Cranberries are the flavour of the moment. Not only are more and more cranberry products appearing on our supermarket shelves, but complementary medicines made from cranberries are also becoming available to treat a variety of conditions.
Added to this is the increase in scientific studies investigating the use of cranberries to treat a number of diseases and infections. The accumulating body of evidence indicates that cranberries may well have therapeutic effects.
A source of potent antioxidants
The cranberry (Vaccinium macrocarpon) has been used as a food and a folk medicine since time immemorial. The American Indian tribes used this tasty berry as a staple ingredient in their diet.
More recently, cranberry extract has been used and tested to treat a number of disease conditions (Jepson & Craig, 2008). At present, the most positive results are being achieved with urinary tract infections (UTIs).
Cranberries contain a number of compounds called proanthocyanidins, which are potent antioxidants. These compounds also have so-called “bacterial anti-adhesion activity”.
This means that proanthocyanidins are capable of preventing harmful bacteria from attaching themselves to body tissues, such as the walls of the urinary tract, where these bacteria can cause infections.
This antibacterial effect has been found to work against both antibiotic-susceptible and antibiotic-resistant strains of bacteria (Howell, 2007). Escherichia coli, a bacteria that's often associated with UTIs, is particularly sensitive to the bacterial anti-adhesion activity of cranberries (Arbor, 2009).
In addition, cranberries have a high benzoic acid content, which when excreted in the urine as a compound called hippuric acid, will lower the pH of the urine and increase the antibacterial effect.
The antioxidant properties of proanthocyanidins are also being investigated to see if cranberries can be used to combat disease progression – specifically the progression that's associated with cardiovascular disease, cancer and diabetes (Arbor, 2009).
Cranberries and urinary tract infections
Millions of women throughout the world suffer repeatedly from urinary tract infections. UTIs are debilitating, unpleasant and often painful. Although the first line of treatment for UTIs is the use of antibiotics, many women find that this condition recurs with monotonous regularity.
According to a review of published studies relating to the use of:
- cranberry extract to combat UTIs (Jepson & Craig, 2008),
- the use of cranberry juice compared to placebo (dummy treatment), other juice or water in seven studies, and
- cranberry tablets compared to placebo in four studies,
… cranberry juice or tablets significantly reduced the incidence of UITs after 12 months.
Cranberry products were more effective in reducing UTIs in women who suffered from recurring infections than in elderly men and women, or individuals, with catheters. Jepson and Craig (2008), therefore, concluded that “there is some evidence that cranberry juice may decrease the number of symptomatic UTIs over a 12-month period, particularly for women with recurrent UTIs.”
These authors did, however, find that the drop-out rate for cranberry treatment was high, which they interpreted as an indication that the use of cranberry juice may not be acceptable over long periods of time.
A recent Arbor Clinical Nutrition Update (2009) reports on a Scottish study conducted among 137 women with recurrent UITs who either received cranberry extract (500mg a day) or an antibiotic, trimethoprim (100mg/day), for 6 months.
There was no significant difference in the number of women who had a recurrence of their infection on either treatment, but the women using cranberry were less likely to withdraw from treatment. It appears that cranberry treatment, using extract-of-cranberry tablets, improves compliance when compared to juice intake.
It is, therefore, reasonable to conclude that cranberry juice or extract in tablet form can be used to treat UTIs and that it will have a similar success rate to using antibiotics. The use of cranberry tablets may perhaps prevent high treatment drop-out rates.
An important factor to remember is that women who take cranberry instead of an antibiotic are not just receiving a treatment for their urinary tract infection, but may also be benefiting from the anti-oxidant properties of this fruit.
Other potential uses of cranberries
As mentioned above, cranberries are very rich in antioxidants, which may help to combat diseases such as cancer, heart disease and diabetes.
So far, the anticarcinogenic properties of cranberries have only been tested in the laboratory and in animal studies. Until more information is available from human studies, it's not possible to state with certainty that cranberries will prevent cancer, but they seem to have the potential to do so.
Cranberries have a very high content of polyphenols (compounds also found in red wine, green tea, black tea, chocolate etc). Polyphenols are known to lower "bad" cholesterol levels and some human studies have shown that drinking cranberry juice for 2-4 weeks lowered the levels of oxidised "bad" (LDL) cholesterol levels (Arbor, 2009).
Another study has indicated that cranberries may increase "good" (HDL) cholesterol. Type 2 diabetics who took cranberry extract (three capsules a day), or placebo for 12 weeks, had a significant decrease in cholesterol levels, but no improvements in glucose control (Arbor, 2009).
Despite these encouraging indications, more well-controlled research will be needed to clarify exactly how cranberries can help to prevent cardiovascular disease.
An interesting aspect of cranberry research is the finding that the antibacterial action of these berries may also help to combat mouth and gum infections (Arbor, 2009).
Source of cranberries in South Africa
Cranberries are not indigenous to South Africa and although some farmers have realised their potential, overall production is not yet on the same relative scale as in the USA, where cranberries are ranked first among the top 20 most commonly consumed fruits (Arbor, 2009).
In South Africa, some supermarkets and green grocers sell dried cranberries, which can be eaten as such or added to breakfast cereals, or fruit and vegetable salads. Ask your green grocer if he stocks cranberries as they're not always well displayed.
Pure or 100% cranberry juice is practically unavailable in South Africa and most of the fruit juices marked “Cranberry” are blends of other juices like apple and pear to which a small percentage of cranberry juice has been added. Such diluted juices will probably not provide the benefit you're looking for.
You should be able to purchase cranberry tablets or capsules from health shops and pharmacies, so enquire if they stock these products.
It is evident that cranberries and cranberry products can make an important contribution to alleviating UITs and possibly help to prevent certain degenerative diseases. Hopefully, pure or full-strength cranberry juice will become more available as juice processors become aware of the potential of this "super fruit".
(Arbor (2009). Cranberries. Arbor Nutrition Updates, 2009 (July), 310:1-4; Howell AB, (2007). Bioactive compounds in cranberries and their role in prevention of urinary tract infections. Mol Nutr Food Res, 51(6):732-7; Jepson RG, Craig JC (2008). Cranberries for preventing urinary tract infection. Cochrane Database Syst Rev (1):CD001321)