Whilst Australians are more than familiar with the cranberry, in America, it is ingrained into November’s Thanksgiving holiday traditions. Sweet but tart cranberry sauce is the quintessential accompaniment to the traditional roast turkey. Several weeks later in the year, its unique flavour brings out the best in Christmas ham, right across North America, the UK and parts of Europe. Americans tuck into approximately 180 million kilograms of the small red berries every year, and 20% of this is consumed during the November-December holiday period.[1]
Figure 1. Wild cranberry bush Figure 2. Traditional roast turkey with cranberry sauce
The first European colonists found cranberry to be both an important food and versatile medicine to the native Americans. With its nutritional and medicinal benefits overlapping, the cranberry was the last fruit to ripen in the autumn of North America. Thanks to this fortunate positioning by mother nature, and its inherent hardiness, including an ability to be stored over the winter months, cranberry was understandably indispensable to native Americans.[2]
Regarding its medicinal use, cranberries were used as a poultice for wounds, and mixed with cornmeal, they were used as part of a recipe to cure blood poisoning.[3] Colonial writers also mention native use of cranberry in mitigating fever, pleurisy and nausea.[4] Early American sailors consumed cranberries during long voyages at sea, in much the same way that limes were utilised by British sailors to prevent scurvy.[5]
The nutritional importance of the fruit may lie in its high vitamin C content. In this sense, native American use somewhat resembled the manner in which many of today’s ‘superfoods’ are used: regular consumption provided preventative health benefits. Indeed, cranberry is believed to be one of the first foods to be marketed as a ‘superfood’, even laying the groundwork for the emergence of other popular superfoods since.[6]
So, cranberry certainly has a distinguished history, but what can modern science tell us about this unique fruit? More importantly, should you consider adding cranberry to your diet or supplement regime? Let’s take a closer look at this well-loved tart berry.
Nutritional and phytochemical content of cranberry
Fresh cranberries are highly nutritious, with an excellent fibre to sugar ratio. They also contain high amounts of vitamins C, K and E, as well as folate and the mineral manganese.[7]
Tables 1 and 2: selected macronutrient and micronutrient levels found in 100g of fresh cranberries.
In addition to the above well-recognised nutrients, cranberry also contains a vast array of phytochemicals such as anthocyanins, flavones, tannins (which include proanthocyanidins) and phenolic derivatives.[8] To list them all is beyond the scope of this article, however in numbers terms, approximately 8000–10 000 total phytochemicals have been detected in each of the three major cranberry species.[9] Truly mindboggling, and in such a small fruit!
Many of the above compounds – vitamin, mineral and phytochemical – are classified as antioxidants, and cranberry has the highest ORAC (Oxygen Radical Absorbance Capacity) value among berries including strawberry, raspberry, blackberry, blueberry, and blackcurrant.[10]
As for the highly valued flavonols, which contain quercetin among others, cranberry shines once more in comparison to the above list.[11] As a matter of fact, quercetin is the major flavonol in cranberries.[12] Flavonols boast antioxidant activity, anticancer and antibacterial properties, and protect against cardiovascular disorders.[13]
Proanthocyanidins (PACs) are found in plants, from their bark, flowers, nuts, and seeds, to their fruits, where they often act as a defense against a variety of stressors. Their astringency in particular, protects plants from pathogens and predators.[14] From a human perspective, PACs give plants colour, aroma, saliva viscosity, astringency, sourness, bitterness, as well as sweetness. Cranberries have a higher PAC content when compared with other berries,[15] and PACs have shown antioxidant, anti-inflammatory, antibacterial, antiviral and anti-carcinogenic effects in human studies.[16]
Cranberry has been examined in all manner of scientific studies – from Petrie dishes to double-blinded, placebo-controlled human trials – and in all its different forms – fresh and dried berries, juices, tablets, capsule and powdered supplements. Let’s now consider how that evidence stacks up.
