When Science Stuffed Up: The Case Against Artificial Sweeteners
Peter sits in front of the television, guiltlessly sipping away at what will calculate to be 2 litres of diet soft drink over the course of the evening. He is happy because he has just finished logging his calories for the day, and is well under target. However, this happiness is fleeting, as tomorrow, despite restricting his caloric intake, Peter will once again weigh in heavier than the previous week. Peter’s story is one all too common in doctor’s and dietitian’s offices around Australia and the world. What is happening here? Why is it that diet soft drinks, despite having no calories and no sugar, do not aid weight loss? Once hailed a magical method for weight loss, epidemiological and experimental research is now demonstrating artificial sweeteners cause more harm than good. With recent calls for a sugar tax in Australia, it is high time we educate ourselves about artificial sweeteners, and their not so sweet health consequences.
Before we jump into this, it is important to first clarify that sweeteners are classified into two broad categories- nutritive and non-nutritive. Essentially, nutritive sweeteners contain sugar and provide energy (i.e. calories). Nutritive sweeteners are the common sweeteners like glucose, fructose, sucrose (table sugar) and corn-based sweeteners. They also include sugar alcohols like xylitol and sorbitol; which still contain calories but no sugar and do not contribute to dental decay (which is why you will find these sweeteners in toothpaste). Non-nutritive sweeteners (NNS), commonly known as artificial sweeteners, are high intensity sweeteners that are essentially calorie and sugar free. For your viewing pleasure, some of the common artificial sweeteners, their food code number, popular brand name/s and food sources are summarised below (please don’t sue Coca-Cola).
You may have noticed that stevia is classified as a non-nutritive artificial sweetener, and questioned my sanity. I can see the sassy girl emoji already, “ah stevia comes from a plant Danielle. Plants are natural.” Although stevia is a herb derivative commonly marketed as a natural product; it is still a calorie free, sugar free hyper intensive sweetener and therefore classed as such (take that sassy girl emoji).
Human research continues to associate artificial sweetener consumption with metabolic disorder and chronic disease; not with long-lasting weight loss. Several population-based studies link intake of diet soda (sweetened with NNS) with increased incidence of obesity and metabolic syndrome similar to, and sometimes greater than, the levels observed with sugar sweetened beverage intake.
A study published in The Journal of Circulation reported a positive relationship between diet soda consumption and metabolic syndrome, larger than that identified with consumption of regular soda. The authors explain “the similar metabolic hazard posed by both regular and diet soft drinks is noteworthy given the lack of calories in the latter.” In simple English, the authors are saying how super strange it is that drinking calorie and sugar free beverages provides a greater risk of disrupting your metabolism than sugar laden soft drink.
“The similar metabolic hazard posed by both regular and diet soft drinks is noteworthy given the lack of calories in the latter.”
Similar results linking consumption of artificial sweeteners to metabolic disease have been observed elsewhere. Of note is a prospective study published The Journal of Obesity. Researchers took normal weight or non-obese adults and tracked their dietary intake. At follow up 7 to 8 years later, they a found intake of more than 21 NNS beverages per week (diet soda, artificially sweetened tea and coffee) was associated with double the risk of obesity compared to non-users at follow up.
More recently, a large cohort study published in The American Journal of Clinical Nutrition, identified an association of both sugar-sweetened beverages and artificially-sweetened beverage consumption with increased risk of type 2 diabetes. The results are clearly, and concernedly, explained in the graph below.
Given the the difficulties in controlling food intake research, the extent to which artificial sweeteners induce metabolic disruption, weight gain and the development of chronic disease in humans is unclear (Is it just the artificial sweeteners? Are people already prone to metabolic dysfunction choosing artificial sweeteners?). What is clear however, is that artificial sweetened food and beverages are an ineffective method of long-term weight loss.
Mechanism of destruction action
Multiple hypotheses attempt to explain why artificial sweeteners do not aid weight loss. Research has suggested that artificial sweeteners may result in a desensitisation to sweetness, increased appetite, dysregulation of energy intake and an undesirable microbiome.
With artificial sweeteners hundreds to thousands of times sweeter than regular table sugar, it is logical that taste buds may become desensitised to sweetness. In a Harvard Health Letter, physician Dr. David Ludwig explains that for habitual consumers of artificial sweeteners “healthful satiating foods that are less sweet — such as fruits and vegetables — may become unappetizing by comparison.”
A study published in The Journal of Physiology & Behaviour, High-intensity Sweeteners and Energy Balance, investigated beyond the desensitisation of taste buds. The research team, lead by Susan Swithers (a professor in psychological sciences and behavioural neuroscientist), suggest the use of non-nutritive sweeteners results in taste no longer serving an accurate predictor of the nutritional content of food, which can lead to metabolic dysregulation. The researchers more eloquently explain;
“The dissociation between the sweet taste cues and the caloric consequences could lead to a decrease in the ability of sweet taste to evoke physiological responses that serve to regulate energy balance.”
To prove their hypothesis, a series of rodent experiments were conducted. With all other factors constant, these experiments demonstrated that, in contrast to glucose sweetened diets, the consumption of high-intensity sweeteners resulted in greater weight gain, greater accumulation of body fat, weakened caloric compensation, and decreased thermogenesis (the increased heat produced by the body after ingesting food). This research also investigated the reversibility of this metabolic damage, by switching rats trained with saccharin-sweetened diets to diets sweetened with glucose. Compared to unchanged controls (saccharin-saccharin, glucose-glucose), rats trained with artificially sweetened diets remained unable to lower their weight to the weight of glucose controls, even when consumption of artificial sweeteners ceased.
Emerging evidence suggests the counterintuitive links between artificial sweeteners may also be attributable to shifts caused to the gut bacteria- the magical microbiome. In a study entitled Artificial Sweeteners Induce Glucose Intolerance by Altering the Gut Microbiota, researchers were able to induce glucose intolerance by adding common artificial sweeteners to the drinking water of lean mice (shock twist with that title hey?). If you aren’t well versed in metabolic lingo, glucose intolerance is a pre-diabetic state of sugar malabsorption. Sequencing the microbial composition of saccharin-drinking mice showed a distinct bacterial composition associated with type 2 diabetes in humans. In order to prove saccharin consumption was the causal factor of metabolic dysfunction, the microbiome of saccharin-drinking mice was transplanted into germ free mice. The transplant of the saccharin altered microbiome into germ free mice also induced glucose intolerance.
But Stevia is different, right?
Although marketed as a natural product, stevia is a highly processed non-nutritive sweetener and limited available research raises concern that stevia may act in the same ways as other artificial sweeteners. The processing chain from Stevia Rebaudiana plant the to the commercialised sweetener is very long. In the aforementioned High-intensity Sweeteners and Energy Balance study, preliminary research on the effects of stevia was conducted. Results showed body weight gain was significantly greater in mice consuming either saccharin or stevia solutions compared to mice consuming glucose solutions.
The truth is there is currently not enough evidence for anybody to make a call whether Stevia is beneficial or detrimental to health. However, I do not want our national food supply to provide the testing ground.
I hope this article has provided insight into the health consequences of non-nutritive artificial sweeteners, including stevia, and done justice to the fascinating research emerging in this area. Understanding the physiological mechanisms by which artificial sweeteners fail to facilitate weight loss, brings us closer to providing answers to Peter and overcoming the obesity crisis. With the potential introduction of a sugar tax in Australia, the food industry will be tempted to use artificially sweeteners to create “sugar free” products. As consumers, it is important we need to know these foods are not healthy alternatives and communicate our food expectations with our dollar.
Originally published at The Isthmus.