The standard book of Barnes et al. published in 2007 on herbal medicines broadly discusses the family speciesRocoe (Zingiberaceae) under the heading of ginger, representing edible plants similar to shell ginger (), which is not explicitly mentioned [ 70 ]. As outlined, ginger is listed by the Council of Europe as a natural source of food flavouring with the category N2, which indicates that ginger can be added to foodstuffs in small quantities, with a possible limitation of a yet unspecified active principle in the final product. Used widely in food as spice, ginger has been listed as generally recognized as safe (GRAS), but some warnings and contraindications have also been added [ 70 ]. Whether these limitations apply to shell ginger has not yet been determined. However, good safety news with respect to the overall Okinawa diet can be derived from serum laboratory data of liver tests with normal values of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) from supercentenarians in Okinawa [ 71 ]. Nevertheless, the efficacy and safety issues of shell ginger, and its relation to longevity in Okinawa are still a puzzle with pieces that have to be put together by additional research.

This present paper will help in the development of herbal drugs with A. zerumbet as ingredient, marketed under strict regulatory guidance. Since this plant has a long history of safe use as traditional medicine, timely regulatory approval should be received, provided clinical studies confirm its efficacy and lack of adverse effects. Less desirable is the manufacture of A. zerumbet in herbal dietary supplements with a much lower level of regulatory marketing restriction, insufficient to ensure consumer safety. An internet search specified a single marketed herbal dietary supplement with A. zerumbet as ingredient manufactured from its leaves, with a proposed daily usage of two capsules containing 250 mg each. However, additional data in publications of peer reviewed journals are not available, especially regarding efficacy, adverse effects, and contraindications; its use is therefore limited and presently not encouraged.

Shell ginger, as described for culinary use in connection with food or beverages, is better classified as A. zerumbet for botanical purposes to clearly identify the plant, differentiating it from common ginger in the English language, which is the botanical Zingiber officinale used as ginger for ginger ice cream, ginger bread, ginger beverages, ginger beer, or ginger ale in many countries. Shell ginger is an exceptional multi-targeted plant for human use, considering various organs, diseases, and mechanistic actions. As it presently stands, the plant’s potential for human life is likely underestimated. The large number of highly qualified agricultural, analytical, chemical, and epidemiological studies on A. zerumbet and longevity in Okinawa is amazing and qualifies this topic as an important one. Many positive effects have been described for A. zerumbet , using experimental models that may or may not be transferrable to human conditions. Under these aspects and to err on the side of caution, it would be premature to classify Alpinia zerumbet as a hidden champion of preventive or therapeutic measures, although the chances are excellent, if additional compelling evidence is provided, that shell ginger is indeed a major contributor towards longevity in Okinawa.

9.2. Future Research

Camelia sinensis (L.) Kuntze) extracts or the chemical drug orlistat are on the market but there are conflicts with respect to potential hepatotoxicity. Also not specifically considered are chemicals and plants such as grape resveratrol, polyphenols from blueberries, phenolic antioxidants from spinach, epicatechin from green tea, and ginkgo ( Ginkgo biloba L.), all with life-expanding effects on C. elegans [ The key question will be whether shell ginger can be introduced as drug to aid body weight loss or prevent body weight gain. For these indications and outside the focus of the present report, other herbs such as green tea ((L.) Kuntze) extracts or the chemical drug orlistat are on the market but there are conflicts with respect to potential hepatotoxicity. Also not specifically considered are chemicals and plants such as grape resveratrol, polyphenols from blueberries, phenolic antioxidants from spinach, epicatechin from green tea, and ginkgo (L.), all with life-expanding effects on 20 ].

With respect to A. zerumbet and longevity in Okinawa, the pioneering work at Ryukyus University of the Okinawa Islands has provided many interesting details. Future animal studies should now focus on the identification of those phytochemical(s) responsible for lifespan extension. For this research, suspected phytochemicals of Alpinia zerumbet should be isolated for studies using the C. elegans model. Experiments are encouraged for comparing lifespan extension by various plants of the Okinawa cuisine. However, since the potential efficacy is based likely on the joint actions of all phytochemicals of Alpinia zerumbet , the use of a single promising chemical in humans can be problematic. Likewise, efficacy of Alpinia zerumbet will probably be improved if used as an adjunct to the Okinawa diet or a food with similar components.

It will be the most important goal for future clinical and epidemiological investigations or new reviews to establish the exact ideal intake of shell ginger and eventually its bioactive compounds. Indeed, there is still some uncertainty from the published reports about the quantity of shell ginger (including plant parts) that the centenarians in Okinawa have actually used over their lifetimes. This question can easily be addressed by retrospective assessment of their food history with the help of expert dietitians and a special questionnaire. On this occasion, other plants with their special parts used by these individuals should also be identified and quantified. Answering all these questions will allow for recommendations that are more specific on how best to use these plants.