THE EFFECTS OF GARLIC ON HUMAN HEALTH

G. Nisticò ^1*

¹European Brain Research Institute, Rome, Italy

*Correspondence to:
Professor Giuseppe Nisticò,
European Brain Research Institute,
Via Regina Elena, Rome, Italy.

Received: 12 October, 2018 Accepted: 28 November, 2018

2279-5855 (2018) Copyright © by BIOLIFE This publication and/or article is for individual use only and may not be further reproduced without written permission from the copyright holder. Unauthorized reproduction may result in financial and other penalties. Disclosure: all authors report no conflicts of interest relevant to this article.

 ABSTRACT

Garlic is a well-known dietary supplement that has numerous health benefits for the human body. It contains different antioxidant compounds that protect the body against cardiovascular and neuroinflammatory diseases. In addition, garlic reduces the activation of microglia in the brain and reduces neuroinflammation. Research has already shown the protective effects of garlic in tumor growth and other diseases. However, more studies are necessary to clarify the specific beneficial effects of garlic and its individual components.

KEYWORDS: garlic, health, allium sativum, inflammation, oxidative stress

INTRODUCTION

Garlic, or Allium sativum L., is a widely consumed spice around the world and contains water-soluble antioxidant compounds such as S-allyl cysteine (SAC) and S-allyl-mercaptocysteine, as well as 5-hydroxymethylfurfural, organosulfur compounds, and polyphenols, amongst others. These compounds have antioxidant, anticancer, antibacterial, antifungal, and immunoregulatory properties, and help protect the body against cardiovascular and neuroinflammatory diseases (1-4). There are many beneficial effects of garlic. However, this paper summarizes only some important clinical aspects and benefits for human health.

DISCUSSION

After 4,000 years of folkloric praise of garlic, which found use by various populations as a restorer and preserver of health and youth (5), modern science has confirmed some of its beneficial actions and researchers are working to define the important medicinal effects of garlic (6). Recent scientific results suggest that garlic may help prevent, and maybe cure, vascular, ageing, and neurological diseases.

Garlic is a chemically unstable vegetable that contains more than 200 different compounds that can favorably influence the course of many diseases. For example, in laboratory studies, and presumably also in vivo, high concentrations of garlic suppress the formation and growth of tumor cells (7-10) and help prevent and counteract atherosclerosis (11) and cardiovascular attack (12). Recently, researchers began investigating the possible role of garlic as a cancer prevention agent. These studies began after it was seen that the Chinese and Italian populations, who consume elevated amounts of garlic as food, seem to suffer less from certain tumors. However, further research is needed to understand the exact mechanisms of garlic compounds in this context.

The consumption of garlic as a food does not necessarily have to be taken raw, but rather consumed in large quantities (13). It has been noted that it would be better to take it cooked, as it does not lose its beneficial characteristics and causes fewer side effects and adverse reactions such as allergy, anemia, and gastric ulcers (14-17). So, the smell and freshness of garlic do not seem to be related to its beneficial power. Dehydrated garlic extracts appear to be less toxic than fresh garlic. However, garlic is recommended in the diet as a healthy element, but not for therapeutic use, as it has been used for centuries by Asian people.

Laboratory studies on animals have shown that garlic: a) suppresses hepatic cholesterol synthesis, lowering serum cholesterol levels and reducing the harmful effect of low-density lipoprotein (LDL) while leaving high-density lipoprotein (HDL) unchanged (18 -20); b) lowers the concentration of blood triglycerides linked to cardiovascular risk (21-23); c) reduces blood clotting with effects similar to aspirin, preventing the formation of clots and cerebral stroke (24); d) promotes the regression of fat deposition on the venules (25); e) negatively influences the action of chemical carcinogens, preventing the formation of tumors (26, 27); and f) protects cells from oxidizing agents and heavy metals, counteracting the ageing process (28). Some of the positive effects of garlic consumption have been reported in the table below (Table I).

Table I. Effects of garlic consumption.

The mechanism of action of the beneficial effects of garlic is not yet known. A possible explanation is due to garlic’s ability to inhibit the formation of nitrosamines, powerful carcinogens of the digestive tract (29, 30). Therefore, the compounds in garlic would be chemopreventive and would counteract the action of some carcinogens that can cause tumors such as breast, esophagus, colon, rectal, and brain tumors. Studies on animals have confirmed the beneficial action of garlic against heart disease by reducing blood pressure values (31-33).

SAC is an important molecule contained in garlic. It is a stable element formed by sulfur linked to a thiol group and is the most prominent bioactive compound in black garlic. SAC has numerous health benefits, giving protection against free radicals, oxidation, tumors, cardiovascular diseases, and neurodegenerative diseases (28, 34, 35).

The odor of garlic can be eliminated by soaking it in about 18% aqueous ethanol for a year at room temperature. This ageing leads to the elimination of odor without altering its antioxidant power, which reduces oxidative damage by eliminating reactive oxygen species (ROS) and lowers the chances of cerebrovascular damage.

Studies on garlic show that it attenuates oxidative action and neuroinflammation, reducing the chances of contracting neurodegenerative diseases, including Alzheimer’s disease (AD) (35,36). In vitro, it has been observed that these healthy effects of garlic protect against cellular damage and the harmful effects caused by the amyloid beta peptide (Ab) (37), a characteristic molecule of AD that forms in brain regions and triggers inflammatory responses, causing neuronal degradation.

Furthermore, garlic has been found to have neuroinflammatory effects by reducing the activation of microglial cells (38,39). When microglia are activated, they release pro-inflammatory cytokines such as IL-1 and tumor necrosis factor (TNF) that are involved in neuroinflammation.

CONCLUSIONS

Garlic has numerous health benefits for the human body. However, more studies are necessary to confirm the specific beneficial effects of garlic and its individual components.

Conflict of interest

The author declares that they have no conflict of interest.

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