For many seeking to manage their weight or reduce sugar intake, diet soda appears to be a guilt-free alternative to traditional sugary drinks. However, emerging research suggests that the relationship between diet soda and health, particularly concerning diabetes risks, is far more complex than initially perceived. This article delves into the current understanding of how diet soda consumption may impact the development of type 2 diabetes and related metabolic issues, examining the evidence and potential mechanisms involved.
The Appeal of Diet Soda
Artificially sweetened beverages, like diet soda, have long been viewed as a "benign" choice because they offer sweetness without the calories and with few nutrients. This has led many to believe they can indulge without consequence, making diet soda a popular choice among those trying to control their weight or manage blood sugar levels. Diet sodas contain sweeteners instead of sugar, which may make them preferable to more sugary options.
Emerging Evidence: Diet Soda and Metabolic Syndrome
Several longitudinal cohort studies have revealed positive associations between diet soda consumption and incident metabolic syndrome, irrespective of initial body fat levels. Metabolic syndrome is a cluster of conditions-increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels-that together increase the risk of heart disease, stroke, and type 2 diabetes.
One study, the Multi-Ethnic Study of Atherosclerosis (MESA), a population-based study of 6,814 adults, found that at least daily consumption of diet soda was associated with a 36% greater relative risk of incident metabolic syndrome compared to non-consumption. This finding adds to the growing body of evidence suggesting that diet soda may not be the harmless alternative it is often made out to be.
The Link Between Diet Soda and Type 2 Diabetes
The association between diet soda and diabetes extends beyond metabolic syndrome. The MESA study also found that daily consumption of diet soda was associated with a 67% greater relative risk of incident type 2 diabetes compared with non-consumption. A 2018 study which included 2,019 people who did not have diabetes at the start of the study found that there was a risk of type 2 diabetes among participants who consumed artificially sweetened sodas, as well as those who consumed sugar-sweetened sodas. Another 2018 study also found that consuming more than 4 cans of diet soda per week was associated with a more than twofold risk of proliferative diabetic retinopathy (PDR) in people with diabetes. PDR is an advanced diabetic eye disease that happens when new blood vessels grow in the retina. The study included 609 adults with type 1 diabetes (n = 73; 12.5%), type 2 diabetes (n = 510; 87.5%), or unknown diabetes type (n = 26; 4.3%). Compared with no consumption, high levels of diet soft drink consumption (more than four 375-mL cans/bottles per week) were independently linked to an approximately 2.5 times increased odds of having proliferative diabetic retinopathy.
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If risk estimates for type 2 diabetes across diet soda categories were calculated in only the participants who did not consume sugar-sweetened soda (n = 2,245), the association with diet soda consumption remained significant.
Unpacking the MESA Study Findings
The MESA study provides valuable insights into the potential mechanisms underlying the association between diet soda and diabetes risk. Of the individual components of metabolic syndrome, only high waist circumference and high fasting glucose were prospectively associated with diet soda consumption. This suggests that the link between diet soda and metabolic syndrome may be driven more by a pre-diabetic condition than the syndrome itself.
Interestingly, when the MESA study adjusted for baseline measures of adiposity (body weight and/or waist circumference), the association between diet soda and metabolic syndrome was no longer significant. However, the association between diet soda and risk of type 2 diabetes remained statistically significant even after adjusting for these measures. This suggests that while changes in body weight or fat distribution may play a role, they do not fully explain the link between diet soda and diabetes risk.
Potential Mechanisms at Play
The exact mechanisms by which diet soda consumption may increase the risk of metabolic syndrome and type 2 diabetes are not fully understood. Several hypotheses have been proposed:
- Increased Desire for Sweetness: Artificial sweeteners may increase the desire for sugar-sweetened, energy-dense beverages and foods. The artificial sweeteners in diet soda trigger the same response in the brain as real sugar. The moment "sweetness” is detected, it signals the body to release hormones to process the sugar. And because diet soda is hyper-sweetened, it can trigger cravings for more sweet, high-calorie foods leading to weight gain and belly fat in particular.
- Disrupted Energy Intake Estimation: Artificial sweeteners may disrupt consumers' ability to accurately estimate energy intake and remaining energy needs, potentially leading to overconsumption and weight gain.
- Changes in Gut Microbiome: Some studies suggest that artificial sweeteners may disturb the balance of bacteria in the digestive tract, called the gut microbiome. Saccharin and sucralose in particular have been shown to dramatically alter healthy bacteria levels in the gut and may affect blood sugar control. Changes in the microbiome caused by artificial sweeteners may also inhibit some aspects of the immune system’s ability to respond to infections. A 2022 study in mice found that long-term consumption of sorbitol altered the gut microbiome and induced glucose intolerance.
