Consumer Knowledge of Garlic for Nutrition Education Programming

Abstract

Garlic intake has been the subject of research for its many potential health benefits. Consumers have continuing interest in food-related topics, food preparation, and growing their own food in small gardens. Garlic has specific agronomic protocols because it is not grown simply from seed. As a culinary aromatic, garlic use may be somewhat mystifying for some. This research study used an online consumer survey with 558 participants to determine basic garlic consumption habits, knowledge of the research related to health benefits of garlic, experience with and interest in growing garlic, and some basic demographic information. The top reason for using garlic, at 64% of responses, was ‘cardiovascular’ benefits, followed by ‘anti-bacterial’ at 45% and ‘blood pressure support’ at 37%. Only 3% of respondents reported that they were currently taking garlic supplements. The top two preferred garlic forms used at home were ‘dried garlic powder’ and ‘fresh, raw garlic,’ at 86% and 83% respectively. We noted a budding interest in growing garlic for home harvest and in educational information, especially when available in online print and video formats. The survey results showed that more programming is needed to emphasize the health benefits of the natural phytochemicals (plant chemicals) contained in garlic as part of an overall balanced diet.

Keywords

garlic, aged garlic extract supplements, plant-based, nutrition, diet, health, Cooperative Extension, gardening

Introduction

Garlic is unique in a class of edible vegetables called alliums that have been the subject of research for their potential medicinal properties. Not only is garlic the most pungent of the allium family of comestibles, but it also is an historically used remedy for ailments since the plant was first discovered and cultivated. Eventually, garlic’s unique healing properties lent itself toward the application of dietary supplements in human health. Especially since the pandemic, consumers are eager to learn to grow their own food. Because of garlic’s multiple facets, possibilities for renewed promotion among consumers and small-scale local gardeners warrants investigation.

The allium family includes garlic, onions, shallots, chives, and leeks. They all have health-promoting properties and can be included in a balanced diet to help prevent chronic disease. Native to Central Asia, garlic and onions have a more than 4,000-year use for culinary and health benefits. Historically, an ancient Egyptian text cites 22 applications for garlic. For example, Hippocrates suggested garlic as a laxative and diuretic, and Aristophenes and Galen promoted its use for treating uterine cancer. Garlic grows wild in some areas of the world, including Central Asia, but garlic is now cultivated on more than 2.5 million acres (1 million hectares) for a worldwide market according to the U.S. Agricultural Research Service.

Garlic has been used in culinary and medicinal applications. Fresh, powdered, oil, aged garlic extract (AGE), black garlic and purple garlic are among the options. Compounds in these varieties have greater potency when cooked, for example, as opposed to some compounds that are emphasized when garlic is eaten raw.

Common bioactive compounds of garlic that have been studied include polysaccharides, saponins, phenolic compounds, and S-allyl-cysteine. The main bioactive components include polyphenols, flavonoids, flavanols, and tannins. High levels of potassium, phosphorus, zinc, and sulfur are found in garlic, along with lesser amounts of selenium, calcium, magnesium, manganese, and iron. The sulfur-containing compounds in garlic are known as alliin, allicin and ajoene, among others. Garlic also contains various enzymes, along with phellandrene, citral, linalool, and geraniol. Overall, some compounds, such as the phenols, are higher in garlic than in many other common vegetables.

Garlic has long been used in a variety of ways for potential health benefits, including cardiovascular, immunity, infection, and oxidative stress. The purported actions of garlic are many: reduction in severity of colds and flu, protection against various alimentary canal cancers among others, protection of the liver, and high level of anti-microbial activity. For example, the Rosato and Caposele varieties from Italy are effective against Penicillum expansum, Aspergillus versicolor and Penicillum citrinum. Some gut-health-promoting prebiotics are found in garlic and in other foods. The properties of some polysaccharides are anti-inflammation, antioxidation, and immunomodulation. They relieve colitis by reducing levels of inflammatory factors and improving the microbiome. Garlic polysaccharides’ other properties include antitumor, anticoagulation, liver protection, and microbiome balance.

Many viruses have threatened human health recently, such as SARS in 2003, MARS in the Mid-East in 2012, Ebola in West Africa in 2014 and of course, COVID-19 worldwide in 2020. Prevention of viral disease stymies current treatment because it emerges and spreads rapidly and has drug-resistance, adapting quickly to treatments as strains mutate. Even though some success has emerged in medical prevention and treatment in lieu of a fast-changing environment; e.g., with herpes simplex, HIV and hepatitis B, some people look to applications of functional foods in order to bolster their immune systems.

