Are all sugars equal? Role of the food source in physiological responses to sugars with an emphasis on fruit and fruit juice

Abstract

High (free) sugar intakes can increase self-reported energy intake and are associated with unfavourable cardiometabolic health. However, sugar source may modulate the effects of sugars due to several mechanisms including the food matrix. The aim of this review was to assess the current state of evidence in relation to food source effects on the physiological responses to dietary sugars in humans relevant to cardiometabolic health. An additional aim was to review potential mechanisms by which food sources may influence such responses. Evidence from meta-analyses of controlled intervention trials was used to establish the balance of evidence relating to the addition of sugars to the diet from sugar-sweetened beverages, fruit juice, honey and whole fruit on cardiometabolic outcomes. Subsequently, studies which have directly compared whole fruit with fruit juices, or variants of fruit juices, were discussed. In summary, the sources of sugars can impact physiological responses, with differences in glycaemic control, blood pressure, inflammation, and acute appetite. Longer-term effects and mechanisms require further work, but initial evidence implicates physical structure, energy density, fibre, potassium and polyphenol content, as explanations for some of the observed responses.

Keywords: Food matrix; Glycaemia; Health; Metabolism; Sugars.

Fig. 1

Contribution of different food physical structures to free sugar intakes in UK adults, and the associations between physical structure of free sugars and mortality. Data in panel A are from the National Diet and Nutrition Survey Panel [1] and in panels B and C, from Kaiser et al. [2]

Fig. 2

Effects of experimental addition and/or substitution of various sugar sources into the diet on fasting glucose concentrations, glycated haemoglobin (HbA_1c) and fasting insulin concentrations. Data are mean differences ± 95%CI redrawn from Ahmed et al. for honey [15] and Choo et al. for all other food sources [16]. SSB, sugar-sweetened beverages. Fructose-containing sugar doses in Choo et al. was a median of 15% energy intake for 4.5 weeks in substitution trials, and 12.2% energy intake for 6 weeks in addition trials. Honey doses in Ahmed et al. were at a median of 40 g of honey for 8 weeks

Fig. 3

Effects of experimental addition and/or substitution of various sugar sources into the diet on circulating inflammatory marker concentrations. Data are mean differences ± 95%CI redrawn from Ahmed et al. for honey [15] and Qi et al. for other food sources [22]. SSB, sugar-sweetened beverages. Fructose-containing sugar doses in Choo et al. was a median of 9% energy intake for 6 weeks in substitution trials, and 8% energy intake for 5 weeks in addition trials. Honey doses in Ahmed et al. were at a median of 40 g of honey for 8 weeks

Fig. 4

Effects of experimental addition and/or substitution of various sugar sources into the diet on systolic blood pressure, diastolic blood pressure and body mass. Data redrawn from Ahmed et al. for all outcomes with honey [15], Qi et al. for blood pressure outcomes with other food sources [25], and Chiavaroli et al. for body mass with other food sources [26]

Fig. 5

Changes in glucose incremental area under the curve (iAUC) and estimated average glucose concentration (eAG) with acute and longer-term addition of catalytic doses of fructose to the diet (fructose addition vs. non-fructose containing comparator). Data are mean differences and 95%CI from Moore et al., [86] Moore et al. [87] and Sievenpiper et al. [93] HbA1c (%) was converted to estimated average glucose (mmol/L) as per Nathan et al. [94]

Fig. 6

An overview of the differences between important sugar sources in nutrient composition and physiological responses when these are either added as excess energy to the diet (A), substituted for other energy sources (S) or added and substituted (A + S) to the diet