One of the most fascinating new areas of raspberry research involves the potential for raspberries to improve management of obesity. Although this research is in its early stages, scientists now know that metabolism in our fat cells can be increased by phytonutrients found in raspberries, especially rheosmin (also called raspberry ketone). By increasing enzyme activity, oxygen consumption, and heat production in certain types of fat cells, raspberry phytonutrients like rheosmin may be able to decrease risk of obesity as well as risk of fatty liver. In addition to these benefits, rheosmin can decrease activity of a fat-digesting enzyme released by our pancreas called pancreatic lipase. This decrease in enzyme activity may result in less digestion and absorption of fat.
Recent research on organic raspberries has now shown organic raspberries to be significantly higher in total antioxidant capacity than non-organic raspberries. Raspberries in the study were grown on farms in Maryland that had been previously certified as organic by the U.S. Department of Agriculture. A series of tests involving free radical scavenging all provided the same results: organic raspberries outperformed their non-organic counterparts in terms of their antioxidant activity. This greater antioxidant capacity was associated with the greater levels of total phenols and total anthocyanins found in organic versus non-organic raspberries. While there are many good reasons to purchase organic versus non-organic foods of all kinds, this study makes it clear that these reasons specifically hold true for raspberries in a profound way.
You'll get significantly more antioxidant support by purchasing raspberries that are fully ripe. Recent studies have measured the total phenolic content, total flavonoid content, and anthocyanin content of raspberries harvested at varying stages of ripeness (from 50% to 100% maturity) and greatest overall antioxidant benefits were associated with full ripeness of the berries. Although it's possible for raspberries to ripen after harvest, this fruit can be highly perishable and can mold quite easily at room temperature. So your most risk-free approach for getting optimal antioxidant benefits from raspberries is to purchase them at full maturity, keep them refrigerated at all times at temperatures between 35-39°F (2°-4°C), and consume them very quickly (within 1 to 2 days after purchase).
Anti-cancer benefits of raspberries have long been attributed to their antioxidant and anti-inflammatory phytonutrients. In animal studies involving breast, cervical, colon, esophageal, and prostate cancers, raspberry phytonutrients have been shown to play an important role in lowering oxidative stress, reducing inflammation, and thereby altering the development or reproduction of cancer cells. But new research in this area has shown that the anti-cancer benefits of raspberries may extend beyond their basic antioxidant and anti-inflammatory aspects. Phytonutrients in raspberries may also be able to change the signals that are sent to potential or existing cancer cells. In the case of existing cancer cells, phytonutrients like ellagitannins in raspberries may be able to decrease cancer cell numbers by sending signals that encourage the cancer cells to being a cycle of programmed cell death (apoptosis). In the case of potentially but not yet cancerous cells, phytonutrients in raspberries may be able to trigger signals that encourage the non-cancerous cells to remain non-cancerous.
Health BenefitsAntioxidant and Anti-Inflammatory BenefitsThe diversity of antioxidant and anti-inflammatory phytonutrients in raspberries is truly remarkable, and few commonly eaten fruits are able to provide us with greater diversity. From a research perspective, here is a partial list of phytonutrients in raspberries that provide us antioxidant and anti-inflammatory benefits:
Anti-Cancer BenefitsGiven the rich antioxidant and anti-inflammatory phytonutrient mixture found in raspberries, it's not surprising to see studies showing raspberry benefits in cancer prevention. Chronic excessive oxidative stress and chronic excessive inflammation can combine to trigger the development of cancer cells in a variety of human tissue. By providing a rich supply of antioxidants, raspberries can help lower risk of oxidative stress, and providing a rich supply of anti-inflammatory nutrients, raspberries can help lower the risk of excessive inflammation. When combined, these results mean decreased risk of cancer formation. In animal studies to date, the cancer types most closely examined in relationship to raspberry intake are cancers of the breast, cervix, colon, esophagus, and prostate.
Recent studies suggest that the anti-cancer benefits of raspberries may extend beyond their basic antioxidant and anti-inflammatory aspects. Phytonutrients in raspberries may also be able to change the signals that are sent to potential or existing cancer cells. In the case of existing cancer cells, phytonutrients like ellagitannins in raspberries may be able to decrease cancer cell numbers by sending signals that encourage the cancer cells to being a cycle of programmed cell death (apoptosis). This signaling is likely to involve activity of the p53 protein that is typically classified as a tumor suppressor protein.