An association between diet soda consumption and subsequent weight gain is plausible. It has been hypothesized that artificial sweeteners may increase hedonistic desires for sweetness and more energy-dense foods. Overconsumption of other foods/beverages may also occur in conjunction with diet beverage consumption owing to overestimation of the number of calories saved by substituting diet beverages for sugar-sweetened beverages. The association between diet beverages and weight gain may be biased by early awareness of energy imbalance, i.e., diet beverage consumption may serve as a proxy for early (failed) attempts to maintain weight.
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The Role of Artificial Sweeteners
Could artificial sweeteners (the constituent unique from sugar-sweetened soda) adversely affect biological processes related to insulin resistance, glucose regulation, and adiposity?
Over the life of the MESA cohort, several artificial sweeteners for sweetening diet beverages have been used by the soda industry. The sweeteners most commonly used in diet beverages had also changed from the initiation of MESA to the most recent examination. These dynamics make it difficult to attribute findings to the biological effects of a particular artificial sweetener.
The most common alternative sweeteners, whether artificial or natural, in diet sodas are:
- Sucralose: A 2013 study showed this sweetener can raise blood sugar higher when carbohydrates are consumed later compared to those who did not consume any sucralose. Sucralose also causes peaks in insulin levels despite not containing sugar.
- Aspartame: Aspartame can increase body weight and fat mass, which may increase the risk of diabetes.
- Acesulfame Potassium (Ace-K): Ace-K has been linked to body weight and fat gain in animal studies.
- Sorbitol: A 2022 study in mice found that long-term consumption of sorbitol altered the gut microbiome and induced glucose intolerance.
- Stevia: A moderate amount of natural stevia leaf is generally a safe alternative to sugar for people with diabetes.
- Erythritol: Consuming a moderate amount should not affect blood sugar or insulin levels. In fact, erythritol has shown protective effects for people with diabetes, though more research is necessary.
Other Potential Health Risks
Studies have shown that even one or two diet sodas a day can have negative health effects:
- AFib & High Blood Pressure: Studies show that drinking just one diet soda per day may increase the risk of cardiovascular problems including AFib (irregular heartbeat) and high blood pressure.
- Dental Problems: Diet sodas often contain phosphoric and citric acids which can erode tooth enamel.
- Headaches: People who are prone to migraines may be more likely to get headaches after consuming artificial sweeteners, such as those found in diet soda.
- Changes in Bone Density: Diet soda contains phosphorus, which may decrease bone density and increase the risk of osteoporosis, especially in older adults.
- Stroke & Dementia: The consumption of artificial sweeteners like aspartame, has been linked to an increased risk of neurological problems like stroke and dementia.
- Kidney Disease & Kidney Stones: Excessive soda consumption, diet or regular, may increase the risk of chronic kidney disease and the formation of kidney stones.
- Nonalcoholic Fatty Liver Disease (NFLD): Research has established a strong correlation between diet soda and NFLD, which affects up to half of people.
- Thyroid Function: Some studies have found that drinking diet soda can cause the thyroid gland to work less efficiently, potentially leading to increased fat storage and weight gain.
- Joint Pain: The artificial sweeteners in diet soda can trigger an inflammatory response in the body and may worsen joint pain.
Alternatives to Diet Soda
Given the potential risks associated with diet soda consumption, what are some healthier alternatives?
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- Carbonated water with a splash of fruit juice: People who drink soda for the refreshing fizz can choose carbonated water instead. Add a splash of fruit juice, such as lime, lemon, or grapefruit, for that sweet kick. The combination is rich in nutrients and rehydrates the body.
- Unsweetened tea: Unsweetened black tea can be a tasty alternative for people who drink soda for the caffeine boost.
- Coffee: Some research suggests that drinking 3 to 4 cups of coffee per day may also help decrease the risk of type 2 diabetes.
- Stevia leaves: People who crave the sweetness of soda might want to consider sweetening tea or carbonated water with whole stevia leaves.
Consistently replacing diet beverages with water in women with type 2 diabetes may contribute to greater weight loss and increases the likelihood of long-term diabetes remission.
Cautions and Considerations
Despite accumulating evidence of the existence of these associations between diet soda and metabolic issues, it is crucial to avoid concluding causality based on observational studies. The possibility of confounding by other dietary and lifestyle/behavioral factors cannot be excluded. While these are observational results and do not prove a cause-and-effect relationship, diet soda is unlikely to be the best option for people looking to manage or prevent type 2 diabetes.
The design of the ideal study, one that is randomized and long-term, is notably lacking. Mechanistic studies in randomized, controlled settings addressing how artificial sweeteners consumed from diet beverages affect early markers of metabolic dysfunction are lacking (especially considering true-to-life exposure to multiple sweeteners). Data such as those presented here and those that preceded them, suggest that such research is needed.