Health Benefits of Cranberry
While familiar nutrients like vitamin C and fiber play a very important role in cranberry’s health benefits, it’s the amazing array of phytonutrients in cranberries that has gotten the special attention of health researchers.
When speaking in general terms about the health benefits of cranberries, it is also important to know that the most commonly consumed form of this food is juice processed from the berries and typically produced by adding generous amounts of sugar. This form of cranberry cannot provide you with cranberry’s full phytonutrient benefits. The cranberry “presscake”—or what is left behind in terms of skins and flesh after the juice has been processed out—typically contains the bulk of the phytonutrients when evaluated in lab studies.
Protection against Urinary Tract Infection (UTI)
Long before researchers started investigating from the standpoint of science, cranberry has been used to help prevent and treat urinary tract infections (UTIs). While the acidity of cranberries was at one time an important target of research, we now know that cranberry’s ability to provide UTI benefits is not primarily related to its acidity, but rather to its proanthocyanidin (PAC) content. The PACs in cranberry have a special structure (called A-type linkages) that makes it more difficult for certain types of bacteria to latch on to our urinary tract linings. Include in these types of bacteria are pathogenic (infection-causing) strains of E. coli—one of the most common microorganisms involved in UTIs. By making it more difficult for unwanted bacteria like E. coli to cling onto the urinary tract linings, cranberry’s PACs help prevent the expansion of bacterial populations that can result in outright infection. The age group in which researchers are least sure about this process involves children—it’s just not clear when cranberry’s health benefits fully extend to this age group. The area where benefits have been most pronounced are in middle-aged women who have experienced recurrent UTIs. In some studies, UTIs in this age and gender group have been reduced by more than one—third through dietary consumption of cranberry.
The discovery that cranberries prevent UTIs by blocking adhesion of bacteria to the urinary tract lining is a discovery that has allowed research on cranberry to expand out in other important directions. In our Digestive Benefits section below, we will describe how prevention of stomach ulcer is one very intriguing new direction in the cranberry research, based on this exact same principle of blocking bacterial adhesion to the lining of an organ system. (In the case of stomach ulcer, it’s the stomach lining that’s at risk, and the bacteria involved are the Helicobacter pyloribacteria.)
For the cardiovascular system and for many parts of the digestive tract (including the mouth and gums, stomach, and colon) cranberry has been shown to provide important anti-inflammatory benefits. It’s the phytonutrients in cranberry that are especially effective in lowering our risk of unwanted inflammation, and virtually all of the phytonutrient categories represented in cranberry are now known to play a role. These phytonutrient categories include proanthocyanidins (PACs), anthocyanins (the flavonoid pigments that give cranberries their amazing shades of red), flavonols like quercetin, and phenolic acid (like hydroxycinnamic acids).
In the case of our gums, the anti-inflammatory properties of cranberry can help us lower our risk of periodontal disease. Chronic, excessive levels of inflammation around our gums can damage the tissues that support our teeth. It’s exactly this kind of inflammation that gets triggered by ongoing overproduction of certain cytokines. (Cytokines are messaging molecules, and the pro-inflammatory cytokines tell our cells to mount an inflammatory response. As messages are sent more frequently and more constantly, the inflammatory response becomes greater.) Phytonutrients in cranberry help reduce this inflammatory cascade of events precisely at the cytokine level. Production of pro-inflammatory cytokines like interleukin 6 (IL-6) and RANTES (Regulated on
Activation Normal T-cell Expressed and Secreted) is lowered by the activity of cranberry phytonutrients. In addition, cranberry phytonutrients inhibit the activity of the enzymes cyclo-oxygenase 1 (COX-1) and cyclo-oxygenase 2 (COX-2). These COX-1 and COX-2 enzymes are key factors in the production of other pro-inflammatory messaging molecules, and by inhibiting these enzymes, cranberry’s phytonutrients significantly lower our risk of unwanted inflammation.
Dietary consumption of cranberry has also been shown to reduce the Risk of chronic, unwanted inflammation in the stomach, large intestine (colon) and cardiovascular system (especially blood vessel linings). We’ll discuss some of these health benefits in more detail in the Digestive Benefits and Cardiovascular Benefits sections of this cranberry profile.