In the case of potentially but not yet cancerous cells, phytonutrients in raspberries may be able to trigger signals that encourage the non-cancerous cells to remain non-cancerous. The role of the a protein complex called nuclear factor kappa B (NFkB) is likely to be involved in this set of events.
DescriptionRaspberries belong to the rose (Rosaceae) family of plants, which houses some of the world's most beloved fruits including apples, apricots, blackberries, cherries, loquats, peaches, pears, plums, and strawberries. Almonds also belong to this diverse family of plants. Among U.S. consumers, raspberries are the third most popular berry and follow right after strawberries and blueberries.
There are over 200 species of raspberries, all belonging to the scientific genus called Rubus. Fortunately, however, many of the raspberry species that are grown commercially can be placed into one of three basic groups: red raspberries, black raspberries, and purple raspberries.
Like their name implies, mature red raspberries can typically be identified by the shade of red in their color, although this red may veer toward the pinkish side. Among all commercially cultivated raspberries, Rubus idaeusor European red raspberry is among the most common.
Black raspberries may actually be dark enough to be indistinguishable from blackberries in terms of color. Here one of the most common commercially grown species is Rubus occidentalis, also sometimes referred to as thimbleberry, scotch cap, or black cap.
The third category of raspberry—purple raspberry—is a category in which reds and blacks have been hybridized (naturally combined). Over time, when red raspberries or black raspberries underwent naturally genetic mutations, yellow raspberries also developed. Even though naturally yellow or golden in color, yellow raspberries are actually special forms of red or black raspberries.
In science terms, raspberries are referred to as "aggregate fruits." Aggregate fruits are actually composed of many small individual fruits that come from multiple ovaries in a single flower. In the case of a raspberry, those small individual fruits are the little juicy spheres that make up the structure of the raspberry. They are also called drupelets, and each one has its own seed.
The word "bramble" refers to the prickly or thorny nature of a plant, and raspberries are sometimes referred to by raspberry growers as "brambles" (even though some species do not have thorns). The bramble nature of the raspberry plant comes into play on a regular basis for raspberry growers. Although the root system of raspberry plants can last for many years, the canes themselves are typically pruned twice a year to allow for spring and fall fruiting.
HistoryScientists aren't entirely sure about the origins of raspberries. Wild raspberries appear on at least five continents, and there is enormous species diversity for this fruit. Some arctic species of raspberry are native to Alaska, the Aleutian Islands, and northern Asia; other species are native to eastern Asia and the Hawaiian islands; still others are native to Europe or to North America. In terms of their first cultivation, we have evidence dating back about 2,000 years in Europe, making raspberries one of the earliest berry crops. Natural trading and traveling may have been important in the spread of raspberries, for example, into North American from eastern Asia across the Bering Strait.
Interestingly, when cultivated raspberries are compared with wild raspberries, they turn out to be quite similar in terms of total phenols and total anthocyanin content. This similarity is especially true when the cultivated raspberries have also been organically grown. Although we might tend to think about a "wild" food as being more rich in nutrients than a cultivated food, this distinction does not hold true for raspberries when it comes to their phenol and anthocyanin antioxidants.
Today, raspberries rank high on the list of the world's most popular berries. Among the 400,000 metric tons of raspberries produced worldwide, Russia, the United States, Serbia, Poland, and Chile rank among the top producers. In the United States, it's the West Coast that is most active in raspberry production, although commercial producers can be found across the country. Interestingly, well over 500 organic farms in the U.S. are now certified for organic raspberry production, and raspberries rank as the third most popular fresh-use berry in the U.S. following strawberries and blueberries. The U.S. also imports about 15,000 metric tons of raspberries from Mexico to meet consumer demand for this fruit.
How to Select and StoreAs raspberries are highly perishable, they should only be purchased one or two days prior to use. The goal when purchasing this fruit is to choose berries that are fully ripe without being overly so. Choose berries that are firm, plump, and deep in color, while avoiding those that are soft, mushy, or moldy. If you are buying berries prepackaged in a container, make sure that they are not packed too tightly, since this may cause them to become crushed and damaged, and that the container has no signs of stains or moisture, indications of possible spoilage. Within the U.S., raspberries are generally available from mid-summer through early fall.
