Although the exact origin of garlic (Allium sativum) is not known, it’s believed to be a native of middle Asia, likely from West China.1 As a medical remedy it’s been used since 2700 B.C. to treat numerous afflictions, from depression to rheumatism to coughs and more, and the journey it’s taken has touched nearly every major civilization.
For example, the Egyptians fed it to slaves to give them strength and endurance; Hippocrates used it as for breathing problems and tumors;2 Pliny the Elder liked it for joint diseases and seizures; Easterners used it to treat diarrhea — and that’s just a short list.
In folk medicine, ancients believed garlic could ward off all kinds of evils including vampires and witches, as well as the black plague.3 On the other hand, as food and medicine, it was so valued that it even was used as a form of payment for slaves while the pyramids were being built. And, when the tomb of King Tutankhamun was opened, they found well preserved garlic cloves dating back to 1325 B.C.4
Garlic is a member of the onion family and one of the oldest known flavorings used on food. Currently, China is the world's largest producer of garlic; 90% grown in the U.S. comes from California. Scientifically, in addition to the multiple other benefits associated with garlic, researchers have found raw garlic improves your body's sensitivity to insulin and may help in the management of Type 2 diabetes.5
Garlic May Increase Insulin Availability
According to the Centers for Disease Control and Prevention,6 more than 30 million people living in the U.S. have diabetes. This is nearly 10% of the population. For the most part, Type 2 diabetes develops more frequently in those over 45 and often presents with few symptoms.
Insulin plays a significant role in how your body utilizes glucose. As you are exposed to higher amounts of glucose, your cells may become insulin resistant, which requires higher levels of insulin to move glucose from your blood into your cells.7 Insulin is produced in your pancreas in response to levels of glucose in your blood,8 and is inactivated in your liver.9
One way of helping to control blood sugar levels is to retain more insulin in your bloodstream to be used by the cells. However, 50% is removed on the first pass through the liver, reducing the amount of insulin for use. Research has demonstrated compounds found in garlic prevent this metabolism of insulin, freeing up more for your body.10
The compounds found in garlic include allicin, allyl propyl disulfide and S-allyl cysteine sulfoxide (alliin). The last is a bioactive compound researchers11 have evaluated for its effect on blood sugar. In one animal study mice were treated with drinking water with and without alliin for eight weeks.
While the animals had no change in body weight, energy or fat deposits, those drinking alliin infused water demonstrated increased insulin sensitivity and a better lipid profile. The researchers believe this may also be attributed to the compounds ability to modulate intestinal gut microbiota.12
Raw Is Better
Researchers have found the effects on blood glucose are much more significant when the garlic is administered in a raw form, rather than cooked. Raw garlic had a “profound effect” in animal studies to reduce glucose and lipid levels, while boiled garlic did not.13
In another animal study,14 researchers sought to evaluate the effect of raw garlic on plasma glucose, metabolic syndrome and oxidative stress in animals suffering from Type 2 diabetes. At the end of an eight-week trial, researchers concluded that “raw garlic homogenate is effective in improving insulin sensitivity while attenuating metabolic syndrome and oxidative stress.”
While researchers have found the use of raw garlic demonstrates a greater effect on glucose control, other studies have found garlic supplements will also demonstrate a decrease in glycated hemoglobin (HbA1c) and lipid profiles without complications.15 The first was a meta-analysis of randomized controlled trials using garlic and individuals with Type 2 diabetes.
In another, researchers16 undertook a single-blind, placebo-controlled, 24-week study with individuals who had fasting blood sugar above 126 mg/dl. They divided 210 individuals into seven groups.
One received the oral hypoglycemic drug metformin; another received a placebo; and the final five were given garlic tablets at doses of 300, 600, 900, 1,200 and 1,500 mg each day. The results showed garlic was “more effective than placebo and comparable to metformin in reducing fasting blood glucose.” There was a dose and duration dependent reduction in fasting blood sugar and improvement in HbA1c.17
Diabetes Is a Metabolic Condition
Metabolic syndrome is defined by a number of conditions occurring at the same time to increase your risk of Type 2 diabetes, heart disease and stroke.18 While having one does not mean you have a greater risk of disease, when they develop together, it raises your risk. The conditions are glucose intolerance, high blood pressure, dyslipidemia and central obesity.19
While the addition of garlic may help improve blood glucose control by affecting insulin metabolism and the action of your gut microbiota, the foods you eat exert an even stronger effect on your blood glucose.20 I recommend using intermittent fasting and a ketogenic diet to help control your blood sugar and reduce your risk of metabolic syndrome.
