Could eating garlic reduce memory problems related to aging?

Consuming garlic helps counteract the age-related changes in intestinal bacteria associated with memory problems, according to a new study conducted on mice. The benefit comes from allyl sulfide, a compound of garlic known for its health benefits.

"Our findings suggest that garlic food administration containing allyl sulfide could help maintain healthy intestinal microorganisms and improve the cognitive health of the elderly," said Jyotirmaya Behera, Ph. D., who leads the research team with Neetu Tyagi, Ph.D., both of the University of Louisville.

Behera will present his research at the annual meeting of the American Physiological Society at the 2019 meeting on Experimental Biology to be held April 6-9 in Orlando, Florida.

The intestine contains billions of microorganisms collectively called intestinal microbiota. Although many studies have shown the importance of these microorganisms in the maintenance of human health, less is known about the health effects associated with changes in gut microbiota that accompany age.

"The diversity of the gut microbiota is reduced in the elderly, a stage of life where neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease develop and where memory and cognitive abilities may decline", said Tyagi. "We want to better understand the link between changes in the gut microbiota and the cognitive decline associated with aging."

For this study, researchers administered oral allyl sulphide to mice aged 24 months, which corresponds to people aged 56 to 69 years. They compared these mice to 4 and 24 month old mice not receiving the dietary supplement based on allyl sulphide.

The researchers observed that older mice receiving the garlic compound exhibited better short- and long-term memory and healthier intestinal bacteria than older mice not receiving treatment. Spatial memory was also altered in 24-month-old mice not receiving allyl sulfide.

Additional experiments revealed that a reduced genetic expression of natriuretic neuron-derived factor (NDNF) in the brain was probably responsible for cognitive decline. This gene, recently discovered by researchers at the University of Louisville, is essential for the consolidation of short and long-term memory.

The researchers found that mice receiving the garlic compound exhibited higher levels of NDNF gene expression. In addition, recombinant NDNF protein therapy in the brain restored the cognitive abilities of older mice that had not received the compound in garlic. The researchers also discovered that the oral administration of allyl sulfide produces hydrogen sulfide gas – a messenger molecule that prevents intestinal inflammation – in the intestinal lumen .

Overall, new findings suggest that dietary allyl sulfide promotes memory consolidation by restoring intestinal bacteria. Researchers continue to conduct experiments to better understand the relationship between gut microbiota and cognitive decline and are investigating how garlic could be used as a treatment in an aging human population.

Provided by
Experimental Biology