As a fruit of the heather family, cranberries are related to blueberries, bilberries, and lingonberries.
The most commonly grown species is the North American cranberry (Vaccinium macrocarpon), but other types of cranberries are found in nature.
Due to their very sharp and sour taste, cranberries are rarely eaten raw.
In fact, they are most often consumed in the form of juice, which is normally sweetened and blended with other fruit juices.
Other cranberry-based products include sauces, dried cranberries, and powders and extracts used in supplements.
Cranberries are rich in various healthy vitamins and plant compounds, some of which have been shown to be effective against urinary tract infections.
The table below presents information on all the nutrients in cranberries (1).
Carbs and Fiber
These are mainly simple sugars, such as sucrose, glucose, and fructose (3).
The rest is made up of insoluble fibers, such as pectin, cellulose, and hemicellulose, which pass through the gut almost intact.
Cranberries also contain soluble fibers. For this reason, excessive consumption of cranberries may cause digestive symptoms, such as diarrhea.
Raw cranberries taste very bitter and sour. They are most often consumed as cranberry juice, which contains virtually no fiber, and is usually diluted with other fruit juices and sweetened with added sugar (4).
Bottom Line: Carbs and fibers are the main nutritional components of cranberries.
Vitamins and Minerals
Cranberries are a rich source of several vitamins and minerals, especially vitamin C.
- Vitamin C: Also known as ascorbic acid, vitamin C is one of the predominant antioxidants in cranberries. It is essential for the maintenance of skin, muscles, and bone.
- Manganese: Found in most foods, manganese is essential for growth, metabolism, and the body’s antioxidant system.
- Vitamin E: A class of essential fat-soluble antioxidants.
- Vitamin K1: Also known as phylloquinone, vitamin K1 is essential for blood clotting.
- Copper: A trace element, often low in the Western diet. Inadequate copper intake may have adverse effects on heart health (5).
Bottom Line: Cranberries are a rich source of several vitamins and minerals, including vitamin C, E, and K1, manganese, and copper.
Other Plant Compounds
Many of these plant compounds are concentrated in the skin, and are greatly reduced in cranberry juice (4).
- Quercetin: The most abundant antioxidant polyphenol in cranberries. In fact, cranberries are among the main fruit sources of quercetin (7, 9, 10).
- Myricetin: A major antioxidant polyphenol in cranberries, myricetin may have a number of beneficial health effects (10, 11).
- Peonidin: A type of anthocyanin antioxidant, which, along with cyanidin, is responsible for the rich red color of cranberries and some of their health effects. Cranberries are among the richest dietary sources of peonidin (7, 9).
- Ursolic acid: Concentrated in the peel, ursolic acid is a triterpene found in high amounts in cranberries. It is an ingredient in many traditional herbal medicines and has strong anti-inflammatory effects (12, 13).
- A-type proanthocyanidins: A class of antioxidant polyphenols, also called condensed tannins, believed to be effective against urinary tract infections (9, 14, 15).
Bottom Line: Cranberries are a rich source of various bioactive plant compounds. Some of these, such as the A-type proanthocyanidins, may be useful as a prevention against urinary tract infections.
Prevention of Urinary Tract Infections
Urinary tract infections are among the most common bacterial infections, especially among women (16).
They are most often caused by the intestinal bacterium Escherichia coli, which attaches itself to the inner surface of the bladder and urinary tract.
Cranberries contain unique phytonutrients known as A-type proanthocyanidins (condensed tannins).
A-type proanthocyanidins prevent E. coli from attaching to the lining of the bladder and urinary tract, making cranberries a potential preventive measure against urinary tract infections (14, 17, 18, 19, 20).
A number of human trials indicate that drinking cranberry juice, or taking cranberry supplements, may reduce the risk of urinary tract infections in both children (22, 23, 24) and adults (25, 26, 27, 28).
Not all cranberry products are effective against urinary tract infections. In fact, proanthocyanidins may be lost during processing, making them undetectable in many products (35).
On the other hand, taking cranberry supplements, which contain sufficient amounts of A-type proanthocyanidins, may be a useful preventive strategy.
If you suspect that you have a urinary tract infection, talk to your doctor. The first-line option should be antibiotic treatment.
Keep in mind that cranberries are not effective for treating infections, they only cut the risk of getting them in the first place.
Bottom Line: Cranberry supplements may reduce the risk of getting urinary tract infections.
Other Health Benefits of Cranberries
Consuming cranberries may have a number of beneficial health effects.
Prevention of Stomach Cancer and Ulcers
Stomach cancer is a common cause of cancer-related death worldwide (36).
Cranberries contain unique plant compounds known as A-type proanthocyanidins, which may cut the risk of stomach cancer by preventing H. pylori from attaching to the lining of the stomach (41, 42, 43, 44).
One trial in 189 men and women suggests that drinking half a liter of cranberry juice daily may significantly reduce H. pylori infections (45).
Supporting this, another trial in 295 children found that daily consumption of cranberry juice for 3 weeks suppressed the growth of H. pylori in about 17% of those who were infected (41).
Bottom Line: Cranberries or cranberry juice may cut the risk of stomach cancer, if consumed regularly.
Cardiovascular disease (heart disease) is the leading cause of death worldwide.
In human trials, cranberry juice, or extracts, have been found to have various beneficial effects on risk factors for cardiovascular disease:
- Increasing the levels of HDL, the "good" cholesterol (50).
- Lowering LDL, the "bad" cholesterol, in diabetics (51).
- Protecting LDL-cholesterol from oxidation (52, 53, 54).
- Decreasing stiffness in blood vessels (arterial stiffness) among people with heart disease (55).
- Lowering blood pressure (52).
- Decreasing blood levels of homocysteine, cutting the risk of inflammation in blood vessels (54).
However, not all studies have found similar results.
Nevertheless, there are strong indications that regular consumption of cranberries may have beneficial effects on heart health.
Bottom Line: Cranberry juice and cranberry extract have been shown to have beneficial effects on several risk factors for heart disease, including cholesterol levels and blood pressure.
Adverse Effects and Individual Concerns
In moderate amounts, cranberries and cranberry products are usually considered safe for most people.
However, excessive consumption may cause stomach upset and diarrhea, and they may also increase the risk of kidney stones in predisposed individuals.
Also called nephroliths, kidney stones form when minerals in the urine reach high concentrations. It is often a painful condition.
The risk of kidney stones can be minimized with dietary modifications.
Most kidney stones are made of calcium oxalate, and excessive amount of oxalate in urine is one of the main risk factors (56).
Cranberries, especially concentrated cranberry extracts, may contain high levels of oxalate. For this reason, they are considered to be a risk factor for kidney stones when consumed in high amounts (57, 58, 59).
They also contain high levels of vitamin C, which is converted to oxalate in some people (60).
Susceptibility to developing kidney stones varies between individuals. In most people, consumption of cranberries probably does not significantly affect kidney stone formation.
However, if you are prone to getting kidney stones, it may be sensible to limit the consumption of cranberries and other high-oxalate foods.
Bottom Line: High consumption of cranberries may increase the risk of kidney stones in predisposed individuals.
Cranberries are widely consumed dried, as a juice, or in supplements.
They are a good source of a few vitamins and minerals, and exceptionally rich in several unique plant compounds.
Some of these may be useful as a prevention against urinary tract infections, stomach cancer, and heart disease.
Simply put, cranberries may be among the healthiest fruits you can eat.