Currently, many are recognizing the power of eating a ketogenic diet to reduce both the glucose load in the body and the need for medication. While you may still find some who recommend strategies that raise blood sugar by eating certain carbohydrates,21 and adding beans and whole grain items to your shopping list,22 I urge you to read my article on lectins and their role in inflammation and chronic disease before you elect to follow such a diet.
One note: While garlic has had a significant impact on blood sugar control and insulin availability, it is important you add this into your regimen slowly, and under the supervision of your physician. Your blood sugar will need to be closely monitored, as will any hypoglycemic medications you may be taking, to avoid dangerous low blood sugar events.
Garlic Power: Organosulfur Compounds
Researchers have found frequent consumption of garlic has been associated with specific health benefits, namely the influence over toxicity and carcinogenicity of environmental toxins.23 Epidemiological studies have found phytochemicals, namely organ sulfites, present in garlic and onion, have an anticarcinogenic effect in experimental models.24
These organosulfur compounds are a subclass of sulfur found throughout the environment and are necessary components of enzymes, proteins and vitamins.25 The exact mechanism organosulfur compounds use in protecting cells against cancer is not clear.
It is known the compounds modulate activity using enzymes and inhibit the formation of DNA adducts,26 or segments of DNA bound to potentially cancer-causing chemicals.27 Organosulfur compounds have also demonstrated activity against cellular proliferation in tumors potentially mediated by starting apoptosis.28
In addition to anticarcinogenic effects, the sulfur compounds commonly found in garlic have antioxidant, anti-inflammatory and antimicrobial properties.29 In a meta-analysis of 39 trials of the effect of garlic on cholesterol and lipid levels, researchers found garlic to be effective in reducing total serum cholesterol when garlic was used for more than two months.30
Another animal study31 presented at the 2019 Experimental Biology conference held in Florida, evaluated the effect of garlic compounds on long- and short-term memory, as well as gut bacteria. The researchers believe their findings suggest daily administration of garlic could achieve improved results in the elderly.32
Organosulfur compounds found in garlic are also linked to a decrease in the synthesis of cholesterol in the liver,33 reducing total cholesterol level. In a test tube, they inhibit platelet aggregation,34 potentially reducing the risk of thrombotic events including stroke and pulmonary embolism and protecting your cardiovascular system.
Black Garlic Packed With More Benefits
One of the powerful organosulfur compounds in garlic is allicin, which is not technically part of a garlic clove, but is produced when the plant is crushed or chopped. Allicin is part of the plants defense system against insects and fungi. It is produced in a reaction between alliin and allicinase found in garlic.35
However, processing such as cooking, aging, dicing or crushing garlic triggers a breakdown in the allicin. To receive these benefits at higher levels consider purchasing aged black garlic. This product was originally developed in Korea and is achieved by processing the garlic in humidity-controlled environments with no additives and no preservatives.
Although some call the process fermenting, it does not involve microbial changes. Garlic cloves transition from the pearly white you are accustomed to seeing, to a black appearance containing a new range of compounds and taste some describe as a “sweet, earthy” flavor.36
In addition to greater health benefits, black aged garlic is also odorless and not as pungent as raw garlic. The product is higher in S-allyl cysteine (SAC), which has demonstrated preventive and protective properties against oxidative stress.37
One of the benefits of SAC found in natural garlic is how well it is absorbed, and it is 100% bioavailable.38 Researchers are confident of the role it plays in the overall health benefits of garlic.39 However, while some benefits may be more effective than fresh garlic, levels of allicin in aged black garlic is low.
How to Make Garlic Part of Your Diet
Although some research has had positive results using garlic supplements, their performance is variable as it depends upon your digestive conditions. Many supplements are enteric-coated to keep them from being destroyed in stomach acid. For this reason, I believe it's much better to get your organosulfur compounds from real food rather than relying on a supplement.
Since allicin is not formed until a raw garlic clove is either crushed or diced, you may want to also consider using aged black garlic. But, whether you choose to use raw or black, you can’t go wrong with garlic. Add garlic to your salad dressing, run it through your juicer or put the cloves directly into your pasture-raised organic beef before cooking to add a rich infused flavor to the beef.
Another way to enjoy your garlic is after it’s sprouted. While you may toss garlic cloves that bright green shoots, researchers40 have found extracts from garlic cloves that have sprouted for five days have higher antioxidant activity than fresh bulbs.
You may easily grow garlic at home in the garden or your house, from cloves you purchase at the store or from seed. This gives you an ample supply of fresh grown, pesticide free garlic for your recipes.
If you’d like to try eating a raw clove of garlic, you’ll want to dice it before swallowing since taking a whole clove doesn’t activate the allicin. Raw garlic may be added to guacamole or salsa or diced into a teaspoon of locally sourced honey before going down the hatch.41