Mixed Findings for Kidney Stone Formation
Contrary to popular opinion, we believe that the latest research shows mixed results for cranberry with respect to kidney stone formation. This area of the health research can be confusing. Kidney stones can be formed from several different mineral-including combinations. The most common type of kidney stones formed in the United States involves a combination of calcium-plus-oxalic acid and are called calcium-oxalate stones. Among U.S. adults who develop kidney stones, about 75% develop calcium-oxalate stones. The other 25% develop a variety of different stones, including calcium-phosphate stones (called brushite stones), magnesium-sulfate containing stones (called struvite stones), and uric acid-containing stones (called urate stones). Since cranberries have the ability to increase the concentration of both calcium and oxalate in the urine, they can increase the likelihood of calcium-oxalate stone formation in susceptible individuals. Urinary uric acid, however, is typically decreased by intake of cranberry, and so risk of urate stones in susceptible individuals can be decreased by intake of cranberry. With other types of kidney stones, mixed effects of cranberry intake have been demonstrated. From our perspective, the bottom line at this point in the research process seems clear: individuals with kidney stone problems of any kind, or known susceptibility to kidney stone formation, should talk with their healthcare provider if considering inclusion of cranberry in their diet. Since 3 out of 4 U.S. adults experiencing kidney stone problems develop calcium-oxalate stones, there’s a good chance for cranberry to be a problematic addition to the diet in the case of U.S. adults with a history of kidney stone formation.
While research in this area is somewhat limited, recent studies on the immune support benefits of cranberry are exciting. In studies on very small numbers of human participants, intake of cranberry extracts has shown the ability to improve multiple aspects of immune function, and to lower the frequency of cold and flu symptoms in the subjects. In several of these studies, the cranberry extracts were standardized to contain a known, higher-end amount of proanthocyanidins (PACs)—somewhat comparable to a double-strength cranberry juice. From our perspective, the doses of cranberry extract used in these studies match up fairly well with generous intake of whole, raw cranberries, and we look forward to future studies focused on precisely that: intake of whole, raw cranberries and resulting changes in cold and flu symptoms.
Following decreased risk of urinary tract infection (UTI), increased health of the cardiovascular system is perhaps the best-researched area of cranberry health benefits. It’s the combined impact of cranberry antioxidants and anti-inflammatory phytonutrients in cranberry that’s responsible here. Oxidative stress and chronic inflammation can place our blood vessel walls at great risk of damage. Once damaged, our blood vessels walls can undergo a process of plaque formation, and our risk of atherosclerosis (blood vessel wall thickening and blood vessel blocking) can be greatly increased. Dietary intake of cranberries and cranberry juice (in normal everyday amounts, unchanged for research study purposes) has been shown to prevent the triggering of two enyzmes that are pivotal in the atherosclerosis process (inducible nitric oxide synthase, or iNOS, and cyclo-oxygenase 2, or COX-2). In both cases, cranberry has also been shown to prevent activation of these enzymes by blocking activity of a pro-inflammatory cytokine- messaging molecule called tumor necrosis factor alpha (TNF-alpha). These anti-inflammatory benefits of cranberry appear to be critical components in the cardiovascular protection offered by this amazing fruit.
The antioxidant components of cranberries also appear to play a key role in cranberry’s cardiovascular benefits. In animal studies, these antioxidant benefits have been clearly associated with decreased risk of high blood pressure. By reducing oxidative stress inside the blood vessels, cranberry extracts consumed by rats and mice have helped prevent overconstriction of the blood vessels and unwanted increases in blood pressure.
Three related phytonutrient compounds—resveratrol, piceatannol, and pterostilbene—deserve special mention with respect to cranberry’s antioxidants. These unique phytonutrients may provide cranberry with some equally unique antioxidant properties, and a special ability to support our cardiovascular system in this regard.
A final area of cardiovascular support provided by cranberry is its ability to help us lower our LDL-cholesterol and total cholesterol, while simultaneously helping us increase our level of HDL-cholesterol. Cranberry most likely helps us achieve these cholesterol-improving changes by helping to improve oxidative and inflammatory aspects of the everyday environment in which our cholesterol-containing molecules must exist. This improved cholesterol control offered by cranberry contributes even further to our decreased risk of blood vessel blocking problems, since excess accumulation of LDL-cholesterol and insufficient amounts of HDL-cholesterol can increase the tendency of our blood vessels to become blocked. All in all, it’s quite amazing how a simple food like cranberry can provide us with cardiovascular benefits at so many different levels, all rolled into one.
Although previously mentioned in this Health Benefits section, the antioxidants found in cranberry are especially important contributors to its potential for health support. From a research perspective, there are two especially important points to consider when thinking about the antioxidant benefits of cranberries. First is the amazing array of antioxidants that are found exclusively in whole cranberries. Cranberry’s special combination of phenolic antioxidants, proanthocyanidin antioxidants, anthocyanin antioxidants, flavonoid antioxidants, and triterpenoid antioxidants is without a doubt unique. Also unique is the particular combination of three antioxidant nutrients—resveratrol, piceatannol, and pterostilbene—found in cranberry. Second are the research findings regarding the synergy between these nutrients. The phytonutrients in cranberry provide maximal antioxidant benefits only when consumed in combination with each other, and also only when consumed alongside of conventional antioxidant nutrients present in cranberry like manganese and vitamin C. When cranberry processing disrupts this antioxidant combination, health benefits from cranberry are decreased. Multiple studies in multiple health benefit areas point to this same conclusion—it’s the overall blend of cranberry antioxidants that provides us with the strongest health benefits.
