With their unique combination of flavonoids and sulfur-containing nutrients, allium vegetables—such as garlic—belong in your diet on a regular basis. There’s research evidence for including at least one serving of an allium vegetable—such as garlic—in your meal plan every day. If you’re choosing garlic as your allium family vegetable, try to include at least 1/2 clove in your individual food portion. If you’re preparing a recipe, we recommend at least 1-2 cloves.
Garlic is a wonderful seasoning to add aroma, taste, and added nutrition to your dishes. We often recommend using raw chopped or pressed garlic in many of our dishes to take advantage of the benefits derived from garlic. However, if you cannot tolerate raw garlic, you can add chopped garlic to foods while they are cooking. It is best to add it towards the end of the cooking process to retain the maximum amount of flavor and nutrition.
Whole books have been written about garlic, an herb affectionately called “the stinking rose” in light of its numerous therapeutic benefits. A member of the lily or Allium family, which also includes onions and leeks, garlic is rich in a variety of powerful sulfur-containing compounds including thiosulfinates (an important example being allicin), sulfoxides (a well-studied example being alliin), volatile organosulfur compounds> like diallyl sulfides, vinyldithiins, ajoene and its derivatives, and also water-soluble organosulfur compounds (inclucing S-allyl-L-cysteine). Some of these compounds are largely responsible for garlic’s characteristically pungent odor, and they are also the source of documented health benefits.
Fairly recent research has linked some of the less well-studied sulfur compounds in garlic to potential support of our cardiovascular health. These sulfur compounds include 1,2-vinyldithiin (1,2-DT), and thiacremonone. The hydrogen sulfide gas (H2S) that can be made from garlic’s sulfides has also been the subject of great research interest. When produced and released from our red blood cells, this H2S gas can help dilate our blood vessels and help keep our blood pressure under control.
Finally, when thinking about the sulfur compounds in garlic, it is important to remember that sulfur itself is a key part of our health. Several research studies have noted that the average U.S. diet may be deficient in sulfur, and that foods rich in sulfur may be especially important for our health. In addition to all of the sulfur-related compounds listed above, garlic is an excellent source of manganese and vitamin B6, a very good source of vitamin C, and a good source of selenium.
Most of the research on garlic and our cardiovascular system has been conducted on garlic powder, garlic oil, or aged garlic extracts rather than garlic in food form. But despite this research limitation, food studies on garlic show this allium vegetable to have important cardioprotective properties. Garlic is clearly able to lower our blood triglycerides and total cholesterol, even though this reduction can be moderate (5-15%).
But cholesterol and triglyceride reduction are by no means garlic’s most compelling benefits when it comes to cardioprotection. Those top-level benefits clearly come in the form of blood cell and blood vessel protection from inflammatory and oxidative stress. Damage to blood vessel linings by highly reactive oxygen molecules is a key factor for increasing our risk of cardiovascular problems, including heart attack and atherosclerosis. Oxidative damage also leads to unwanted inflammation, and it is this combination of unwanted inflammation and oxidative stress that puts our blood vessels at risk of unwanted plaque formation and clogging. Garlic unique set of sulfur-containing compounds helps protect us against both possibilities—oxidative stress and unwanted inflammation.
The following provides a list of sulfur-containing garlic’s constituents that help lower our risk of oxidative stress:
* “Allyl polysulfides” is a general term that refers to a variety of compounds.
On the anti-inflammatory side of the equation, garlic’s 1,2-vinyldithiin (1,2-DT) and thiacremonone are the compounds that have been of special interest in recent research. Both compounds appear to work by inhibiting the activity of inflammatory messenger molecules. In the case of thiacremonone, it is the inflammatory transcription factor called NFkappaB that gets inhibited. In the case of 1,2-DT, the exact anti-inflammatory mechanisms are not yet clear, even though the release of inflammatory messaging molecules like interleukin 6 (IL-6) and interleukin 8 (IL-8) by macrophage cells has been shown to be reduced in white adipose tissue by 1,2-DT. The combination of anti-inflammatory and anti-oxidative stress compounds in garlic makes it a unique food for cardiovascular support, especially in terms of chronic degenerative cardiovascular conditions like atherosclerosis.
