Here’s a case of something that tastes good but is also good for you. If you love berries, you will be pleased to learn that these delicious fruits contain an arsenal of phytochemical compound with the potential to combat cancer. Not only that, unlike certain cancer-fighting food that must be eating fresh, freezing berries does not reduce cancer-fighting capabilities.
Vividly colored, delicately scented, and naturally sweet, berries belong to an exclusive class of foods that have won a place in our diet thanks to their evocative fragrance and wonderful flavor. The high nutritional value and cancer-fighting properties of berries come almost as an unexpected bonus.
It seems that the raspberry (from the earlier raspis berry, possibly from raspis, “a sweet, rose-colored wine”, or the Old French Raspe, also meaning Raspberry) has long been a highly prized fruit. According to Greek mythology, even the gods of Olympus enjoyed this extraordinarily exquisite berry. As one story relates, the young Zeus was suffering from dreadful fits punctuated by furious cries while in hiding on a Cretan mountainside from the murderous instincts of his terrible father, Cronus. In an attempt to calm Zeus down, his nursemaid, the nymph Ida, tried to pick a raspberry for him from the bramble bushes on the mountainside. She scratched her breast on the thorns of the bushes and her blood flowed onto the raspberries. The berries, which had been white at that time, would forever thereafter be tinted a brilliant scarlet red.
This legend has carried on through time, and even by the beginning of the 1st century CE, Pliny The Elder still believed Mount Ida was the only place where raspberries grew. Even though it is likely that raspberry bushes originated in the mountainous regions of East Asia rather than in Greece, scientists nonetheless gave the plant the name of Rubus idaeus, or Ida’s bramble, in homage to the myth.
As well as having a truly delightful flavor, raspberries have long played a role in the traditional medicine of many cultures, whether as an antidote, as used in Russia, or to postpone aging, as used in China. As we now know, raspberries contain large amounts of a very powerful anticancer molecule, ellagic acid, and are a fascinating food.
The strawberry is the fruit of a very tough, resistant plant that grows wild in most regions of the world, both in the Americas and in Europe and Asia.
Because of its widespread presence, it is likely that the origin of eating wild strawberries is inseparable from the origin of human beings themselves, a fact attested to by the discovery of a great many strawberry seeds in prehistoric dwellings.
The Romans named the strawberry fragum because of its exquisite scent, and this is where the word “fragrance” comes from. The ancient strawberry (fragaria vesca) grew exclusively in the under bush, but the Romans did not value its flavor as much as its scent. In his book The Bucolics, the Roman poet Virgil wrote, “Young people who gather budding flowers and fruits, flee this place; the cold snake lies in the grass.” It would seem that it was the hope of a pleasant assignation that drew Roman adolescents to the strawberry bushes, and not a desire to pick fruits.
STRAWBERRY SYMBOLS AND MYTHS
For Westerners, the strawberry’s red color, tender flesh, sweet juice, and resemblance to the heart have made it a synonym for temptation and indulgence, as well as love and sensuality. And while the origin of the strawberry may be less poetic than that of the raspberry, several symbols, myths, and legends are associated with this berry. For example, some native people of North America recount the legend that the souls of the dead can only forget the world of the living after having found and eaten a giant strawberry. Eating the strawberry is said to sate the soul’s appetite and enable it to rest in peace for all eternity.
Strawberries were also used long ago for beauty treatments, including fighting wrinkles and toning the skin. Madame Thérésa Tallien (1773-1835), a Parisian fashion icon who survived the French Revolution, allegedly added the juice of 20 pounds (9 kilograms) of strawberries to her warm bath water to in order to preserve her skin’s legendary fresh, firm texture. This unthinkable waste of fruit gave her the confidence to display herself at the opera wearing only a sleeveless white silk tunic and no underwear.
The only dark side of the strawberry is that this fruit, like a number of foods (such as chocolate, bananas, and tomatoes), often causes false food allergies. This is because of its propensity to stimulate the release of histamine by the immune system, which can result in a number of unpleasant symptoms, such as asthma, or an outbreak of hives. These pseudo-allergies do not involve the formation of specific antibodies, however, and are not as serious as a true strawberry allergy. Remaining relatively rare in adults, a true allergy to strawberries account for less than 1 percent of all food allergy.
It appears that strawberry cultivation began in France around the middle of the 14th century, following the efforts of gardeners to transplant wild strawberry plants into the royal gardens. Considerable efforts were made, which is a certain indication of a royal infatuation of the fruit.