One further point about cranberry antioxidant research seems worthy of mention. In several research studies, cranberries were unable to provide significant antioxidant benefits when those benefits were measured in terms of blood values. In these studies, it took a much closer look at activities going on inside of our cells to demonstrate the antioxidant benefits of cranberries. The need to look inside of our cells to find cranberry antioxidant benefits may be telling us that the special value of cranberries may often involve metabolic events that are taking place “behind the scenes.” In other words, these benefits may sometimes be missed in more broadly focused research studies, and cranberry may in fact have a stronger research track record than previously assumed.
No area of cranberry research has been more intriguing in the past 10 years than research on cranberry and cancer, even though the majority of studies in this area have involved lab studies on human cancer cells or animal experiments. On a virtual year-by-year basis, scientists continue to identify new mechanisms that establish cranberries as anti-cancer agents. These mechanisms are now known to include: blocked expression of MMPs (matrix metalloproteinases); inhibition of ODC (ornithine decarboxylase enzymes); stimulation of QRs (quinone reductase enzymes); inhibition of CYP2C9s (Phase I detoxification enzymes); and triggering of apoptosis (programmed cell death) in tumor cells. It’s important to point out that this amazing list of anti-cancer properties in cranberry is not sufficient to establish cranberry as a food to be used in the treatment of cancer. However, it is a list that appears consistent with other studies of cranberry and cancer showing dietary intake of this food to help prevent cancer occurrence. These cancer-preventive benefits of cranberry are especially likely in the case of breast, colon, lung, and prostate cancer.
None of the cancer-related benefits of cranberries should be surprising, since cranberry is loaded with antioxidant and anti-inflammatory nutrients. Chronic excessive oxidative stress (from lack of sufficient antioxidant support) and chronic excessive inflammation (from lack of sufficient anti-inflammatory compounds) are two key risk factors promoting increased likelihood of cancer. With its unique array of antioxidant and anti-inflammatory nutrients, cranberry seems ideally positioned to help us lower our risk of cancer development.
Digestive Tract Benefits
When you add up the health-related benefits of cranberry for our mouth and gums (decreased risk of periodontal disease), stomach (decreased risk of stomach ulcer), and colon (decreased risk of colon cancer), it’s impossible not to conclude that cranberry is unique among fruits in its ability to provide us with digestive tract benefits. Every category of phytonutrient known to be provided by cranberry is also known to play a role in digestive tract support. In the case of cranberry’s proanthocyanidins, it’s decreased adherence of the bacterium Helicobacter pylori to our stomach wall that’s made possible by intake of cranberry. In the case of cranberry’s flavonoids, anthocyanins and triterpenoids, provide antioxidant and anti-inflammatory benefits that decrease our risk of colon cancer, and also our risk of periodontal disease.
Recent research has also shown that cranberry may be able to help optimize the balance of bacteria in our digestive tract. Participants in one recent study involving cranberry juice intake (in amounts of approximately 2 ounces per day and over the course of about 3 months) were able to increase the numbers of Bifidobacteria in their digestive tract while maintaining other bacterial types (Bifidobacteria are typically considered to be a desirable and “friendly” type of bacteria). As a result, the relative amount of Bifidobacteria was increased, and the bacterial environment of the digestive tract may have become more favorable. Given the vast array of phytonutrients in cranberry and the known connection between so many of these phytonutrients and digestive tract health, we expect to see the digestive benefits of cranberry becoming more and more apparent in future research on this incredible berry.
What’s New and Beneficial About Cranberries
- For many years, researchers believed that the ability of cranberries and cranberry juice to help prevent urinary tract infections (UTIs) was partly related to the strong acidity of the cranberries. Recent research has shown that it’s not the acidity of the cranberries, but the unusual nature of their proanthocyanidins (PACs) that is related to prevention of UTIs. The special structure of these PACs (involving A-type linkages between their components) acts as a barrier to bacteria that might otherwise latch on to the urinary tract lining. In many studies, the UTI-preventing benefits of cranberries are somewhat modest and limited to women who have recurrent UTIs. But this whole area of investigation has opened the door to an understanding of other possible cranberry benefits. For example, stomach ulcers are often related to overgrowth and over-linking of one particular type of stomach bacteria (Helicobacter pylori) to the stomach lining. In much the same way as cranberries may help prevent bacterial attachment to the lining of the urinary tract, they may also help prevent attachment of bacteria to the stomach lining. There is already some preliminary evidence that cranberry may help protect us from stomach ulcer in this way. We expect to see future studies confirming this fascinating type of health benefit.
