Garlic Health Benefits and Side Effects

Written by: Christopher Karam | ✔️ Medically Reviewed by: Dr. Riad M., M.D - G.P and Micheal B., M.D | Last Updated: 2020 June 24

What Is Garlic?

The name garlic is derived from an Old English word - Garleac, which means spear leek. Asia is the native source for garlic and was discovered almost 5000 to 6000 years ago.

Garlic is botanically known as Allium sativum belonging to the Alliaceae family. Garlic is an underground grown crop widely used to prepare many foods due to its savory and spicy flavor.

Garlic is one of the core Mediterranean cooking ingredients which is frequently consumed in Asian, European, Middle Eastern, and African regions and cuisines.

bulb garlic whole stock healthy diet benefits

Garlic is part of the group of allium vegetables, which includes shallots, leeks, chives, scallions, and onions. Allium vegetables are rich in flavonols, flavanols, and organosulfur compounds, which have the added benefit of reducing your risk of cancer.

Nutritional Facts and Information

Garlic is full of nutritional value due to its macronutrients, micronutrients, and bioactive nutrients. Raw garlic is made up of 65% moisture, of which 97% of garlic's active ingredients are water-soluble, while the remaining 3% are fat-soluble.

Raw garlic contains carbohydrates, protein, fiber, and free form branched-chain amino acids. There are also many vitamins and micronutrients present in garlic as well such as

  • Vitamin A

  • Vitamin C

  • B-complex vitamins

  • Potassium

  • Phosphorus

  • Zinc

  • Sulphur

  • Magnesium

  • Calcium

  • Iron

  • Sodium

  • Selenium

  • Manganese

Garlic even has a high phenolic acid and saponin content. Saponins are antioxidants that have antimicrobial properties that help your body remove fungi, bacteria and viruses.

S-alkyl cysteine sulfoxides (alliin) and the γ-glutamyl-S-alkyl cysteine are two of the sulphur compounds. Allicin is the main thiosulfate present in garlic providing the majority of its health benefits.

The saponin chemical also improves immune function by stimulating the production of T-cells and reduces oxidative stress.

Due to all of the sulfur compounds found in garlic, when metabolized it produces a sulphide and that gets released through our lungs and skin, giving off a bad smell.

This is why garlic odor stays in our bodies for an extended period before being fully flushed out. The most prominent sulfur compound found in garlic is aliin.

The History Of Garlic

It was the Asian ancestors that had first discovered the health benefits of garlic in 2000 B.C, much earlier than scientific research has just recently explained.

In the last 35 years where there have been multiple scientific studies on the medicinal properties, health benefits and side effects of garlic.

peeled garlic plate healthy benefits stock

Up until the 12th century, garlic was used for sun heat relieving effects. Garlic was sliced and rubbed over the skin to prevent harmful sun rays and UV damage, a time when most of the labor was done in extreme heat conditions.

The plague was an epidemic that spread over the European regions during the middle ages. Europeans ate whole garlic cloves to protect themselves against the black plague, boosting their immune systems and resistance to fungus, microbes, and viruses.

During World War 1 and 2, injured soldiers were treated with garlic, as a natural antiseptic to prevent gangrene as well as the loss of blood and muscle tissue.

Ancient Egyptians believed that garlic can prevent many different ailments, and the Asians used garlic as a traditional medicine for treating:

  • Hypertension

  • Tuberculosis

  • Bronchitis

  • Rheumatic arthritis

  • Intestinal worms

  • Dysentery

  • Liver disorders

  • Diabetes

  • Fevers

The Greek physician Hippocrates also acknowledged the health benefits of garlic against:

  • Parasitic infections

  • Poor digestion

  • Respiratory problem

  • Fatigue

It was only until the early 20th century, where garlic was first introduced in American cuisine. The nutritional value of garlic is excellent, which is the source of garlic’s health benefits.

Cooking With Garlic

Fresh garlic cloves are staple a household kitchen ingredient, health and dieting superfood, as well as a powerful medicinal and immune-boosting properties that help fight against a variety of health disorders.

