Garlic is vegetable related to onion, chives and leeks. Garlic is used as a flavoring agent in cooking and as a herbal supplement. It originated from Europe and western Asia and has been used throughout ancient history to prevent a wide variety of conditions.

The compound in garlic (Allium sativum or Allicin) is responsible for many health benefits.

This article will discuss what the science says about garlic and health. But firstly, let’s look at the nutritional profile of garlic.

Nutritional Facts of Garlic

Many of the health benefits of garlic are thought to be due to its active ingredient allicin.

Garlic is a good source of omega 3 and 6 fats. It also contains good sources of manganese (8% Daily Value), vitamin B6 (6% DV), fibre (1% DV), vitamin C (5% DV), calcium (2% DV), selenium (2% DV), phosphorus (1% DV), iron (1% DV), magnesium (1% DV) and zinc (1% DV) (1). The percent daily value is calculated on 3 garlic cloves.

Health Benefits of Garlic

These health benefits of garlic are thought to be related to its antimicrobial, antithrombotic, antitumor, hypolipidemic, anti-arthritic and hypoglycemic agents (2).

1. Decreases Bad Fats in the Blood

Abnormally high levels of “bad” fats increase the risk of heart disease. “Bad” fats include cholesterol, triglycerides and low-density lipoproteins cholesterol (LDL). Garlic has been shown to improve heart health and reduce cholesterol and bad fats and increase good fats such as high-density lipoprotein cholesterol (HDL) (3,4).

Garlic has been shown to protect the cardiovascular system through its antioxidant properties. Garlic scavenges free radicals that damage cells (5). A good quality study examined the effects of a time-released garlic powder tablet. Allicor taken 600mg daily had a positive impact on good and bad fats in 42 men aged 35-70 with moderate levels of cholesterol.

An improvement was found after 8 to 12 weeks of the treatment. Cholesterol levels decreased by 7.6% compared with the control group. LDL cholesterol fell by 11.8% and HDL cholesterol increased by 11.5% (6). Due to the effectiveness of garlic as a treatment and the minimal side effects reported, garlic may be an alternative cholesterol-lowering option in individuals with slightly elevated cholesterol (7).

2.  Decreases Blood Pressure

Blood pressure is the pressure put on the heart whilst it pumps blood around the body. High blood pressure or hypertension, occurs when the heart is under too much stress pumping blood around the body.

Garlic has been shown to reduce blood pressure. Individuals in the treatment group received garlic doses of either 300mg, 600mg, 900mg, 1200mg and 1500mg in divided doses per day for 24 weeks. Individuals not in the treatment group either received a blood pressure medication or placebo.

Blood pressure readings were recorded at 0, 12 and 24 weeks. Both Systolic and Diastolic blood pressure significantly decreased in the treatment groups compared to the medication and placebo groups (8). Aged garlic extract was studied in 50 individuals who were taking blood pressure medication, and had uncontrolled blood pressure readings.

Aged garlic may be an effective and tolerable adjunct treatment to existing medications used to treat individuals with uncontrolled high blood pressure (9). 

3. Reduces the Formation of Blood Clots

Garlic has been associated with a possible antithrombotic agent in early animal studies (10,11). The benefit of reducing the blood clots reduces the risk of developing strokes and heart attacks (12).

4. Reduces Severity of Sickness

Garlic appears to increase immune function by stimulating cells in the immune system such as macrophages, lymphocytes, natural killer cells, dendritic cells, and eosinophils. These cells work together to kill bad bacteria (13).

A 12-week study found that the participants taking 1 capsule of garlic were sick less often with the common cold virus compared to the placebo group. The number of days of sickness decreased and recovery was also faster (14).

Another study showed similar results (15).

5. Decreases Blood Glucose

If left untreated, high blood glucose levels can cause other health conditions and increase the risk of heart disease.

A 12-week trial of using garlic showed that patients with metabolic syndrome had an increase in the hormone that helps fats and glucose to be metabolized by the body effectively. This trial also shows promising results in the area of heart disease (16).

6.  Cancer Prevention and Treatment

Cancer is a condition characterized by the rapid growth of abnormal cells causing organ death. Garlic has been shown to lower the risk of cancers such as esophageal, stomach and prostate cancers (17).

Animal and test tube studies using garlic show anti-cancer effects in stomach, colon, head and neck, lung, breast and prostate (18). Ajoene, another sulfur compound of garlic has been shown to reduce the size of skin tumors (basal cell carcinoma) in a small human study of 17 patients (19). 

7. Minimizes Bone Loss in Post-menopausal Women

Menopause is a risk factor for bone loss. Bone loss occurs through the decrease in the protective bone hormone, estrogen.

A study looked at the relationship between increasing pro-inflammatory cytokine activity and postmenopausal bone loss in women taking garlic. For a month, 44 post-menopausal women were randomly assigned either 2 garlic tablets or the placebo.

The study showed promising results that garlic could be helpful in minimizing bone loss in post-menopausal women (20).

Potential Side Effects of Garlic

It can cause allergic reactions in susceptible people. People allergic to garlic have experienced difficulty breathing, closing of your throat, dermatitis, hives, swelling and other skin symptoms (20).

It causes bad breath and body odor (21,22).

Other side effects may include nausea, bloating, gas, a burning feeling in the stomach and other gastrointestinal issues (23).

Conclusion

Early research into garlic has shown it helps improve health. Garlic may be a promising treatment for heart disease, the common cold, diabetes and cancer. There are still too few studies on humans to recommend garlic as medication in the prevention or treatment of diseases.

Although scientific evidence supports the benefits of garlic in improving health and a range of medical conditions, more human studies are needed to understand the mechanisms by which garlic works, dosages and long-term effects. Even though some people experience side-effects, garlic is well tolerated. In the meantime, enjoy your garlic in cooking and reap the benefits related to the nutrient-rich nutritional profile it contains.

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ABOUT THE AUTHOR

Natalie Thompson, APD is a non-dieting Accredited Practicing Dietitian passionate about inspiring positive changes in eating and lifestyle behaviors to help improve health while nurturing relationships with food and body.

After graduating with a Masters of Nutrition and Dietetics and Bachelor of Human Nutrition, Natalie Thompson worked in clinical dietetics in the community and in residential aged care with a non-government organization servicing the older adult and disabled population and the Department of Veterans’ Affairs. She also has her my own private practice.

Natalie Thompson has a Bachelor of Human Nutrition from University of Newcastle with a Master of Nutrition and Dietetics from Griffith University. You can connect with Natalie on LinkedIn