Continuing on from our last topic on gluten, I thought it would be good to look at an area that is a perfect example of the issues that surround observational studies: artificial sweeteners!
The myth that artificial sweeteners are bad for your health probably comes from aspartame scares and conspiracy theories from the U.S in the 1970s-80s. In terms of weight gain and type 2 diabetes, they are linked with this due to observational studies – which observe the association between sweetener usage and higher BMI (body mass index). There is also a common theme of fear surrounding the unnatural nature of laboratory produced sweeteners.
But what does the science say? Here you will see the conflicting outcomes:
“There was no consistent evidence that intense sweeteners cause insulin release or lower blood sugar in normal subject” Renwick & Molinary et al. (2010)
“At least daily consumption of diet soda was associated with a 36% greater relative risk of incident metabolic syndrome and a 67% greater relative risk of incident type 2 diabetes compared with non-consumption” Nettleton et al. (2009)
These two studies are good examples of where the confusion may lie – the former statement is from a review of extensive in vivo (people) studies that show there is no effect of sweeteners on insulin release, whilst the second, observational study highlights that people who are daily consumers of diet drinks have insulin related issues such as metabolic syndrome (a precursor stage to type 2 diabetes) and type 2 diabetes.
What is going on here? The answer is, people with higher BMI and subsequent metabolic issues are using diet versions of drinks in order to lose weight – and it is purely the association of the prevalence of their use that is clouding the outcome.
How effective are diet drinks for weight loss?
A meta-analysis of 15 randomized control trials showed switching to diet versions resulted in “significant reductions in all outcomes examined”, which included BMI, fat mass and waist circumference. Miller & Perez et al. (2014)
Another meta-analyses on all studies that involved substituting sucrose (table sugar) for aspartame (a low calorie sweetener) showed that “using foods and drinks sweetened with aspartame instead of those sweetened with sucrose is an effective way to maintain and lose weight without reducing the palatability of the diet” De la Hunty et al. (2006)
The outcomes are conclusive for weight loss – switching all your intake to diet versions is an effective way to lose weight, and is probably the easiest thing to do to help you lose weight if you do have regular non-diet, high calorie drinks in your diet.