Scientific and clinical research over the past 30 years has repeatedly shown garlic to be both preventive and therapeutic for cancer and cardiovascular diseases, the most common maladies of our times.
Garlic (Allium sativum L.), despite being used in medicine for thousands of years, continues to interest researchers and physicians given its wide spectrum of actions: garlic can not only kill bacteria, worms and fungi but also builds immunity and leaves the natural beneficial bacteria that live in our gut intact.
Although folk medicine has exploited the biological activity of garlic, we are yet to understand fully how garlic works; however, the therapeutic properties of garlic and other members of the garlic family (e.g., the onion and shallot) have been traced to their sulfur-containing components.
The major parent sulfur compounds present in intact garlic bulbs are odourless derivatives of sulfur-containing amino acids, e.g., alliin. Crushing, grinding, or cutting a clove of garlic releases allinase, an enzyme that transforms alliin into allicin, which is another sulfur compound. Allicin, which has not been detected in intact garlic cloves, is the main component of freshly pulped or crushed garlic. The compound is slightly soluble in water and is responsible for the characteristic pungent odour and flavour of garlic. Allicin is a highly reactive but also a very unstable compound—after consumption, neither blood nor urine shows a trace. Commercial garlic preparations do not contain allicin, and its instability makes it an unlikely candidate for the biological activity of garlic in vivo. It is possible, however, that allicin is an intermediate step in the pathway that leads to biologically important sulfur compounds. In solution, allicin is easily transformed into oil-soluble sulphides, mostly diallyl sulfide (DAS), diallyl disulfide (DADS) and diallyl trisulfide (DATS), and the focus of our research is the pharmacology of these three compounds.
The three molecules differ in the number of sulfur atoms they contain. Diallyl trisulfide (DATS) contains sulfane sulfur, a particularly reactive form of reduced sulfur that can regulate the activities of many proteins. Whereas DADS can be transformed into a form containing sulfane sulfur, DAS does not contain this form of sulfur at all. Therefore, we want to find out whether the ability to generate sulfane sulfur is directly connected to the pharmacological activity of garlic-derived sulfur compounds within a cell.
So far, our studies show that both DADS and DATS increase the level of sulfane sulfur and glutathione in the liver (glutathione is responsible for detoxifying many drugs and for the beneficial effects of antioxidants). In addition, these two compounds also lower the level of free radicals in animal tissues. We found that in animals suffering from tumours, DADS and DATS increased the levels of glutathione and sulfane sulfur in the liver. These results suggest that garlic compounds may be used for protecting normal tissues during chemotherapy.
Epidemiological studies have shown a clear link between garlic-rich diets and low incidence of gastrointestinal cancers. Studies on anticancer properties of garlic-derived sulfur compounds are particularly interesting because cancer cells show only traces of sulfane sulfur. It has even been suggested that one of the causes of uncontrolled growth of cancer cells is the lack of regulatory effect of sulfane sulfur.
The second topic of our laboratory studies on animals is arterial hypertension and the mechanism of hypotensive action of garlic. Again, epidemiological data point to the hypotensive effect of regular consumption of garlic in those suffering from hypertension, and our studies may prove the hypotensive potential of different sulfur compounds and the link between sulfane sulfur and hydrogen sulfide (H2S), a foul-smelling gas that actively regulates the functioning of the circulatory system. Since a deficiency of H2S contributes to artetial hypertension, H2S donors such as garlic-derived polysulfides should lower the blood pressure in animals.
To conclude, garlic or sulfur compounds derived from it have shown promising results in the treatment of cancer and cardiovascular diseases and may prove equally useful in preventing them.
Jagiellonian University in Krakow