In fact, a close relationship between royalty and strawberries appeared several times in France’s history. In 1368, Jean Dudoy, at the time gardener to King Charles V, transplanted no fewer than 1,200 strawberry plants into the royal garden at the Louvre in Paris. And when Louis XIII went to Aquitaine in 1622 to quell the region’s Protestant rebellion, his daily meal included strawberries in wine and sugar, along with a strawberry cream tart.
At the beginning of the 17th century, French explorers who went to North America brought back from their travels an interesting variety, the scarlet strawberry (Fragaria virginiana). This strawberry was cultivated in a large scale in the greenhouses at Versailles under Louis XIII and Louis XIV. In fact, Louis XIV was so fond of strawberries that he could eat them to the point of indigestion.
The strawberry we know nowadays is very different from the one consumed at that time and results from selections made from two varieties of strawberry plants that differ from those in Europe. We owe the variety of strawberries eaten today all over the world to Amédée-François Frézier, whose name (similar to the French word for strawberry plant, “fraisier”) may have preordained him to play a major role in the history of strawberries. Frézier was an officer and cartographer in the French military assigned in 1712 to observe the Spanish ports and plans for the fortification of the western coast of South America. While in the Chilean coast, Frézier noticed the variety of strawberry plants with white fruits, the Chilean white strawberry (Fragaria chiloensis). He successfully took five plants of this variety back to France, and while they did not bear fruit, their blooms made it possible to pollinate other species, especially F. Virginiana. This crossbreeding gave birth to the ancestor of the strawberry now grown in every continent, Fragaria ananassa.
The use of strawberries and of the strawberry plant itself for therapeutic purposes appears to be very ancient. The Ojibwa, native North Americans from southeastern Ontario, prepared infusions using strawberry leaves to treat stomach upsets, as well as gastrointestinal disorders like diarrhea. But strawberries were not only well known for their purgative properties, the renowned Swedish botanist Carolus Linnaeus (1707-78) was convinced that an intensive course of treatment using strawberries was responsible for his miraculous recovery from an attack of gout. In another case, the French philosopher Bernard le Bovier de Fontenelle, who live to the age of 100 (1657-1757), attributed the secret of his longevity to annual treatments based on strawberry cures. While we may find these anecdotes amusing, they do not contradict recent scientific data that tends to indicate that strawberries might actually be an important food for cancer prevention.
BLUEBERRIES AND BILBERRIES
A close relative of the European bilberry (Vaccinium myrtillus), the blueberry (Vaccinium angustifolium) is a species native to northeastern North America, where it has long been a part of the diet. Native North Americans revered this fruit, which they believed had been sent to them by the gods to help them survive a famine. Europeans newly arrived in North America quickly adopted the blueberry into their own diet.
Native North Americans prized the blueberry not only for food, but also for its medicinal properties. Among other things, they made an infusion from the plant’s roots to relieve stress from pregnancy, as well as an infusion of the leaves to tone the body and reduce colic in children. The Algonquin firmly believed in the blueberry’s properties as a relaxant and served the plant’s flowers to treat madness.
In Europe as well, the bilberry was used to cure several common ailments, such as diarrhea, dysentery, and scurvy. It has long been thought that this fruit has the ability to treat blood circulation disorders, as well as some eye diseases like diabetic retinopathies, glaucoma, and cataracts; some physicians still use it part of such treatments. This use becomes all the more interesting because we now know that diabetic retinopathies, for example, are diseases caused by the uncontrolled angiogenesis of retinal vessels, a process similar to that which supports tumor growth by means of formation of a new blood vessel network.
As we will explain later, findings from recent scientific studies suggest that the anthocyanidins, a class of molecules particularly plentiful in blueberries and bilberries, may be responsible for the antiangiogenic effects of these fruits and could be put to use to limit tumor growth.
Despite their bright red color and characteristic tangy flavor, cranberries are members of the genus Vaccinium and are closely related to blueberries and bilberries. Just like the blueberry, the cranberry has a European cousin (Vaccinium vitis-idaea), but the best-known varieties are those that come from North America, Vaccinium oxycoccus (little fruits) and Vaccinium acrocarpon (large fruits), with the large fruits being the variety now cultivated for commercial purposes.
As a general rule, cranberries play a relatively limited role in the modern Western diet, except, of course, as an accompaniment to the Christmas or Thanksgiving turkey, the latter use stemming from a tradition established in 1621 when the Pilgrims celebrated their first harvest in Massachusetts.
