless watermelons. Seedless watermelons will typically appear to contain some white seeds even though they are labeled as seedless. These white seeds are not actually seeds, but only empty seed coats.
Ten years ago, it was somewhat rare to find seedless watermelons in the marketplace. Today, up to 85% of all watermelons produced in the U.S. are estimated to be seedless. This great increase in the availability of seedless watermelons is due to the vastly increased use of "non-bearing pollinators" by watermelon growers. Previously, growers were required to interplant rows of acreage with seeded, fruit-bearing watermelons in order to pollinate their seedless varieties. Today, they are able to pollinate with plants that produce flowers needed by bees, but yield no fruit. These non-fruit-bearing plants allow pollination to continue, but in a less time-consuming and space-consuming way. It's possible to grow seedless watermelons most anywhere that seeded watermelons will grow. Some of the more common seedless varieties include Fandango, Super Cool, Honeyheart, King of Hearts, Queen of Hearts, Crimson Trio, Scarlet Trio, and SuperSweet.
Some common varieties of seeded watermelon include Jubilee, Royal Jubilee, Royal Sweet, Crimson Sweet, Sangria, Fiesta, Sugar Baby, Baby Doll, and Charleston Gray. A 15–20 pound diploid, seeded watermelon will typical contain hundreds of seeds.

History

Watermelons are generally believed to have originated in Africa several thousand years ago and to have traveled over time from Africa to Asia to Europe to North America. Their arrival in Asia and the Middle East is believed to date back to approximately 900–1,000 A.D., and their arrival in Europe is estimated to have occurred in 1300–1400 A.D. It was not until Europeans began to colonize North America that watermelons arrived in what is now the U.S.
Today, over four billion pounds of watermelon are produced each year in the U.S. About 85% of watermelons are purchased in fresh form by consumers. Although there is some watermelon production in virtually all states, about three-fourths of all U.S. watermelons are grown in Florida, California, Texas, Georgia, and Indiana. On an average, per person basis, we eat over 15 pounds of fresh watermelon each year.
On a global basis, China is by far the largest watermelon-producing country and accounts for over half of all world production. The European Union countries, Iran, Turkey, Egypt, Brazil, and the United States are the next largest watermelon producers, but each produces less than 5% of the world total.

How to Select and Store

If you are purchasing a pre-cut watermelon that has already been sliced into halves or quarters, choose the flesh that is deepest in color and lacks any white streaking. If the watermelon is seeded, the seeds should also be deep in color, or white.
When purchasing a whole, uncut watermelon, there are several features to you'll want to evaluate. The first is its weight. A fully ripened watermelon will feel heavy for its size. Heaviness in a watermelon is a good thing because the water content of a watermelon will typically increase along with ripening, and a fully ripened watermelon will be over 90% water in terms of weight, and water is one of the heaviest components in any food
Second, look for a watermelon with a relatively smooth rind that is slightly dulled on top. The top and the bottom of a watermelon are worth determining and examining on a watermelon. The bottom or "underbelly" of a watermelon is the spot where it was resting on the ground. If that "ground spot" is white or green, the watermelon is unlikely to be fully ripe. A fully ripened watermelon will often have a ground spot that has turned creamy yellow in color. Opposite from the ground spot will be the top of the watermelon. In a fully ripened watermelon, that spot will typically not be shiny but somewhat dulled. The green color may appear in many different shades, however, from light green to deeper shades.
Perhaps most controversial about ripeness testing of a watermelon is whether or not to give it a thump. We've read many arguments both pro and con. However, among experts who recommend thumping, most seem to agree that a fully ripened watermelon will have a deeper, hollower "bass" sound rather than a solid and shallow "soprano" sound.
Finally, some grocers will be willing to core an uncut watermelon so that you can have an actual taste. (If you decide not to purchase the melon, the grocer can slice it up and sell it in sliced form.) So consider requesting this if you are uncertain as to the quality.
Uncut watermelons are best stored at temperatures of 50-60°F (10–16°C). In many regions, room temperatures will typically be warmer than 60°F and may be less than ideal for whole watermelon storage due to increased risk of decay. Better storage temperatures will typically be found in cellars or basements that are partly or completely below ground level. While we've seen one study showing increases in lycopene content when whole watermelon was stored at a temperature of 68°F (20°C), we believe that a fully-ripe or close-to-fully-ripe melon will already have outstanding lycopene content and that it would be better for you to err on the safe side in terms of decay risk if you are planning to wait several days before slicing open your watermelon.
Like temperatures above 60°F (16°C), temperatures much below 50°F (10°C) are not recommended for storage of uncut watermelons. This is due to increased risk of chilling-type injury that can decrease shelf life and flavor. (Therefore, the refrigerator would not be a good place for you to store a whole, uncut watermelon for this reason.)
With uncut, whole watermelon, one final storage precaution would be the avoidance of contact with high ethylene-producing foods like passion fruit, apples, peaches, pears, and papaya. Watermelons are ethylene-sensitive fruits that may become overly ripe too quickly under these circumstances.
Once cut, watermelons should be refrigerated in order to best preserve their freshness, taste, and juiciness. Store your cut watermelon in a sealed, hard plastic or glass container with a lid.

