According to the largest USDA study of the antioxidant content of food, cranberries are among the top five foods with the highest antioxidant content per serving. (1) The study included samples of more than 1,100 commonly consumed foods and beverages. It represents the largest ever systematic screening of antioxidants in food.
Antioxidants are substances that protect cells from oxidative stress and the effects of free radicals. Free radicals are continually produced in the human body. Breathing air, digesting food, or being exposed to second-hand smoke or the sun all produce free radicals. Experts believe free radicals play a role in heart disease, cancer, and other diseases.
There are hundreds if not thousands of antioxidants in foods. Examples of some of the antioxidants found in cranberries include (2):
- Ellagic acid
- Vitamins A, C and E
Research suggests that antioxidants from food are more beneficial for human health compared to dietary supplements. Antioxidants seem to work best when combined with other antioxidants and nutrients naturally present in food.
Plant-based foods like fruits, vegetables, nuts, and grains contain more antioxidants than animal products, like meat and dairy. In the USDA study, the top 300 foods were plant-based products while the bottom 300 foods were animal products.
While much more research needs to be done on the effects of antioxidants on human health, research supports the beneficial role of antioxidant-rich fruits and vegetables in a healthful diet.
Cranberries—available in many convenient forms including dried cranberries, 100% cranberry juice, and cranberry sauce—are a wonderful way to add an antioxidant-rich fruit to your daily diet.
(1) Halvorsen, BL, Carlsen MH, Phillips KM, Bohn, SK, Holte K, Jacobs DR, and Blomhoff R. Content of redox-active compounds (ie antioxidants) in foods consumed in the United States. Am J Clin Nutr 2006;84:95-135. Full article available at http://www.ajcn.org/cgi/reprint/84/1/95
(2) McKay DL and Blumberg JB. Cranberries (Vaccinium macrocarpon) and Cardiovascular Disease Risk Factors. Nutr Rev 2007;11: 490-502. use courtesy of Cranberry Marketing Committee.
Since the early 1990s researchers have been studying the effects of cranberry juice products on urinary tract health. More recently, researchers have examined cranberries’ ability to promote heart health. Today researchers around the world are studying other potential health benefits of cranberries. While much of this research is preliminary, it is exciting to consider the possible benefits of this humble little red berry.
Based on research showing cranberries contain proanthocyanidins (PACs), substances that interfere with bacteria’s ability to attach to cells lining the bladder walls, researchers in Canada and Japan have been investigating the effects of cranberry extracts on bacteria that cause tooth decay and gum disease. (1-4) These tissue and cell culture studies have shown promising results; cranberry extracts weaken the ability of bacteria to attach to teeth and gums. Does eating cranberries or drinking cranberry juice have this effect? We don’t know yet because human studies have not been performed; however, the anti-adhesion effect of cranberry juice products has been demonstrated for urinary tract health. It is likely that cranberry products have a similar benefit for dental health.
Cancer Prevention & Treatment
According to the National Cancer Institute, diets rich in fruits and vegetables may reduce the risk of some types of cancer and other chronic diseases. One of the reasons why this may be true is that fruits and vegetables contain antioxidants, substances that protect cells from DNA damage and other “injuries” that can increase risk of cancer and other chronic diseases.
A large USDA study of the antioxidant content of more than 1,100 foods showed that cranberries are among the top five foods with the highest antioxidant content per serving. (5) Cranberries contain a number of substances with antioxidant activity, including anthocyanins, flavonols, and proanthocyanidins. These substances reduce oxidative stress, decrease cellular inflammation, and protect DNA, thereby reducing risk of cellular changes that could lead to cancer initiation and progression. (6)
In addition to potentially reducing risk of cancer, cranberries are also being investigated as a way to improve the effectiveness of chemotherapy for ovarian cancer. (7) Researchers at Rutgers University demonstrated in cell culture studies that human ovary cancer cells resistant to platinum chemotherapy drugs became up to six times more sensitized to the drugs after exposure to the cranberry compounds compared to cells that were not exposed to the compounds, which were obtained from juice extracts. The researchers believe the A-type proanthocyanidins (PACs) that are unique to cranberries bind to and block certain tumor promoter proteins found in the ovary cancer cells, making the cancer cells become more vulnerable to attack from the drugs. This study is very preliminary. Further research is needed to confirm these findings, and to determine if the same benefit is seen in women undergoing chemotherapy for ovarian cancer. What is seen in cell studies is not always replicated in human studies.
