Evidence-based review for garlic and cancer in the perspective of food labeling

The need for evaluating health claims

The increasing amount of information available regarding the health benefits of foods has resulted in consumer interest in health issues. This information has become a leading factor in purchasing decisions. Therefore, labeling and advertising should not be misleading. The requirement to protect consumers and ensure their right to accurate information on food functionality has led to the introduction of regulations about health claims throughout the world. In the United States, health claims were first authorized by FDA after enactment of the Nutrition Labeling and Education Act of 19901. The Codex Committee on Nutrition and Foods for Special Dietary Uses recently made new guidelines on the scientific substantiation for health claims2. In Korea, the Health/Functional Food Act was signed into law in 2002 and a new regulatory framework for making health claims came into effect in 20043. In order to protect consumers from false or misleading claims, many countries have been using an evidencebased review system for evaluating health claims4.

Concerning the garlic

Garlic is widely consumed as spices in Korea and belongs to the vegetables of the Allium genus that is characterized by a high content of organosulfur compounds and flavonoids. A variety of components, including nonsulfur compounds, work synergistically to provide various health benefits5. The major compound known to contribute to the pharmacological effect is the sulfur-containing compounds, such as dially6. Currently, there is no claim about garlic intake and cancer risk reduction in the area of food labeling. Thus the scientific evidence for garlic intake with respect to the risk of different types of cancer was evaluated using the US FDA’s Evidence-Based Review System for the Scientific Evaluation of Health Claims7.

Garlic intake and cancer risk

There are numerous animal and in vitro studies that provide evidence for a relationship between garlic intake and risk reduction of cancers. Also, several studies have reported an inverse association in humans. Nineteen human studies were identified and reviewed for evaluating the strength of the evidence supporting the relationship between garlic intake and the risk reduction of different cancers, based on the perspective for food labeling. On the basis of this evidence-based review, it was concluded that there was no credible evidence to support a relationship between garlic intake and a reduced risk of gastric, breast, lung, or endometrial cancer. Very limited evidence was found to support a relationship between garlic consumption and reduced risk of colon, prostate, esophageal, larynx, oral, ovary, and/or renal cell cancers. There are several other reviews that evaluated the association between garlic intake and reduction of cancer risk. In 2000, the Agency for Health Research Quality (AHRQ) reported that intake of garlic supplement might be associated with decreased odds of multiple cancers; however, the ability to interpret existing data was substantively limited by marked variability in types of garlic preparations that have been studied and inadequate definition of active constituents in the various preparations8. Recently, the American Institute for Cancer Research (AICR) published their review on the relationship between food, nutrition, physical activity and the prevention of cancer9. According to their review, only colon cancer risk reduction may be associated with garlic consumption. These results are very similar to our conclusions. Garlic is generally used in small amounts for seasoning, thus it is very difficult to analyze the quantity of garlic consumption through the food frequency questionnaire. Moreover, there are too many variables that can affect the chemical composition, such as the preparation, from raw garlic or cooked to extracted products or whole garlic, and the conditions of cultivation. For these reasons, most systematic review results indicated that the effects of garlic are very limited in reducing the risk of cancer.

Further research are needed…

Considering the large base of basic research published until recently, garlic must have a lot of beneficial effects in human health. However, for delivering the information to the average consumer, more systematically designed research is needed. We anticipate that this research will enable the beneficial health effect of garlic to be further confirmed.

  1. US Public law. The nutrition labeling and education act of 1990, Pub. L. No. 101-535 (Nov. 1990).
  2. Codex Alimentarius Commission. Report of the 29th session of the codex committee on nutrition and food for special dietary uses. 2007. Internet: (accessed 11 March 2008).
  3. Kim JY, Kim DB, Lee HY. Regulations on health/functional foods in Korea. Toxicology 2006;221:112-8.
  4. US Food and Drug Administration. Qualified health claims. Internet: (accessed 11 March 2008).
  5. Amagase H. Clarifying the real bioactive constituents of garlic. J Nutr 2006;136:712S-25S.
  6. Milner JA. Preclinical perspectives on garlic and cancer. J Nutr 2006;136:827S-31S.
  7. Kim JY, Kwon O. Garlic intake and cancer risk: an analysis using the food and drug administration’s evidence-based review system for the scientific evaluation of health claims 2009:89:257-64.
  8. Mulrow C, Lawrence V, Ackerman R, et al. Effects on cardiovascular risks and disease, protective effects against cancer, and clinical adverse effects. Evidence Report/Technology Assessment. 20 (Prepared by San Antonio Evidence-based Practice Center under Contract No. 290-97-0012). Rockville, MD: Agency for Healthcare Research and Quality, 2000. (AHRQ Publication no. 01-E023).
  9. World Cancer Research Fund / American Institute for Cancer Research. Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective. Washington, DC: AICR, 2007.