The Cancer Research
Cherries are among foods highest in melatonin, which shows cancer-preventive potential in laboratory studies. Limited human research on cherries as a source of melatonin has investigated the potential to improve sleep, but little is known about whether eating melatonin-rich cherries contributes to cancer prevention.
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 foods containing dietary fiber DECREASE the risk of:
- Colorectal cancer
- 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 foods containing vitamin C may DECREASE the risk of:
- Lung cancer (in people who smoke) and colon 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
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 increase cells’ antioxidant and anti-inflammatory defenses against damage that could lead to cancer in 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 colon), creating an environment in the body less likely to support cancer.
Vitamin C is a powerful antioxidant. Most of the antioxidant protection from cherries comes from polyphenols, but vitamin C adds to the effects. In lab studies, vitamin C protects cells’ DNA by trapping free radicals, and it helps renew the antioxidant ability of Vitamin E. In cell studies, vitamin C also inhibits formation of carcinogens and supports the immune system.
Melatonin is a hormone people produce in response to darkness, and is found in a few foods. Melatonin is best known for helping to regulate the body’s circadian rhythms. Decades of cell and animal studies show that melatonin also supports antioxidant defenses by scavenging free radicals that could damage DNA and stimulating the body’s antioxidant enzymes, as well as promoting DNA repair. Melatonin has been especially studied for ability to decrease growth of both estrogen-receptor-positive and -negative breast cancer in isolated cells and in animals. Such studies also show decreased growth of prostate and other cancers, with effects seen all across stages of cancer development.
Perillyl alcohol can interfere with growth of cancer cells in laboratory studies. It also inhibits growth of several types of cancer in animals, apparently through effects on cancer cells themselves and by inhibiting the process of angiogenesis that tumors rely on to spread. So far, this effectiveness has not been demonstrated from human consumption however.
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.
Short-term human intervention trials with cherries most often involve tart, rather than sweet, cherries. Most, but not all, have been randomized controlled trials that included use of placebos. With daily consumption of cherries, cherry juice or dried cherry powder, many demonstrated reductions in markers of oxidative stress and inflammation. Beyond the influence of overall fruit consumption in large population studies, more research is needed to understand the impact of cherry consumption on cancer risk.
Dietary Fiber: Observational population studies link high dietary fiber consumption with reduced risk of colorectal cancer. One meta-analysis of 16 prospective studies also links dietary fiber with lower risk of breast cancer. However, analysis for the AICR/WCRF Third Expert Report considered potential for an association of dietary fiber and this and several other cancers, and found the evidence too limited to support a conclusion.
Vitamin C: Population studies comparing people with higher and lower levels of vitamin C in their diets, and especially levels circulating in their blood, link higher amounts with lower overall risk of cancer. This effect is larger when comparing people with very low levels to moderately increased levels than comparing people with moderate and much higher levels. Higher levels of vitamin C from foods are linked with lower risk of lung cancer among people who smoke tobacco, although not in those who used to smoke or who have never smoked. People with more vitamin C in their diet are also less likely to develop colon cancer. That’s even after adjusting for other risk factors for colon cancer, such as alcohol, red meat and tobacco. Evidence for both lung and colon cancer is rated as Limited Suggestive in the AICR/WCRF Third Expert Report, and more research is needed.
Polyphenol compounds: Higher levels of anthocyanins in the diet were strongly associated with lower levels of markers of inflammation, and flavan-3-ols were linked with lower levels of oxidative stress in cross-sectional analysis of a large population study.
Tips for Selection, Storage and Preparation
- Cherries can be classified as sweet or tart. Sweet cherries are the most popular for eating raw, although you can use them for cooking.
- When purchasing fresh, select firm, glossy, plump cherries with stems attached. The darker they are; the riper. Avoid shriveled or bruised fruits.
- You’ll find it easier to cut dried cherries if you oil your knife or kitchen scissors beforehand.
- Refrigerate unwashed cherries for up to ten days in a plastic bag. Or to minimize bruising, spread a single layer on a shallow pan and cover with plastic wrap.
- Check occasionally and remove any that have gone bad before they cause others to spoil.
- For cooking, pit cherries either by hand (pull with your forefinger and thumb or push with a chopstick) or with a pitter.
- You can poach cherries (great for sauces) by dropping them into simmering water and cooking for 1 to 3 minutes until soft. Use 2:1 ratio cherries to water: If you have 2 cups of cherries, use 1 cup of water.
- Dried cherries are delicious in salads and hot or cold cereal. You can also add dried cherries to baked goods like muffins and cookies to keep them moist.
- Keep a bag of cherries in the freezer and add to oatmeal while it cooks, or layer with yogurt and granola for a quick breakfast.
- Add cherry juice and whole cherries to sparkling water for a cooling summer beverage.
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