The many potential benefits of garlic are affected by the various pre- and post-harvest methods employed in the growing cycle. In pre-harvest activities, genotype is the first consideration. The selection of a particular cultivar may result in an increase in total phenolics. The differing colors of some cultivars also affect nutrition: vitamin C and total fractionated oil are higher in purple varieties, and total phenolic compounds and flavonoid content are higher in white garlic. Harvesting garlic later in the season allows for the compounds to travel from the leaves into the bulbs, where they are most frequently utilized for culinary or medicinal purposes. In post-harvest, it is important to consider processing in order to maintain quality.

Garlic has been applied to maintain health and treat disease throughout history. In some published research, aged garlic extract (AGE) in dietary supplements is shown to improve immune system function, decrease severity of cold and flu symptoms, reduce obesity-induced inflammation, and increase healthy microbial activity in the gut. Some of the ways garlic has been prepared for consumption in health maintenance are garlic powder, garlic oil, and commercial extracts. AGE is commonly found in dietary supplements throughout the retail environment. AGE is made by slicing garlic cloves and storing them in a water-ethanol solution until the volatile components are converted into stable compounds.

Some of the marketing claims for AGE and other garlic-infused dietary supplements include fighting free radicals, reduction of cold and flu symptoms, reduction of upper respiratory tract infections, supporting immunity, inhibition of blood platelet formation, lowering of blood pressure, and lowering of blood lipids. There is some evidence in the research for garlic’s efficacy; however, a variety of preparations have been used across a variety of methods in studies, and some preparations have varying levels of quality, therefore, not one single brand of AGE can be conclusively recommended.

Home-based food production and preparation became very popular during the global pandemic, and research has shown significant public health benefits and practices of gardening that can be applied during times of crisis. Further, consumer interest in garlic has grown. In addition, enhancing flavor in foods with the addition of salt-free herbs and spices (such as garlic powder or fresh garlic) can decrease salt content in recipes and potentially reduce the risk for chronic disease.

Garlic in moderation is considered safe, especially when consumed in foods. Further, garlic consumption has shown potential health benefits linked to its lipid-lowering, antioxidant and anti-inflammatory effects in several randomized controlled trials. Too much garlic, however, especially when eaten raw, can promote upset stomach or heartburn. Food consumption has a major impact on health at all stages of life, from birth through advanced age, and a dietary pattern based on science-based research can reduce the risk for chronic disease, according to the U.S. Dietary Guidelines for Americans.

Although dietary supplements of various types are popular among consumers, they cannot replace a healthful diet; the Food and Drug Administration uses different criteria for overseeing supplements compared with foods and drugs.

Study Purpose and Design

The purpose of this survey was to assess the level of consumer interest, knowledge, and experience with using (i.e. cooking, eating) and growing fresh garlic. We wanted to determine general knowledge, including historic/folkloric as well as scientific research results, to get a sense of background reference points from which consumers orient themselves. Through efforts of the Cooperative Extension program, the results will be used to create local and national educational programming and online materials for consumers and growers in their homes and within their local communities.

Mixed methods were used to collect data from consumers, relying on the survey tool administered through Qualtrics (Provo, UT). The study was approved by North Dakota State University Internal Review Board protocol #IRB0005164 on April 24, 2024. Twenty questions were asked; of those, four were solely quantitative where participants selected responses from a provided list, ten were quantitative combined with a qualitative optional write-in answer, five were demographic, and the final question pertained to the anonymous prize drawing. All questions were designated as being optional for the participant to answer, allowing for skipping questions. As a survey, the basis for data collection relied on quantifiable questions and answers in order to observe larger trends. However, a number of the questions (10/14) had options for qualitative answers; that is, open-ended responses, which resulted in broader, richer data.

Questions were developed into three areas of inquiry: consuming garlic, health benefits of garlic, and growing garlic. Consuming garlic questions were based on prior experience of Cooperative Extension community-based educational programming in food and nutrition. Health benefits of garlic questions were based on the literature, and growing garlic questions were asked as initial inquiry into what might be consumers’ current experience (or inexperience) they had in personal-scale garlic cultivation.