Chopped, sliced, juiced, or minced garlic is added in a variety of different cuisines to not only add a spicy-garlic flavor, but to also add its health benefits, healthy plant-based compounds, and enhance the nutritional value of the dish.

When cooking, you may notice

Fresh garlic is a practical, cheap, and flexible cooking ingredient that pairs well with many other ingredients, herbs, spices, and cooking oils such as:

garlic kitchen onion spoon healthy weight loss stock

Garlic Health Benefits

Allicin is a sulfuric compound found in raw garlic that’s responsible for releasing a neurotransmitter that can produce a burning sensation due to heat release on your tongue.

Allicin also has free radical scavenging properties and is one of the primary bioactive ingredients present in garlic.

The activation of these nerves causes vasodilatation which increases blood flow, oxygen levels, and decreases blood pressure.

Multiple research studies found that the antioxidants, phenolic acids, and steroidal properties found in garlic are beneficial to your overall health. Some of the health benefits include:

  • Reduces inflammation

  • Prevents oxidative and free radical damage

  • Helping with weight loss and fat oxidation

  • Reduces the risk of type 2 diabetes

  • Preventing heart disease

1. Used in Many Cooking Recipes

Cooking and using roasted garlic destroys all of its allicin content, antioxidants, and healthy plant-based compounds, which are all sensitive to heat and chopping.

Because most of the vitamins and minerals found in garlic are water-soluble, they easily get destroyed during cooking, blending, or crushing. Water-soluble vitamins include vitamin C and B-complex vitamins.

Antioxidants are fat soluble, which means that cooking, heating, or frying garlic won’t affect its levels of vitamin k.

Raw garlic cloves rarely consumed, which is where all of garlic’s health benefits reside. The application of heat with peeling, cutting, chopping, mincing, or juicing raw garlic is common in many dishes. All methods of processing will decrease the health benefits of garlic.

Research experts suggest that you should avoid eating whole garlic cloves because the Allicin compound only becomes active when the garlic cloves are crushed and broken down.

Allicin promotes weight loss by increasing your metabolism, prevents heart disease, cancer, and diabetes. Adding crushed garlic to your diet maintains the health benefits and overall nutritional content.

garlic kitchen peeled blub healthy stock

The temperature you need to use when cooking garlic needs to be medium-high at most, as high heat destroys the nutrients and decrease the healthy plant-based compounds, antioxidants, and the overall nutrition of fresh garlic.

Peeled and crushed raw garlic cloves with too much exposure to oxygen can break its defence mechanism and cause the garlic to turn green, which is a form of pickling when left in the open air.

Freshly crushed garlic cloves are a healthier alternative when looking to add flavor and nutrition to your food. As the color of garlic cloves turn a light green pigment, garlic loses some of its benefits due to the release of its sulphur and nitrogen contents.

If you want to leave your garlic out without having it turn green, covering the clove with an acid such as lemon juice can prevent the garlic from greening.

The application of garlic isn’t limited to just cooking, but it has a wide range of health-boosting, disease clearing and preventative benefits due to its medicinal plant-based compounds.

There are multiple scientific reports which display some of the health benefits of garlic. The health claims are highly conclusive as garlic extract and supplements are available in many pharmacies, online retailers, and supermarkets in North America.

2. Garlic is a Natural Antibiotic

Garlic has a broad-spectrum of antibacterial properties. Similar to coconut oil, it's mostly effective against micro-organisms, including bacteria, viruses, fungi, and parasites.

The allicin present in garlic can react with the enzymatic functions of the infection, suppresses their growth, and helps fight the infection.

The strong antimicrobial property of garlic is also great for fighting stomach infections, and most effective against stomach bacteria such as Helicobacter Pylori, and preventing of stomach ulcers.

Garlic can also help treat athlete's foot, yeast infections (candida albicans), and colon infections by either applying it to the area or by ingesting it.

3. Increases HDL cholesterol and Heart Health

Garlic lowers bad LDL cholesterol without affecting your levels of good HDL cholesterol levels. This is done by limiting the production of bad LDL cholesterol in the liver.