Native North Americans, on the other hand, had always prized this fruit. They ate it in every form imaginable, but mainly dried. The cranberry is an ingredient in a preserved dish called pemmican, which consists of dried meat and fat prepared and then stored to be eaten during the long months of winter. Without a scientific understanding, native peoples were making use of the cranberries’ high benzoic acid content, a natural agent that allow food to be preserved longer. Nowadays, cranberries are often consumed as juice. This is a shame, since commercial juice contains large quantities of sugar and far fewer of phytochemical molecules that give cranberries beneficial properties.
One of the best-known reasons to consume cranberries, in popular tradition, is to combat urinary infections. By observing native North Americans using it to treat bladder and kidney disorders, European settlers realized that this little fruit had powerful therapeutic properties. Once again, a traditional medicinal cure has been shown to have a scientific basis; it was later observed that some compounds in cranberries prevent bacteria from adhering to the cells of the urinary tract, and thus reduce the risk of an infection developing in the tissue. As we will see later on, such molecules in cranberries, which are also found in blueberries, may also play a role in cancer prevention.
THE ANTICANCER POTENTIAL OF BERRIES
Berries are seasonal fruits and usually make up only a relatively limited part in the diet. It has only been recently, therefore, that researchers have begun to examine their potential impact on cancer prevention, and the results obtained to date are very interesting. Studies have shown that eating blueberries and strawberries on a regular basis is associated with a decline of about 30 percent in the risk of hormone-dependent breast cancer (ER-). This protection is not surprising, since researchers who are interested in the anticancer activity of various foods constantly mention berries as being important foods for cancer prevention.
Let’s look at why this is so.
Of all the phytochemical compounds associated with berries, ellagic acid is without doubt the one most likely to interfere in cancer development. This molecule is an unusual-looking polyphenol found mainly in raspberries and strawberries, as well as some nuts, like hazelnuts and pecans. However, even though raspberries appear at first glance to have a higher amount of ellagic acid than strawberries, we must bear in mind that 90 percent of the molecule in raspberries is found in the seeds, whereas in strawberries 95 percent of it is in the flesh. It is therefore possible, even probable, that the molecule in strawberries is more easily assimilated than that in raspberries. Along the same lines, it is interesting to note that “Orleans,” a variety strawberry containing very high levels of ellagic acid (as well as other phytochemical compounds) was recently developed in Canada, which makes it likely the first “Nutra preventive” strawberry known to date.
The anticancer potential of the main food sources of ellagic acid – that is, strawberries and raspberries – has been studied by observing the behavior of cancer cells grown under laboratory conditions, as well as in laboratory animals subject to a treatment that causes the formation of cancer.
Strawberry extracts, as well as raspberry extracts, are able to thwart the growth of tumor cells, but this ability is directly connected to the quantity of polyphenols in these fruits and not to their antioxidant potential. In animals, studies have shown that a diet containing a relatively high proportion of strawberries or raspberries (5 percent of the diet) causes a significant reduction in the number of the tumors of the esophagus caused by NMBA (or N- nitrosobenzylmethylamine), a powerful carcinogen. Similar results have been observed in humans after the administration of strawberry polyphenol extracts. So including these berries in your diet is an effective weapon in the prevention of the esophageal cancer. And you can enjoy them out of season, since freezing does not harm their anticancer properties.
At first glance, the mechanisms by which ellagic acid interferes with cancer development resemble those we have described for a number of other foods. Currently available findings indicate that ellagic acid prevents the activation of a process that converts carcinogenic substances into cellular toxins. These toxins lose their ability to react with DNA and are no longer able to set off the mutations that may trigger cancer.
Ellagic acid also appears to increase cells’ ability to defend themselves against toxic attack by stimulating the mechanisms that cells use for eliminating carcinogenic substances. That said, our own research results indicate that ellagic acid might be a more versatile anticancer molecule than was previously thought. We have discovered that this molecule is a powerful inhibitor of two proteins essential for tumor vascularization (VEGF and PDGF), the angiogenesis process described earlier. In fact, just as we observed in some of the components of green tea, ellagic acid is almost as powerful as some of the molecules developed by the pharmaceutical industry to interfere with cell activities leading to the formation of blood vessel networks in tumors. Given the importance of angiogenesis in the occurrence and progression of these tumors, it goes without saying that ellagic acid’s antiangiogenic activity most certainly adds to its anticancer potential and, therefore, that strawberries and raspberries deserve special attention in any strategy for preventing cancer through diet.
Anthocyanidins are a class of polyphenols responsible for the vast majority of the red, pink, purple, orange, and blue colors of many fruits and vegetables. For example, an anthocyanidin called delphinidin is responsible for the dark blue color of blueberries, while the cyanidin in cherries gives them their striking red color. These pigments are particularly plentiful in berries, which can contain up to 500 milligrams per 100 grams (3 ½ ounces). People who eat large amounts of these fruits every day may reach a daily anthocyanidin intake of 200 milligrams. This makes anthocyanidin one of the most frequently consumed classes of polyphenols.
