Dementia, such as Alzheimer’s disease and vascular dementia, is the result of neurodegeneration. Alzheimer’s disease can be caused caused by the accumulation of peptide plaques resulting in deficit of cholinergic functions. Most drugs in the prevention of Alzheimer’s disease are anticholinesterase inhibitors that help to increase the level of the neurotransmitter acetylcholine. Another mechanism that can cause Alzheimer’s disease is inflammation and degeneration of neurons. The balance between pro- and anti-inflammatory mediators in important in the process of neuro-inflammation.
Isoflavones improve memory in rodents
Isoflavones in soybeans have been reported to act a an acetylcholinesterase inhibitor. They improved memory in rodents using different models. Bagheri and his team found that a pretreatment with the isoflavone genistein ameliorated beta-amyloid-induced impairment of short-term spatial memory in rats through an estrogenic pathway and by inducing attenuation of oxidative stress [1]. Another study found that soybean isoflavones reduced the cytokine cascade and inflammatory response induced by beta-amyloid 1-42 which could result in the improvement of spatial learning and memory ability impairment in the rats [2]. A Chinese study investigated the effect of isoflavone aglycone on the learning and memory performance of mice and explored its neural protective mechanism. Isoflavone aglycone decreased the formation and deposition of insoluble debris and relieved the resulted toxicity and damage to neurons. This study concluded that isoflavone aglycone may effectively protect the nervous system [3].
Tempeh isoflavones are more effective than soybean isoflavones
A study conducted at the University of Teknologi in Malaysia compared the neuroprotective effects between total isoflavones from soybean and tempeh on rats subjected to amnesia using scopolamine. Tempeh is a fermented soyfood that is commonly found in Indonesia and Malaysia. Both tempeh and soybean isoflavones improved cholinergic activity by increasing acetylcholine levels and inhibiting acetylcholinesterase. Isoflavones from tempeh were more effective in reducing inflammation than isoflavones from soybeans. The study concluded that soybeans and tempeh might be useful in the management and prevention of dementia and Alzheimer’s disease [4].
References
[1] Bagheri M et al. Genistein ameliorates learning and memory deficits in amyloid beta(1-40) rat model of Alzheimer’s disease. Neurobiol Learn Mem. 2011 Mar;95(3):270-6.
[2] Ding B et al. Soybean isoflavone alleviates beta-amyloid 1-42 induced inflammatory response to improve learning and memory ability by down regulation of Toll-like receptor 4 expression and nuclear factor-κB activity in rats. Int J Dev Neurosci. 2011 Aug;29(5):537-42.
[3] Yang H et am. Mechanism of isoflavone aglycone’s effect on cognitive performance of senescence-accelerated mice.B rain Cogn. 2011 Jun;76(1):206-10.
[4] Ahmad A et al. Total isoflavones from soybean and tempeh reversed scopolamine-induced amnesia, improved cholinergic activities and reduced neuroinflammation in brain.Food Chem Toxicol. 2014 Mar;65:120-8.