The reason, in both cases, appears to be these foods contain high levels of anti-oxidants -- chemicals thought to protect against organ damage. Often foods such as honey or blueberries, which are dark in color, contain extra amounts of anti-oxidants.
"Typically, the more color in food, the better it is for you," said Nicki Engeseth, assistant professor of food chemistry at the University of Illinois, Urbana.
In one study presented at the meeting, Jim Joseph, director of the neuroscience laboratory in the Human Nutrition Research Center on Aging at Tufts University, fed blueberry rich chow to one group of mice and gave another group regular food for 11 months. The mice were genetically engineered to develop an Alzheimer's-like brain disease.
When the animals were tested, the blueberry-fed mice were able to perform behavior tests better than the other mice, and when the animals were sacrificed, Joseph said their brains appeared strikingly different. Although both groups of mice developed the brain deposits seen in Alzheimer's Disease, the blueberry-fed animals retained significantly more behavior-signaling nerve cells or neurons than did the mice on the regular chow diet.
Joseph suggested a chemical in blueberries known as anthocyanis -- the substance that gives fruits and vegetables their color -- might be helpful in protecting the brain.
"We think these compounds can make the brain resistant to oxidative stress, strengthening the brain against the ravages of time," he told United Press International.
Whether the results seen in mice translate into protection among humans awaits further study, but Joseph said, "I eat blueberries every day now for breakfast."
Engeseth fed various drinks containing honey or sugar to 25 healthy volunteers and then measured their blood cholesterol levels 60 minutes and 90 minutes after they ingested the drinks. She compared the water and honey drinks to water alone, tea alone, tea and honey and tea and sugar.
"While the tea drinks showed some lowering of cholesterol when compared to water alone, only the water and honey combination resulted in a statistically significant difference in cholesterol levels," Engeseth told UPI.
She said the decreases appeared similar to those seen in studies done with fruits and vegetables. The anti-oxidants in honey appear to prevent oxidation of low density lipoprotein cholesterol -- the so-called bad cholesterol. Oxidation of LDL cholesterol is the initial step in the cascade of molecular events leading to development of blood vessel blockages that can cause heart disease, she explained.
In her experiments, Engeseth used buckwheat honey -- a particularly dark grade of honey -- because previous studies found it had the highest level of anti-oxidant chemicals. Honeys less dark in color also contain high levels of anti-oxidants. Even the light-colored honeys contain some anti-oxidants, she said.
Further studies are being undertaken to determine if animals fed with honey have fewer genetic mutations, also thought to be caused by oxidation.
Engeseth's work was funded partially by the National Honey Board. Joseph's work with blueberries was funded by the Alzheimer's Association and the U.S. Department of Agriculture, however further studies will receive some grant support from the Wild Blueberry Association of North America and the North American Blueberry Council.
"On the basis of what we know now about honey, I would say that honey is a good substitute for table sugar or corn syrup," Engeseth said, although she cautioned against overuse in patients such as diabetics that have sugar-restricted diets.
Joseph suggested people should eat more fruits and vegetables in their regular diets. "The more stuff you eat with different color, the more likely you will be to strengthen your brain," he said.