Eating garlic may be good for your brain, particularly as you age. The pungent herb may protect brain health by fighting age-related changes in gut health linked to cognitive function, according to University of Louisville researchers.
The study, which was presented at the American Physiological Society’s 2019 annual meeting, adds more credence to garlic’s status as a superfood, and support for its powerful medicinal properties, which have been valued since ancient times.
A high diversity of gut bacteria tends to be associated with better health, but as you age, gut diversity may decline. At the same time, neurodegenerative diseases including Alzheimer’s and Parkinson’s tend to develop in later life, leading researchers to look into the association between changes in gut microbiota and cognitive decline associated with aging, and how garlic may help.
Garlic Compound Improves Gut Bacteria, Memory
The study involved 24-month-old mice, which is equivalent to between 56 and 69 years in humans. Some of the mice received allyl sulfide, a compound in garlic, which led to improved long- and short-term memory, as well as healthier gut bacteria, compared to mice that didn’t receive the supplement.
Mice taking the garlic compound also had higher gene expression of neuronal-derived natriuretic factor (NDNF), a gene required for memory consolidation. Reduced gene expression of NDNF may be linked to cognitive decline.
“Our findings suggest that dietary administration of garlic containing allyl sulfide could help maintain healthy gut microorganisms and improve cognitive health in the elderly,” study author Jyotirmaya Behera, Ph.D., said in a press release.
The link between gut bacteria and neurological health is not new. People with dementia, for instance, have a different makeup of gut microbiota compared to those without. Researchers further explained in the journal Protein & Cell:
“New researches indicate that gastrointestinal tract microbiota are directly linked to dementia pathogenesis through triggering metabolic diseases and low-grade inflammation progress.
A novel strategy is proposed for the management of these disorders and as an adjuvant for psychiatric treatment of dementia and other related diseases through modulation of the microbiota (e.g. with the use of probiotics).”
That garlic could act as a key modulator of gut microbiota is a more novel concept, although perhaps it shouldn’t be, as garlic is a source of inulin, a type of water-soluble prebiotic fiber. Inulin assists with digestion and absorption of your food and plays a significant role in your immune function.
Inulin is a fructan, which means it is made up of chains of fructose molecules. In your gut, inulin is converted into short-chain fatty acids (SCFAs) that are then converted to healthy ketones that feed your tissues.
Aged Garlic Extract May Benefit Your Brain
Previous research has also highlighted the benefits of a specific type of garlic — aged garlic extract (AGE) — for brain health. Known to have strong anti-inflammatory effects, AGE improved short-term recognition memory and relieved neuroinflammation in rats with an Alzheimer’s-like disease.
The study used fresh garlic that was aged in order to create aged garlic extract, which produces beneficial organosulfur compounds including s-allyl cysteine (SAC), which is found in far greater quantities in aged garlic and black fermented garlic than it is in raw garlic.
AGE also contains thiosulfinates that have antioxidant effects, and more than 350 studies have demonstrated its safety and effectiveness in humans. AGE may protect the brain in a number of ways, including:
- Protect against neurodegenerative conditions
- Prevent brain injury following ischemia
- Protect neuronal cells against apoptosis
- Preventing β-amyloid-induced oxidative death
“Moreover,” researchers explained in the journal Nutrients, “treatment with AGE or S-allyl cysteine has been shown to prevent the degeneration of the brain’s frontal lobe, improve learning and memory retention, and extend life span.”
Aged garlic extract has also been found to improve gut microbiota, including increased microbial richness and diversity after three months of use. AGE and SAC have even been highlighted as potential preventative and therapeutic agents for Alzheimer’s disease. That being said, fresh garlic has also shown promise for memory function, including one study in which rats fed garlic had increased memory retention.
Garlic Fights Infections, Cancer
Garlic has immune stimulating properties and as such may be useful for fighting off a variety of infections. When 146 adults received either a placebo or garlic supplement for 12 weeks, those taking the garlic had significantly fewer colds and if they were infected they recovered faster.
In another study involving AGE (aged garlic extract), those taking the garlic had reduced cold and flu severity, reduced symptoms and fewer days of suboptimal functioning or missed work or school. “Garlic contains numerous compounds that have the potential to influence immunity,” according to researchers in the Journal of Nutrition.
“These results suggest that AGE supplementation may enhance immune cell function and may be partly responsible for the reduced severity of colds and flu reported. The results also suggest that the immune system functions well with AGE supplementation, perhaps with less accompanying inflammation.”
Toward this end, the cancer-fighting effects of garlic are also well established. Garlic has been shown to kill cancer cells in laboratory studies, as well as shown promise when consumed via your diet.
Those who consume high amounts of raw garlic also appear to have a lower risk of stomach and colorectal cancers. Furthermore, among people with inoperable forms of colorectal, liver or pancreatic cancer, taking an extract of aged garlic for six months helped to improve immune function, which suggests it may be useful for helping your immune system during times of stress or illness.