The survey was distributed via email listservs and e-newsletter subscriptions of various Extension food and nutrition networks across the country known to one of the co-authors, and through social media (Facebook) to reach a diverse audience. A total of 558 respondents completed the survey, which opened on May 1, 2024 and closed on June 6, 2024. The authors’ goal was to reach 500 respondents, which is common in this type of research, so the response rate for this type of survey was considered a success.

Data Analysis and Results

DEMOGRAPHICS

The survey participants (558) were from half the states (25) in the United States, with 86% of survey respondents from the Midwestern states of North Dakota, Minnesota, Iowa, Nebraska, Ohio and South Dakota. Most reported being female (85%), preferred materials in English (99%), and they ranged in age from 18 to 80 and older, with most participants in the 40 to 69 age range. Tables 1 to 6 summarize the results of the survey questions.

Discussion

As shown in Table 1, most survey respondents (85%) reported that they and/or at least one other householder ate garlic. Because our pool of survey participants was drawn from already established email listservs, social media (Facebook), a column reaching numerous newspapers, and digital newsletter subscribers of food and nutrition information, we expected a fair amount of interest in garlic as we would other food and nutrition topics. However, our survey solicited information that would help us further understand the degree to which enthusiasm or interest in the specific topic of garlic would extend. The results within the garlic use or consumption category of questions supported that assumption, either by personal response or household interest, as almost all of the participants or their household members reported eating garlic.

Frequency of garlic consumption was fairly regular, on a weekly basis, and the main reason for consumption was for the taste, followed by health benefits. One respondent reported in the ‘other’ answer line that “aroma is better when using fresh raw garlic,” and another stated “I think it’s the healthiest option.” We also wanted to find out why respondents did not use fresh raw garlic in their meals, with the majority selecting the answer response that indicated it was too difficult to prepare. Even though there are new and old tools available to help home cooks prepare garlic from the fresh state, one respondent summed up the disadvantage well with “the time it takes to clean the garlic press.” In terms of garlic form used, the top two responses were ‘dried garlic powder’ and ‘fresh, raw garlic,’ at 86% and 83% respectively. Close behind were ‘preserved, raw garlic in jar’ (63%) and ‘dried garlic salt’ (50%). Most people reported using garlic every week at a rate of 53%, followed by every day and every month at 14% and 15% respectively. Twelve percent of respondents said they used fresh, raw garlic only a few times a year, with 6% reporting they never use it. About 41% noted that the health benefits of garlic was a reason for using it, followed by 27% saying they use it because of others in the household, with 5% reporting no use at all, but interested in learning more. Those respondents that don’t use fresh, raw garlic in their meals selected the reason as too difficult to prepare, at 58%, whereas not liking the taste came in almost in last place at 4% of the responses, marking all that apply.

When respondents could choose more than one answer, we saw percentages jump, as many forms of garlic were consumed, especially garlic powder along with fresh raw garlic. Enthusiasm showed itself in almost every question asked, and in question 2, one respondent, replying to what form garlic was eaten, commented, “any form we can find it.” Respondents reported using garlic in canning (food preservation), cooking and stir fry applications. A wide variety of other forms were reported, from pickled to confit.

More qualitative responses were reported for not using fresh, raw garlic, with the most saying it is too inconvenient because of its sticky and smelly qualities, along with saying that there were other forms of garlic more convenient to use (12 count). Next in line of descending responses were lack of time (7 count), no availability because of rural area or food desert (5 count), use both fresh and jar (3 count), and spoils quickly (3 count).

One of the themes we noted from the survey that was first revealed in the garlic use category of questions was the lack of availability of fresh, raw garlic, noting that rural area grocery stores do not stock it or have trouble keeping the fresh article in stock: “Fresh garlic of good quality is not readily available in small town grocery stores; what they have is often dried out.” Another repeated the sentiment: “not available in my small town grocery,” and later in the survey “I want to plant garlic for my own use because I think it would taste better than what I purchase in a grocery store.” Thus, we found that some stores do not keep good stock of fresh garlic on hand, which could be true for other types of fresh produce as well.

Conclusion

Using garlic in culinary applications and growing garlic are two educational programming opportunities ripe for promotion, especially in lieu of post-pandemic efforts of consumers to become more self-sustaining in ensuring their own food supply lines locally and independently. These efforts are backed by the many studies showing the potential benefits of garlic for human health, which should be included in educational programming due to the lack of knowledge of health benefits shown in our garlic survey results. Programming for growing garlic will most likely be pursued separately from consuming garlic. The survey did not specifically ask if respondents would like to grow garlic if given the opportunity, but the optional qualitative responses showed about 26/76 of respondents would be open to programming about growing garlic.

