Are Sweeteners Safe?

Weight Gain

There is some evidence that the brain has a different response to sweeteners than sugar, increasing appetite for sweet foods. When fruit flies were given sweetener, in addition to their normal fruit fly diet, over a prolonged period of time they increased food and calorie intake (1). Although they didn’t observe any weight gain (yes they used tiny little fruit fly scales)! This increased food intake is thought to occur because the brain typically associates a sweet taste with an influx of calories. When the body doesn’t get those calories (like when you’re eating low calorie sweeteners) it can trigger a particular fasting response in the brain, upping appetite and the need for sugar! FYI, this theory would also apply to natural sweeteners.

And it is true that sweetened or ‘diet’ beverage consumption is higher in people who are over weight or obese (2). Although this does not mean that the sweetened drinks cause obesity, that would be a very simplistic conclusion to draw, it merely states that more overweight people are drinking diet sodas. This could be due to lots of different factors including this demographic being more likely to choose drinks marketed as ‘diet’.

In really good quality, well designed human studies, where more variables can be controlled (called randomised control trials, RCTs), there is a big lack of evidence for sweeteners causing weight gain. In fact in many trials, sweeteners have been found to help with weight loss (3).

Basically

It would appear that in humans, sweeteners have little effect on appetite and can promote weight loss if used as a tool to reduce calorie intake as part of a weight loss plan. Although, theoretically high intakes of sweetened food and drink over a prolonged period of time could promote cravings and an increase in food intake. Sweeteners' effect on body weight probably comes down to the context of its role in the overall diet.

Cancer

There has long been speculation that artificial sweeteners can cause cancer. This stems from one particular study in the 1970’s that found that bladder cancer increased in rats given saccharin. However, since then it has been highlighted that this was due to a rat specific problem in metabolising saccharin and therefore does not apply to humans. Other than this, there is a lack of evidence for sweeteners' involvement in cancer risk in rats (8) and in humans (9), including a review looking at almost 600,000 people (10). Cancer Research UK says “the best evidence shows that artificial sweeteners in our food and drink, like aspartame, do not increase the risk of cancer.”

Basically

Sweeteners have been linked to cancer in rodent models using extremely high doses however this does not seem to translate biologically to humans.

Which sweeteners to use and which avoid?

Aspartame

Aspartame may be linked to headaches in those predisposed to migraines, lower mood in those predisposed to depression and increased brain activity in children with epilepsy. Those with the rare metabolic disorder phenylketonuria (PKU) cannot metabolise an amino acid in aspartame. You should avoid aspartame if you belong to any of these groups.

Sucralose

Baking with sucralose is probably a bad idea, as the sucralose can react at high temperatures creating potentially carcinogenic compounds called chloropropanols. Sucralose may also alter the gut microbiome.

Saccharin

Saccharin may alter the gut microbiome.

Stevia

Stevia has been found to lower blood pressure in people with hypertension and lower blood sugar in people with diabetes. Stevia may alter the gut microbiome.

Erythritol

Erythritol has been linked to improved blood vessel health, but can cause gas and diarrhoea in large doses.

Xylitol

Xylitol has been linked to improved tooth health and reduced dental decay. It can cause gas and diarrhoea in large doses. It is also toxic to dogs.

Consistently eating large amounts of nutrient void, processed foods whether sweetened with sugar, artificial or natural sweeteners is probably not a good idea if it is creating persistent cravings or displacing healthy foods out of your diet. If you are avoiding nutrient dense foods regularly in favour of these nutrient void processed options, you should consider making some changes. Drink less sugar or sweetened beverages by choosing water or whole fruit smoothies, and reduce the amount of weight watchers/ diet snacks you eat by including more naturally occurring sweetness in fruit and yoghurt etc. Sweeteners, like sugar, and like anything in our diet, can have a detrimental effect if eaten to excess and if you develop an unhealthy habit around it. Sweetened food can be included in a diet as a sometimes food or drink ideally with the focus predominantly on nutritious, whole foods.

Basically

You are unlikely to reach the toxic consumption level for any of the sweeteners, however some sweeteners may have health concerns for particular individuals. Natural sweeteners seem to have less reported side effects. However, it is not a good idea to displace healthy, nutritious foods from your diet in favour of processed foods, whether it’s ‘diet’ or full sugar options.