Tips for Preparing and Cooking

Tips for Preparing Watermelon

Wash the watermelon before cutting it. Due to its large size, you will probably not be able to run it under water in the sink. Instead, wash it with a wet cloth or paper towel.
Depending upon the size that you desire, there are many ways to cut a watermelon. The flesh can be sliced, cubed, or scooped into balls. Watermelon is delicious to eat as is, while it also makes a delightful addition to a fruit salad.
While many people are just accustomed to eating the juicy flesh of the watermelon, both the seeds and the rind are also edible and nutrient-rich. (In fact, in many parts of the world, watermelon seeds are widely enjoyed as a snack and pickled watermelon rind has a rich culinary tradition.) If you choose to eat the rind, we recommend purchase of certified organic watermelon. (The reason for this suggestion is an increased risk of unwanted contaminants like pesticide residues on the outer skin of non-organic watermelon.)

How to Enjoy

A Few Quick Serving Ideas

  • Purée watermelon, cantaloupe and kiwi together. Swirl in a little plain yogurt and serve as refreshing cold soup.
  • In Asian countries, roasted watermelon seeds are either seasoned and eaten as a snack food or ground up into cereal and used to make bread.
  • A featured item of Southern American cooking, the rind of watermelon can be marinated, pickled, or candied.
  • Watermelon mixed with thinly sliced red onion, salt and black pepper makes a great summer salad.
  • Watermelon is a wonderful addition to fruit salad. And fruit salad can be made days ahead since cut fruit, if chilled, retains its nutrients for at least 6 days.

WHFoods Recipes That Feature Watermelon

Individual Concerns

Watermelon is not a commonly allergenic food, is not known to contain measurable amounts of oxalates or purines and is also not included in the Environmental Working Group's 2012 report "Shopper's Guide to Pesticides" as one of the 12 foods most frequently containing pesticide residues.
During the past decade, non-organic watermelons grown in part of China became the topic of widespread controversy in the popular press following the use of a synthetic growth stimulator called forchlorfenuron in their cultivation. A combination of heavy rainfall and potential overuse of the growth stimulator actually caused many watermelons on farms in Jiangsu Province to burst open, drawing media attention to this practice. While we are not aware of any data on widespread use of synthetic growth stimulators in the production of non-organic watermelon, we have seen one study predicting residues of forchlorfenuron in the range of 1-5 ppb in watermelons raised with the use of this synthetic growth stimulator. If you are seeking to lower your risk of contamination with all synthetic additives in watermelon and other foods, we recommend purchase of certified organic watermelon, since synthetic growth stimulators and other synthetic additives are prohibited in organic food production.

Nutritional Profile

Watermelon is an unusual fruit source of the carotenoid lycopene and a rich source of phenolic antioxidants. Watermelon contains cucurbitacin E, a triterpene anti-inflammatory phytonutrient, and unusual amounts of the amino acid citrulline. Watermelon is a very good source of vitamin C. It is also a good source of pantothenic acid, copper, biotin, potassium, vitamin A (in the form of carotenoids), vitamin B1, vitamin B6, and magnesium.
For an in-depth nutritional profile click here: Watermelon.