- Many cranberries are water-harvested. Water-harvesting means that the cranberries are grown in bogs and floated in water to allow for easy harvesting. For many years, water-harvesting of cranberries has been looked upon as an industry convenience. It’s simply easier to harvest berries that are floating on the surface. However, recent research has shown that the anthocyanin content of cranberries (the phytonutrients that give the berries their amazing red color) is increased in direct proportion to the amount of natural sunlight striking the berry. If berries floating on top of water get exposed to increased amounts of natural sunlight (in comparison to other growing and harvesting conditions), they are likely to develop greater concentrations of anthocyanins. These greater concentrations of anthocyanins are likely to provide us with stronger health benefits. In other words, water-harvesting may turn out to provide more than just harvest convenience. If it can expose cranberries to greater amounts of natural sunlight, it can increase phytonutrient health benefits that involve the unique antioxidant and anti-inflammatory properties of anthocyanins.
- A substantial number of recent studies have shown that whole cranberries consumed in dietary form—in comparison with purified cranberry extracts consumed in either liquid or dried supplement form—do a better job of protecting our cardiovascular system and our liver. Several groups of researchers have summarized their health benefit findings by pointing out that it is the synergy among cranberry nutrients (rather than individual cranberry components) that is responsible for cranberry’s health benefits. This synergy is only found in the whole berry as consumed in food form. This rule about whole dietary intake appears to apply to the antioxidant benefits, anti-inflammatory benefits, and anti-cancer benefits of cranberry.
- Over the past 5 years, scientists have identified an increasing number of mechanisms that help explain the anti-cancer properties of cranberries. These mechanisms are now known to include: blocked expression of MMPs (matrix metalloproteinases); inhibition of ODC (ornithine decarboxylase enzymes); stimulation of QRs (quinone reductase enzymes); inhibition of CYP2C9s (Phase I detoxification enzymes); and triggering of apoptosis (programmed cell death) in tumor cells. The cancer-preventive benefits of cranberries are now known to extend to cancers of the breast, colon, lung, and prostate.
In our Healthiest Way of Eating Plan, we encourage the consumption of 5-10 servings of fruits-plus-vegetables (combined) eat day. We believe that the balance between fruits and vegetables can vary from day to day, depending upon personal health factors, personal taste preferences, and optimal combining of foods in recipes as well as meals. We recognize that our recommendation calls for a more generous amount of fruits and vegetables than the amount recommended by the Centers for Disease Control (CDC) at the U.S. Department of Health and Human Services (DHHS). The CDC recommends between 1.5-2.5 cups of fruit and 2.5-4.0 cups of vegetables per day, as well as a target goal of at least 5 fruit-plus-vegetable servings (combined) per day. With respect to berries, the CDC approach provides the example of strawberries, and explains that 8 large strawberries count as 1 cup. If all fruit for the day were to be obtained from strawberries, the CDC recommendation would translate into 12-20 strawberries for the day as a way of meeting a requirement for 1.5-2.5 cups of fruit. We recommend that you set your fruit goals higher than these CDC amounts. Based on the scientific research, we believe it’s going to take closer to 3 fruit servings per day to provide you with optimum health benefits. With respect to berries in particular, we recommend that you include berries at least 3-4 times per week within your fruit servings. In several of our sample meal plans, we include berries on a daily basis! It would definitely not be a mistake for you to include a serving of berries in your daily meal plan! At the same time, we recognize that the fruit group contains many outstanding fruit options, and personal preferences (as well as local and seasonal availability) can vary greatly. Also, remember that large strawberries—at about 18 grams per berry and 8 berries per cup—stand at one end of the berry range in terms of size and recommended amount. Most berries are considerably smaller in size and weight, and a one-cup serving allows you to eat a lot more berries! With blueberries, for example, the average weight per berry is closer to 1-2 grams, and a cup’s worth of blueberries means about 100-150 berries. For cranberries and raspberries, the amount would be similar.
Among the fruits and vegetables richest in health-promoting antioxidants berries such as cranberries rank right up there at the top of the list. Antioxidants are essential to optimizing health by helping to combat the free radicals that can damage cellular structures as well as DNA. Provided that you do not experience any digestive difficulty, we recommend enjoying cranberries raw because they provide you with the best flavor and the greatest benefits from their vast array of nutrients, and may also offer the benefit of digestion-aiding enzymes. When you think about the flavors, nutrients, and enzyme content of raw fruit, it is no surprise that for thousands of years both in Asia and along the Mediterranean, people have been eating raw fruit for dessert, not only as a delicious and nutritious ending to a meal but also as a potential digestive aid.