Raspberries are a highly perishable fruit, so extra care should be taken in their storage. If you do not plan to eat your raspberries upon arrival back at home, they should be stored in your refrigerator. Before storing in the refrigerator, remove any berries that are molded or spoiled so that they will not contaminate the others. Place the unwashed berries back in their original container or spread them out inside of a glass or plastic container that has a lid and can be sealed. Raspberries will keep fresh in the refrigerator for one or two days. When taking your raspberries out of the refrigerator for consumption, try not to leave them at room temperature any longer than necessary (one to two hours), and also try to avoid placing them directly in strong sunlight. These steps will help prevent spoilage.
Raspberries freeze very well. Wash them gently using the low pressure of the sink sprayer so that they will maintain their delicate shape and then pat dry with a paper towel. Arrange them in a single layer on a flat pan or cookie sheet and place them in the freezer. Once frozen, transfer the berries to a heavy plastic freezer bag or plastic freezer container that can be sealed and return them to the freezer where they will keep for up to one year.
Within this context of How to Select and Store, we would like to point out the often dramatic differences we've seen between whole raspberries and products containing processed forms of raspberries. Unless provided with information from the manufacturer, it's difficult to be sure that you are getting substantial raspberry benefits from products that contain raspberries in processed forms. Processing in this case may include drying, juicing, fermenting into wine, straining, or filtering. For example, if the seeds of the raspberries have been removed during processing, many key phytonutrients may be lost or greatly reduced. Exposures to heat during processing may also result in substantial phytonutrient loss. We've seen studies that make us cautious about the preservation of nutrient richness in most processed forms of raspberry, including wines produced in the absence of seeds, baby foods produced with the use of heat and filtering, and commercial drying of raspberry for creation of an industrially versatile powdered form. While there are ways to make wine and baby food and other raspberry-containing products that avoid great damage to raspberry phytonutrients, it can be difficult to determine how careful manufacturers have been in their food production. For this reason, we recommend that you stick with whole raspberries in fresh or frozen form when purchasing them at the grocery and incorporate them into recipes using the minimal type of processing that you would be undertaking in your own kitchen.
Tips for Preparing and CookingTips for Preparing RaspberriesAs raspberries are very delicate, wash them very gently, using the light pressure of the sink sprayer if possible, and then patting them dry. They should be washed right before eating or recipe preparation so that they do not become water-soaked and are not left at room temperature for too long. Do not use any berries that are overly soft and mushy unless you will be puréeing them for a sauce or coulis.
How to EnjoyA Few Quick Serving Ideas
Mix fresh raspberries in with creamy millet porridge for a sweet morning breakfast treat.
While at first glance it may seem unusual, the flavor combination created by sprinkling fresh raspberries with balsamic vinegar will send your palate to heaven.
Plain yogurt mixed with raspberries, honey, and freshly chopped mint is delicious eaten as is or used as a topping for waffles or pancakes.
Depending upon how much sweetener you use, homemade raspberry coulis can be used as a sauce for either savory poultry dishes or sweet desserts.
Raspberry Fruits Compared to Raspberry LeafIn this Individual Concerns section, we would like to make one additional note about the difference between raspberry fruit and raspberry leaf. Raspberry leaf has a long history of use in botanical medicine and is widely available in the U.S. and other countries in tea form. While raspberry leaf has been used to support function in various body systems (including the digestive tract), it's best-known use has been in conjunction with pregnancy and childbirth. While these medically related uses of raspberry leaf may be well worth discussing with your healthcare practitioner, it's important to treat them as separate and distinct from the benefits of raspberry fruit as ordinarily consumed in whole food form.
In obese persons with type 2 diabates, adiponectin is not produced in sufficient amounts or, if adequately produced, remains too inactive. This inadequacy of adiponectin in obese persons with type 2 diabetes is a key problem for regulation of their blood sugar and blood fats. By activating adiponectin, the tiliroside in raspberries can help improve insulin balance, blood sugar balance, and blood fat balance in obese persons with type 2 diabetes. In studies to date, there is no indication that raspberry tiliroside will stop weight gain or prevent fat accumulation. But it may be able to help prevent unwanted consequences of too much body fat and compromised regulation of blood sugar, blood insulin, and blood fats.
