NASA-funded study parses the brain protecting powers of blueberries and strawberries
by Craig Weatherby
Even as the agency frets over the space shuttle’s fragile tiles and foam, NASA has to think about protecting astronaut’s bodies from the subtler dangers of space flight. For decades, it’s been funding research into the special physical stresses of life in outer space, such as loss of bone mass in zero gravity.
The ill effects of cosmic radiation present one of the challenges of extended stays in space stations, or flights to distant planets.
Because the gasses in our atmosphere absorb some of the cosmic rays from the stars, people on passenger jets receive substantially more radiation than they’d get at ground level. And when humans enter the atmosphere-free environs of outer space—even the near-earth orbits used by the space shuttle and the current international space station—the problem is much more serious.
Accordingly, NASA funds research into ways to ameliorate the damage that radiation can do to the cells in astronauts’ bodies, with special attention to their neurons (brain cells). An astronaut faced with life-or-death situations requiring maximum mental acuity can ill-afford to suffer premature, radiation-induced senility.
Antioxidants for astronauts?
Food-borne antioxidants are known to offer potent protection from the unstable, cell-damaging molecules called free radicals, which are generated by radiation, among other environmental and dietary factors.
And the polyphenol pigments that make blueberries blue and strawberries red are among the most powerful found in plants foods.
As part of its radiation-protection research program, NASA funded a study conducted by scientists at Boston’s Tufts University and the University of Maryland at Baltimore. If you follow antioxidant research you’ll know that Tufts is home to the USDA’s Human Nutrition Research Center on Aging, whose researchers have authored hundreds of enlightening studies on food-derived antioxidants.
Prominent among the USDA-Tufts center researchers is Dr. Barbara Shukitt-Hale, who led the team that published exciting new NASA-funded research on berries, radiation, and brain health.
Last year, Dr. Shukitt-Hale joined in publishing a research project that tested the effects of blueberry extract supplements in elderly rats’ brains (de Rivera C 2005). After just two months, rat chow containing two percent blueberry extract reversed or retarded normal age-related decline in the aging animals’ brain function speed.
So when NASA came knocking, it seemed logical to test the effects of blueberries against cosmic radiation. But the Boston-Baltimore team decided to test strawberries as well, to see if the two fruits might bring different protective benefits to astronaut’s brains. And theirs was a smart decision, because the study findings suggest that these two berries produce overlapping but distinct benefits (Shukitt-Hale 2006).
Berries’ brain-protective powers put to divergent tests
Dr. Shukitt-Hale and her colleagues conducted a three-month study in 60 male rats that were divided into three groups of 20 each. During the first two months, one group’s rat chow contained a small amount of blueberry extract, while another group’s rat chow contained a small amount of or strawberry extract (two percent of the feed in each case). The third group received plain, un-supplemented chow.
At the end of this period, half the rats in each of the three groups were exposed to radiation of a kind known to mimic the aging-related cognitive declines seen in older rats and humans, which are driven in large part by direct cell damage from free radicals and by the inflammation this damage elicits in the brain.
One month later, all of the rodents were subjected to two tests of brain function: a maze challenge designed to test their spatial orientation/navigation capacity, and a test of “reversal learning” capacity. In a reversal learning challenge, behavior that was rewarded at first is punished, and vice versa.
New findings offer clues to different berries’ varying benefits
As expected, all of the rodents exposed to radiation—whether they were in the berry or plain chow groups—fared worse on both tests, compared with the un-radiated animals. The researchers also found that brain levels of dopamine (a marker for brain signaling) were lower in the irradiated animals.
However, the blueberry-fed and strawberry-fed groups did much better on both brain-function tests compared with the controls that did not receive berry extracts.
And, intriguingly, the researchers detected real differences between the blueberry and strawberry groups. The strawberry group excelled in the maze test, while the blueberry group excelled in the test of reversal learning.
In other words, the similar but non-identical groups of polyphenol compounds found in each of the two fruits seemed to benefit different regions of the brain to different degrees.
But it seems likely that each type of berry exerts beneficial effects in both parts of the brain. Even though the striatum area of brain is closely associated with movement, balance, and walking, it is also needed for reversal learning. And while the hippocampus is critical to memory, it is essential to good spatial orientation and navigation.
As Dr. Shukitt-Hale’s team said in a press release, “These findings suggest that multiple mechanisms may be involved in the beneficial effects of high-antioxidant fruits on ageing as well as radiation.”
Bottom line: variety is valuable to berries’ brain benefits
Many recent news stories have highlighted the brain-enhancing potential of blueberries, and the fact that they contain the highest levels of antioxidants among common commercial species.
But as the results of this preventive-nutrition study and so many like it demonstrate, the key to an anti-aging diet is to eat a wide variety of fruits, vegetables, and other powerfully disease-preventive foods.
- Shukitt-Hale B, Carey AN, Jenkins D, Rabin BM, Joseph JA. Beneficial effects of fruit extracts on neuronal function and behavior in a rodent model of accelerated aging. Neurobiol Aging. 2006 Jul 10; [Epub ahead of print]
- de Rivera C, Shukitt-Hale B, Joseph JA, Mendelson JR. The effects of antioxidants in the senescent auditory cortex. Neurobiol Aging. 2006 Jul;27(7):1035-44. Epub 2005 Jun 13.