Education about garlic consumption, including preparation, cooking, storing, and preserving garlic, is ongoing, and the survey results showed that more programming is needed to emphasize the health benefits of the natural phytochemicals (plant chemicals) contained in garlic. General education on garlic supplements, including the research, could be provided to supply background for our constituents, allowing them to make savvy decisions between choosing freshly prepared nutritious food or dietary supplements that have scientific backing.

Future research could expand to an international audience and include separate and more detailed questions about consuming, growing garlic and using garlic in worldwide cuisine. We were limited by the geographic aspects of growing garlic; different growing zones in the U.S. and throughout the world require different information about growing conditions. The survey did not inquire about food deserts or fresh food availability, which came up in some of the responses for consuming garlic. However, programming for growing and using garlic would be advantageous for a global audience.

More information about garlic is available in the applicable garlic section within the resources: www.ag.ndsu.edu/fieldtofork

References

1. Nicastro HL, Ross SA, Milner JA. Garlic and onions: their cancer prevention properties. Cancer Prev Res. 2015;8(3):181-189.
2. Simon PW. The origins and distribution of garlic: How many garlics are there? USDA Agricultural Research Service. 2020; https://www.ars.usda.gov/midwest-area/madison-wi/vegetable-crops-research/docs/simon-garlic-origins
3. Shang A, Cao S-Y, Xu X-Y, Gan R-Y, Tang G-Y, Corke H, et al. Bioactive compounds and biological functions of garlic (Allium sativum L.). Foods. 2019;8:246.
4. Recinella L, Gorica E, Chiavaroli A, Fraschetti C, Filippi A, Cesa S, et al. Anti-inflammatory and antioxidant effects induced by Allium sativum L. extracts on an ex vivo experimental model of ulcerative colitis. Foods. 2022;11:3559.
5. Ansary J, Forbes-Hernández TY, Gil E, Cianciosi D, Zhang J, Elexpuru-Zabaleta M, et al. Potential health benefit of garlic based on human intervention studies: a brief overview. Antioxidants. 2020;9:619. doi:10.3390/antiox9070619.
6. Martins N, Petropoulos S, Ferreira ICFR. Chemical composition and bioactive compounds of garlic (Allium sativum L.) as affected by pre- and post-harvest conditions: a review. Food Chem. 2016;211:41-50.
7. Martini N. Garlic. J Prim Health Care. 2014;6,(4):337-338.
8. Shao X, Sun C, Tang X, Zhang X, Han D, Liang S, et al. Anti-inflammatory and intestinal microbiota modulation properties of Jinxiang garlic (Allium sativum L.) polysaccharides toward dextran sodium sulfate-induced colitis. J Agric Food Chem. 2020;68:12295-12309.
9. Rouf R, Uddin SJ, Sarker DK, Islam MT, Ali ES, Shilpi JA, et al. Antiviral potential of garlic (Allium sativum) and its organosulfur compounds: a systematic update of pre-clinical and clinical data. Trends Food Sci Technol. 2020;104:219-234.
10. Kitakaze T, Inoue M, Ashida H. Aged garlic extract prevents alcohol-induced cytotoxicity through the induction of aldehyde dehydrogenase 2 in the liver of mice. Mol Nutr Food Res. 2023;67:2200627.
11. Kingsley, J, Donati K, Litt J, Shimpa N, Blythe C, Vavra J, et al. Pandemic gardening: A narrative review, vignettes and implications for future research. Urban For. Urban Green 2023;87:128062.
12. Tomic-Obrdalj H, Keser I, Ranilovic J, Palfi M, Gajari D, Cvetkovic T. The use of herbs and spices in sodium-reduced meals enhances saltiness and is highly accepted by the elderly. Food Qual Pref 2023;105:104789.
13. National Institutes of Health. Garlic. NCCIH 2020; https://www.nccih.nih.gov/health/garlic#
14. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition. https://www.dietaryguidelines.gov/resources/2020-2025-dietary-guidelines-online-materials
15. U.S. Food and Drug Administration. What’s New in Dietary Supplements. 2024; https://www.fda.gov/food/dietary-supplements/whats-new-dietary-supplements