The cranberry is the fruit of a group of evergreen dwarf shrubs, or trailing vines, in the genus Vaccinium subgenus Oxycoccos. They grow up to 2 m long, 5 to 20 cm in height and are found in acidic bogs in the cooler regions of the Northern Hemisphere. In North America, Native Americans were the first to consume cranberries. They used the berries in a variety of foods, wound medicine and dye. The berries are initially white, but turn a deep red when fully ripe. They have an acidic taste. Cranberries are a major commercial crop in certain American states and Canadian provinces. Most cranberries are processed into products such as sweetened dried berries, juice and sauce. Dried berries are also available in tablet or capsule form. Most cranberry preparations are highly sweetened with sugar, corn syrup, saccharin or fructose to enhance palatability. In recent years there has been a rapidly growing recognition of cranberries for their nutrient content and antioxidant properties, giving them status as a “superfruit”.

Health benefits of cranberries

Historically, cranberry juice has been used to prevent kidney stones and “bladder gravel”, as well as to remove toxins from the blood. Cranberries have also been recommended as an adjunctive treatment for Candida infections. Cranberry juice exerts fungistatic effects against dermatophytic and other fungi, but has no effect against Candida albicans.

Cranberry juice contains a chemical component, a high molecular weight non-dializable material (NDM) that can inhibit and even reverse the formation of plaque by Streptococcus mutans pathogens that cause tooth decay. Raw cranberries and cranberry juice are abundant in anthocyanidin flavonoids, cyanidin, peonidin and quercetin. These compounds have been shown to have powerful cytotoxic effects against human cancer cells in-vitro. There has been an increasing focus on the potential role of cranberry polyphenolic constituents in preventing several types of cancer. Cranberry tannins also have anti-clotting properties.

Cranberries in the treatment of bladder infections

For many decades cranberry juice has been believed to reduce bacterial infections of the bladder. Studies in recent years have shown that the juice can effectively treat bacterial infections in the urinary system. Research has demonstrated that an effect occurs from a component of the juice that inhibits bacterial attachment to the bladder and urethra. A randomized, double-blind, placebo controlled trial performed in Boston and published in JAMA [1] studied 153 elderly women. The study showed that subjects drinking cranberry juice for more than a month had a significantly lower incidence of bladder infection than those taking a placebo juice. Two glasses of cranberry juice a day can help to prevent urine infections, especially in people who are more vulnerable.

Inhibiting bacteria with cranberry juice

Cranberry juice contains phytochemicals which inhibit the activity of Escherichia coli; the bacteria most often responsible for cystitis. The phytochemicals, condensed tannins or proanthocyanidins, stop the bacteria sticking to mucosal surfaces lining the bladder and gut. This process helps to clear bacteria from the urinary tract. The chemicals in cranberry juice may have this effect on other bacteria too. Drinking the juice is now being recommended as a way to reduce the risk of dental decay and stomach ulcers caused by Helicobacter pylori.

Dental plaque is composed primarily of oral bacteria attached to the tooth and gum surfaces. This plaque is composed of hundreds of species and can be resistant to saliva and mechanical brushing. Plaque is a major cause of periodontal disease. A study published in the Journal of the American Dental Association [2] reported that a unique cranberry juice component, a high-molecular-weight nondialysable material (NDM), has the ability to reverse and inhibit the coaggregation of certain oral bacteria responsible for dental plaque and periodontal disease in-vitro.

Cranberries and the treatment of peptic ulcers

Peptic ulcers are increasingly being linked to infection by Helicobacter pylori bacteria, rather than to stress and/or stomach acidity. A high-molecular-weight nondialysable constituent of cranberry juice has been demonstrated to inhibit the adhesion of H. pylori to human gastric mucus in-vitro [3], suggesting that this may be the mechanism whereby the berries may be beneficial in the prevention of peptic ulcers. In Western countries approximately 50% of people above the age of 60 are affected by peptic ulcers. Around 25 million Americans will suffer from peptic ulcers at some point in their lives.

