Cranberry Juice: Health Benefits and Side Effects

Cranberry juice is famous for its many health benefits. 

It is rich in antioxidants and may prevent urinary infections, promote heart health, support digestion, help keep blood sugar levels under control, and it may even contribute to the prevention of cancer.

No surprise that it has captured the attention of many health enthusiasts and those seeking natural remedies.

But are any of these claims really backed up by science? Let's explore the scientific evidence.

8 Benefits of cranberry juice

The potential benefits of cranberry juice include:

1. Promotes Urinary Tract Health

A clinical study conducted in the mid-1990s showed a notable reduction in bacteria in the urine of female residents in a long-term care facility after only one month of consuming cranberry juice (1).

The key player behind this benefit is a group of compounds in cranberries known as proanthocyanidins. These work by preventing harmful bacteria, such as E. coli, from attaching to the walls of the urinary tract.

• A study that analysed proanthocyanidins from different food sources, including cranberry, grape, green tea, and chocolate, showed that cranberry was by far the best at preventing E. coli adhesion (2).

• A study with women who had a history of high urinary tract infection recurrence showed that daily consumption of concentrated cranberry extract for 12 weeks helped prevent further infections (3). Follow-up showed that those who continued to take cranberry remained infection-free, highlighting its long-term effectiveness.

Cranberry especially good for the elderly population, who are more susceptible to urinary tract infections.

• A study on elderly women demonstrated that cranberry effectively reduced the occurrence of urinary tract infections (4).

• Another study with hospitalised patients found that those who consumed cranberry juice twice daily experienced less E. coli infections (5).

2. Rich in Antioxidants

When it comes to antioxidant power, cranberry juice stands out. Cranberries contain various antioxidants, including flavonoids, anthocyanins, and phenolic acids (6).

The table below lists the most important antioxidants found in cranberries and their approximate content in the fruit (7).

Antioxidant	Milligrams per 100 Gram of Whole Cranberry Fruit
Flavonols, total	21.96
Quercetin	15.09 ± 1.06
Myricetin	6.78 ± 1.67
Kaempferol	0.09 ± 0.03
Anthocyanins, total	91.57
Cyanidin	41.81 ± 2.86
Peonidin	42.10 ± 3.64
Delphinidin	7.66 ± 1.93
Flavan-3-ol monomers	7.26
(‑)Epicatechin	4.37 ± 0.93
(‑)Epigallocatechin	0.74 ± 0.28
(‑)Epigallocatechin gallate	0.97 ± 0.48
(+)‑Catechin	0.39 ± 0.16
Proanthocyanidins, total	411.5

• Cranberries have a high content of flavonoids and phenolic acids.

• In fact, among a group of 22 fruits studied, cranberry exhibited the highest level of polyphenols (8).

• These antioxidants play a crucial role in protecting the body from oxidative damage.

3. Promotes Heart Health

Several scientific reviews have highlighted the potential cardiovascular benefits of cranberries (9, 10). 

• In one study, a single dose of 500 mL of cranberry juice, significantly increased plasma antioxidant capacity in volunteers. Surprisingly, blueberry juice had no such effects (11).

• Another study found that cranberry juice, when compared to a control containing sugars and vitamin C, significantly raised the plasma antioxidant capacity in normal subjects (12). Moreover, triglycerides levels in both test groups went up, mainly because of the sugar content of both beverages. But interestingly, the cranberry juice managed to help prevent oxidative damage from these triglycerides. 

This is very important, because the oxidation of lipoproteins is associated with the development of atherosclerosis (13). Another study, demonstrated that oxidised LDL was significantly decreased in healthy men, who received cranberry juice for 14 days (14).

However, not all studies support these claims. One study on healthy female volunteers showed no significant effects of cranberry juice on blood plasma lipids or antioxidant capacity (15).

4. Supports Digestive Health

Cranberry juice is good for the digestive health in several ways. It could help prevent infections, it is good for a healthy gut microbiome and it contains fiber, which could help prevent constipation.

In addition to its efficacy in preventing bladder infections, cranberry juice has also been found to be effective in preventing stomach infections.

• For example, it could help prevent H. pylori infection, which is linked to an increased risk of gastric cancer (16).

• A clinical trial supports this, showing lower levels of H. pylori infection in adults who consume cranberry juice (17). 

In addition, cranberry juice contains some dietary fiber, which is good for maintaining a healthy digestive system.

• The fiber in cranberry juice can help regulate bowel movements by absorbing water and softening the stool. 

• Additionally, the fiber in cranberry juice supports a healthy gut microbiome by providing nourishment to beneficial gut bacteria, which can improve digestion, boost immune function, and improve mood.

However, keep in mind that whole cranberries, have a higher firer content than juice. And cranberry juice with pulp will have a higher fiber content compared to processed juice with no pulp.

5. Boosts Immune System

Vitamin C, also known as ascorbic acid, is a powerful antioxidant that plays a crucial role in supporting a healthy immune system (18). 

• Cranberry juice contains lots of vitamin C, and could therefore support the body defend itself against infections and promote overall health.

• Vitamin C is also involved in the synthesis of collagen, a protein essential for maintaining the integrity of skin, tissues, and cartilage.

• In addition to vitamin C, cranberry juice also contains vitamin E, vitamin A, and vitamin K. 

