They suggest the food could help prevent Alzheimer's disease, rapidly increasing around the world.
Alzheimer's disease is characterized by numerous senile plaques resulting in neuronal loss. The beta-amyloid peptide that makes up these plaques has been shown to lead to brain dysfunction, causing learning and memory impairment in rodents.
The new study found that the brown rice, which has been soaked in water to induce slight germination and contains around 13 times the amount of oryzanol and 15 times the gamma-aminobutyric acid (GABA) of polished rice, both improved the learning ability of mice and prevented impairment of spontaneous alternation behaviour in the animals.
GABA, an inhibitory neurotransmitter, is sometimes taken to enhance sleep quality. It is also used increasingly in bodybuilding supplements for its effect on growth hormone levels.
In contrast, the beta-amyloid protein impaired spontaneous alternation behaviour in the control group fed polished or white rice, a staple of the Asian diet.
The FANCL team, in collaboration with Meijo University researchers, suggest that the large amount of GABA in the brown rice may enhance glutamate release and the sensitivity of NMDA receptors. Activation of these receptors is thought to underlie learning and memory.
Oryzanol also contains ferulic acid ester, which scavenges free radicals and may fight oxidative stress possibly leading to the beta-amyloid damage.
There are currently nearly 18 million people with dementia in the world - the most common cause of this dementia is Alzheimer's disease. By 2025 this figure will rise to 34 million, with 71 per cent of these likely to live in developing countries.
Writing in an early online publication of the Biological & Pharmaceutical Bulletin, published by the Pharmaceutical Society of Japan, the researchers say they will next compare the effects of brown rice with pregerminated brown rice to confirm the current findings.
FANCL markets a pre-germinated brown rice product in Japan.