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Glycaemic and insulinaemic properties of some German honey varieties

Abstract

The glycaemic and insulinaemic response to different German honey varieties have not been studied so far. Eight German honey grades differing in their floral source and carbohydrate composition were tested. Isoglucidic test meals (25 g carbohydrate) and a 25 g glucose reference were given to 10 clinically and metabolically healthy, fasting individuals (31.5±8.1 years of age (mean±s.d.), two women). Glycaemic and insulinaemic index were calculated by the recommended FAO/WHO measure. Five of the eight tested honey varieties show a low glycaemic index below 55; for six of the eight tested varieties, the glycaemic load was lower than 10 (portion size of 20 g honey). Glycaemic index and insulinaemic index correlated significantly with the fructose content of honey varieties. The results show that glycaemic index and insulinaemic response depend on the fructose content of honey. Therefore, specific honey varieties may be recommended for subjects with impaired glucose tolerance instead of saccharose in food preparations.

Main

Postprandial glycaemic response has basic relevance to chronic diseases that are associated with hyperinsulinaemia and central obesity (1998). Glycaemic index (GI) is a standardized measure recommended by FAO/WHO to classify the blood glucose response after intake of carbohydrates. As a composite biological carbohydrate, honey is regularly used as a natural sweetener and as a traditional medicinal agent. Honey grades vary in their glycaemic response and some honey varieties have a low GI (Bogdanov et al., 2008). It has been suggested that floral sources of honey and the fructose-to-glucose ratio are responsible for the difference in glycaemic response. However, insufficient data are available for honey varieties, particularly for German products. In addition, the mechanism explaining the low GI response to some honey species is still unknown (Ischayek and Kern, 2006). The aim of this study was to determine whether the GI and insulinaemic responses of eight varieties of German honey differ in their floral source and carbohydrate composition.

Ten clinically and metabolically healthy, fasting individuals (two women, eight men; age 31.5±8.1 years) were each given isoglucidic (25 g carbohydrate) single servings of eight German honey varieties and a 25 g glucose reference within a 2-week period. Each test was performed at OGTT conditions (8.00–10.00 a.m.) in identical subjects. Capillary blood glucose and plasma insulin were measured through finger-prick samples before (0 min) and at 15, 30, 45, 60, 90 and 120 min after the consumption of each test honey by clinically routine micromethods. Glucose was determined by an enzymatic (Glucoseoxidase) amperometric method (EBIO plus, Eppendorf/EKF, D-39179 Magedburg) immediately after sampling. The GI and insulinaemic index (II) of each test food were calculated geometrically by expressing the incremental area under the blood glucose and plasma insulin response curve (IAUC), respectively, of each test food as a percentage of each individual's IAUC for the 25 g glucose reference. In addition, glucose load was calculated as the product of the test food's GI and the amount of available carbohydrate in a reference serving size of a 20 g honey portion.

The honey samples tested were provided by the ‘German beekeeper association’ (Deutscher Imkerbund e.V.), Wachtberg, Germany. Food chemistry analyses were performed by the ‘LAVES-Institut für Bienenkunde’, Celle, Germany. Written informed consent was obtained from all individuals participating in the study. The study protocol was approved by the local ethical committee. For statistical analyses, SPSS software (version 14.0) was used.

The composition of the honey varieties tested is given in Table 1. Owing to a variation in the fructose and glucose content, there is a broadly divergent fructose–glucose ratio as well. The greatest variation in the carbohydrates analysed can be declared in the melezitose content; in contrast to all other varieties, forest honey shows a significantly higher melezitose content (10 g/100 g honey). Five of the eight tested honey varieties show a low GI below 55. Only for forest honey is a high GI above 70 determined. For six of the eight tested varieties, the glycaemic load is lower than 10 (portion size of 20 g honey).

Table 1 Composition and properties of the honey varieties examineda

The changes in glucose and insulin levels in response to glucose control, as well as the response to the two honey species with the lowest (linden flower honey, heated) and highest (forest honey) GI and II values, are shown in Figure 1a and b. GI values differ at a range of 80% and II values differ at a range of 29% in the honey varieties examined. There is no statistically significant correlation between GI and II values. In addition, the insulin–glucose ratios do not show a fixed value, but vary at a range of 73%.

