Garlic (Allium sativum L.) has long been regarded as a healthy vegetable. It is a member of the Lily family (Liliaceae). For many ancient peoples it was both food and medicine. We know of Egyptians, Greeks, Romans, Chinese and Babylonians all using garlic and its extracts to treat a range of ailments. Garlic was used to treat wounds – a practice long followed into the Second World War. It has long been thought that the pungent component, allicin is the main compound responsible for many of its health benefits including lowering blood sugar levels. Garlic also contains other nutrients and vitamins: vitamins C and B6, selenium and manganese.
Garlic possesses antidiabetic, antihyperglycemic, cardioprotective, antihypertensive, antilipiperoxidative, antiviral, antilice, antifilarial, antiinflammatory, antioxidant, and antidyslipidemic activity (Badole et al., 2013).
Nutrition Facts (per 100g)
Dietary Fiber-2g 8% RDA
Protein-6.5g 13% RDA
Vitamin C-31mg 52% RDA
Thiamin-0.2mg 13% RDA
Riboflavin-0.1mg 6% RDA
Niacin-0.7mg 4% RDA
Vitamin B6-1.2mg 62% RDA
Pantothenic Acid 0.6mg 6% RDA
Calcium-180mg 18% RDA
Iron-1.7mg 9% RDA
Magnesium-25mg 6% RDA
Phosphorus-155mg 15% RDA
Potassium-400mg 11% RDA
Zinc-1.2mg 8% RDA
Copper-0.3mg 15% RDA
Manganese-1.7mg 84% RDA
Selenium-14.2mcg 20% RDA
Garlic extracts have been shown to have antidiabetic benefits especially in type-2 diabetes. In one rat study, an ethanolic extract was administered to either normal or rats treated with streptozotocin which made them diabetic (Eidi et al., 20
06). Levels of garlic extract given were varied between 0.1, 0.25 and 0.5 g/kg body wt. The extract was compared with an antidiabetic drug, glibenclamide (600 micrograms/kg) and the garlic was more effective. It appears an ethanolic extract is effective at reversing the effects of diabetes- certainly in rodents.
In terms of the mechanism, it is thought that in clinical studies, the components in garlic lower blood glucose levels by competing with sites for insulin in the liver (Badole et al., 2013). This leads to an increased production of insulin. It has been shown in research on both animals and humans that people eating garlic have ‘better control’ of their blood sugar levels and to be a therapy for treating diabetes. Whilst much of this benefit is ascribed to allicin, there are many sulphur-containing compounds which have a benefit.
Garlic And A Reduction In Cancer
Eating garlic is associated with a reduction in cancer risk although not all cancers. At the experimental cell level, extracts and individual components block the growth of experimentally induced tumours from various tissues – uterus (Hussain et al., 1990), colon, breast and skin (Milner, 1996; 2001).
Cholesterol Lowering Benefits
Modest reductions in total cholesterol levels were possible based on a study of 29 high-quality clinical studies which assessed performance on 1,794 subjects (Reinhart et al., 2009). Garlic was mainly consumed in the form of garlic powder in many of these studies.
One meta-analysis of 39 trials shows that garlic can also reduce total serum cholesterol levels and low-density lipoprotein cholesterol, especially in those with a high starting blood cholesterol content (above 200mg/dL). Garlic needs to be consumed for longer than 2 months for any modest benefit to be seen (Reid et al., 2013).
Amongst nutritionists, the jury is still out on whether garlic truly has a strong impact on reducing cardiovascular disease !
Whilst hypercholesterolemia is associated with an increased risk of heart disease, there are many other aspects which need to be tackled as part of a treatment to improve cardiovascular health.
Badole, S.L., Ghule, A.E., Wagh, N.K. (2013) Chapter 15 – Antidiabetic Activity of Allium Sativum. In: Bioactive Food as Dietary Interventions for Diabetes. pp. 157-161 https://doi.org/10.1016/B978-0-12-397153-1.00015-9
Eidi, A., Eidi, M., Esmaeili, E. (2006) Antidiabetic effect of garlic (Allium sativum L.) in normal and streptozotocin-induced diabetic rats. Phytomedicine 13 (9-10) pp. 624-629 https://doi.org/10.1016/j.phymed.2005.09.010
Essman, E.J. (1984) The Medical Uses of Herbs. Fitoterapia, 55 pp. 279–289
Hussain, S.P., Jannu, L.N. and Rao, A.R. (1990) Chemopreventive Action of Garlic on Methylcholanthrene-Induced Carcinogenis in the Uterine Cervix of Mice. Cancer Letter., 49 pp. 175–180
Milner, J.A. (1996) Garlic: Its Anticarcinogenic and Antitumorigenic Properties. Nutr. Rev., 54, A82–S86
Milner, J.A. (2001. A Historical Perspective on Garlic and Cancer. J. Nutr., 131: 1027S–1031S.
Rahman, M. S. (2007). Allicin and other functional active components in garlic: health benefits and bioavailability. International Journal of Food Properties, 10(2), pp. 245-268
Ried, K., Toben, C., & Fakler, P. (2013). Effect of garlic on serum lipids: an updated meta-analysis. Nutrition reviews, 71(5), pp.. 282-299 https://academic.oup.com/nutritionreviews/article-abstract/71/5/282/2460203
Reinhart, K. M., Talati, R., White, C. M., & Coleman, C. I. (2009). The impact of garlic on lipid parameters: a systematic review and meta-analysis. Nutrition Research Reviews, 22(1), pp. 39-48. https://www.cambridge.org/core/journals/nutrition-research-reviews/article/impact-of-garlic-on-lipid-parameters-a-systematic-review-and-metaanalysis/55EF1BC57199D56182B409857E599C3E
Sahebkar, A., Serban, C., Ursoniu, S., & Banach, M. (2016). Effect of garlic on plasma lipoprotein (a) concentrations: a systematic review and meta-analysis of randomized controlled clinical trials. Nutrition, 32(1), pp. 33-40. https://www.nutritionjrnl.com/article/S0899-9007(15)00279-8/fulltext