Sugar Alcohol Sweeteners as Alternatives to Sugar with Special Consideration of Xylitol

Introduction: Dental caries is a diet-associated disease which continues to be a serious health problem in most industrialized and developing countries. Strategies to maximize caries prevention should automatically consider the use of sugar substitutes. It is important that public health authorities are made cognizant of the availability of new polyol-type sugar substitutes. Review Summary: Clinical studies have shown that xylitol, a natural, physiologic sugar alcohol of the pentitol type, can be used as a safe and effective caries-limiting sweetener. Habitual use of xylitol-containing food and oral hygiene adjuvants has been shown to reduce the growth of dental plaque, to interfere with the growth of caries-associated bacteria, to decrease the incidence of dental caries, and to be associated with remineralization of caries lesions. Numerous public regulatory bodies have endorsed the use of xylitol as a caries-limiting agent. Other sugar alcohols that have been successfully used as sugar substitutes include D -glucitol (sorbitol), which, howReceived: June 10, 2010 Accepted: December 26, 2010 Prof. Kauko K. Mäkinen Institute of Dentistry, University of Turku Lemminkäisenkatu 2 FI–20520 Turku (Finland) Tel. +358 40 5561 063, E-Mail kauko.makinen @ uusikaupunki.fi © 2011 S. Karger AG, Basel 1011–7571/11/0204–0303$38.00/0 Accessible online at: www.karger.com/mpp Mäkinen Med Princ Pract 2011;20:303–320 304 that will assist in the reduction of dental caries. About 25 years ago, the 1986 Report of the Sugars Task Force published by the United States Food and Drug Administration (FDA) concluded that scientific evidence supports the conclusion that ‘current average 90th percentile level of sugar [of US population groups] contribute significantly to caries experience’ [1] . The report by the Task Force continued with the statement that ‘the consumption of sucrose and fermentable carbohydrates facilitates the development of plaque, dental caries, and periodontal disease’. The US Surgeon General’s Report on Nutrition and Health [2] in turn stated that of the 13 leading health problems, dental disorders ranked second in direct cost. A large number of authoritative reviews published before and after the FDA report have essentially reached similar conclusions. In spite of significant advances made in its prevention, dental caries is still alarmingly prevalent in most geographic locations, making this disease of great social, medical and economic importance. It is therefore necessary that public health policy concerning oral health allow the promotion and endorsement of food ingredients which can contribute to reducing the incidence of dental caries. Strict sugar restriction over an extended period will most likely lead to caries reduction. Additional dental benefits can be achieved if sugar is replaced with safe and non-cariogenic substitutes in confectioneries and related food products. The strategy of sugar substitution should thus be considered and recommended. The objective of this review is to summarize clinical caries trials carried out with common, simple dietary sugar substitutes, the sugar alcohols (polyols). In manufacturing and metabolic processes, these substances can be derived from their corresponding aldose sugars. Hence, such sugar alcohols can be called alditols. Since the majority of those trials have been carried out with xylitol and D -glucitol (sorbitol), the present treatise will focus on these sweeteners. Because xylitol has received the most attention during the past 40 years, special emphasis will be given to this sweetener. Xylitol is a pentitoltype molecule with special microbiologic and physicochemical properties that are assumed to contribute to caries prevention. D -Glucitol in turn is a hexitol-type bulk sweetener, its molecular structure resembling that of D -glucose. The purpose here is also to report on available public endorsement practices of xylitol-associated limitation of dental caries in various countries. Finally, a fourcarbon member of this homologous alditol series, erythritol, will be briefly discussed owing to its great potential as a future sugar substitute of the sugar alcohol nature. Erythritol has appeared in texts as meso -erythritol and i -erythritol, meso in this case standing for optical inactivity. Normally, erythritol can be used without a prefix. The simple ‘ladder’ structure formulas of these three alditols are shown in figure 1 . Discussion of other dietary alditols, such as D -mannitol, galactitol, the arabitols, D -ribitol, and disaccharide polyols, including palatinit, maltitol and lactitol, will be presented in another context. Palatinit is an equimolar mixture of D -glucopyranosyl-1,6sorbitol and D -glucopyranosyl-1,6D -mannitol, while maltitol and lactitol can be derived from maltose and lactose, respectively. Xylitol has gained broad success in biomedical and other applications. Therefore, it is appropriate to first provide a concise overview of the uses of xylitol. This will facilitate understanding the dental health-associated position, among other medical uses, of xylitol (and other alditols). Namely, the same physicochemical, biochemical and microbiologic profiles of xylitol will rule, regardless of the target tissues and therapeutic strategies involved. Consequently, excluding purely technochemical, pharmaceutical, cosmetic and related applications, several biomedical and nutritional uses and effects of xylitol investigated during the past 40 years are shown in table 1 . The versatility of xylitol becomes immediately obvious. Among the uses shown, dental caries will thus constitute the focus of this review. The present review was primarily designed for an audience that includes public health authorities, medical practitioners and other health care professionals who need to update their knowledge on sugar alcohol-type sugar substitutes. D -Glucitol, xylitol, and erythritol have been promoted within the dental and food sciences fields as safe and efficacious caries-limiting sugar substitutes that also exert other interesting pharmacologic effects. The Chemical Profile of Alditols The simple alditols are crystalline substances varying in taste from faintly sweet (galactitol) to very sweet (erythritol and xylitol, which are almost isosweet with sucrose). These molecules are characterized by the following common sugar alcohol properties: • Absence of a reducing carbonyl group. This makes the alditol molecules chemically somewhat less reactive than the corresponding aldoses and ketoses. Some alditols thus normally avoid those chemical reactions that make many dietary hexose-based sugars acidogenic and cariogenic in human dental plaque.