Figure 1
figure1

Change in glucose (a) and insulin (b) levels of two honey species (linden flower honey, heated; lowest GI value of the samples tested; forest honey; highest GI value of the samples tested) compared with glucose control. Glucose (mg/100 ml) and insulin (pmol/l) values are given as differences vs 0-min values.

When the carbohydrate contents of the different honey varieties are correlated with glycaemic and insulinaemic properties, significant correlations can be established between GI and II and the fructose content of the honey varieties: r(GI/fructose) −0.851, P=0.007; r(II/fructose) −0.810, P=0.015 (Figure 2). The melezitose content in forest honey is responsible for the high GI value in this honey species (P=0.001). The fructose–glucose ratio, as well as all the carbohydrates listed and the sum of carbohydrates, does not significantly influence the GI and II characteristics of the honey varieties.

Figure 2
figure2

Correlation between fructose content and GI in the eight honey varieties tested.

Honey can be defined as a carbohydrate-rich food, and the main content of honey, approximately 80% of its mass, consists of carbohydrates, particularly fructose and glucose. However, recently published research has suggested that floral sources of the honey species may influence GI and that some honey varieties show a lower GI than do others (Samanta et al., 1985; Foster-Powell et al., 2002; Henry et al., 2005; Ischayek and Kern, 2006).

When the sugar profile and the fructose–glucose ratio of the honey species tested in this study were compared, variable fructose content and a broadly divergent fructose–glucose ratio were found. Fructose content varies within a range of 43.5%, leading to a fructose–glucose ratio from 0.97 to 1.62. In comparison with data regarding US honey varieties showing fructose contents within a range between 34.8 and 39.8% and fructose–glucose ratios within a range between 1.03 and 1.12, our results show that sugar profile in the tested German honey species clearly differ from US data (Ischayek and Kern, 2006). This may be the reason for the finding that, in contrast to other published data with regard to glycaemic indexes in honey species, most of the honey varieties tested in this study—except for forest honey with a high GI of 88.6—showed a favourable GI lower than 55.

It has been suggested that the respective GI and the corresponding fructose–glucose ratio are negatively correlated and that the GI of honey varieties is decreased with an increased fructose–glucose ratio. In our study, the fructose content rather than the fructose–glucose ratio was significantly correlated to the GI response. In addition, the high melezitose content in the forest honey tested was significantly responsible for its high GI value as well. However, neither the relative carbohydrate content nor any carbohydrate species other than fructose and melezitose showed a relevant influence on the glycaemic and insulinaemic response in the honeys investigated. Comparable with observations in other carbohydrate-rich foods, the corresponding glucose and insulin response did not show a significant intercorrelation. In the honeys tested, the insulinaemic response calculated as II could not be predicted by glycaemic response. Nevertheless, the insulin increase after honey intake generally did not reach the amount of the control curve after glucose ingestion, but varied at a clearly smaller range, approximately 55% of the control response.

The results impressively document favourable glycaemic as well as insulinaemic characteristics after consumption of the honey varieties tested. With regard to the low GI values in most of the honey species, these honey varieties may be recommended for individuals with impaired glucose tolerance or insulin resistance instead of saccharose in meals, particularly breakfast preparations (Wolever and Mehling, 2003; Galgani et al., 2006; Wolever et al., 2006). This information may be useful for predicting the glycaemic effects of composite breakfast meals and for improving the postprandial metabolic response as well as appetite regulation (Flint et al., 2006).

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Acknowledgements

The honey samples tested were provided by the ‘German beekeeper association’ (Deutscher Imkerbund e.V.), Wachtberg, Germany. Food chemistry analyses of the honey varieties tested were performed by the ‘LAVES-Institut für Bienenkunde’, Celle, Germany.

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Deibert, P., König, D., Kloock, B. et al. Glycaemic and insulinaemic properties of some German honey varieties. Eur J Clin Nutr 64, 762–764 (2010). https://doi.org/10.1038/ejcn.2009.103

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Keywords

  • honey
  • glycaemic index
  • homa index
  • insulin response

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