James Suckling, Research Fellow, Centre for Environment and Sustainability & Institute for Sustainability, University of Surrey (UK)

SWEET has been exploring the ramifications of replacing added sugar with sweeteners and sweetness enhancers (S&SE) from multiple perspectives. One of these is the sustainability ramifications of that replacement. An early finding of the project was that there were very few sustainability studies of sweeteners and no studies at all of sweetness enhancers! So, our first task was to fill this gap with our own studies.

Environmental life cycle assessments (LCAs) are an important part of understanding sustainability. During SWEET we studied four sweeteners (stevia Rebaudioside A, sucralose, aspartame and neotame), and one sweetness enhancer (thaumatin). The links are to previous blogs. We have been very fortunate to have a flurry of studies published throughout 2023, and the links are at the bottom of this blog. However, the nature of scientific publication means that the studies have all been focused on each single ingredient. It would be illuminating to take a step back and look at the broader picture: what do the studies tell us about S&SEs collectively?

The group of S&SE we have here are not exhaustive, but they do offer an insight into different types of ingredient: stevia Reb A and thaumatin are plant-based; aspartame and neotame are artificial; and sucralose is part plant-based, being a modification of sugar produced from sugarcane, or sugar beet. The comparisons shown here are to sugar on a sweetness equivalence basis. Why is this important? Sweeteners never replace sugar on a like-for-like weight basis. Because they are much sweeter than sugar, a small mass of sweetener can replace a much larger amount of sugar. To give an idea, stevia Reb A is about 250-time sweeter than sugar, aspartame 200-times, sucralose 600-times and neotame a huge 8000-times sweeter! This means that for neotame, in theory, 0.125 g can replace 1 kg of sugar.

Figure 1 shows the sweeteners compared to sugar on a sweetness equivalence basis. Five impact categories are shown, by way of example, out of the sixteen reported in the studies. In each category the impact of the sweetener is normalised to that of sugar: i.e., less than 1 means lower impact, greater than 1 means higher impact. Global warming, land use, water consumption are perhaps the most widely recognised. Marine eutrophication is a measure of fertiliser run-off from agricultural processes, and the potential for that to cause issues such as algal blooms. Stratospheric ozone depletion is a measure of emission of gases which contribute to effect such as the ozone hole over the Antarctic. Across all of these impact categories, the sweeteners have a markedly reduced impact compared to sugar. In fact, across all of the 16 impact categories reported in the studies, in only 1 instance was impact thought to be higher. This was for sucralose in the category called ‘mineral resource scarcity’. And that was considered due to an estimate made during the ‘baseline’ study. Further analysis of the estimate showed that the impact of sucralose might also be lower.

Figure 1: comparison of sugar to sweeteners on a sweetness equivalence basis.

Figure 1: comparison of sugar to sweeteners on a sweetness equivalence basis.

For thaumatin, the sweetening mechanism is slightly different. It acts as a sweetness enhancer, meaning that it can be added to sugar, making the sugar taste sweeter. This means that a smaller amount of sugar can be used without loss of sweet taste. Therefore, in the second graph, the comparison is for 800 grams of sugar mixed with 0.4 mg thaumatin, to the 1 kg of sugar that they can replace. The graph shown that across all impact categories, environmental impact is reduced. Interestingly, it is reduced to about 80% of the original 1 kg sugar, which is the fraction of 800 g in 1 kg. In essence, this means that thaumatin barely contributes any impact when increasing sweetness of sugar. This result was again seen across all 16 impact categories reported in the study.
Figure 1: comparison of sugar to sweeteners on a sweetness equivalence basis.

Figure 2: comparison of sugar to thaumatin on a sweetness equivalence basis.

These findings show that all the S&SE we studied can, in almost every impact category, reduce the environmental impact when replacing the sweet taste of sugar. This is a very positive finding, because, at a basic level, replacing sugar’s sweet taste is not deemed to cause unintended consequences for the environment. Moreover, the choice of S&SE does not affect the result, meaning that an individual S&SEs sustainability need not be a factor in decision making regarding which one to use. For drinks this means that there is great opportunity to replace sugar and reduce environmental impact.

Is this the whole picture for sugar replacement? Not entirely. It is not always possible to replace a bulk quantity of sugar with a tiny amount of sweetener. For instance, sugar plays an important technical function in formulations such as cakes or biscuits, such as mouth feel or hydroscopic control. Just taking sugar out, and not replacing those bulk technical functions, will result in a rather unpleasant cake! Therefore, we still need to understand the ramification of replacing sugar in solid formulations. Work in this area is on-going, and we hope to be able to report on that soon, too.