The Cancer Research
Blueberries contain numerous phytochemicals and nutrients, many of which are well studied in the laboratory. They also contain dietary fiber, which can act in several ways to lower cancer risk, including helping with weight control. Excess body fat increases the risk of seven different cancers, and dietary fiber can increase the feeling of fullness.
What Current Evidence Shows: AICR/WCRF Expert Report and its Updates (CUP)
Blueberries are fruits that contain dietary fiber. After a systematic review of the global scientific literature, AICR/WCRF weighed the strength of the evidence linking these factors to lower risk for several cancers.
|Diets high in:||CONVINCINGLY lower risk of the following cancers:|
|Foods containing dietary fiber||Colorectum|
|Diets high in:||PROBABLY lower risk of the following cancers:|
|Fruits||Mouth, Pharynx, Larynx
Source: Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective and the 2011 Continuous Update Project (CUP): Colorectal Cancer.
”…the more you look at these foods, the more you see what a complex mixture of protective compounds they have.”
- Karen Collins, MS, RD, CDN.
Open Areas of Investigation: Laboratory Research
Laboratory research is extensive on blueberry compounds such as flavonoids and ellagic acid.
- Vitamin C protects cells’ DNA by trapping free radicals and inhibiting formation of carcinogens.
- In cell studies, blueberry extract and anthocyanins, as well as ellagic acid and the urolithins that form from it, decrease free radical damage to DNA that can lead to cancer. They also decrease growth and stimulate self-destruction of mouth, breast, colon and prostate cancer cells.
- In animal studies, blueberries decrease inflammatory cytokines, esophageal cancer and pre-cancerous changes in the colon, although impact on colon cancer is less clear. In other animal studies, blueberries decrease estrogen-induced mammary cancer and DNA damage.
- Pterostilbene increases self-destruction of lung, stomach, pancreatic and breast cancer cells. In an animal study, it also decreased formation of pre-cancerous colon polyps and reduced markers of inflammation.
- Dietary fiber reduces cells’ exposure to cancer-causing substances, and healthful gut bacteria use it to produce short-chain fatty acids that protect colon cells.
Open Areas of Investigation: Human Studies
Most human studies look at overall fruit consumption. Comparing people with and without cancer, the studies show lower risk of several cancers in those who eat more fruits compared to those who eat relatively few.
Studies are not clear about how well we absorb anthocyanins and ellagic acid from the digestive tract. Several studies show that eating blueberries increases antioxidant activity in the blood, although results vary and the studies do not show consistent signs of preventing DNA damage.
Bacteria in our colon convert the ellagitannins and ellagic acid to urolithins, which can be absorbed and seem to offer antioxidant, anti-inflammatory and direct anti-cancer effects. In addition, unabsorbed compounds may exert protective effects inside the digestive tract. This research is ongoing.