Scientific Name: Cranberry
Other Names: American Cranberry, Arandano, Mossberry, Vaccinium species

Who is this for?

Uses

Cranberries and cranberry juice have long been thought to fight urinary tract infections (UTIs). In the 1800s, early researchers believed that cranberry products made the urine acidic, thereby killing organisms that need alkaline urine to survive. However, approximately 4 quarts of cranberry juice or about 3 pounds of cranberries per day would be needed to maintain an acid level high enough to kill bacteria in the bladder. Today, chemicals in cranberries are believed to prevent infective organisms from attaching to the bladder and other parts of the urinary tract. The ability of cranberries to eliminate already-attached bacteria is limited, so cranberry products are more effective at preventing UTIs than treating them. Studies have shown that drinking between one ounce and 10 ounces of cranberry juice per day can help prevent UTIs from returning in women who are prone to having UTIs. Cranberry may also reduce the ammonia smell of urine by reducing the number of both bacteria and white blood cells in it.

In laboratory and animal studies, cranberries have shown some heart protective and anti-cancer effects, as well. Cranberries contain high percentages of chemicals known as flavonoids and phenols, which both act as antioxidants in the body. Antioxidants moderate a chemical process called oxidation, which produces oxygen free radicals, natural chemicals that may suppress immune function and damage body cells. Both heart disease and cancer may be worsened by oxygen free radicals. Laboratory studies indicate that antioxidants such as those in cranberries may prevent the formation of arterial plaques (deposits of fats and blood cells that may block arteries), relax blood vessels, and keep cancer cells from spreading. Additional laboratory and human research suggests that cranberries may also lower cholesterol by interfering with the transport of dietary fats. However, much more research is needed to prove or disprove these effects for humans.

Precautions

Cranberries contain chemicals called oxalates, which may contribute to the formation of some types of kidney stones. Drinking large amounts of cranberry juice (more than about a quart per day) or taking concentrated cranberry supplements may increase the risk of developing kidney stones. Therefore, individuals who have or who ever have had kidney stones should not consume very large amounts of cranberries or use supplemental cranberry products.

Cranberries and cranberry juice are naturally sour. Commercial cranberry products may have significant amounts of sugar added to make them taste better. Individuals with diabetes may want to use artificially sweetened cranberry products or limit their consumption of regular cranberry sauce, juice, or cocktail.

What side effects should I watch for?

No side effects have been associated with taking cranberry supplements or consuming multiple servings of cranberry products. However, cases of diarrhea or upset stomach have been reported after the consumption of very large amounts (up to 4.25 quarts or 4,000 ml) of cranberry juice in one day.

What interactions should I watch for?

Recently, published cases have reported that chemicals in cranberries may interfere with the effects of the blood-thinning drug, warfarin. In one case, the effects of warfarin were decreased, but in several other instances, warfarin's effects were increased. One case resulted in death. Therefore, the use of supplemental cranberry products is not recommended for individuals who take warfarin.

No other interactions have been reported between cranberries and prescription drugs, non-prescription drugs, other herbal supplements, or foods. However, not all potential interactions involving cranberries may be known. Be sure that your doctor and pharmacist are aware of all the prescription and non-prescription medicines you take before you begin to use cranberry capsules or take large doses of cranberries or cranberry juice.

Some interactions between herbal products and medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how cranberries interact with drugs, herbals, and foods and the severity of those interactions, please use our Drug Interactions Checker to check for possible interactions.

Should I take it?

Although a number of different types of cranberries or similar berries grow wild in most cool parts of the world, the most commonly cultivated species of cranberry is one of the few fruits that originated in North America. Cranberries of this type are now grown commercially in New England, other northern states, and Canada. They are the round, bright red berries common in the cranberry sauce or relish that is often served at Thanksgiving dinner. They grow on perennial bushy vines that keep their leaves all year, although the leaves turn brown during the winter. Up to 6 feet long, these cranberry vines have short stems that produce light pink flowers in the spring. Ripe berries are harvested in the fall -- usually after the areas where they grow are flooded with water. Because cranberries float, they are easily shaken from the bushes into the water and then gathered into nets and taken to processing plants. During the winter, the fields remain flooded, the water freezes, and the ice serves as insulation for the plants.

Cranberries were originally named "craneberries" by early New England settlers, possibly due to a supposed resemblance of the flower to the head of the cranes that lived along the coast. Over the years, the name was shortened to "cranberries". Native People used cranberries for food and also for a red dye. In the 1700s, cranberries were recognized as a source of vitamin C and sailors carried them on shipboard to prevent the vitamin C deficiency condition known as scurvy. The berries are now used mainly as food but also as medicine. Because the berries are sour, many foods and drinks made from them contain large amounts of sugar.

Dosage and Administration

Nutritionally, one serving is considered to be about one-half cup (55 grams) of cranberries, about 6 ounces (180 ml) of pure cranberry juice, or about 18 ounces (540 ml) of cranberry juice cocktail. Commercially available cranberry drinks -- usually designated as "cocktails" -- are only about 35% pure juice. Because cranberry juice is so sour, it is usually diluted with water and sweetened to be acceptable as a beverage. In studies, daily doses of cranberry juice cocktail have ranged from about one ounce (30 ml) to 10 ounces (300 ml) for preventing UTI or 3 ounces (90 ml) to 6 ounces (180 ml) for lessening urine odor. Fresh cranberries may be substituted for pure cranberry juice at a ratio of about one ounce of cranberries to 3 ounces of juice.

Although no standard dose for cranberry supplementation is reported in scientific literature, dried cranberry juice concentrate may be available as capsules or tablets, which are generally taken in doses of 300 mg or 400 mg twice a day.

Summary

Chemicals in cranberries may prevent bacteria from sticking to the walls of the urinary tract, thereby decreasing the chance of urinary tract infections. They may also reduce the ammonia odor of urine. Antioxidant effects associated with cranberries may also help protect against heart disease, high cholesterol, and cancer.

Risks

Oxalates in cranberries may cause some types of kidney stones. Individuals with diabetes should avoid commercial cranberry products because they usually contain high amounts of sugar.

Side Effects

Drinking extremely large quantities of cranberry juice cocktail has been associated with gastrointestinal upset.

Interactions

Cranberries may alter the effects of warfarin.

Last Revised April 17, 2006

References

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Note: The above information is not intended to replace the advice of your physician, pharmacist, or other healthcare professional. It is not meant to indicate that the use of the product is safe, appropriate, or effective for you.

In general, herbal products are not subject to review or approval by the U.S. Food and Drug Administration (FDA). They are not required to be standardized, meaning that the amounts of active ingredients or contaminants they contain may vary between brands or between different batches of the same brand. Not all of the risks, side effects, or interactions associated with the use of herbal products are known because few reliable studies of their use in humans have been done.

This information is provided for your education only. Please share this information with your healthcare provider and be sure that you talk to your doctor and pharmacist about all the prescription and non-prescription medicines you take before you begin to use any herbal product.

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