Throughout the holiday season, from Thanksgiving through Christmas, cranberries are a popular dietary item. However, based on their health benefits that range from antibacterial to prebiotic, they may be a fruit you’ll want to include in your menu planning year-round.

Cranberries are a superfruit based on their high antioxidant and nutrient content. The plants are native to North America so, under the right conditions, it is possible to grow your own. They are perennial vines that flourish when grown in water or on dry land and send out runners measuring up to 6 feet long.1

Short vertical branches develop from the runners and from these the berries form. Commercial plants are grown in bogs, but home gardeners can plant cranberries in well-draining soil with a pH of less than 5. The next consideration is irrigation since alkaline water will affect the pH of the soil. The plants need cold weather for about three months of the year to trigger a dormant phase.

The U.S. Department of Agriculture recognizes the North American cranberry (Vaccinium macrocarpon) as the standard in the U.S.2 The European variety is grown in parts of central Europe and produces smaller fruit with a different acid profile. The major producing states in the U.S. are Massachusetts, New Jersey, Oregon, Wisconsin and Washington.

Each day you make small choices that affect your overall health. Before reaching for a protein bar or carrot sticks to snack on, think about a tart bowl of cranberries. They are loaded with vitamin C, fiber and phytonutrientsthat offer protection from several health conditions.

The fruit is probably best known for the role it plays in preventing urinary tract infections (UTIs). However, it takes a large concentration of proanthocyanins to affect the biofilm of certain bacteria in the urinary tract walls.3 This means cranberry juice is not the form you want to use since it’s nearly impossible to get the concentration you need without overdosing on sugar.

Researchers are continuing to identify the compounds responsible for the benefits you get from eating cranberries. Pectic oligosaccharides and xyloglucan are two classes of biologically active compounds that have been newly recognized in cranberries.4

The oligosaccharides have demonstrated activity similar to other dietary oligosaccharides. This includes the effect it has on microbial growth and bacterial biofilm formation. Researchers theorize this may be one of the beneficial contributing factors to your urinary tract.

Soluble oligosaccharides are found in high concentrations in cranberries but the difficulty in detecting these compounds may have led to the contributions they make remaining largely unrecognized. A paper published in 2019 also analyzed the beneficial effects cranberries may have in people with chronic kidney disease(CKD).5

Many of the complications that arise from CKD are also linked to an increased risk of cardiovascular mortality, including gut dysbiosis, inflammation and oxidative stress. Data suggest that cranberries may have anti-inflammatory and antioxidant effects.

This has caused researchers to call for a better understanding of this mechanism to ascertain if supplementation could target these complications found in people with CKD. Although the mechanism of action to date has been poorly understood, one review showed health care professionals commonly recommend cranberries for women who are prone to recurrent UTIs.6

A double-blind randomized placebo-controlled trial in a long-term care facility, where urinary tract infections can have dangerous consequences, demonstrated that cranberry capsules reduce the incidence of UTIs.7 When capsule supplementation was compared against juice, it was apparent the extract reduced the rate of UTI by 50% but the juice did not offer the same benefit.8

Polyphenols are a category of naturally occurring plant chemicals that are thought to play a role in the regulation of metabolism, chronic disease, cell proliferation and weight maintenance. Over 8,000 have been identified and a variety of studies demonstrated the anti-inflammatory and antioxidant properties may have a therapeutic effect against several prevalent health conditions.9

However, while highly effective when consumed in food, it is necessary to use caution when consuming isolated compounds as overconsumption can lead to harmful effects. Although a deficiency in polyphenolsdoes not cause classical symptoms of deficiency, they have been called “lifespan essentials,” since your body requires them to protect against a range of chronic diseases.10

For example, a systematic review of studies published through June 2018 identified randomized control trials that analyzed the effect of cranberry supplementation on cardiovascular and metabolic risk factors. The researchers found the results demonstrated a reduction in body mass index and systolic blood pressure.11

After further analysis, the data showed that a reduction in systolic blood pressure was more statistically significant when participants’ mean age was 50 or older. Another subgroup analysis suggested an increase in HDL cholesterol in studies where the mean age of participants was less than 50.

The researchers concluded that supplementation “may be effective in managing systolic blood pressure, body mass index and high-density lipoprotein in younger adults.”12 A small Interventional study of 78 participants who were overweight or obese with abdominal adiposity demonstrated that using a high polyphenol cranberry extract beverage for eight weeks had significant health effects on the individuals.13

Compared to a placebo, a single dose at the beginning of the study elevated the participants’ nitric oxide and reduced-to-oxidized glutathione ratio. After eight weeks of intervention, the researchers measured lower fasting C-reactive protein levels, serum insulin and an increase in HDL. They concluded:14

Chemoprotective Properties of Cranberries

As discussed, cranberries are rich in bioactive compounds. Researchers have found in lab studies that these compounds may target the inhibition of cancer cell proliferation against 17 different cancers.15

In one study published in early 2020, researchers built on their previous study that had demonstrated whole cranberry supplementation had a chemoprotective effect against colon cancer in an animal model.16 They then sought to determine what effects secondary metabolites of cranberry could have on inhibiting colon cancer.