In addition to the ability of garlic to help prevent our blood vessels from becoming blocked, this allium vegetable may also be able to help prevent clots from forming inside of our blood vessels. This cardiovascular protection has been linked to one particular disulfide in garlic called ajoene. Ajoene has repeatedly been shown to have anti-clotting properties. It can help prevent certain cells in our blood (called platelets) from becoming too sticky, and by keeping this stickiness in check, it lowers the risk of our platelets clumping together and forming a clot.
Equally impressive about garlic is its ability to lower blood pressure. Researchers have known for about 10 years that the allicin made from alliin in garlic blocks the activity of angiotensin II. A small piece of protein (peptide), angiotensin II helps our blood vessels contract. (When they contract, our blood is forced to pass through a smaller space, and the pressure is increased.) By blocking the activity of angiotensin II, allicin form garlic is able to help prevent unwanted contraction of our blood vessels and unwanted increases in blood pressure.
More recently, however, researchers have found that garlic supports our blood pressure in a second and totally different way. Garlic is rich in sulfur-containing molecules called polysulfides. It turns out that these polysulfides, once inside our red blood cells (RBCs), can be further converted by our RBCs into a gas called hydrogen sulfide (H2S). H2S helps control our blood pressure by triggering dilation of our blood vessels. When the space inside our blood vessels expands, our blood pressure gets reduced. (H2S is described as a “gasotransmitter” and placed in the same category as nitric oxide (NO) as a messaging molecule that can help expand and relax our blood vessel walls.) Interestingly, our RBCs do not appear to use processed garlic extracts in the same way that they use polysulfides in food-form garlic.
Garlic’s numerous beneficial cardiovascular effects are due to not only its sulfur compounds, but also to its vitamin C, vitamin B6, selenium and manganese. Garlic is a very good source of vitamin C, the body’s primary antioxidant defender in all aqueous (water-soluble) areas, such as the bloodstream, where it protects LDL cholesterol from oxidation. Since it is the oxidized form of LDL cholesterol that initiates damage to blood vessel walls, reducing levels of oxidizing free radicals in the bloodstream can have a profound effect on preventing cardiovascular disease.
Garlic’s vitamin B6 helps prevent heart disease via another mechanism: lowering levels of homocysteine. An intermediate product of an important cellular biochemical process called the methylation cycle, homocysteine can directly damage blood vessel walls.
The selenium in garlic can become an important part of our body’s antioxidant system. A cofactor of glutathione peroxidase (one of the body’s most important internally produced antioxidant enzymes), selenium also works with vitamin E in a number of vital antioxidant systems.
Garlic is rich not only in selenium, but also in another trace mineral, manganese, which also functions as a cofactor in a number of other important antioxidant defense enzymes, for example, superoxide dismutase. Studies have found that in adults deficient in manganese, the level of HDL (the “good form” of cholesterol) is decreased.
Our cardiovascular system is not the only body system that may be able to benefit from garlic’s anti-inflammatory properties. There’s preliminary evidence (mostly from animal studies, and mostly based on garlic extracts rather than whole food garlic) that our our musculoskeletal system and respiratory system can also benefit from anti-inflammatory compounds in garlic. Both the diallyl sulfide (DAS) and thiacremonone in garlic have been shown to have anti-arthritic properties. And in the case of allergic airway inflammation, aged garlic extract has been show to improve inflammatory conditions (once again in animal studies).
Even more preliminary is research evidence showing that some inflammatory aspects of obesity may be altered by sulfur-containing compounds in garlic. Specifically, there is one stage in development of the body’s fat cells (adipocytes) that appears to be closely related to status of our inflammatory system. Fat cells cannot become fully themselves unless they are able to progress from a preliminary stage called “preadipocytes” to a final stage called “adipocytes.” One of the sulfur compounds in garlic (1,2,-vinyldithiin, or 1,2-DT) appears able to lessen this conversion of preadipocytes into adipocytes, and the impact of 1,2-DT appears to be inflammation-related. Even though very preliminary, this research on 1,2-DT is exciting because obesity is increasingly being understood as a disease characterized by chronic, low level inflammation and our inflammatory status is precisely where garlic’s 1,2-DT has its apparent impact.