In-Depth Nutritional Profile

In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Watermelon 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

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling."Read more background information and details of our rating system.
Watermelon, diced, fresh
1.00 cup
152.00 grams
Calories: 46
GI: medium
NutrientAmountDRI/DV
(%)
Nutrient
Density
World's Healthiest
Foods Rating
vitamin C12.31 mg16.46.5very good
pantothenic acid0.34 mg6.82.7good
copper0.06 mg6.72.6good
biotin1.52 mcg5.12.0good
potassium170.24 mg4.91.9good
vitamin A43.24 mcg RAE4.81.9good
vitamin B10.05 mg4.21.6good
vitamin B60.07 mg4.11.6good
magnesium15.20 mg3.81.5good
World's Healthiest
Foods Rating
Rule
excellentDRI/DV>=75% OR
Density>=7.6 AND DRI/DV>=10%
very goodDRI/DV>=50% OR
Density>=3.4 AND DRI/DV>=5%
goodDRI/DV>=25% OR
Density>=1.5 AND DRI/DV>=2.5%
In-Depth Nutritional Profile for Watermelon

References

  • Abdelwahab SI, Hassan LEA, Sirat HM et al. Anti-inflammatory activities of cucurbitacin E isolated from Citrullus lanatus var. citroides: Role of reactive nitrogen species and cyclooxygenase enzyme inhibition. Fitoterapia, Volume 82, Issue 8, December 2011, Pages 1190-1197.
  • Altas S, Kizil G, Kizil M et al. Protective effect of Diyarbakir watermelon juice on carbon tetrachloride-induced toxicity in rats. Food and Chemical Toxicology, Volume 49, Issue 9, September 2011, Pages 2433-2438.
  • Charoensiri R, Kongkachuichai R, Suknicom S et al. Beta-carotene, lycopene, and alpha-tocopherol contents of selected Thai fruits. Food Chemistry, Volume 113, Issue 1, 1 March 2009, Pages 202-207.
  • Collins JK, Wu G, Perkins-Veazie P et al. Watermelon consumption increases plasma arginine concentrations in adults. Nutrition, Volume 23, Issue 3, March 2007, Pages 261-266.
  • Dimitrovski D, Bicanic D, Luterotti S et al. The concentration of trans-lycopene in postharvest watermelon: An evaluation of analytical data obtained by direct methods. Postharvest Biology and Technology, Volume 58, Issue 1, October 2010, Pages 21-28.
  • Edwards AJ, Vinyard BT, Wiley ER et al. Consumption of watermelon juice increases plasma concentrations of lycopene and beta-carotene in humans. J Nutr 2003 Apr;133(4):1043-50. 2003.
  • Iakshmi AJ and Kaul P. Nutritional potential, bioaccessibility of minerals and functionality of watermelon (Citrullus vulgaris) seeds. LWT - Food Science and Technology, Volume 44, Issue 8, October 2011, Pages 1821-1826.
  • Martins MJ, Negrao MR and Azevedo I. Watermelon: the value of higher plasma arginine concentrations. Nutrition, Volume 23, Issue 6, June 2007, Page 517.
  • Paris HS, Amar Z and Lev E. Medieval emergence of sweet melons, Cucumis melo (Cucurbitaceae). Ann Bot. 2012 Jul;110(1):23-33. Epub 2012 May 30.
  • Perkins-Veazie P and Collins JK. Flesh quality and lycopene stability of fresh-cut watermelon. Postharvest Biology and Technology, Volume 31, Issue 2, February 2004, Pages 159-166.
  • Perkins-Veazie P, Collins JK. Carotenoid changes of intact watermelons after storage. J Agric Food Chem. 2006 Aug 9;54(16):5868-74. 2006. PMID:16881688.
  • Poduri A, Rateri DL, Saha SK et al. Citrullus lanatus 'sentinel' (watermelon) extract reduces atherosclerosis in LDL receptor-deficient mice. J Nutr Biochem. 2012 Aug 16. [Epub ahead of print].
  • Tlili I, Hdider C, Lenucci MS et al. Bioactive compounds and antioxidant activities of different watermelon (Citrullus lanatus (Thunb.) Mansfeld) cultivars as affected by fruit sampling area. Journal of Food Composition and Analysis, Volume 24, Issue 3, May 2011, Pages 307-314.
  • Tlili I, Hdider C, Lenucci MS et al. Bioactive compounds and antioxidant activities during fruit ripening of watermelon cultivars. Journal of Food Composition and Analysis, Volume 24, Issue 7, November 2011, Pages 923-928.
  • Valverde A, Piedra L, Aguilera A et al. Analysis and residue levels of forchlorfenuron (CPPU) in watermelons. J Environ Sci Health B. 2007 Sep-Oct;42(7):801-7.

