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Garlic and Other Alliums: The Lore and the Science

Garlic and Other Alliums: The Lore and the Science by Eric Block. Cambridge, UK: Royal Society of Chemistry Publishing, 2010. Hardcover; 474 pages. ISBN: 978-0854041909. $49.95. Available in ABC's online catalog #577.

Probably every adult on earth is familiar with the unique sulfur-related flavors and scents of garlic (Allium sativum, Alliaceae) and onions (A. cepa,). Millions also associate garlic with some type of health benefit, often handed down from grandparents. A major purpose of this book is, as succinctly stated in the subtitle, to help the reader understand the history and multi-cultured background of the lore and how the lore has been supported or not supported by modern scientific investigation.

The author has done an excellent job of fulfilling this purpose. There is certainly not a more skilled person to handle this task than Professor Eric Block, who has spent about 40 years studying and deciphering the complex chemistry of sulfur compounds associated with the Allium plants and the types of transformation compounds found in kitchen preparations of garlic and onions. In his extensive travels, he has studied and photographed how the Alliums are used and revered worldwide. This experience and his interest in history have resulted in many unique and very interesting features not expected in a strictly scientific book, such as Alliums in art (see especially Appendix 2), literature, and architecture, and uses as herbicides and pesticides.

Although the book goes into great and important detail describing the chemistry of Allium-derived sulfur compounds, every attempt is made to explain things in a manner that can be understood by non-professionals. Marvelous parallels and deviations are described between the sulfur chemistry of garlic and onions, highlighting the important differences that occur between 2-propenyl and 1-propenyl compounds and the critical importance of the unique Allium enzymes, alliinase and lachrymatory factor synthetase. The author also describes several new mass spectral methods that have allowed the identification of short-lived sulfur compounds and proof of mechanistic pathways. The history of the discovery of garlic’s sulfur compounds is well described and includes unique photos of several of the early (pre1950) founding scientists. Appendix 1 contains an extensive table of the cysteine sulfoxides (flavor precursors) content of 39 Allium species.

While the author has had limited experience in conducting clinical trials, he has done an admirable job of critically reviewing the evidence and the meta-analyses on clinical trials of garlic supplements for cardiovascular effects and epidemiological studies on the possible anticancer associations. He is thorough in listing and describing worldwide expert panel reviews on the possible health benefits of garlic, such as those by the National Center for Complementary and Alternative Medicine (NCCAM) at the US National Institutes of Health, Health Canada, The European Scientific Cooperative for Phytotherapy (ESCOP), and the World Health Organization (WHO). The author describes the levels of evidence that are used to assess human health benefits and the elements that should be part of any high-quality randomized clinical trial. Because garlic has been used for centuries for what we now would call its antimicrobial effects, the author provides an extensive table in Appendix 1 on the in vitro antimicrobial activity of allicin, ajoene, and the allicinderived allyl sulfides on 41 different bacteria, fungi, and protozoa. He also expounds upon the adverse effects that some Allium compounds (thiosulfinates) can cause, with alarming photos of topical (skin) garlic burns that can occur when too much fresh garlic is applied for too long.

Garlic: The Science and Therapeutic Application of Allium sativum L. and Related Species, the first scientific book in English on the chemistry and possible health effects of garlic, was published in 1996 by Williams & Wilkins (and was co-edited by this reviewer). With 2,500 references, that book represents an exhaustive review of the scientific literature on garlic to that date. The 2010 book by Block, with its 1,100 references, is the second most extensive scientific book on the chemistry and medicinal studies on garlic. It provides, among many other unique features, important updating of the chemistry and health studies that have been conducted in the intervening 14 years. When the 1996 book was written, numerous clinical trials on the cardiovascular effects of garlic products had shown more positive effects than the also numerous trials that have been conducted since then, probably due to inferior quality in the conduct of the earlier trials. Hence, Block’s book summarizes and emphasizes the serious doubts that exist about the effects of garlic on serum cholesterol and platelet aggregation, although the effects on lowering blood pressure among hypertensive individuals has been supported by two recent meta-analyses. Thus, Block’s book is an important and complementary reference work to the aforementioned 1996 publication. Non-scientists should find much of the book to be most interesting, while anyone with a serious interest in the chemistry and possible health benefits of the Alliums will find the book to be essential reading.

— Larry D. Lawson, PhD Research Director, Silliker, Inc, Utah Laboratory Orem, UT