Anti-Microbial Effects of Artificial Sweeteners in Humans - 2/3rds of a Can of Diet Coke May Have a Sign. Effect on the Gut Microbiome, but the Relevance is Questionable
|2/3 of this can may suffice to make a difference. Whether this difference is (a) relevant or (b) irrelevant is yet as questionable as whether the changes the scientists observed will (i) have a negative (ii) a positive or (iii) no effect.
The one thing about the myth of the bad sweetener that has yet not been completely debunked, though, revolves around their negative effects on the human gut microbiome.
You will remember from my previous post on this topic that - as (unfortunately) usual - all empirically valid data we have is based on rodent trials. In our mammalian cousins, the consumption of artificially sweetened products on top of an obesogenic diet has in fact been shown to have an additional effect on the modulation of the gut bacteria that appears to make turn an already "bad" diet into a nightmare (learn more). It is yet still very questionable, which part of the research can be translated to humans and to which subgroup of the population this would apply. Even if we assume a 1:1 translation from rodent to human, we would after all have to exclude most of you, because none of you will be consuming a hypercaloric, hyper-processed high fat + high carbohydrate diet (at least that's what I'd hope).
If we trust the results of a soon-to-be-published observational study from the George Mason University, though, our gut microbiomes could be in danger - although no one knows for sure.
|Sweeteners, pre- and probiotics are not the only foods / supplements that can have a major impact on the bacterial ecosystem in your gut. Only recently scientists have found that the ergogenic effects of glutamine may also be mediated by the gut | more
Even if the good guys are unconditionally good, the ambiguous results of pertinent research clearly indicates that this doesn't imply that all of use will benefit from exogenous provisions of bacteria. There are for example both positive and negative associations for certain strains of bifidobacterium or lactobacillus species (Million. 2011), so that supplementation is mostly based on guessing which are good based on individual studies. This is also why I personally believe that tweaking the environment and thus steering the gut microbiome into the right direction with prebiotics, is a more viable and promising strategy than the ingestion of bazillions of preformed bacteria aka probiotics.
To predict some of the consequences of possible difference in the bacterial make-up Frankenfeld et al. applied a phylogenetic investigation of the communities by reconstruction of unobserved states (PICRUSt) in order to predict mean relative abundance of gene function.
|Table 1: There were no sign. differences in BMI, energy intake, total carbohydrate and added sugar intake or the "quality" of the diet (as assessed on the Healthy Eating Index) between AS consumers and non-consumers (Frankenfeld. 2015)
|Don't be a fool, stevia will mess with your microbiome just like if not even more than "unnatural" sweeteners.
I just want you to know that stevia is not the "healthy alternative", just because it's "natural". In fact, for stevia we even know that it will kill lactobacilli, i.e. those bacteria of which we think that they are the good guys (learn more about how stevia messes with the gut micriobome).
- Bacteriodetes and Firmicutes had the highest median abundances and together accounted for the majority of the bacterial class representation in all individuals.
- The median Bacteriodetes:Firmcutes ratio did not significantly differ across aspartame non-consumers (0.96, range: 0.15-2.97) and consumers (1.08, range: 0.69-1.87), (median test p-value=0.60).
- There was no overall visual clustering of individuals by acesulfame-K consumption .
- Overall bacterial diversity evaluated with UniFrac analysis was different across consumers and non-consumers, but there were no significant differences in relative abundance of gene function across consumers and non-consumers (Figure 3).
- There were no observable difference in the three individuals who consumed both aspartame and acesulfame-K (Supplemental Figure 1).
|Figure 1: Yes, there were differences in the bacterial make-up of the gut microbiome of the four groups, but no one can tell you what these or the vast individual differences in the groups mean for your health (Frankenfeld. 2015) !
- the ratio of mostly "bad" gram-negative bacteriodetes and "good" gram positive bacteria remained the same - it's thus hard to argue that the subjects who consumed artificial sweeteners had an unhealthier gut microbiome
- there was no general reduction in gut bacteria, which would indicate a general anti-microbial effect of artificial sweeteners as it occurs with antibiotics - it's thus hard to argue that the anti-microbial effects (which don't exist) of artificial sweeteners would leave you similarly defenseless and open to colonization with "bad" bacteria as antibiotics.
- the gene essays say that despite the differences in the numbers of certain bacteria, the gene expression is the same - it's thus hard to argue that there was an epigenetic effect of artificial sweeteners that precipitates us to obesity or even makes us sick / diabetic / whatever
Against that background, there may be an urgent need for future research and technological development that would allow us to go beyond observing changes in the number and ratio of largely unknown gut bacteria that are (as of now) completely meaningless for us.
- Daly, Kristian, et al. "Dietary supplementation with lactose or artificial sweetener enhances swine gut Lactobacillus population abundance." British Journal of Nutrition 111.S1 (2014): S30-S35.
- Frankenfeld, Cara L., et al. "High-intensity sweetener consumption and gut microbiome content and predicted gene function in a cross-sectional study of adults in the United States." Annals of Epidemiology (2015).
- Langille, Morgan GI, et al. "Predictive functional profiling of microbial communities using 16S rRNA marker gene sequences." Nature biotechnology 31.9 (2013): 814-821.
- Million, M., et al. "Obesity-associated gut microbiota is enriched in Lactobacillus reuteri and depleted in Bifidobacterium animalis and Methanobrevibacter smithii." International journal of obesity 36.6 (2012): 817-825.