From a medical history standpoint, the antibacterial and antiviral properties of garlic are perhaps its most legendary feature. This allium vegetable and its constituents have been studied not only for their benefits in controlling infection by bacteria and viruses, but also infection from other microbes including yeasts/fungi and worms. (One particular disulfide in garlic, called ajoene, has been successfully used to help prevent infections with the yeast Candida albicans.) Very recent research has shown the ability of crushed fresh garlic to help prevent infection by the bacterium Pseudomonas aeruginosa in burn patients. Also of special interest has been the ability of garlic to help in the treatment of bacterial infections that are difficult to treat due to the presence of bacteria that have become resistant to prescription antibiotics. However, most of the research on garlic as an antibiotic has involved fresh garlic extracts or powdered garlic products rather than fresh garlic in whole food form.
Overgrowth of the bacterium Helicobacter pylori in the stomach—a key risk factor for stomach ulcer—has been another key area of interest for researchers wanting to explore garlic’s antibacterial benefits. Results in this area, however, have been mixed and inconclusive. While garlic may not be able to alter the course of infection itself, there may still be health benefits from garlic in helping to regulate the body’s response to that infection.
While not as strong as the research evidence for cruciferous vegetables, research on the allium vegetables—including garlic—shows that these vegetables have important anti-cancer properties. Interestingly, high intake of garlic (roughly translated as daily intake of this food) has been found to lower risk of virtually all cancer types except cancer of the prostate and breast cancer. However, moderate intake of garlic (roughly translated as several times per week) has been repeatedly found to lower risk of only two cancer types—colorectal and renal cancer. This difference between “high” versus “moderate” garlic intake may be a real difference that suggests we all need to eat more garlic if we want to maximize its cancer-related benefits. Or it may be a difference that is more related to research complications involving the options given to research participants when reporting their food intake. Still, garlic has a consistent track record with respect to general anti-cancer benefits, and there are good research reasons for classifying garlic as an “anti-cancer” food.
The allyl sulfides found in garlic may play a key role in its cancer-prevention benefits. These garlic compounds are able to activate a molecule called nuclear erythroid factor (Nrf2) in the main compartment of cells. The Nrf2 molecule then moves from the main compartment of the cell into the cell nucleus, where it triggers a wide variety of metabolic activities. Under some circumstances, this set of events can prepare a cell for engagement in a strong survival response, and in particular, the kind of response that is needed under conditions of oxidative stress. Under other circumstances, this same set of events can prepare the cell to engage in programmed cell death (apoptosis). When a cell recognizes that it has become too compromised to continue functioning in a healthy manner with other cells, it stops proceeding through its own life cycle and essentially starts to dismantle itself and recycle its parts. It’s critical for a cell to determine whether it should continue on or shut itself down, because cells that continue on without the ability to properly function or communicate effectively with other cells are at risk of becoming cancerous. The ability of garlic’s allyl sulfides to activate Nrf2 suggests that garlic may be able to help modify these all-critical cell responses and prevent potentially cancerous cells from forming.
One especially interesting area of research on garlic and cancer prevention involves meat cooked at high temperatures. Heterocyclic amines (HCAs) are cancer-related substances that can form when meat comes into contact with a high-temperature cooking surface (400°F/204°C or higher). One such HCA is called PhIP (which stands for 2-amino-1-methyl-6-phenylimidazopyridine). PhIP is thought to be one reason for the increased incidence of breast cancer among women who eat large quantities of meat because it is rapidly transformed into DNA-damaging compounds.
Diallyl sulfide (DAS), one of the many sulfur-containing compounds in garlic, has been shown to inhibit the transformation of PhIP into carcinogens. DAS blocks this transformation by decreasing the production of the liver enzymes (the Phase I enzymes CYP1A1, CYP1A2 and CYP1B1) that transform PhIP into activated DNA-damaging compounds. Of course, your best way to prevent formation of PhIP is not to bring your meat into contact with a 400°F/204°C cooking surface in the first place. But this area of research still bolsters our view of garlic as an allium vegetable with important cancer-preventive properties.
