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 12 cancers, and dietary fiber increases the feeling of fullness.
Current Evidence: AICR/WCRF Expert Report and its Updates (CUP)
Blueberries are fruits that contain fiber. After a systematic review of the global scientific literature, AICR/WCRF analyzed how these factors affect the risk of developing cancer. This comprehensive review of decades of research concluded that there is strong – probable - evidence that:
- foods containing dietary fiber DECREASE the risk of colorectal cancer
- a diet high in fruits along with non-starchy vegetables DECREASE the risk of lips, mouth, tongue and other aerodigestive cancers
Evidence categorized as "probable" 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 probable judgement is strong enough to justify recommendations.
Source: AICR/WCRF. Diet, Nutrition, Physical Activity and Cancer: A Global Perspective, 2018.
”…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.