Within this context of obesity and blood sugar regulation, another aspect of raspberry phytonutrients has captured the attention of researchers involving the ability of raspberry extracts to block activity of an enzyme called alpha-glucosidase. Alpha-glucosidase is a starch-digesting enzyme, and when it becomes active in the digestive tract, it increases the breakdown of starches into sugars. These sugars get absorbed up into the bloodstream and can cause excessively high levels of blood sugar following a meal. (This process is called postprandial hyperglycemia.) By blocking activity of alpha-glucosidase, raspberry extracts may make it possible for persons with type 2 diabetes (or obese persons experiencing problems with blood sugar regulation) to better manage their blood sugar levels.
We've been asked about the exact glycemic idex (GI) value for raspberries, and unfortunately, have not been able to find food research substantiation for any exact value. We've seen estimates for many berries that fall into the 40-50 GI range, and for most researchers, that would place them in the low GI category. Since one cup of fresh raspberries provides about 15 grams of total carbohydrates and only 5-6 grams of sugar (compared with 8 grams of dietary fiber), a modest serving of fresh raspberries (for example, 1/2 cup) is likely to be a very good fit in most diets, even diets focused on stabilization of blood sugar.
Obesity and Blood Sugar BenefitsPerhaps the most fascinating new areas of research on raspberries involve management of obesity and type 2 diabetes. In the case of obesity, two compounds in raspberries have received special focus: raspberry ketone (also called rheosmin) and a type of flavonoid called tiliroside.
Raspberry ketone is a compound that naturally occurs in raspberries, but unlike its name suggests, it is by no means exclusive to this fruit. Raspberry ketone is contained in a wide variety of plants, although not usually in such sizable amounts as are found in raspberries. Turkish rhubarb is one such plant. Larch, yew, maple, and pine are trees that contain amounts of raspberry ketone, and in some studies, pine needles have been used as a source of this compound for experimental purposes.
The chemical name for raspberry ketone is 4-(4-hydroxyphenyl) butan-2-one. Researchers are equally familiar with raspberry ketone under the name of rheosmin, and since 1965, it's been included on the Food and Drug Administration's (FDA's) Generally Recognized As Safe (GRAS) list as an approved food additive. The primary use of rheosmin as a food additive has been for flavor and aroma.
The rheosmin found in raspberries can increase metabolism in our fat cells by increasing enzyme activity, oxygen consumption, and heat production in certain types of fat cells. By boosting fat metabolism in this way, we may be less likely to deposit fat in our fat cells, and we may be able to use up some of the fat that is stored there. By improving our fat cell metabolism, we may also be able to reduce the number of pro-inflammatory messaging molecules that are produced by our fat cells. As a result, we may be less likely to experience some of the inflammation-based problems that typically accompany obesity.
In addition to these benefits, rheosmin found in raspberries can also decrease activity of a fat-digesting enzyme called pancreatic lipase that is produced by our pancreas. By decreasing the activity of this enzyme, we may digest and absorb less fat—another potential plus when trying to deal with the consequences obesity.
In addition to the rheosmin found in raspberries, scientists have also focused on the obesity-related benefits of a second compound called tiliroside. Tiliroside is a type of flavonoid (called a glycosidic flavonoid) that is found in many plants of the rose family, including rose hips, strawberries, and raspberries. In preliminary studies, tiliroside has been show to activate a special hormone called adiponectin that is produced by our fat cells. (The "adipo" part of this word means "fat," which is also why our fat cells are also called "adipocytes.")
The vast majority of these phytonutrients are not only provided by raspberries, but provided in amounts that are significant in terms of protecting us against the dangers of oxidative stress and the dangers of excessive inflammation. By helping to scavenge free radical molecules, and by helping to regulate the activity of enzymes that could trigger unwanted inflammation, the phytonutrients in raspberries help lower our risk of chronic diseases that are associated with chronic oxidative stress and chronic inflammation. These chronic diseases include obesity, type 2 diabetes, hypertension, and atherosclerosis. The ellagic acid found in raspberries deserves special mention as an anti-inflammatory compound. This phytonutrient has been shown to help prevent overactivity of certain pro-inflammatory enzymes (including cyclo-oxygenase 2, or COX-2) as well as their overproduction. In animal studies, intake of ellagic acid has been shown to reduce numerous aspects of unwanted and excessive inflammation, including aspects associated with Crohn's disease.