Nutritional content of unsweetened cranberry juice (19):

Nutrient	Amount per 100g
Energy	46 kcal
Carbohydrates	12.2 g
Protein	0.39 g
Fiber	0.1 g
Sugar	12.1 g
Vitamin C	9.3 mg
Vitamin E	1.2 mg
Vitamin A	2 µg
Calcium	8 mg
Iron	0.25 mg
Vitamin K	5.1 µg

6. Could help control blood sugar

There is some evidence that cranberry juice could help control blood glucose levels, but the results are mixed.

• According to a study on type 2 diabetics, cranberry juice consumption results in a more favourable insulin response compared to the control group. Although the evidence is not very convincing (20).

• Another study explored the effects of cranberry powder, equivalent to 240 mL of cranberry juice per day, on diabetics (21). They observed no effect on glucose control. The authors suggested that cranberry powder is possibly less effective than the fresh juice, because of how it is processed.

In 2008, a Japanese study investigated the effects of cranberry powder versus a placebo in individuals with type 2 diabetes (22).

• After 12-weeks there was no difference in fasting glucose levels, but the cranberry did seem to lower total cholesterol and low-density lipoprotein (LDL) levels.

• Also, the ratio between the "good" and "bad” cholesterol improved.

7. Could help with weight loss

Many people claim that cranberry juice can help with weight loss. There is some scientific evidence for that, but it is very limited.

• A recent clinical trial investigated the effects of cranberry on people with non-alcoholic fatty liver disease. The participants followed a weight loss diet. Interestingly, the people who received cranberry supplements in addition to their diet, had lower insulin levels (23). This is significant, because high insulin levels can prevent fat loss.

• A recent animal study indicated that cranberry could help with weight loss, but that your genes likely play a role whether it is effective for you (24).

8. Potential anti-cancer effects

Cranberries contain various beneficial compounds like flavonols, proanthocyanidins, ursolic acid, and anthocyanins, which can collaborate to prevent the development of tumours.

• These compounds exert their anti-cancer effects through multiple mechanisms, including triggering programmed cell death (apoptosis), inhibiting proteins involved in tissue invasion, and inhibiting oxidative and inflammatory processes (25).

Apoptosis, or programmed cell death, is believed to be a significant factor in the ability of certain compounds to inhibit tumor growth.

• Recent studies indicate that cranberry may also rely on the induction of apoptosis to effectively restrict the growth of tumour cells. Cranberry compounds like quercetin and ursolic acid are shown to induce apoptosis (26). 

• Studies demonstrated the ability of cranberry to induce apoptosis in breast tumour models, and cranberry extract has been observed to increase apoptosis in breast cancer cells (source). 

• Research also found, that cranberry extract could induce in vitro apoptosis in oesophageal adenocarcinoma (27) and gastric cancer cells (28). 

Probably ineffective for:

Prevention of tooth decay

Even though cranberry juice contains large quantities of calcium which is considered beneficial for strengthening bones and teeth. Still it is not a good idea to drink cranberry juice for strong teeth.

This is because the juice is acidic and also contains sugar, which can both lead to tooth decay.

Prevention of kidney stones

Cranberry juice is likely not effective for the prevention of kidney stones. 

Human clinical studies report conflicting results regarding the relationship between cranberry consumption and kidney stone formation. 

• Some studies indicate that people who have previously experienced uric acid or calcium oxalate stones, might face a potential risk when consuming cranberry products (29).

• On the other hand, other studies show that consuming cranberries may reduce some of the risk factors associated with kidney stones (30).   

The information on whether cranberry consumption could prevent kidney stone formation or not is very conflicting. It is possible that cranberry juice consumption even increases the risk of kidney stones (31).

Side effects of cranberry juice

Consuming cranberry juice in moderate amounts is generally considered safe. However, excessive intake of cranberry juice can lead to some side effects, including:

• diarrhoea 

• upset stomach

• fluctuations in blood sugar levels

Because it is mildly acidic, even moderate cranberry juice intake can cause side effects, including:

• acid reflux

• irritated gums

• irritated lips

• unusual taste in mouth

Allergies

If you are sensitive to some of the allergens present in cranberries, you might experience additional side effects. These side effects include (32): 

• asthma

• swelling

• itching

• hives

• food intolerance symptoms

Children

The American Academy of Pediatrics suggests restricting fruit juice consumption in toddlers and children and discourages giving juice to babies. If parents wish to include cranberry juice in their children's diet, it is recommended to offer it in limited amounts (33).

Warfarin and other blood thinners

People taking blood-thinning medications should be careful with cranberry juice, as it may interact with their medication.

• There is particular evidence that cranberry juice could interact with and strengthen the effects of the blood thinner warfarin (34).

There are a number of other drugs that cranberry juice could interact with.

It is advisable to consult with a healthcare professional to determine whether it is necessary to limit or avoid cranberry juice while on blood-thinning or other medication.

Wrap up

• Incorporating cranberry juice into your diet, may potentially support heart health, reduce inflammation, improve cholesterol levels, and enhance blood vessel function.

• When selecting cranberry juice, opt for options without added sugars or artificial additives.

• While cranberry juice can be a beneficial addition to your diet and may offer some protection against certain health issues, it is not a substitute for medical treatment.