They used cranberry ethyl acetate extract and polyphenol extract to determine the free radical activities. After administration in an animal model, they found these substances significantly suppressed colon cancer cell proliferation without any noticeable adverse effects.17 Laboratory studies demonstrated the mechanism of cancer inhibition included:18

The researchers found the data in their literature review strongly supported:19

In similar action that cranberries take against biofilm in the urinary tract wall, researchers have found compounds in cranberries have antibacterial and antiviral biofilm activity in the oral cavity.

Using a selected cranberry extract rich in polyphenols, researchers evaluated the minimum inhibitory concentration and minimum bactericidal concentration against six bacterial pathogenic biofilms commonly found in the oral cavity.20

The activity of the extract was measured in the lab, and data showed there was significant inhibition against Streptococcus oralis, Actinomyces naeslundii and Veillonella parvula. Additionally, compounds in the cranberry extract interfered with periodontal pathogenic biofilms in the first six hours of development.

The human mouth has a complex oral microbial communitywith more than 700 different species. Disturbing the equilibrium in a complex ecosystem can shift the balance to over-representation of pathogenic species. Streptococcus mutans is a dominant species found in supragingival plaque, which subjects the teeth to high concentrations of metabolites and ultimately results in dental disease.21

Bacteria in the biofilm are metabolically active, which triggers changes in pH and increases the loss of minerals from teeth. Another study evaluated the biological properties of cranberry juice against S. mutans biofilms in the mouth.22

They found topical application with one-minute exposure two times a day could reduce the biomass and glucan content of the biofilm. The researchers concluded the data “holds promise as a natural product to prevent biofilm-related oral diseases.”

Your gut health plays a powerful role in your immune system, cardiovascular health and mood. People with a healthy gut microbiome are better able to fight off infectious agents like bacteria, fungus and viruses. Your gut and brain also communicate through nerves and hormones, helping to maintain general health and mood.23

Bacteria in your gut produce neurochemicals used to regulate physiological processes and about 95% of your serotonin, which has an influence over your gastrointestinal activity and your mood.24

Additionally, your gut bacteria have an effect on common risk factors for heart disease, including obesity, Type 2 diabetes and blood pressure. Each of these factors raise your risk of heart disease.25 Suffice it to say, when you take care of your gut microbiome, they are primed and ready to take care of you.

One way you can influence the balance of bacteria is through the food you eat. Some foods you eat have complex carbohydrates that microorganisms in your gut require for nutrition. These are called prebiotics as they are the food source that feed the healthy bacteria. Prebiotic complex carbohydrates include pectin, inulin and resistant starches.26

These are molecules that humans cannot digest but are necessary for healthy microbial growth. One study published by the University of Massachusetts at Amherst discovered that some beneficial bacteria in the gut thrive on the carbohydrates found in cranberries.27

Researchers were excited by the potential impact to health this may have. Nutritional microbiologist David Sela from the University of Massachusetts at Amherst participated in the study and explained:28

If you’d like to include cranberries in your diet, consider adding them to your salad, pop some in your smoothie and add them to chutneys, relishes or salsas. The tart flavor goes well with grain-free pancakes or try tossing with spinach and chicken salad. If you slice them before adding to your food, they’re easier to chew.29

Sources and References

1 Gardening Know How, Cranberry Vine Care

2 Massachusetts Cranberries, How Cranberries Grow

3 Food.NDTV, May 4, 2016

4 MDPI, 2020;25(4)

5 Royal Society of Chemistry, 2019;10:3103

6 Advances in Nutrition, 2016;7(3)

7 Journal of the American Geriatric Society, 2014;62(1)

8 American Journal of Obstetrics and Gynecology, 2015;213(2)

9 Frontiers in Nutrition, 2018;5:87

10 British Journal of Nutrition, 2008;99:S55

11, 12 Clinical Nutrition, 2020;39(3)

13, 14 European Journal of Nutrition, 2019;58(3)

15, 18, 19 Antioxidants, 2016;5(3):27

16, 17 Journal of Agricultural and Food Chemistry, 2020;68(25)

20 MDPI, 2020;9(2)

21 PLOS|Pathogens, 2013;9(10)

22 Caries Research, 2006;40(1)

23 UC Davis Health, July 22, 2019

24 American Psychological Association, That Gut Feeling

25 Harvard Health Publishing, August 2018

26 Cleveland Clinic, Probiotics

27, 28 Science Daily, July 10, 2017

29 SFGate, December 7, 2018, Recipe Tips