Stomach ulcers are caused by a type of bacteria called Helicobacter pylori. Studies (8, 9) suggest that cranberry products may reduce the incidence of stomach ulcers the same way cranberries promote urinary tract health and oral health; proanthocyanidins (PACs) in cranberries interfere with the bacteria’s ability to attach, in this case, to the stomach wall. As of May 2008, only one double-blind, randomized, controlled clinical study on humans has been published. (10) All subjects in this study were taking oral antibiotics, and all subjects who received antibiotics plus cranberry juice had lower levels of bacteria in their stomachs. Only women receiving cranberry juice plus antibiotics had statistically significant decreases in bacteria. Further research is needed to determine if this finding was a fluke or if women receive a greater benefit than men.
- Yamanka A, Kouchi T, Kasai K, Kato T, Ishihara K, Okuda K. Inihibitory effect of cranberry polyphenol on biofilm formation and cysteine proteases of porphyromonas gingivalis. J Periodontal Res. 2007; 42(6):589-92
- Labrecque J, Bodet C, Chandad F, Grenier D. Effects of a high-molecular-weight cranberry fraction on growth, biofilm formation and adherence of Porphyromonas gingivalis. J Antimicrob Chemother. 2006 Aug;58(2):439-43
- Bodet C, Chandad F, Grenier D. Anti-inflammatory activity of a high-molecular-weight cranberry fraction on macrophages stimulated by lipopolysaccharides from periodontopathogens. J Dent Res. 2006 Mar;85(3):235-9.
- Bodet C, Piche M, Chandad F, Grenier D. Inhibition of periodontopathogen-derived proteolytic enzymes by a high-molecular-weight fraction isolated from cranberry. J Antimicrob Chemother. 2006 Apr;57(4):685-90. Epub 2006 Feb 10.
- Halvorsen, BL, Carlsen MH, Phillips KM, Bohn, SK, Holte K, Jacobs DR, and Blomhoff R. Content of redox-active compounds (ie antioxidants) in foods consumed in the United States. Am J Clin Nutr 2006;84:95-135. Full article available athttp://www.ajcn.org/cgi/reprint/84/1/95
- Neto CC. Cranberry and blueberry: evidence for protective effects against cancer and vascular diseases. Mol Nut Food Res. 2007;51(6):653-64.
- Singh AP, Vorsa N. Cranberries may improve therapy for ovarian cancer. (unpublished data) Poster presentation at 2007 American Chemical Society meeting, Boston, MA.
- Gotteland M., Brunser O, Cruchet S. Systematic review: Are probiotics useful in controlling gastric colonization by Helicobacter pylori? Aliment Pharmacol Ther. 2006 Apr 15;23(8):1077-86.
- Johnson-White B, Buquo L, Zeinali M, Ligler FS. Prevention of nonspecific bacterial cell adhesion in immunoassays by use of cranberry juice. Anal Chem. 2006 Feb 1;78(3):853-7.
- Shmuely H, Yahav J, Samra Z, Chodick G, Koren R, Niv Y, Ofek I. Effect of cranberry juice on eradication of Helicobacter pylori in patients treated with antibiotics and a proton pump inhibitor. Mol Nutr Food Res. 2007; 51(6):746-51. use courtesy of Cranberry Marketing Committee.