Recent research has shown that garlic may be able to improve our metabolism of iron. When iron is stored up in our cells, one of the key passageways for it to be moved out of the cell and returned into circulation involves a protein called ferroportin. Ferroportin is protein that runs across the cell membrane, and it provides a bridge for iron to cross over and leave the cell. Garlic may be able to increase our body’s production of ferroportin, and in this way, help keep iron in circulation as it is needed.
For a small vegetable, garlic (Allium sativum) sure has a big, and well deserved, reputation. And although garlic may not always bring good luck, protect against evil, or ward off vampires, characteristics to which it has been assigned folklorically, it is guaranteed to transform any meal into a bold, aromatic, and healthy culinary experience. Garlic is a member of the Lily family and is a cousin to onions, leeks and chives.
Garlic is arranged in a head, called a “bulb,” which averages about 2 inches in height and diameter and consists of numerous small separate cloves. Both the cloves and the entire bulb are encased in paper-like sheathes that can be white, off-white, or have a pink/purple hue. Although garlic cloves have a firm texture, they can be easily cut or crushed. The taste of garlic is like no other—it hits the palate with a hot pungency that is shadowed by a very subtle background sweetness. While elephant garlic has larger cloves, it is more closely related to the leek and therefore does not offer the full health benefits of regular garlic.
Fresh, dried and powdered garlic are available in markets throughout the year, however, fresh varieties from California are in season from June through December.
Native to central Asia, garlic is one of the oldest cultivated plants in the world and has been grown for over 5000 years. Ancient Egyptians seem to have been the first to cultivate this plant that played an important role in their culture.
Garlic was not only bestowed with sacred qualities and placed in the tomb of Pharaohs, but it was given to the slaves that built the Pyramids to enhance their endurance and strength. This strength-enhancing quality was also honored by the ancient Greeks and Romans, civilizations whose athletes ate garlic before sporting events and whose soldiers consumed it before going off to war.
Garlic was introduced into various regions throughout the globe by migrating cultural tribes and explorers. By the 6th century BC, garlic was known in both China and India, the latter country using it for therapeutic purposes.
Throughout the millennia, garlic has been a beloved plant in many cultures for both its culinary and medicinal properties. Over the last few years, it has gained unprecedented popularity since researchers have been scientifically validating its numerous health benefits.
Currently, China, South Korea, India, Spain and the United States are among the top commercial producers of garlic.
For maximum flavor and nutritional benefits, always purchase fresh garlic. Although garlic in flake, powder, or paste form may be more convenient, you will derive less culinary and health benefits from these forms.
Purchase garlic that is plump and has unbroken skin. Gently squeeze the garlic bulb between your fingers to check that it feels firm and is not damp.
Avoid garlic that is soft, shriveled, and moldy or that has begun to sprout. These may be indications of decay that will cause inferior flavor and texture. Size is often not an indication of quality. If your recipe calls for a large amount of garlic, remember that it is always easier to peel and chop a few larger cloves than many smaller ones. Fresh garlic is available in the market throughout the year.
At WHFoods, we encourage the purchase of certified organically grown foods, and garlic is no exception. Repeated research studies on organic foods as a group show that your likelihood of exposure to contaminants such as pesticides and heavy metals can be greatly reduced through the purchased of certified organic foods, including garlic. In many cases, you may be able to find a local organic grower who sells garlic but has not applied for formal organic certification either through the U.S. Department of Agriculture (USDA) or through a state agency. (Examples of states offering state-certified organic foods include California, New York, Oregon, Vermont, and Washington.) However, if you are shopping in a large supermarket, your most reliable source of organically grown garlic is very likely to be garlic that displays the USDA organic logo.
Store fresh garlic in either an uncovered or a loosely covered container in a cool, dark place away from exposure to heat and sunlight. This will help maintain its maximum freshness and help prevent sprouting, which reduces its flavor and causes excess waste. It is not necessary to refrigerate garlic. Some people freeze peeled garlic; however, this process reduces its flavor profile and changes its texture.
Depending upon its age and variety, whole garlic bulbs will keep fresh for about a month if stored properly. Inspect the bulb frequently and remove any cloves that appear to be dried out or moldy. Once you break the head of garlic, it greatly reduces its shelf life to just a few days.
