The Cancer Research
Apples provide dietary fiber and polyphenol compounds that partner with gut microbes to create an environment that may help to reduce the risk of cancer. Observational population studies link apples with a lower risk of the estrogen receptor-negative (ER-) form of breast cancer.
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
- Weight gain, overweight and obesity*
*This is important, because there is strong evidence that excess body fat increases the risk of at least 12 different cancers.
- 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
Flavonols influence gene expression and cell signaling in ways that increase antioxidant, anti-inflammatory and carcinogen-deactivating enzymes in cell and animal studies. They inhibit cancer cells’ growth, suppress ability to spread and activate signaling that leads to self-destruction of abnormal cells. Flavonols dial down the expression of oncogenes (genes that have the potential to cause increased cell growth that can lead to cancer) and increase the expression of tumor suppressor genes.
Flavan-3-ols influence gene expression and cell signaling in ways that increase antioxidant, anti-inflammatory and carcinogen-deactivating enzymes in cell and animal studies. They inhibit cancer cells’ growth, suppress ability to spread and activate signaling that leads to self-destruction of abnormal cells. They dial down the expression of oncogenes (genes that have the potential to cause increased cell growth that can lead to cancer) and increase the expression of tumor suppressor genes.
Triterpenoids, such as those found in the peel of apples, can increase antioxidant, anti-inflammatory and carcinogen deactivating enzymes by influencing cell signaling pathways and gene expression in cell and animal studies. They decrease growth and increase the self-destruction of cancer cells.
- Human Studies
Human studies related to apples and cancer risk compare groups of people who consume relatively high and low amounts of total fruit, dietary fiber or apples specifically.
People who eat more fruits have a lower risk of several types of cancer. This probably reflects combined protection from many different nutrients and compounds they contain.
Greater consumption of apples specifically was associated with a lower risk of estrogen receptor-negative (ER-) breast cancer (but not ER+) in an analysis of many population studies, and with a lower risk of lung cancer in another analysis. This analysis also showed links between apples and lower risk of other cancers, but not in the type of studies (prospective cohorts) considered the strongest.
Dietary fiber: Observational population studies link high dietary fiber consumption with reduced risk of colorectal cancer. One analysis of multiple prospective studies also links dietary fiber with a lower risk of breast cancer. However, analysis for the AICR/WCRF Third Expert Report considered the potential for an association of dietary fiber and this and several other cancers and found the evidence too limited to support a conclusion.
- Lower cancer risk with eating patterns high in dietary fiber could reflect higher levels of a variety of nutrients and phytochemicals in high-fiber foods. However, research shows that different types of dietary fiber could play a role in reducing cancer risk.
- Apples are high in viscous fibers such as pectin. These fibers form a gel that slows down the body’s absorption of carbohydrates. Ongoing research is looking at how this might reduce elevated levels of insulin and insulin resistance that seem to support cancer development.
- Apples also include fermentable fibers and compounds that gut bacteria use to produce short-chain fatty acids (SCFAs), such as butyrate. In rodent and human clinical trials, these SCFAs reduce markers of inflammation and oxidative stress and show effects on gene expression that could reduce cancer development.
- Tips for Selection, Storage and Preparation
- Popular varieties for eating raw include the sweet Red Delicious, Golden Delicious and Gala, and the more tart Braeburn and Fuji.
- Varieties that hold their texture in cooking and baking include Cortland, Jonagold, Pippin, Granny Smith, and Ida Red.
- Refrigerate apples in a plastic bag away from strong-odored foods and use within three weeks.
- If one apple is damaged or rotting, remove it so that it does not affect others.
- Chopped apples add a nice sweetness and texture to vegetable salads and extra crunch to fruit salads.
- Bake or stew apples with vegetables such as carrots, winter squash and sweet potatoes.
- For a quick dessert, core apples and stuff with raisins and cinnamon. Top with a tablespoon of cider or water, cover with waxed paper and microwave for 2 minutes each.
- Sliced apples turn brown quickly when exposed to air. Minimize browning by dipping the apples in water with lemon or other citrus juice.
- Substitute applesauce for up to 1/2 of the oil to lower calories and fat in baked goods such as quick breads and cakes.
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