Cranberries and atherosclerosis

A primary cause of atherosclerosis is the accumulation of low density lipoprotein (LDL), or “bad cholesterol”, in arteries. This leads to restricted blood flow. In the advanced stages of the disease blood flow may be decrease severely, or cease completely, resulting in angina (chest pain), a thrombosis (blood clot) and/or myocardial infarction (heart attack). Atherosclerosis is a primary cause of cardiovascular disease. According to the American Heart Association one person in the US dies every 33 seconds from a cardiovascular illness. Flavonoids have been demonstrated to function as powerful antioxidants and may reduce the risk of atherosclerosis. Cranberries contain significant amounts of flavonoids and polyphenolic compounds that have been demonstrated to inhibit low density lipoprotein oxidation [4]. Ongoing research suggests that cranberries may offer benefits in the prevention of atherosclerosis.

Cranberries and anti-aging

Studies carried out at the Human Nutrition Research Center on Aging at Tufts University have shown positive anti-aging effects associated with diets high in antioxidants and other phytonutrients. Results suggest that diets containing fruit and vegetables with high Oxygen Radical Absorbance Capacity (ORAC) values may provide protection against chronic age-related problems such as loss of coordination and memory. Cranberries score high on the antioxidant scale.

Side effects of cranberries

In 2004 the MHRA, the UK agency dealing with drug safety, advised patients taking warfarin not to drink cranberry juice after adverse effects (such as increased incidence of bruising) were reported. These effects were possibly due the presence of salicylic acid. This acid is native to polyphenol-rich plants such as the cranberry. However, in the period 2006-2008, several reviews of case reports and pilot studies did not detect this interaction in subjects taking warfarin and consuming 250 mL cranberry juice daily.

Drinking cranberry juice in large amounts can cause diarrhea and stomach upset. Cranberries contain relatively high levels of oxalate, a substance that may increase the risk of kidney stones in people who are susceptible to this condition. Cranberry juice may decrease the effectiveness of antacid medications. It may also increase the absorption of proton pump inhibitor drugs. Patients with diabetes should use sugar-free cranberry products.

Cranberry dosages

Pure cranberry juice has a naturally sour taste. As a consequence, the juice is commonly marketed as a mixture of cranberry juice (at least 25% by volume), sweeteners, and vitamin C. The recommended dosing for urinary tract infection (UTI) prophylaxis is based on more recent positive clinical studies that used one tablet of concentrated cranberry extract (300 to 400 mg) twice daily, or 8 oz of pure unsweetened cranberry juice three times daily. The recommended dose of cranberry juice (not cocktail) as a preventative of UTI is 12 to 32 fluid ounces (360 to 960 ml). The optimal preparation and doses are unknown.

Nutrients and antioxidant content of cranberries

The principal active components of cranberries are phytochemicals (proanthocyanidins and anthocyanins), carbohydrates (glucose, fructose), organic acids (ascorbic acid, benzoic acid, citric acid, quinic acid, malic acid), vitamin C, triterpenoids, catechins and lectins. The cranberry fruit is high in antioxidants. The organic acids are responsible for the sour taste of cranberries. Cranberries are rich sources of vitamins including vitamin A, carotene, thiamine, riboflavin, niacin, and vitamin C. Many essential minerals, such as sodium, potassium, calcium, magnesium, phosphorus, copper, sulfur, iron and iodide, are also found in cranberry. With an ORAC score of 1750 units per 100 g, the cranberry ranks near the top of 277 commonly consumed foods in the United States.

References

1. Avorn J, Monane M, Gurwitz JH, Glynn RJ, Choodnovskiy I, Lipitz LA. (1994). Reduction of bacteriuria and pyuria after ingestion of cranberry juice. JAMA 271: 751-4.

2. Weiss EI, Lev-Dor R, Kashamn Y, Goldhar J, Sharon N, Ofek I. (1998). Inhibiting interspecies coaggregation of plaque bacteria with a cranberry juice constituent. JADA 129: 1719-1723.

3. Burger O, Weiss E, Sharon N, Tabak M, Neeman I, and Ofek I. (2002). Inhibition of Helicobacter pylori adhesion to human gastric mucus by a high-molecular-weight constituent of cranberry juice. Critical Reviews in Food Science & Nutrition. 42(3 Suppl). 279-284.

4. Reed, J. (2002). Cranberry flavonoids, atherosclerosis and cardiovascular health. Critical Reviews in Food Science & Nutrition, 2002. 42(3 Suppl.): 301-316.

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