According to some data, in addition to having high antioxidant activity, anthocyanidins may have a major impact on cancer development. For example, adding various anthocyanidins to cells isolated from tumors triggers an array of processes, such as the cessation of DNA synthesis and cell growth, leading to cell death by apoptosis (cell suicide). One of the anticancer effects of anthocyanidins also seems to be linked to the ability to inhibit angiogenesis. We have actually discovered that an anthocyanidin in blueberries, known as delphinidin, can inhibit the activity of the VEGF receptor associated with the development of angiogenesis, in concentrations close to those that can be attained through food. It is interesting to note that this activity is without doubt linked to delphinidin’s antioxidant nature, since a very similar molecule found in large quantity in bilberries, malvidin, has an antioxidant activity identical to that of delphinidin, but show no ability whatsoever to interfere with the receptor.
The anticancer potential of the anthocyanidins in blueberries and the ellagic acid in strawberries and raspberries suggests that including these fruits in the diet might have extraordinary repercussions for cancer prevention. All berries contain large amounts of ellagic acid or anthocyanidins, but only black raspberries and blackberries contain both, so it is likely that these fruits may also prove to be valuable allies. Among the same line, recent studies show that black raspberry extracts hinder the progression of esophageal cancer in animals can cause the adenomatous polyps (a common type of polyp) to regress in individuals at high risk for colon cancer (also known as familial rectocolic polyposis).
Proanthocyanidins are complex polyphenols consisting of several units of the same molecule, catechins, forming a chain of variable length. These polymers can form complexes with proteins, especially the proteins in saliva, a property responsible for the astringency of foods containing these molecules.
Proanthocyanidins are plentiful in the seeds, flowers, and bark of many plants but only a limited number are found in edible foods. If we exclude cinnamon and cocoa, which are very significant sources but cannot be consumed daily in large amounts (though some might choose to disagree in the case of cocoa!), cranberries and blueberries are the best food sources of these molecules. The other berries discussed in this article contain much less, although strawberries’ proanthocyanidin content makes them stand out favorably in comparison with several other foods. In the case of cranberries, it is important to note that cranberry juice contains far fewer proanthocyanidins than the fruit in its nature state and cannot therefore be considered a significant source of these molecules.
Proanthocyanidins are particularly known for having exceptional antioxidant power. This was demonstrated during the second voyage of French explorer Jacques Cartier (1491-1557) to Canada. He set sail in May of 1535, but Cartier and his crew were compelled to spend the winter in what is now Quebec. The crew suffered terribly with scurvy, and as Cartier wrote in 1535 in his logbook, “The mouth became so disgusting and rotten because of the gums that almost all of the flesh fell off, right to the roots of the teeth, most of which fell out.” Domagaya (an Iroquois who had accompanied Cartier to France when he returned there after the first voyage to Canada) showed Catier how to make an herbal tea from the bark and needles of a Canadian conifer believed to be Thuja Occidentalis (Canadian white cedar). The sailors drank the tea and were quickly cured.
Science now shows that their swift recovery was due to the herbal tea’s exceptional proanthocyanidin content, which made up for the absence of vitamin C in the sailors’ diet. In term of cancer prevention, studies on the anticancer potential of proanthocyanidins are just beginning, but results obtained to date are encouraging. In the laboratory, adding these molecules inhibits the growth of some kinds of cancer cells, notably those derived from the colon, suggesting that proanthocyanidins might play a role in preventing the development of cancer. This agrees with certain population studies showing that people consume the highest amounts of proanthocyanidins have lower risk of getting colon, stomach, and prostate cancer. At the same time, it has been more and more clearly established that proanthocyanidins have the property of disrupting the development of new blood vessels through angiogenesis and might therefore help maintain microtumors in a dormant state by preventing them establishing the blood supply necessary to fuel their growth. Lastly, we should mention that studies indicate that proanthocyanidins reduce estrogen synthesis and might therefore help counter the harmful effects of having too high a level of such hormone in the blood.
Even though the mechanisms responsible for these biological effects are still not understood, there are no doubt that proanthocyanidins have very intriguing characteristics from the perspective of cancer prevention and that introducing foods high in these molecules, like cranberries and chocolate, can only be beneficial.
Everyone should be happy to introduce these delicious fruits into the daily diet. Whether for their powerful antiangiogenic activity or their antioxidant properties, berries are an important source of anticancer phytochemical compounds and deserve a special place in a diet aiming to prevent cancer.