Garlic Aids Memory by Boosting Gut Health
Consuming garlic helps counteract age-related changes in gut bacteria associated with memory problems, according to a new study conducted with mice. The benefit comes from allyl sulfide, a compound in garlic known for its health benefits.
Some 5.8 million people in the U.S. have Alzheimer’s disease, with that figure predicted to hit 14 million by 2050. The cause of the neurodegenerative condition is unknown, and there are no treatments for it. Allyl sulfide “has many health benefits and is known for its detoxifying agents,” the authors wrote.
“Our findings suggest that dietary administration of garlic containing allyl sulfide could help maintain healthy gut microorganisms and improve cognitive health in the elderly,” said Jyotirmaya Behera, who led the research team with Neetu Tyagi from University of Louisville.
Behera presented the research Monday at the American Physiological Society’s annual meeting during the 2019 Experimental Biology meeting in Orlando, Fla.
The gut contains trillions of microorganisms collectively referred to as the gut microbiota. Although many studies have shown the importance of these microorganisms in maintaining human health, less is known about health effects linked to gut microbiota changes that come with age.
“The diversity of the gut microbiota is diminished in elderly people, a life stage when neurodegenerative diseases such as Alzheimer’s and Parkinson’s develop and memory and cognitive abilities can decline,” said Tyagi. “We want to better understand how changes in the gut microbiota relate to aging-associated cognitive decline.”
For the study, the researchers gave oral allyl sulfide to mice that were 24 months old, which correlates to people between 56 and 69 years of age. They compared these mice with 4- and 24-month-old mice not receiving the dietary allyl sulfide supplement.
The researchers observed that the older mice receiving the garlic compound showed better long- and short-term memory and healthier gut bacteria than the older mice that didn’t receive the treatment. Spatial memory was also impaired in the 24-month-old mice not receiving allyl sulfide.
The team believe memory problems could be caused by the neuronal-derived natriuretic factor (NDNF) not being expressed fully in the older mice, as animals who took the garlic supplement had greater expression of the gene. And when older mice that didn’t take the garlic compound had NDNF protein therapy, their memory improved. The researchers also found that oral allyl sulfide administration produces hydrogen sulfide gas — a messenger molecule that prevents intestinal inflammation.
Overall, the new findings suggest that dietary allyl sulfide promotes memory consolidation by restoring gut bacteria. The researchers are continuing to conduct experiments aimed at better understanding the relationship between the gut microbiota and cognitive decline and are examining how garlic might be used as a treatment in the aging human population.
“There’s a growing body of evidence to suggest there’s a link between brain and gut health, so it’s always exciting to see new research in this area,” said Dr. James Pickett, head of research at the Alzheimer’s Society. “This project is in its infancy and only carried out in mice, so we can’t say eating garlic reduces age-related memory problems or impacts gut health at this stage.
“We’re investing in research to examine how bacteria in the gut can influence brain function and health. In the meantime, what we do know is what is good for the heart is good for the head: A healthy, varied diet and getting plenty of exercise can help to reduce risk of dementia.”
In a separate study published in 2018, researchers found that what people eat in middle age doesn’t affect their risk of developing dementia as they grow old. But experts suggested the findings weren’t a green light to eat unhealthy foods.