The complicated biology of garlic

April 26, 2018

Researchers today generally agree that eating garlic, used for thousands of years to treat human disease, can reduce the risk of developing certain kinds of cancers, cardiovascular disease, and type 2 diabetes. Nevertheless, in a review published April 26 in the journal Trends in Pharmacological Sciences, researchers in the UK argue that explaining exactly how garlic affects human health--and getting consistent results during clinical trials--is more complex, because of the vast array of compounds garlic produces.

Garlic's unique flavor comes from sulfur compounds. Like other members of the allium family, the plant absorbs sulfate from the soil and incorporates it into amino acids and sulfur storage molecules. These sulfur storage molecules can then be broken down into approximately 50 different sulfur-containing compounds when the garlic is prepared and eaten. "These molecules give the plants an ecological advantage when they're growing out in the wild. As it happens, they're also biologically active within mammalian cells and tissues," says senior author Peter Rose, a biochemist at the University of Nottingham.

These compounds are well studied in garlic, and there is research to suggest that they are important in producing the health effects for which garlic is renowned. Understanding how they produce those effects is less clear, however, in part because how we prepare garlic affects which sulfur compounds we end up consuming. Chopping fresh garlic, fermenting garlic in alcohol, and pressing garlic for oil, for example, all yield different sulfur compounds. "Each of these preparative forms could have a different effect within mammalian systems. And that's what makes this research so complex, because we don't really understand how these compounds are metabolized in humans and it's very difficult to identify common mechanisms of action for these molecules," he says.

While there's no right or wrong way to prepare your garlic, this quirk of garlic's biochemistry could explain why studies of the plant's effects on humans have had such mixed results. "When it comes to human intervention studies, there's been quite a lot of disparity. Sometimes the consumption of and exposure to these compounds has biological effects, and other times, it does nothing. I think it needs reinvestigating, just because of the sheer complexity of the diversity of these sorts of compounds and the different distribution of them between different garlic products," he says.

Rose and his colleagues are particularly interested in how these sulfur compounds might affect gaseous signaling molecules like nitric oxide and hydrogen sulfide, which are naturally produced by our bodies. Gaseous signaling molecules play an important role in cell communication and maintaining homeostasis, and altered levels of them are present in many diseases. Recent research in vitro has linked the kinds of sulfur compounds we get from garlic to increased production of these molecules, suggesting that this might be the common mechanism by which the different sulfur compounds affect the human body.

There's still a lot of research to be done, but Rose believes that someday we might be able to identify other plants that stimulate the production of these gases or modify garlic, onions, and other alliums to be more efficient at producing them once ingested. "There is a lot of possibility within this area for finding approaches that could reduce the risk of diseases and improve human health, but it all comes back to those fundamental questions of what actually happens to these compounds when we metabolize them. There's a whole spectrum of human work that still needs to be done to further explore some of these weird and wonderful sulfur compounds that we find within our diets," he says.

He also believes that it's important to remember that garlic isn't some kind of magic bullet. "I don't think there is one individual plant species that is a cure-all, but there are certainly plant species that are strongly associated with reducing disease risk within humans. Variety is the spice of life, but understanding the chemistry of some of your spices is probably a very advantageous thing to do."
-end-
Trends in Pharmacological Sciences, Rose et al.: "Garlic and gaseous mediators" http://www.cell.com/trends/pharmacological-sciences/fulltext/S0165-6147(18)30061-0

Trends in Pharmacological Sciences (@TIPS_news), published by Cell Press, is a monthly review journal that contains succinct articles on the most exciting recent developments in pharmacology and toxicology research. Topics covered in the journal range from molecular to behavioral pharmacology, and from current techniques to theoretical pharmacology. Visit: http://www.cell.com/trends/pharmacological-sciences. To receive Cell Press media alerts, please contact press@cell.com.

Cell Press

Related Diabetes Articles from Brightsurf:

New diabetes medication reduced heart event risk in those with diabetes and kidney disease
Sotagliflozin - a type of medication known as an SGLT2 inhibitor primarily prescribed for Type 2 diabetes - reduces the risk of adverse cardiovascular events for patients with diabetes and kidney disease.

Diabetes drug boosts survival in patients with type 2 diabetes and COVID-19 pneumonia
Sitagliptin, a drug to lower blood sugar in type 2 diabetes, also improves survival in diabetic patients hospitalized with COVID-19, suggests a multicenter observational study in Italy.

Making sense of diabetes
Throughout her 38-year nursing career, Laurel Despins has progressed from a bedside nurse to a clinical nurse specialist and has worked in medical, surgical and cardiac intensive care units.

Helping teens with type 1 diabetes improve diabetes control with MyDiaText
Adolescence is a difficult period of development, made more complex for those with Type 1 diabetes mellitus (T1DM).

Diabetes-in-a-dish model uncovers new insights into the cause of type 2 diabetes
Researchers have developed a novel 'disease-in-a-dish' model to study the basic molecular factors that lead to the development of type 2 diabetes, uncovering the potential existence of major signaling defects both inside and outside of the classical insulin signaling cascade, and providing new perspectives on the mechanisms behind insulin resistance in type 2 diabetes and possibly opportunities for the development of novel therapeutics for the disease.

Tele-diabetes to manage new-onset diabetes during COVID-19 pandemic
Two new case studies highlight the use of tele-diabetes to manage new-onset type 1 diabetes in an adult and an infant during the COVID-19 pandemic.

Genetic profile may predict type 2 diabetes risk among women with gestational diabetes
Women who go on to develop type 2 diabetes after having gestational, or pregnancy-related, diabetes are more likely to have particular genetic profiles, suggests an analysis by researchers at the National Institutes of Health and other institutions.

Maternal gestational diabetes linked to diabetes in children
Children and youth of mothers who had gestational diabetes during pregnancy are at increased risk of diabetes themselves, according to new research published in CMAJ (Canadian Medical Association Journal).

Two diabetes medications don't slow progression of type 2 diabetes in youth
In youth with impaired glucose tolerance or recent-onset type 2 diabetes, neither initial treatment with long-acting insulin followed by the drug metformin, nor metformin alone preserved the body's ability to make insulin, according to results published online June 25 in Diabetes Care.

People with diabetes visit the dentist less frequently despite link between diabetes, oral health
Adults with diabetes are less likely to visit the dentist than people with prediabetes or without diabetes, finds a new study led by researchers at NYU Rory Meyers College of Nursing and East Carolina University's Brody School of Medicine.

Read More: Diabetes News and Diabetes Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.