A new method of studying health related supplements and food compounds suggests that polyphenols, allegedly behind the benefits of superfoods such as blueberries and broccoli, don't make it past intestinal villi.

Experts Challenge Super Food Claims: Healthy-Giving Properties of B...

While there's no doubt foods such as broccoli, blueberries and whole grains contain polyphenols - compounds that have antioxidant and anti-inflammatory properties - the academic experts contend that little of these health-giving properties actually make it past the gut. "Polyphenols may well work when cells are exposed to them directly, such as under laboratory conditions, but what needs to be established is how effective they are when consumed as part of a food. If they don't actually get through the gut membrane and into the rest of the body, then they're not a super food,"...

... a single layer of cells grown in a laboratory environment that develops the characteristics and functions of the micro-villi, the tiny hair-like projections that aid efficient absorption found mainly in the small intestine," Dr Opara said. "This method allows us to look at what nutrients pass through into the body and could be used to test food supplements, drugs and foodstuffs. We found that while some compounds may have a local effect in the gut itself, in terms of the rest of the body the impact could be negligible." [emphasis mine]

This doesn't explain why studies on lab animals found benefits from blueberries, and Chinese women who ate the most cruciferous vegetables had the least cancer. If polyphenols don't make it into the body, some other explanation for such correlations must be sought.