Aspartame update: “Diet” and regular soda equally raise insulin levels in saliva, study suggests

Although it is commonly believed that artificial sweeteners like aspartame do not raise insulin levels in the same way as sugar, a new clinical trial challenges this idea. International researchers found that salivary insulin levels increased one hour after consuming a soft drink, for both regular and diet drinks — sweetened with artificial sweeteners.

Insulin levels in saliva did not change after consuming test drinks — water or a drink with low sucrose content. Scientific research found a correlation between insulin levels in saliva and blood.

The researchers also detected aspartame in the saliva after consuming an artificially sweetened drink, with the most substantial outcomes for diet soft drinks.

“This is the first study that reports aspartame secretion in saliva,” the study’s authors reveal.

They explain that if sugar substitutes like aspartame are excreted in their unaltered form in saliva, this re-stimulates the taste buds and is swallowed again, “thus remaining longer in the digestive tract.”

According to the study, it has been suggested that as low- and no-calorie sweeteners bind to and stimulate sweet-tasting receptors, the “release of insulin might occur, which in turn could lower blood glucose levels and result in weight gain and increased appetite.” However, the authors note that current knowledge is inconclusive.

Study set-up 
The single-blind study, published in Food Research International, included 15 healthy participants who consumed a different drink for five days — a diet soft drink, a regular soft drink, water with sweeteners, a drink with low sucrose content (3.5 g) and water.

On each day, the researchers collected saliva before taking the drink and after test-drink intake at 15 min, 30 min, 60 min and 120 min intervals. They measured salivary aspartame, total protein, alpha-amylase — an enzyme that helps the body digest sugar — and insulin levels in the saliva.

Total protein and alpha-amylase levels did not change during the two-hour test time.

The study participants also evaluated whether they perceived a sweet or sour taste 30–120 min after consuming the drinks. This was reported most frequently (80%) after consuming artificially sweetened beverages — diet soft drinks and water with sweeteners.

Salivary insulin levels increased one hour after consuming a soft drink, for both regular and diet drinks.Effects on insulin and blood glucose 
The new study joins scientific literature on artificial sweeteners, with conflicting outcomes.

For example, last month, US-based researchers suggested that low- and no-calorie sweeteners, such as aspartame, support healthier eating habits by reducing sugar and calorie intake. After reviewing well-designed randomized controlled trials, the authors concluded in a whitepaper that the sweeteners “do not impact blood glucose and insulin levels.”

Although the whitepaper’s authors concede that reports challenge these claims, they assert that these are based on observational data.

Alternatively, the World Health Organization (WHO) concluded that non-sugar sweeteners do not have long-term benefits in reducing body weight. The agency cautioned that they may have undesirable effects, such as the risk of type 2 diabetes or cardiovascular disease. However, experts flagged scientific limitations of the review as many of the studies included in the WHO review were of low or very low certainty.

Meanwhile, a growing body of research is uncovering ways to reduce blood sugar spikes. Researchers in the Philippines discovered the genes responsible for low and ultra-low glycemic index in rice and formulated varieties that do not cause high insulin spikes.

At the upcoming Fi Europe trade show, start-up SolvEat will debut a botanical blend to maintain healthy blood sugar levels while following a regular diet.

Assessing aspartame’s safety 
As a rigorously researched ingredient in the food industry, the safety of aspartame has been re-evaluated several times.

Most recently, the WHO and FAO Joint Expert Committee on Food Additives (JECFA) reconfirmed the current acceptable daily intake level of aspartame through a risk assessment earlier this year.

This evaluation followed a classification of aspartame as “possibly carcinogenic to humans” by the International Agency for Research on Cancer (IARC).

Although IARC’s classification has a minimal immediate impact on companies using aspartame after JECFA’s review, experts note companies may gradually shift away from using the sweetener in the future as public scrutiny of its safety continues.

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