AICR Food Facts  >  Foods That Fight Cancer

Ongoing Areas of Investigation

• Laboratory Research

  Oranges contain a variety of nutrients and phytocompounds that show potential to protect against cancer in laboratory studies.

  Vitamin C is a powerful antioxidant. In lab studies, it 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.

  Flavanones (such as oranges’ hesperidin) 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 and ability to spread, and activate signaling that leads to self-destruction of abnormal cells. In these laboratory studies, flavanones dial down expression of oncogenes (genes that have potential to cause increased cell growth that can lead to cancer) and increase expression of tumor suppressor genes.

  Terpenes function as antioxidants in cell studies. They also decrease growth and reproduction of isolated cancer cells. These terpenes, mainly limonene, lie in oranges’ essential oils, which are found in tiny sacs in the flavedo (the outer colored portion of the peel). It’s possible that cold-pressed juice from juice extractors would provide some amount of these terpene compounds, but it’s not clear how the amount would compare to amounts effective in laboratory studies, and eating the fruit (without the peel) would not provide these compounds.

• Human Studies

  Human studies related to oranges and cancer risk compare groups of people who consume relatively high and low amounts of total fruit, citrus fruit, or nutrients found in oranges.

  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.

  Citrus fruit: Limited evidence ties citrus fruit specifically to lower risk of stomach cancer, according to the AICR/WCRF Third Expert Report. Analysis for the report also links citrus fruit consumption and lower risk of lung cancer, but relatively large variation in results of different studies (heterogeneity) means that further research is needed.

  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 greater comparing people with very low levels to moderately increased levels than comparing people with moderate to 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 associated with 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.

  Dietary Fiber: Observational population studies link high dietary fiber consumption with reduced risk of colorectal cancer. Analyses combining 16 to 20 prospective cohort studies also link dietary fiber with lower risk of breast cancer. However, analysis for the AICR/WCRF Third Expert Report evaluated potential for an association of dietary fiber with this and several other cancers, and found the evidence too limited to support a conclusion.

  • Viscous fiber is a type of soluble dietary fiber that forms a gel in the digestive tract, slowing action of digestive enzymes and thus slowing the rise in blood sugar after eating. By helping to reduce insulin resistance and elevated levels of insulin, this could potentially help reduce cancer risk. Viscous fiber’s actions in the gut may also contribute to reducing circulating estrogen levels. Such effects could help explain why some studies link greater soluble dietary fiber and lower breast cancer risk.
  • Foods containing dietary fiber probably reduce risk of weight gain, overweight and obesity. Some studies suggest that viscous fiber may contribute to this effect by increasing feeling of fullness. By supporting a healthy weight, foods rich in fiber indirectly contribute to lower risk of the 12 or more cancers related to excess body fat.
• Common Questions

  Q: Does orange juice provide the same nutrients and phytocompounds as eating an orange, or are healthful components lost in processing?

  A: Consuming most of your fruit consumption as solid, whole fruit instead of juice is recommended — but headline hype suggesting that even 100% orange juice is nothing but sugar is untrue.

  Fiber and Phytocompounds: Solid fruit provides dietary fiber – important for reducing cancer risk – that is missing from juice. But contrary to common belief, eating the solid fruit does not necessarily provide you with more of the fruit’s phytocompounds. Many phytocompounds found in oranges are especially concentrated in the peel. Commercial production of orange juice includes the peel in the juicing process, and these compounds are present in 100% juice. Although some processing methods may decrease phytocompound content, limited evidence suggests that we may absorb these compounds out of the gut better from juice. These laboratory studies that mimic human digestion need to be interpreted with caution, but the evidence available today supports 100% juice as a good source of the protective compounds.

  Weight management: Evidence is not clear about the common question of whether whole fruit is more helpful than juice for managing a healthy weight. Each cup (8 fluid ounces) of orange juice contains about 110 calories. Food labels identify that as one serving of juice, but you’d need to squeeze several oranges to get that much juice. The juice from one medium orange – a smaller portion than many people would drink – contains only 60 calories. But if you compare equal amounts of orange sections and 100% orange juice (fresh or reconstituted from frozen), although calorie and sugar content on average is slightly higher in juice, there’s likely a greater difference between individual oranges. On the other hand, the fiber you get from eating an orange can help fill you up, and it also takes longer to eat a whole orange. Slower eating often leads people to consume fewer calories. Nonetheless, human studies don’t show a clear link between fruit juice consumption and weight gain.

  Bottom Line: As you cut down on soft drinks and other sugar-sweetened drinks, it’s best to replace them with water rather than large amounts of even 100% fruit juice. But there’s no reason for most people to avoid juice, since studies show that it often helps to meet recommendations for fruit in a healthy diet, including for people with limited budgets or medical circumstances that make eating solid fruit difficult. If you enjoy juice, keep it to one moderate size portion and work to increase total fruit consumption by adding more solid fruit to your habits.