Garlic is probably the best researched and most commonly used herb in the world. Native to Central Asia, garlic is now used in most every country’s ciusine. Mention of garlic can be found in the ancient medical tests of Egypt, India, China, Greece and Rome, some dating as far back as 5,000 years. This world-renowned cure-all herb has been touted for everything from weight loss and infections to low energy, dysentery, snake bites and low libido (1). A search through the research literature of todays yields over 4,000 citations on garlic, suggesting it is just as popular in modern times as it was in ancient times.
Much of the research on garlic has focused on the organosulfur compounds, or OSCs, found in the whole clove, which are responsible for its flavor and distinct smell. While allicin is probably the best recognized of the OSCs, there are actually many different types of OSCs found in garlic. Some of these compounds, like allicin are dependent of enzymes that are activated when garlic is crushed, chopped, or chewed. Others, like those found in aged garlic supplements, are formed during the aging process or are formed as breakdown product of other OSCs (2). These OSCs are believed to be responsible for the majority of the health benefits of garlic though polyphenolic compounds and prebiotic fibers in garlic may also contribute to its health benefits.
Probably the best researched and most celebrated benefit of garlic is its ability to benefit the cardiovascular system. Indeed, garlic has long been used for conditions that affect the cardiovascular system. Research studies show that garlic supplements are quite ueful for the treatment of uncontrolled hypertension, lowering blood pressure by about 10 mmHg systolic and 8mmHg diastolic, similar to standard blood pressure medications. (3) Mechanisms by which garlic reduces blood pressure include inhibiting the aggregation of platelets, thus keeping the blood flowing smoothly (4), relaxing the blood vessels, and even blocking production of hormones that cause blood pressure to increase (5). Garlic may also benefit the cardiovascular system by reducing LDL cholesterol levels and modulating inflammation (6).
ANTIMICROBIAL and ANTIVIRAL
As far back as 1858, Louis Pasteur carried out experiments to confirm the historically recognized bacteria-fighting activity of garlic (7). Today garlic is recognized for its ability to fight not only bacteria, but also fungi, viruses and parasites (8). The OSCs in garlic appear especially beneficial for limiting the growth and even killing H. pylori, a microbe that commonly infects the stomach and causes ulcers (9). Research into the effects of garlic on the immune system show that it can increase the responsiveness of several important antiviral immune cells such as Natural Killer cells and specialized gamma delta T cells (10). Ultimately the increase in immune cell function has been related to fewer symptoms and reduced severity of cold flu as well as less time missed from work (11). Beside fighting microbes directly, garlic may serve as a prebiotic, helping to strengthen the good bacteria so they are better able to fight off infectious agents in the first place (12). Garlic also reduces the inflammatory compounds that certain microbes produce (13).
Although much more research is needed to fully understand this connection, the OSCs in garlic are believed to support the body’s detoxification processes. First, OSCs support the detoxification process, helping the body to neutralize and eliminate carcinogens and toxins. Other studies indicate that garlic supplementation increases the liver’s levels of glutathione and other important antioxidant enzymes involved in detoxification processes. Furthermore, because many toxic compounds are eliminated from the body through the process knows as sulfation, by providing extra sulfur, garlic helps provide substrate to facilitate elimination of harmful compounds by the liver (14,15).
The OSCs found in garlic display remarkably utility, benefiting not only the health of the body but also the health of the brain. Some of the most interesting benefits of OSCs include their ability to increase growth of new nervous system tissue, protect the brain from beta-amyloid plaque induced inflammation and damage, and strengthen the blood-brain barrier (16,17). Studies in an effective intervention-preventing inflammation from causing brain dysfunction (18). Other studies show garlic increases the brains natural antioxidant defenses, helps with neurotransmitter signaling, and OSCs act as antioxidants themselves (19). Overall, there exists a solid body of preclinical evidence suggesting garlic supplements have a promising future as prophylactic treatments for the development of neurodedegenerative conditions, such as Alzheimer’s disease (20,21).
Several of the OSCs found in garlic have been investigated for their ability to modulate inflammation (22,23). Many of these studies have focused on garlic-related anti-inflammatory effects in the gastrointestinal tract. These studies suggest garlic modulates inflammatory reactions to pharmaceuticals, toxins, and pathogens in the gastrointestinal tract, making it applicable to a large portion of the population (22). References available upon request.