Ingesting garlic also has blood-thinning benefits and also prevents blood from clotting inside the blood vessels. This can also be a negative side effect depending on what conditions you may have.

peeled garlic lemon healthy cutting board stock

Additionally, the lower blood pressure you get out of eating garlic helps your heart fight off and reduce the risk of hypertension.

4. Garlic is Anticarcinogenic

The increasing rates of cancer became a great threat to mankind in the late 1900s. Two researchers, named Weisberger and Pensky first demonstrated the anti-tumour properties of garlic in 1958.

In addition to that find, multiple other preclinical and clinical trials were conducted with garlic. This was to determine the anticarcinogenic health benefits of garlic against a variety of different cancers, including gastric, colorectal, and liver cancer.

Both in vivo and in vitro (in human and in glass) studies found that active chemicals found in garlic targets the specific cell cycle, induces cell death, and helps the reparation of damaged blood vessels, thus providing anti-carcinogenic health benefits.

The anticarcinogenic research study also recommended the daily intake be one clove of garlic. This can also reduce the risk of gastric cancer by 9%, weekly consumption of more than 28 grams of garlic can reduce the risk of colorectal and gastric cancers as well.

5. Helps Stabilize Blood Sugar Levels

Garlic helps to control blood sugar levels in experimental animal studies. A human trial also reported that the metformin drug, a conventional treatment for type 2 diabetes taken alongside a serving of garlic offers better blood sugar control in patients with diabetes.

On the glycemic index (GI) scale, garlic has a score of 28. A glycemic index score between 1 and 55 has a low impact on blood sugar levels, this range also includes foods like apples, almond milk, greek yogurt, baked beans and lentils.

Garlic has more than 350 active chemical compounds that contribute to its large list of health benefits and stabilizing your blood sugar levels.

The allyl propyl disulphide and S-allyl cysteine sulfoxide chemical compounds raise insulin levels, reducing insulin sensitivity. This bypasses the inactivation of insulin from the liver, making it so that there’s more insulin available in the body.

Naturally raising insulin levels is a large benefit to diabetics as well as people suffering from type 1 and type 2 diabetes.

6. Improves Brain Health and Functioning

The accumulation of free radicals in the body leads to a decrease in brain health and functionality. In severe conditions too much free radical damage can lead to the development of Alzheimer’s disease.

Garlic is a very potent antioxidant that reduces the rate of oxidative and free radical damage in brain tissue, improving cognitive health and function.

peeled garlic bulb healthy diet stock

Research conducted in China also found that sallylcystein (a sulphuric compound found in garlic) has a preventive health benefit against the degeneration of the brain's frontal lobes.

Many research articles prove that garlic also improves cognitive intelligence in the form of efficiency, health, and improves the efficacy of neurotransmitters.

7. Boosts Immune System Strength

The antioxidant and antimicrobial properties of garlic improve immune system functions. Additionally, the nutrients like vitamins B6, vitamin C, selenium, and manganese present in garlic can also boost immune system strength.

Researchers found that garlic may inhibit antibiotic-resistant bacteria (like Staphylococcus Aureus) from growing by improving immune functioning.

The respiratory conditions like colds and coughs can also be treated by garlic due to its decongestive and expectorant (mucus relieving) properties.

The anti-viral property of garlic is effective against HIV by increasing natural killer cell activity within the body.

8. Garlic Helps With Weight Loss

Allicin is a compound found in garlic that gets released when the cloves are being cut or broken up.

Additionally, a single garlic clove is around 3 grams in weight and 5 calories, making it a lightweight and low-calorie addition to your recipes. Allicin is an antioxidant that reduces inflammation and helps with weight loss.

Research showed that the same amount of food consumption without allicin being supplemented led to an increase in body weight, whereas animals treated with an allicin supplement (garlic or pills) maintained a stable weight and witnessed a reduction of body weight.

9. Improves Bone Health

It's well documented that the phytoestrogenic effects of garlic have preventive effects against bone loss, especially for women going through premature menopausal syndrome.

Phytoestrogens are plant-based compounds found in many fruits, vegetables, and some grains. Phytoestrogens have many health benefits that complement the ones already found in garlic:

  • Prevents osteoporosis

  • Relieves menstrual issues

  • Minimizes acne

  • Improves heart health

Garlic also helps to restore calcium content in the bones by modifying intestinal enzyme functions, which increases the calcium absorption rate, preserving bone mass and strength.