Saturday, 19 April 2014

Grapefruit

Grapefruit
GrapefruitTart 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.

Grapefruit, pink, fresh
0.50 medium
(128.00 grams)
Calories: 41
GI: low
NutrientDRI/DV

 vitamin C58.7%


 copper6.6%

 vitamin A6.5%

 fiber5.6%


 biotin4.2%

 vitamin B14.1%

This chart graphically details the %DV that a serving of Grapefruit provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Grapefruit can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Grapefruit, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

Health Benefits

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. (PLEASE NOTE: Lycopene is only found in pink and red grapefruit. White grapefruit does not provide this carotenoid.) 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.
Choosing to regularly eat lycopene-rich foods, such as pink grapefruit, and drink green tea may greatly reduce a man's risk of developing prostate cancer, suggests research published the Asia Pacific Journal of Clinical Nutrition (Jian L, Lee AH, et al.)
In this case-control study involving 130 prostate cancer patients and 274 hospital controls, men drinking the most green tea were found to have an 86% reduced risk of prostate cancer compared, to those drinking the least.
A similar inverse association was found between the men's consumption of lycopene-rich fruits and vegetables such as tomatoes, apricots, pink grapefruit, watermelon, papaya, and guava. Men who most frequently enjoyed these foods were 82% less likely to have prostate cancer compared to those consuming the least lycopene-rich foods.
Regular consumption of both green tea and foods rich in lycopene resulted in a synergistic protective effect, stronger than the protection afforded by either, the researchers also noted.
Practical Tips: Get in the habit of drinking green tea and eating lycopene-rich foods.
  • Take a quart of iced green tea to work and sip throughout the day or take it to the gym to provide prostate protection while replenishing fluids after your workout.
  • Pack a ziploc bag of apricots and almonds in your briefcase or gym bag for a handy snack.
  • Start your breakfast with a half grapefruit or a glass of grapefruit, apricot, papaya or guava juice.
  • Begin lunch or dinner with some spicy tomato juice on the rocks with a twist of lime. Snack on tomato crostini: in the oven, toast whole wheat bread till crusty, then top with tomato sauce, herbs, a little grated cheese, and reheat until the cheese melts.
  • Top whole wheat pasta with olive oil, pine nuts, feta cheese and a rich tomato sauce for lunch or dinner.
  • For a delicious dessert, drizzle a little honey over a half grapefruit and broil for 2 minutes. Serve topped with a fresh mint leaf.

