black and white photo of opened soft drink cansShare on Pinterest
A recent study has found that both diet and regular soft drinks can increase salivary insulin levels. Image credit: zepp1969/Getty Images.
  • Some people swap out regular sweetened beverages for diet versions, but their long-term effects on health are unclear.
  • A recent study found that diet and regular soft drinks increased salivary insulin levels.
  • The results indicate the potential harm of too much consumption of diet and regular soft drinks. However, further research is needed in this area.

What people eat and drink affects many areas of life. Some people often try to reduce their intake of soda and other sugary beverages for health reasons.

Some also opt for drinking diet versions that use artificial sweeteners and have fewer calories. However, some of the effects of diet soft drinks are unclear.

A​ study now published in Food Research International compared how different beverages influenced salivary insulin levels.

The study found that both regular and diet soft drink intake resulted in higher salivary insulin levels. It also found that levels of the artificial sweetener aspartame in saliva were higher with the consumption of diet soft drinks.

This research further highlights some of the potential impacts of substituting regular soft drinks for diet. However, further research is required to understand the full effects and what this may mean for recommendations for artificial sweetener use.

Do diet sodas raise insulin levels?

T​his study was a single-blind study that included fifteen participants. Participants were healthy adults between 18 and 45 years, with no history of diabetes or abnormal blood sugar levels.

Researchers excluded certain participants based on factors that could influence saliva levels and taste perceptions. They wanted to look at how consuming certain beverages influenced four key elements:

  1. aspartame excretion in saliva — aspartame is a common artificial sweetener
  2. salivary insulin levels — insulin is a hormone that allows the body’s cells to use glucose for energy; problems with insulin levels and the body’s response to insulin can lead to diabetes
  3. total protein (TP)
  4. alpha-amylase (AMI) — this enzyme helps the body digest sugar.

I​n theory, diet soft drinks should not raise a person’s insulin levels, but the results of this study challenge that idea.

Dietitian Karen Z. Berg, not involved in this research, explained why this study poses some important questions:

“Usually, insulin is released after we eat carbohydrates that increase our blood sugar levels, so it’s normal to have greater insulin after drinking a regular soda. Theoretically, insulin should not be released after drinking diet soda since it should not raise blood sugar, and not call for insulin to be released. It has been heavily debated, whether artificial sweeteners can in fact raise blood sugar and insulin levels.”

Impact of certain drinks on insulin levels

For data collection, the study researchers asked participants to consume several beverages while blindfolded. Drinks included diet soft drinks, regular soft drinks, mineral water with artificial sweeteners, plain water with a small amount of added sucrose, and plain water.

Researchers then collected saliva samples from participants and analyzed the samples. They found that “total protein and alpha-amylase levels did not differ in response to any ingested test-drink.”

Thus, the main points of interest in the study’s results were the drinks’ impacts on aspartame and insulin levels.

First, researchers detected aspartame in saliva for an extended time. This indicates it stays in the body for a longer time frame and can thus potentially impact the body’s response to the sweetener.

Researchers further found that salivary insulin levels increased after consuming regular soft drinks and diet soft drinks. They noted that salivary insulin levels may correlate with serum levels of insulin.

They further found that increased levels of salivary aspartame with diet soft drink consumption correlated with increased levels of salivary insulin.

Berg told Medical News Today she did not find the findings all that surprising.

“It’s no secret that both regular soda and diet sodas have negative health implications. This study, while super small, had an interesting approach to studying saliva after consumption of these beverages,” she told us.

“I am not surprised to see that subjects who drank both regular and diet sodas had increased insulin levels an hour after consumption. While diet sodas have been heavily pushed for weight loss and better blood sugar control, more and more research is coming out that is proving these beverages have the opposite effect. I hope this encourages larger studies like this.”

– Karen Z. Berg

Clinical implications

The results of the study indicate that diet soda still influences insulin levels, even though these artificially sweetened beverages are sugar-free and low-calorie.

Dr. Brian Black, an osteopathic physician specializing in family medicine and American Osteopathic Association member, not involved in the current research, explained some of the potential dangers when it comes to insulin levels.

“Insulin release is an essential part of blood sugar regulation, cellular metabolism, and muscle growth,” he told us. “In high quantities, insulin levels can lead to complications including weight gain due to the promotion of excess fat deposition and increased cardiovascular risk due to hypertension and atherosclerosis.”

“High and inappropriate long-term insulin exposure can lead to micro and macrovascular complications associated with the morbidity and mortality increase in diabetics including retinopathy, erectile dysfunction, neuropathy, kidney disease, myocardial infarction, and stroke,” noted Dr. Black.

If further research confirms these findings, it could further discourage the use of diet sodas. People may be more cautious about their use rather than seeing them as a perfect substitute for regular soft drinks.

“Certainly, further studies are needed to confirm data on direct health measures,” Dr. Black noted. “However, health messaging should note that substituting sugary beverages with aspartame beverages may not lead to health benefits and could cause harm.”

“The public would benefit from awareness of potential long-term metabolic health consequences that may exist with artificial sugar use in diet beverages,” he added.

Study limitations and continued research

T​his research has some key limitations to consider. First, it only included a small number of participants, and most of these were women, indicating the need for more extensive studies and more balanced sample sizes. It also had a short time frame, which suggests the need for studies with a longer follow-up time.

Researchers noted that they could not accurately measure concentrations of acesulfame, another artificial sweetener, in the artificially sweetened beverages. This could have impacted the results, and it indicates the need for further research.

The study authors also cautioned that they were unable to give due consideration to every ingredient present in the soft drinks they used. Other ingredients might also have influenced the study results.

Dr. Black noted some of the following limitations of the data:

“This study had a limited focus and a very limited sample size. It is not clear if the findings of this study can be generalized with any significance to the general population at large. This study was not double-blinded and thus could have contained bias. This study was short-term and can not be extrapolated to long-term health outcomes, especially on topics as complex as diabetes.”

Regardless, the study opens the door for greater research, which may ultimately impact clinical recommendations and health choices.

“The study does provide some insights into the relationship between aspartame consumption, salivary secretion, and insulin levels. It could thus serve as a launching pad for a better understanding of the effect of various drinks, including diet drinks containing aspartame, on health outcomes in diabetes,” Dr. Black concluded.