The first step to using garlic is to separate the individual cloves. An easy way to do this is to place the bulb on a cutting board or hard surface and gently, but firmly, apply pressure with the palm of your hand at an angle. This will cause the layers of skin that hold the bulb together to separate.
Peel garlic with a knife or alternatively, separate the skin from the individual cloves by placing a clove with the smooth side down on a cutting board and gently tapping it with the flat side of a wide knife. You can then remove the skin either with your fingers or with a small knife. If there is a green sprout in the clove’s center, gently remove it since it is difficult to digest.
Chopping or crushing stimulates the enzymatic process that converts the phytonutrient alliin into allicin, a compound to which many of garlic’s health benefits are attributed. In order to allow for maximal allicin production, wait at least 5 minutes before eating or cooking the garlic. Also observe this 5-minute “time out” period before adding any high acidic ingredient to the garlic (for example, lemon juice). Ingredients with a pH below 3.5 can also deactivate the enzymatic process.
Since crushing and chopping are the food preparation steps that activate garlic’s enzymes, these steps can help you obtain many of garlic’s special benefits. For example, research has shown that microwaving or boiling garlic in uncrushed, whole clove form will deactivate its enzymes, preventing these enzymes from working. For this reason, we recommend that you chop or crush the garlic cloves prior to heating. According to research on garlic preparation methods, it only takes 60 seconds of microwaving whole cloves to lessen some of garlic’s health benefits. By contrast, many of garlic’s health benefits (including its anti-cancer properties) are preserved if the whole cloves are crushed and allowed to sit for 10 minutes prior to cooking.
We recommend using raw garlic in many of our recipes. If it is a cooked dish you are preparing and you cannot tolerate raw garlic, add chopped garlic towards the end of the cooking time to retain maximum flavor and nutrition. Too much heat for too long will reduce the activity of the health-promoting sulfur compounds that have formed by letting it sit for 5-10 minutes; it will also make garlic bitter. Therefore expose garlic to heat for as little time as possible (5-15 minutes).
If you would like to combine garlic with oil, we recommend that you avoid high-temperature heating of this oil-garlic mixture. Keeping the heat at 250F/121C or lower will help preserve the health benefits of both the garlic and the oil. This same principle applies to the oven roasting of garlic bulbs themselves. We do not recommend the 350F/177C temperature range that you will find in many recipes and on many websites. Once again, a lower temperature is needed to help preserve health-protective compounds in garlic.
We actually include garlic as an ingredient in so many of our recipes. To find these just go to the Recipe Assistant on the Recipes page and click on “garlic” in the “Food to Include” box.
If you’d like even more recipes and ways to prepare garlic the Nutrient-Rich Way, you may want to explore The World’s Healthiest Foods book.
The Johns Hopkins Lupus Center has recently listed garlic as a food to be avoided by persons diagnosed with lupus (systemic lupus erythematosus, or SLE). While we have not seen any published research documenting lupus flare-ups with garlic intake, and while the Lupus Foundation of America has suggested on its website that “occasional use is cooking is not likely to cause significant problems for most people,” we have heard directly from website visitors who have experienced problems in this area. If you are a person diagnosed with lupus, we recommend a consult with your healthcare provider to decide about inclusion or avoidance of garlic in your meal plan.
Do not store garlic in oil at room temperature. Garlic-in-oil mixtures stored at room temperature provide perfect conditions for producing botulism, regardless of whether the garlic is fresh or has been roasted.
The sulfur compounds in garlic are perhaps its most unique nutrients. There are literally dozens of well-studied sulfur molecules in garlic, and virtually all of them have been shown to function as antioxidants. In addition, many provide us with anti-inflammatory benefits. The very presence of sulfur in some many different garlic compounds may also play an important role in our nourishment.
Additionally, garlic is an excellent source of manganese and vitamin B6. It is also a very good source of vitamin C and copper. In addition, garlic is a good source of selenium, phosphorus, vitamin B1 and calcium.
In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn’t contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food’s in-depth nutritional profile that includes values for dozens of nutrients – not just the ones rated as excellent, very good, or good – please use the link below the chart.) To read this chart accurately, you’ll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food’s nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration’s