Cranberries + Urinary Tract Infections
Many people know that cranberries help maintain urinary tract health. Research is now showing just how cranberry juice promotes urinary tract health…and why cranberries are the only food with this benefit. For many years, people thought drinking cranberry juice was beneficial because the juice was thought to increase the acidity of urine in the bladder and therefore kill the bacteria that cause urinary tract infections. This is not the case. It turns out that cranberries contain compounds called proanthocyanidins (PACs) that have strong bacterial anti-adhesion properties. PACs interfere with the ability of bacteria to adhere to the cells that line the bladder wall. Instead of sticking to the bladder wall and causing an infection (and the subsequent pain), the bacteria get flushed out in the urine. While other foods like apple juice, grape juice and green tea contain proanthocyanidins (PACs), cranberries are the only food that contain PACs with A-type linkages (as opposed to B-type linkages). The unique molecular structure explains why cranberries are the only food associated with urinary tract health. E. coli bacteria cause 80-90% of urinary tract infections. Proanthocyanidins (PACs) from cranberries affect E. coli cells in three ways. Cranberry PACs (1) change the shape of the E. coli from rods to sphers, (2) alter the cell membranes, and (3) compress tendrils on the outside of the cells, which affects E. coli’s ability to attach to cells lining the bladder wall. All of these effects inhibit the bacteria’s ability to attach to cells lining the bladder wall. The anti-adhesion property of cranberry juice and cranberry juice cocktail has been demonstrated in many lab and human studies. (1-3) However, only one study has examined the anti-adhesion property of sweetened dried cranberries. (4) This small pilot study of five human subjects compared the effects of sweetened dried cranberries and unsweetened raisins. Only the subjects who consumed the dried cranberries exhibited anti-adhesion activity. More research is needed to support this finding, but it looks like sweetened dried cranberries may also help promote urinary tract health.
Where can I find nutritional information on cranberries?
The USDA’s National Nutrient Database for Standard Reference provides nutritional data for raw cranberries, dried cranberries, cranberry sauce and cranberry juice cocktail.
Do cranberries grow on a tree or a bush?
Neither. The American Cranberry (Vaccinium macrocarpon) is a low-growing, vining, woody perennial plant with small, alternate, oval leaves. The plant produces horizontal stems or runners up to 6 feet (2 m) long. Short vertical branches 2 to 8 inches (5 to 20 cm) in height, called uprights, grow from buds on the runners and produce both vegetative and fruit buds. Each fruit bud may contain as many as seven flowers.
Do cranberries grow in or under water?
No. It is a common misconception that cranberries are grown in water. Water is used during harvest to float the fruit for easier collection, and during the winter months to protect the plants from freezing and desiccation. The rest of the year the fruit is grown on dry beds.
Can I freeze fresh cranberries?
Yes. In fact cranberries freeze very well either whole or sliced. When sealed in an airtight container, frozen cranberries will keep for nearly a year.
How much cranberry juice should I drink a day?
Drinking 8 – 16 oz of cranberry juice cocktail each day is recommended to maintain urinary tract heath and prevent urinary tract infections.
How are free radicals produced in the body?
The body produces free radicals through normal metabolic pathways (i.e. extracting energy from the food we eat). Exposure to the sun’s ultraviolet radiation, tobacco smoke, and exposure to certain naturally occurring chemicals can also be sources of free radical production. In short, we are exposed to potential sources free radical production every day of our lives.
What is a free radical?
Normally the molecules that make up our body have an even number of electrons orbiting around a nucleus. A free radical is any molecule with an odd number of electrons. These “unstable” molecules attempt to “stabilize” themselves by capturing an electron from another molecule. The cells in the body where this process is occurring can become injured. The cell may malfunction or even become malignant.
What is an antioxidant?
Antioxidants are compounds that neutralize free radicals when they are formed. The human body is capable of producing antioxidants naturally, but under conditions of stress this antioxidant production can be severely impaired. Fruits and vegetables, including cranberries, provide an excellent source of additional antioxidants.
What are Proanthocyanidins (PACs)?
Proanthocyanidins (PACs) are in the flavanol family – a class of polyphenols. The PACs found in cranberries have a different structure than those found in other fruits and vegetables which are associated with their anti-adhesion properties. Cranberry PACs help prevent the adhesion of certain harmful bacteria, including E. coli associated with urinary tract infections, onto cell walls.
What are polyphenols?
Polyphenols include several classes of phytonutrients, including flavanols found in cranberries, that are naturally occurring in fruits and vegetables. In addition to their antioxidant capacity, polyphenols have been shown to provide protection from some bacterial pathogens, cancer, cardiovascular disease and inflammation.