Grapefruit Juice Ranked among Those Highest in Antioxidant Activity

Not all fruit juices are the same. They differ markedly in the variety of phenolic compounds and antioxidant activity, according to Alan Crozier, Professor of Plant Biochemistry and Human Nutrition, who, with colleagues at the University of Glasgow, evaluated 13 commercially available popular juices.
Concord grapes came out on top with the highest and broadest range of polyphenols and the highest overall antioxidant capacity. (The main components in purple grape juice were flavan-3-ols, anthocyanins, and hydroxycinnamates, together accounting for 93% of the total phenolic content.)
Other top scorers were cloudy apple juice, cranberry juice and grapefruit juice.
Results for the red grape juice were said to be equal to those for a Beaujolais red wine. Interestingly, however, white grape juice, mainly containing hydroxycinnamates, had the lowest total phenolic content.
The products analyzed were: Spray Classic Cranberry; Welch's Purple Grape; Tesco Pure Pressed Red Grape; Pomegreat Pomegranate; Tesco Pure Apple (clear); Copella Apple (cloudy); Tesco Pure Grapefruit; Tesco Value Pure Orange (concentrate); Tropicana Pure Premium Smooth Orange (squeezed); Tropicana Pure Premium Tropical Fruit; Tesco Pure Pressed White Grape; Tesco Pure Pineapple; Del Monte Premium Tomato.
Dr. Crozier's findings come shortly after those of the Kame project, which indicated that long-term fruit juice consumption can provide protection against Alzheimer's disease (Dai et al., Am J Med), and suggest that, since each fruit juice contains its own array of protective phenols, drinking a variety may offer the best protection. Practical Tip: "The message is to mix these juices during the week. That way you will get all the compounds with anti-oxidant activity. If you drink only one juice you risk missing out on the compounds in the others," explained Crozier.

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 Individual Concerns 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 1/2 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.

Protection against Colon Cancer

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'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.

Description

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.

History

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.

How to Select and Store

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.
For the most antioxidants, choose fully ripened grapefruit:
Research conducted at the University of Innsbruck in Austria suggests that as fruits fully ripen, almost to the point of spoilage, their antioxidant levels actually increase.
Key to the process is the change in color that occurs as fruits ripen, a similar process to that seen in the fall when leaves turn from green to red to yellow to brown—a color change caused by the breakdown and disappearance of chlorophyll, which gives leaves and fruits their green color.
Until now, no one really knew what happened to chlorophyll during this process, but lead researcher, Bernard Krä utler, and his team, working together with botanists over the past several years, has identified the first decomposition products in leaves: colorless, polar NCCs (nonfluorescing chlorophyll catabolytes), that contain four pyrrole rings—like chlorophyll and heme.
After examining apples and pears, the scientists discovered that NCCs replace the chlorophyll not only in the leaves of fruit trees, but in their very ripe fruits, especially in the peel and flesh immediately below it.
"When chlorophyll is released from its protein complexes in the decomposition process, it has a phototoxic effect: when irradiated with light, it absorbs energy and can transfer it to other substances. For example, it can transform oxygen into a highly reactive, destructive form," report the researchers. However, NCCs have just the opposite effect. Extremely powerful antioxidants, they play an important protective role for the plant, and when consumed as part of the human diet, NCCs deliver the same potent antioxidant protection within our bodies. . Angew Chem Int Ed Engl. 2007 Nov 19;46(45):8699-8702.
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 and Cooking

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.

How to Enjoy

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.

Individual Concerns

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.

Nutritional Profile

Grapefruit is an excellent source of vitamin A (in the form of carotenoids) and vitamin C. It is also a good source of pantothenic acid, copper, dietary fiber, potassium, biotin, and vitamin B1. 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

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling."Read more background information and details of our rating system.
Grapefruit, pink, fresh
0.50 medium
128.00 grams
Calories: 41
GI: low
NutrientAmountDRI/DV
(%)
Nutrient
Density
World's Healthiest
Foods Rating
vitamin C44.03 mg58.725.8excellent
pantothenic acid0.36 mg7.23.2good
copper0.06 mg6.72.9good
vitamin A59.33 mcg RAE6.62.9good
fiber1.41 g5.62.5good
potassium177.92 mg5.12.2good
biotin1.28 mcg4.31.9good
vitamin B10.05 mg4.21.8good
World's Healthiest
Foods Rating
Rule
excellentDRI/DV>=75% OR
Density>=7.6 AND DRI/DV>=10%
very goodDRI/DV>=50% OR
Density>=3.4 AND DRI/DV>=5%
goodDRI/DV>=25% OR
Density>=1.5 AND DRI/DV>=2.5%
In-Depth Nutritional Profile for Grapefruit

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