What is cranberry, and what compounds does it contain?

Cranberry is the fruit of Vaccinium macrocarpon, an evergreen shrub from North America in the same genus as blueberry. Proanthocyanidins are one of the compound groups it contains in large amounts: a 2023 study found 41.7–108 mg per gram of dried fruit. Cranberry is eaten as juice, sauce and sweetened dried cranberries, and the sugar content of these products differs widely: 100 g of sweetened dried cranberries has 72.6 g of sugars, against 4.27 g in raw fruit.

In short:

• What it is: the fruit of Vaccinium macrocarpon (American or large cranberry), heath family (Ericaceae)
• Where it grows: wet habitats in the northeastern and north-central parts of North America, cultivated in bogs
• Main compounds: proanthocyanidins (41.7–108 mg/g dry weight), anthocyanins, flavonols, citric and malic acid, ursolic acid
• Types of proanthocyanidins: both B-type and A-type
• Sugar: from 4.27 g per 100 g in raw fruit to 72.6 g in sweetened dried cranberries

What is cranberry?

Cranberry is the red berry of a low, evergreen shrub. The US National Center for Complementary and Integrative Health (NCCIH) describes it as an evergreen shrub that grows in wet habitats in the northeastern and north-central parts of North America, and says Native Americans and European settlers used it for dyes and food.

Scientific name and family

Its scientific name is Vaccinium macrocarpon. NCBI Taxonomy, the US National Library of Medicine's database of species, lists it in the heath family (Ericaceae), in the genus Vaccinium, the same genus as blueberry and bilberry. Its common names there are "American cranberry" and "large cranberry".

The fresh fruit is a crop of cool, wet bogs in North America, and all the fruit in the studies below was grown in the United States.

How much sugar is in cranberry products?

It depends a great deal on the product. Raw cranberries are sour and low in sugar, so sugar is often added to juice drinks and dried cranberries.

Source: USDA FoodData Central (raw, dried, sweetened, juice, unsweetened, juice cocktail). "—" means no value is listed.

Removing the water concentrates everything, and sugar is added when cranberries are sweetened and dried, so 100 g of sweetened dried cranberries has about 17 times the sugars of 100 g of raw fruit.

Is there vitamin C in cranberries?

Some. USDA lists 14 mg of vitamin C in 100 g of raw cranberries and 9.3 mg in 100 g of unsweetened juice. The Thai Reference Daily Intake (Thai RDI) for vitamin C is 100 mg a day, so 100 g of raw cranberries supplies 14% of it, below the 15% at which a food counts as a source of vitamin C. Sweetened dried cranberries have only 0.2 mg per 100 g.

What compounds are in cranberries?

Cranberries contain several groups of plant compounds. Xue and colleagues (2023), at the University of Massachusetts Dartmouth, analysed the fruit of nine cultivars harvested from bogs in Massachusetts on the US east coast and in Oregon on the west coast in 2016 and 2017.

The main groups

• Proanthocyanidins (PACs): 41.7–108 mg per gram of dried fruit across all samples
• Anthocyanins: the red pigments of the skin
• Flavonols: another group of flavonoids
• Organic acids: citric and malic acid, which give the sour taste
• Triterpenoids: ursolic acid and oleanolic acid

Does the growing region change the amounts?

Yes. The same study found clear differences between the two regions, across cultivars and in both seasons.

Anthocyanins were more than twice as high in Oregon fruit, while organic acids and ursolic acid were higher in Massachusetts fruit. The researchers link these differences to climate. The limits: the study covers nine cultivars from two growing areas in the US, and proanthocyanidins were measured by one method (BL-DMAC with a cranberry standard), so figures from other methods are not directly comparable.

What are proanthocyanidins, and what types are there?

Proanthocyanidins are chains of flavan-3-ol units, such as catechin and epicatechin, joined together. They are common in plant foods, but the way the units are joined differs.

B-type and A-type

In B-type proanthocyanidins, neighbouring units are joined by a single bond. In A-type proanthocyanidins, they are joined at two points: the usual bond plus an extra bond through an oxygen atom. You can see this in the formulas of two dimers made of two epicatechin units listed in PubChem:

The extra link removes two hydrogen atoms, so procyanidin A2 is 2 g/mol lighter than procyanidin B2.

How long are the chains?

They range from single units to long chains. A 2004 study by the same USDA group, which analysed proanthocyanidins in common foods in the United States, found that in the US diet single units, two-unit chains and three-unit chains made up 7.1%, 11.2% and 7.8% of proanthocyanidins, and chains longer than three units 73.9%.

Which foods have A-type proanthocyanidins?

Few, among the foods studied. Gu and colleagues at the US Department of Agriculture (2003) screened 88 foods and found proanthocyanidins in 39 of them: 19 fruits, eight cereals and beans, seven nuts, two beverages, two spices and one vegetable. B-type was the only kind in 21 foods and the main kind in the rest. Of these 88 foods, only plum, avocado, peanut, curry and cinnamon were identified as sources of A-type proanthocyanidins, in addition to cranberry. In cranberry and peanut, the A-type links were found both at the end of the chains and between the units inside them.

Where in the berry are these compounds?

Mostly in the skin. Grace and colleagues (2012), at North Carolina State University, compared fresh cranberries with separated skin and flesh. Anthocyanins were found in the skin. Proanthocyanidins were higher in the skin than in the flesh, with one exception: the A2 dimer was concentrated in the flesh. Freeze-drying the berries caused no detectable loss of anthocyanins or proanthocyanidins.

How much is in juice, sauce and dried cranberries?

Processing changes the amounts. Pressing, concentrating, cooking and drying can separate, heat or oxidise these compounds. Grace and colleagues measured common cranberry products:

Commercially processed products had significantly lower levels than fresh and home-made preparations, and anthocyanins broke down more easily than proanthocyanidins. Sweetened dried cranberries had 7.9 mg of anthocyanins and 64.2 mg of proanthocyanidins per 100 g. The limits: these are US products bought for one study, and the amounts in a product depend on its recipe and process.

Is there a recommended daily amount of cranberry?

No. Cranberry is a fruit, and proanthocyanidins are plant compounds, not nutrients, so neither has a value in the Thai Reference Daily Intakes (Thai RDIs). The Thai RDIs cover nutrients such as vitamin C, which cranberry contains in small amounts.

Who should be careful with cranberry?

Effects that can occur

NCCIH says cranberry taken by mouth is generally thought to be safe. Excessive amounts can cause stomach upset and diarrhoea, especially in young children.

People taking regular medication

NCCIH says cranberry may interact with some medicines, and that study results on this do not agree. It advises people taking medicines to talk with a healthcare provider before using cranberry or other herbal products. Anyone taking regular medication should speak to a doctor or pharmacist.

People who are pregnant or breastfeeding

NCCIH says some studies suggest cranberry is safe in the amounts found in food during pregnancy and breastfeeding, but the evidence is not conclusive for larger amounts. People who are pregnant or breastfeeding should speak to a doctor before using it in larger amounts.

If you are pregnant, breastfeeding, take regular medication or are under a doctor's care, speak to a doctor or pharmacist before taking dietary supplements.

Dietary supplements are not intended to prevent, treat or cure any disease.