The Cancer Research
Cranberries provide a modest amount of vitamin C, but the main source of cranberries’ potential for cancer prevention comes from their package of phenolic compounds. These include polyphenols, found in most berries, as well as a relatively unique type of proanthocyanidin. Because many of these compounds are complex molecules broken down by gut microbes, there is potential for broad effects on the gut microbiota and inflammation. Individual differences in gut microbes could mean that people differ in cancer protection from cranberries.
Interpreting the data
After a systematic review of the global scientific literature, AICR/WCRF analyzed how fruits and their nutrients affect the risk of developing cancer.
“Convincing” or “probable” evidence means there is strong research showing a causal relationship to cancer—either decreasing or increasing the risk. The research must include quality human studies that meet specific criteria and biological explanations for the findings.
A convincing or probable judgement is strong enough to justify recommendations.
- There is probable evidence that non-starchy vegetables and fruit combined DECREASE the risk of:
- Aerodigestive cancers overall (such as mouth, pharynx and larynx; esophageal; lung; stomach and colorectal cancers)
“Limited suggestive” evidence means results are generally consistent in overall conclusions, but it’s rarely strong enough to justify recommendations to reduce risk of cancer.
- Limited evidence suggests that fruit may DECREASE the risk of:
- Lung cancer (in people who smoke or used to smoke tobacco) and squamous cell esophageal cancer
- Limited evidence suggests that non-starchy vegetables and fruit combined may DECREASE the risk of:
- Bladder cancer
Ongoing Areas of Investigation
- Laboratory Research
Tannins such as proanthocyanidins are complex compounds that are mostly unabsorbed from the digestive tract. Some researchers consider these likely to be the cranberry phytocompounds most protective against cancer.
In cell studies, proanthocyanidins are antioxidants that seem to influence gene expression to decrease growth of cancer cells and increase their self-destruction. However, this may not reflect what occurs when they are consumed in food, especially in cells outside of the gut. Microbes in the gut break them down to form other phytochemicals that might have anti-inflammatory effects throughout the body.
Anthocyanins influence cell signaling in ways that increase antioxidant, anti-inflammatory and carcinogen-deactivating enzymes in cell and animal studies. They inhibit cancer cells’ growth and ability to spread, and activate signaling that leads to self-destruction of abnormal cells.
Phenolic acids show potential to increase cells’ antioxidant and anti-inflammatory defenses against damage that could lead to cancer, based on cell and animal studies. Emerging evidence in animal studies suggests they may also improve glucose metabolism and decrease insulin resistance, and alter the gut microbiota (microbes living in the digestive tract), creating an environment in the body less likely to support cancer.
Triterpenoids (such as ursolic acid) can increase antioxidant, anti-inflammatory and carcinogen deactivating enzymes by influencing cell signaling pathways and gene expression in cell studies. They also decrease growth and increase self-destruction of isolated cancer cells.
Cranberries, provided in limited animal studies as freeze-dried fruit, powders, extracts or purified compounds, can increase antioxidant enzyme activity, decrease oxidative stress and reduce inflammation and tumor incidence in the colon. These cranberry products inhibit a variety of different types of cancer in animal models.
Laboratory studies need to be interpreted with caution, partly because they may use phytochemicals in concentrations far beyond levels that would circulate in the body. Also, the bioavailability and activity of phytocompounds like those in cranberries depends not only on what’s in the fruit, but also on how they are broken down by the gut microbiota, taken up into the blood and circulated through the body.
- Human Studies
Human studies related to cranberries and cancer risk mainly compare groups of people who consume relatively high and low amounts of total fruit or berries; few human studies address cranberry consumption specifically.
People who eat more fruits have lower risk of a wide range of cancers. This probably reflects combined protection from many different nutrients and compounds they contain.
Flavonoids: People whose diets were higher in anthocyanins had lower levels of markers of inflammation, and those with diets higher in flavonols showed lower levels of oxidative stress, in cross-sectional analysis of a large population study.
One short-term study of a small group of healthy older adults found that cranberry phytocompounds were absorbed and antioxidant defense capacity increased for several hours following consumption of cranberry juice.
- AICR-Supported Studies
- Tips for Selection, Storage and Preparation
- Whole fresh or frozen cranberries provide larger amounts of phytocompounds than other forms.
- Choose cranberries that are firm and not shriveled.
- Commercial cranberry juice and sauce also contribute noteworthy amounts of cranberry phytocompounds, although amounts of many are reduced by at least half by heat and removal of skin and seeds during processing. Because of cranberries’ tart taste, most juice is sold sweetened or as part of a blend with other fruit juices. In each 6-ounce glass, sugar content is like that of apple or pineapple juice with one extra teaspoon of sugar added.
- Dried cranberries offer almost no vitamin C, but they do provide some phytocompounds, including ursolic acid and proanthocyanidins.
- Unlike most other berries, you can refrigerate cranberries for up to two months.
- For longer storage, freeze cranberries in the bags in which you purchased them. Or wash, dry and freeze in a single layer on a cookie sheet; then store in an airtight container or freezer bag for nearly a year.
- Store dried cranberries in an airtight container at room temperature for up to three months; check expiration date on packaged berries.
- Add dried cranberries to cereal, oatmeal or plain yogurt.
- Balance fresh cranberries’ tartness by mixing with other fruits, such as oranges, apples and pears for a relish or salsa.
- Experiment with cranberries added to rice or whole-wheat stuffing.
- Try fresh or dried cranberries as a colorful addition to a green or carrot salad.
- Enjoy the flavor contrasts by combining dried cranberries with vegetables like Brussels sprouts or with apples and red cabbage over pork.
- Add fresh, frozen or dried cranberries to muffins and quick breads. Do not thaw frozen cranberries before adding them to the batter.
- Mix dried cranberries with nuts and other dried fruit to make trail mix.
- Add cranberries to baked apples or apple crisp.
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