According to research study reports, garlic supplements helped improve bone mineral content and bone tensile strength, which supports the recent claims that garlic can prevent osteoporosis, bone weakening and degradation.

pack of garlic cloves healthy diet stock hd

10. Prevents Liver and Kidney Disease

Acetaminophen is one of the most common painkillers and antipyretic drugs used in today's medicine, having similar effects to ibuprofen it’s used to reduce the severity and pain of fevers.

There are common side effects of using the acetaminophen drug, it can damage your liver and kidney if taken to often at high dosages.

The antioxidants found in garlic prevent drug-induced liver and kidney toxicity. The risk of liver disease and kidney disease may also be reduced, as long as garlic isn’t taken alongside any painkillers or antipyretic drugs.

Garlic Side Effects and Detriments

There is a specific recommended dose for garlic as its plant-based compounds are so potent. Because of the large list of potential side effects of garlic, excessive intake can cause additional issues.

Like most other herbs, this can produce some lighter, common side effects such as:

  • Nausea

  • Vomiting

  • Burning sensation in mouth, throat or stomach

  • A major increase in body heat, causing sweating

  • Lightheadedness and many others.

The recommended daily amount is one to two cloves of raw garlic per day, that's sufficient to get all of the health benefits.

However, if you go overboard and begin to consume 4 to 5 cloves daily. You must stop all garlic consumption if you experience any minor side effects such as:

  1. Over Sensitive Skin or Bruising

  2. Ease of Bleeding (for example, gums or nosebleeds)

  3. Bad Breath and/or Body Odors

  4. Heart, Mouth, or Throat burn

  5. Nausea, Vomiting, Excess Gas, Diarrhea

Garlic also does not work well with medications used for blood clots and should not be used unless reviewed by a medical professional who can assess your situation if you suffer from any serious medical condition such as cancer, asthma, depression, heart-related issues, high blood pressure or cholesterol, and others.

If you are expecting to have surgery or any other major medical procedure you need to stop taking garlic 2 weeks ahead of time.

Rating and Recommendation

Extremely Recommended

The following guideline can help consumers select the best application when it comes to using garlic, not only as a kitchen ingredient but also as a health-boosting product.

The bulbs of garlic can be stored for several months, but when they become dried, moldy, loose, and frayed, these become signs of aged garlic bulbs.

The nutrients found in fresh garlic are deactivated with ageing, heating, and brusing, becoming less effective as well as providing lesser health benefits over time.

Garlic can reduce your risk of cancer, symptoms of the common cold, and cardiovascular disease risk factors.

Here’s the list of health benefits of garlic:

  1. Used in many cooking recipes

  2. Is a natural antibiotic

  3. Increases good HDL cholesterol and heart health

  4. Is anticarcinogenic

  5. Helps stabilize blood sugar levels

  6. Improves brain health and functioning

  7. Boosts immune system strength

  8. Helps with weight loss

  9. Improves bone health

  10. Prevents liver and kidney disease

Here’s the list of side effects of garlic:

  1. Nausea, vomiting

  2. Burning sensation in mouth, throat, or stomach

  3. A major increase in body temperature and sweating

  4. Lightheadedness

  5. Over Sensitive Skin or Bruising

  6. Increased Bleeding (gums or nosebleeds)

  7. Bad Breath and/or Body Odors

  8. Heart, Mouth, or Throat burn

  9. Excess Gas

  10. Diarrhea

Look for the freshest garlic bulbs which have a tight peel, those have the maximum amount of active healthy ingredients and it’s the clearest sign of freshness.

Garlic can be stored for several months without rotting if it’s unpeeled and stored properly in a fridge. Dried, moldy, loose, and frayed peels are signs of aged garlic bulbs, which could be possibly inedible.

All of the nutrients found in garlic get reduced with ageing and cooking, making it less effective at fighting infections and providing much fewer benefits.