A review of cranberry’s health benefits
Cranberry (whole or extract) has shown efficacy against cystitis and urinary tract infections (UTIs), cancer, cardiometabolic diseases, diabetes and obesity, tooth decay and periodontitis, and Helicobacter pylori infection amongst a range of others.[17] With so many conditions examined, we’ll focus on two broad areas where cranberry shines: UTIs and cardiometabolic health.
Cranberries for preventing urinary tract infections: Many trials have assessed cranberry’s effects on urinary tract health.[18][19][20][21][22][23] Consumption of the berry was previously thought to acidify the urine, and this was believed to be the main mechanism by which cranberry decreased the risk of UTIs.[24] This was since found not to be the case, rather, it is the particular type of PACs in cranberry, which wrap around E. coli (the most common cause of UTIs), and interfere with the bacteria’s adherence to the cells lining the urinary tract.[25]
Figure 3. Proanthocyanins as inhibitors of P-fimbriae during bacterial uroepithelial attachment.[26]
Despite the many positive results stemming from conducted trials, there has also been suggestions of potential bias, due to the funding some trials have received from cranberry product manufacturers.
To help draw a line under these suggestions, a 2023 Cochrane review investigated the efficacy of cranberry juice, tablets and capsules, to prevent UTIs.[27] Whilst Cochrane reviews are not immune to their own share of criticism, they do boast a very good reputation within the scientific community, with their stance against bias being among their strongest attributes. 50 trials met the assessment criteria and included 8857 participants. The review found little or no benefit in elderly and institutionalised people, pregnant women, or those with bladder dysfunction or incomplete emptying. The results did, however, support the use of cranberry to reduce the risk of symptomatic infections in women with recurrent UTIs, as well as in children, and in people susceptible to UTIs following interventions.[28]
Cardiometabolic effects: Cranberry’s strong antioxidant potential helps prevent cellular oxidative stress in humans, and this has prompted researchers to investigate the berry’s impact upon chronic disease processes. Consuming cranberry juice has shown the capacity to significantly reduce circulating lipid oxidation, a key step in the development of atherosclerosis, in metabolic syndrome.[29]
A 2015 double-blind, placebo-controlled trial investigated the effects of low-calorie cranberry juice on a variety of cardiometabolic risk factors including blood pressure, triglycerides and glucose.[30] After the 8-week trial, participants consuming the cranberry juice had lower diastolic blood pressure than those consuming a flavour, colour and energy–matched placebo beverage. The effect of the juice’s impact on blood pressure was calculated to represent a 15% decrease in risk of stroke and a 10% decrease in risk of coronary heart disease.[31] The authors speculated that it was the high quercetin content of cranberries favourably impacting blood pressure, as this was seen in previous humans trials.[32] Cranberry also reduced triglycerides, inflammatory C-reactive protein, and fasting glucose.
Systematic reviews combining the results of multiple clinical trials have also gleaned positive effects on cardiometabolic health. A 2020 systematic review and meta-analysis found that cranberry significantly reduced systolic blood pressure, especially in people 50 years and over, as well as body mass index.[33] A 2021 meta-analysis of randomized control trials performed on patients with metabolic syndrome, found that cranberry consumption had beneficial effects on waist circumference.[34] And a 2024 meta-analysis revealed a significant decrease in the total cholesterol to HDL cholesterol ratio, and homeostasis model assessment of insulin resistance (HOMA-IR) with cranberry consumption. When they analysed capsules, tablets and powders only, cranberry was found to significantly decrease the fasting insulin levels of the participants.[35]
So, this unique little fruit that was instrumental in supporting early settlers in their nation-building endeavours, also became a quintessential culinary staple to one of the most well-loved holiday traditions, then helped kickstart the superfood craze of the 1990s and early 2000s? Plus, it actually contains at least 8000 beneficial phytochemicals. And on top of this, it protects against urinary tract infections and cardiometabolic conditions?
Now that is a superfood in anyone’s language!
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