Second study finds berry skins lower animals' blood fat and cholesterol levels
by Craig Weatherby
To the many studies that demonstrate blueberries’ likely health benefits we can now add two more, presented at the 233rd meeting of the American Chemical Society (ACS): one bearing on colon cancer and the other on heart health.
Let’s review the colon cancer study first.
Colorectal cancers are among the most curable if a diagnosis is made early, and research indicates that some 80 percent may be vulnerable to prevention or serious retardation by diet.
As the Rutgers-based cancer research team noted in their presentation, epidemiological studies show that fish fat and olive oil reduce the risk of colon cancer, while diets high in saturated fat and calories place people at higher risk.
And as they also said, animal studies indicate that diets high in saturated fat promote colon cancer, while diets low in calories or high in fish fat or olive oil do not.
The results of various epidemiological and animal studies allow researchers to focus on the most likely sources of naturally occurring chemopreventive agents, including berries.
Study #1: Berry compound versus colon cancer
Using a grant from the National Cancer Institute, at team of USDA and academic researchers led by Rutgers University researcher Bandaru Reddy conducted a small study in 18 rats (Reddy BS et al 2007).
The animals were given a chemical (azoxymethane) that initiates the mechanism by which humans develop colon cancer.
Half of the rodents had their diet supplemented with pterostilbene: an antioxidant, anti-fungal compound similar to resveratrol from grapes.
After eight weeks, the pterostilbene-supplemented group had 57 percent fewer pre-cancerous lesions in their colons.
The blueberry compound also acted to block two key colon-cancer risk factors: 1) the uncontrolled spread of colon tissue cells and 2) genes that promote inflammation.
Dr. Reddy expressed the significance of the results in a press release: “The results of the study suggest that naturally occurring components offer an attractive alternative for the prevention of colon cancer. Our results may support dietary prevention of colon cancer and health benefits of blueberries.”
Study #2: Blueberry skins beat drug for lowering blood fat levels
In addition to the cancer findings, blueberries showed cardiovascular benefits in a hamster study presented at the national meeting of the American Chemical Society (Rimando AM et al 2007).
A team led by Agnes Rimando—who co-authored the colon cancer study—fed hamsters a high-cholesterol diet that also contained loads of blueberry skins (7.6 percent of the diet), and divided them into three groups.
- High-cholesterol control diet
- High-cholesterol control diet containing 7.6 percent blueberry skins
- High-cholesterol control diet plus ciprofibrate (cholesterol-lowering drug)
Compared with hamsters fed the control diet, the animals fed berry skins averaged 38 percent lower blood levels of triglycerides, 19 percent lower blood levels of LDL cholesterol, and a 37 percent lower total cholesterol level.
These reductions were substantially bigger than those seen in the group given cholesterol-lowering ciprofibrate.
Hamsters given blueberry skins in their feed also excreted three times as much dietary fat, compared with the animals given ciprofibrate (60 percent of their waste vs. only 21 percent).
It was also clear that it was the phyto-chemicals, not the fiber, in the skins that reduced blood fat and cholesterol levels, since giving the hamsters an ethanol extract of the skins matched the effects of feeding them whole skins.
While the “doses” of pterostilbene and skins were high, they needed to be to yield measurable results in a short time.
It is likely that smaller amounts of either berry factor would exert similar beneficial effects, albeit to smaller extents.
The lesson seems clear: as well as making great flavor and pies, blueberries deliver bountiful health benefits.
- Reddy BS, Newmark H, Suh N, Rimando AM, Rao CV. Novel approaches for colon cancer prevention by types of dietary fat, pterostilbene and other food components. Abstract: AGFC 009. American Chemical Society 233rd national meeting, March 25 2007. Accessed online March 25, 2007 at http://membership.acs.org/a/agfd/cornucopia/Spring2007.pdf
- Rimando AM, Yokoyama WH, Patny A, Avery MA, Mizuno CS. Blueberry skins lower plasma and liver cholesterol and triglycerides in hypercholesterolemic hamsters. AGFC 038. American Chemical Society 233rd national meeting, March 25 2007. Accessed online March 25, 2007 at http://membership.acs.org/a/agfd/cornucopia/Spring2007.pdf