The list of nutrients affected during ageing or cooking are all water-soluble vitamins and minerals:

  • Vitamin C

  • Thiamin (Vitamin B1)

  • Riboflavin (Vitamin B2)

  • Niacin (Vitamin B3)

  • Pantothenic acid (Vitamin B5)

  • Pyridoxine (Vitamin B6)

  • Folic acid (Vitamin B7)

  • Cobalamin (Vitamin B8)

Proper storage is a good practice when storing garlic to prevent the growth of mold and age. Always keep in mind that chopping or smashing garlic cloves triggers an important chemical reaction that releases allicin, which has most of the health benefits of garlic.

However, high heat exposure can reduce the release effectiveness of allicin. Therefore, after chopping the garlic cloves wait between 5 to 10 minutes for the reaction to complete and settle before cooking it at a medium to high heat.

The range of side effects are based on the dosage and your daily garlic intake, you should not have more than 10 grams of garlic per day. There are other nuance effects like bad breath and body odor that comes from eating too much garlic.

Eating mint leaves, chopped, diced, or whole can prevent the odor of garlic from escaping through your mouth or body after consuming a garlic heavy meal.

Although the benefits are well documented, garlic can't be recommended for people undergoing serious surgeries or diseases because allicin is a strong blood thinner.

Frequently Asked Questions

Keep in mind that the nutrition facts, benefits, and natural plant compounds found in garlic are deactivated with ageing and are less effective overtime, providing lesser health benefits the longer the exposure to oxygen.

Here’s the full list of health benefits of garlic:

1. It's used in many cooking recipes

2. Is a natural antibiotic

3. Increases good HDL cholesterol and heart health

4. Garlic is anticarcinogenic

5. Helps stabilize blood sugar levels

6. Improves brain health and functioning

7. Boosts immune system strength

8. Helps with weight loss

9. Improves bone health

10. Prevents liver and kidney disease

Garlic is full of potent plant-based compounds and antioxidants, you don't need a large quantity to get the full list of health benefits.

For adults, it's recommended to have 2 cloves (1 teaspoon) of raw garlic per day. Which is also equal to about 2 to 3 garlic supplement tablets, containing around 10 mg to 14 mg per supplement tablet.

Garlic is an easy plant to grow but should be grown in the ground, or in raised garden beds. Not suitable to be grown in containers.

Plant the garlic cloves in March, or between September and November. Colder climates are better for growing garlic.

To sow garlic into the soil, plant each clove (with skin intact) pointed upwards 3 to 5 cm deep (1 to 2 inches). Separating each clove 10 to 14 cm (4 to 6 inches) apart.

The size of the clove is relevant to the size of the bulb. Using rich and light soil (not compact), add a good amount of compost a few weeks before planting. Keeping the pH of the soil above 6.0.

Black garlic is made by browning the bulb in a Maillard reaction instead of caramelization. Creating a chemical reaction between the amino acids which reduces the amount of sugar in the garlic turning the color black and intensifying the flavor.

Popularized by Asian cuisine, you must first dehydrate the bulb of garlic.

Fully wrapped in tin foil, let the bulbs sit in an oven or salamander oven for 4 to 9 weeks at 52°C to 60°C (125°F to 140°F). Do not pull out the garlic until the entire bulb is completely black.

Articles and Sources

bulbs of garlic

Garlic Nutrition Facts

Serving Size 100 g (about 3.5 Oz or 0.44 Cups)

Amount Per Serving
Calories 133 Calories from Fat 5
% Daily Value*
Total Fat 0.6 g 1 %
Saturated Fat 0.1 g 0 %
Polyunsaturated fat 0 g
Monounsaturated fat 0 g
Trans Fat 0 g
Cholesterol 0 mg 0 %
Sodium 17 mg 1 %
Potassium 401 mg 11 %
Total Carbohydrate 33 g 11 %
Dietary Fiber 2.1 g 9 %
Sugars 1 g
Protein 6.4 g
Vitamin B6 62 % Vitamin C 52 %
Vitamin E 11 % Vitamin K 0 %
Manganese 23 % Selenium 6 %

Calories per gram:

Fat: 9 | Carbohydrate: 4 | Protein: 4

Source: USDA's Nutrient Database

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