A diet of antioxidant-rich fruit and vegetables could be an effective way of protecting the brain against the ravages of time, according to new studies from the US.
Researchers at the University of South Florida Center for Aging and Brain Repair and the James A. Haley Veterans Hospital, writing in the Journal of Neuroscience, claim that evidence from their animal studies show a correlation between antioxidants and brain function.
"If these pre-clinical findings translate to humans, it suggests that eating a diet high in antioxidant-rich fruit and vegetables may help reverse declines in learning and memory as you get older," said Paula Bickford, lead author of both studies and a professor at the USF Center for Aging and Brain Repair.
In the first study, co-authored by USF's M. Claire Cartford, older rats fed a diet rich in spinach for six weeks showed a reversal in the normal loss of learning that occurs with age. The rats that ate food containing 2 per cent freeze-dried spinach learned to associate the sound of a bell tone with a subsequent puff of air faster than those fed regular rat food, the study found.
The test measured how quickly the rats learned to blink, after hearing the tone, in anticipation of the oncoming puff of air - a conditioned response shown to slow with age in rodents and humans.
Spinach is rich in antioxidants, which scientists say can counteract free radicals generated in the body during normal metabolism and exposure to pollution, ultraviolet light or radiation. An excess of free radicals can damage cellular lipids, protein and DNA, and studies suggest that a lifelong accumulation of free radicals can slow mental processes in old age and may be a factor in Alzheimer's and Parkinson's diseases.
The second study, co-authored by Carmelina Gemma of USF and James A. Haley VA Hospital, found that the benefit of a diet high in fruit and vegetables depends on the levels of antioxidant nutrients in the fruits and vegetables. Furthermore, the researchers suggest, the protective effect of antioxidants may be linked to their ability to reverse age-related accumulations of potentially harmful inflammatory substances in the brain.
The USF researchers compared three groups of older rats. One group ate a diet supplemented by spirulina, a blue-green algae high in antioxidant activity. The second group was fed a daily ration of apple, a food moderate in antioxidant activity, with their rat food. The third group ate a cucumber-enriched diet, low in antioxidant activity.
Aged rats fed either spirulina- or apple-enriched diets for two weeks demonstrated improved neuron function, a suppression of inflammatory substances in the brain, and a decrease in malondialdehyde (MDA), a marker for oxidative damage. In fact, spirulina reversed the impairment in adrenergic neural function normally associated with ageing. There was no improvement in rats fed a diet supplemented with cucumber.
The research has hopeful implications for the prevention of neurodegenerative disorders in an increasingly ageing population, but must still be tested in humans, Dr Bickford said.