Diet Soft Drinks

How Safe Are They?

It is commonly accepted that people with diabetes can drink artificially sweetened soft drinks – diet soda, to most people – without risk of raising their blood glucose level. This belief is based on the American Dietetic Association’s categorization of diet soda as a “free food,” which means that it contains less than 20 calories and 5 grams of carbohydrate per serving.

But new research suggests that consumption of diet soda may not be as harmless as the conventional wisdom holds. Although diet sodas don’t directly raise blood glucose level, several recent studies have concluded that people who drink diet soda daily have a higher risk of developing Type 2 diabetes as well as metabolic syndrome, a term used to describe the common combination of high blood pressure, abnormal blood lipid (cholesterol and triglyceride) levels, insulin resistance, and excess abdominal fat.

These puzzling findings certainly fly in the face of accepted nutrition science, and they raise the question: How could beverages so low in calories and carbohydrate increase the chance of developing Type 2 diabetes and its related risk factors?

Types of sweeteners

Diet sodas (as well as some other beverages and food products) are currently sweetened with a variety of types of low-calorie sweeteners, including the following:

Saccharin is one of the oldest artificial sweeteners still in use and has been on the market since 1977. It is the sweetening agent found in Sweet’N Low. Although use of saccharin has declined somewhat during the past 20 years, it is still used – along with aspartame – to sweeten the popular diet soda Tab.

Aspartame, the sweetener found in Equal and NutraSweet, has been in use since 1981. It is 200 times sweeter than sugar and is widely used in sodas and snack foods. Because it breaks down into its chemical components – phenylalanine and aspartic acid – in the body, aspartame should not be consumed by individuals who have phenylketonuria, a rare genetic disease in which the body is unable to process phenylalanine. If unchecked, this disorder can result in seizures, developmental problems, and brain damage. (In most US states, newborns are routinely screened for phenylketonuria.)

Acesulfame potassium (often called acesulfame K) was approved by the US Food and Drug Administration (FDA) in 1988. It is about 180 times sweeter than sugar. Because it has a slightly bitter aftertaste, acesulfame K is usually blended with other sweeteners for use in beverages and foods. It is sold under the names Sunett and Sweet One.

Sucralose is the artificial sweetener found in Splenda. It has been used since 1998 and is about 600 times sweeter than sugar. It is often used in baked goods and snack foods (as well as diet beverages) because it does not break down when heated.

Stevia is a sweetener that, unlike the others listed here, is not synthetically produced. It is derived from the leaves of stevia rebaudiana, an herb grown in Brazil and Paraguay that is related to the daisy plant. A component of the stevia leaf, rebaudioside A, was recognized by the FDA as safe for use in foods and beverages in December 2008. This sweetener can be found in Sprite Green and Zevia low-calorie sodas and is also available in single-serving packets under the brand names Truvia, PureVia, OnlySweet, and Stevia Extract in the Raw. Another brand of stevia sold in single-serving packets, SweetLeaf, contains both rebaudioside A and another purified stevia component called stevioside. According to information from the company, SweetLeaf was given the go-ahead by the FDA to sell this product as a food ingredient in August 2009. Stevia products that contain the whole leaf or other, less-purified extracts of stevia are sold as dietary supplements, not sweeteners.

Neotame is one of the newest artificial sweeteners to garner FDA clearance, in 2002. It is estimated to be 6,000—13,000 times sweeter than sugar. It is not yet in widespread use in the United States, but due to its positive review by the World Health Organization’s Joint Expert Committee on Food Additives and its widespread use in Europe, Australia, South America, Russia, and Mexico, neotame is expected to gain popularity as a sweetener in US diet sodas.

Alitame is a sweetener that has not yet gotten the FDA’s OK. Like aspartame, it is made up of two amino acids, aspartic acid and alanine. If cleared for use in foods and beverages, it is expected to gain widespread acceptance due to its stability at high cooking and baking temperatures.

Cyclamate is a sweetener that was banned in the United States in 1969 after a study showed that feeding large amounts (the equivalent of 350 cans of soda a day) to laboratory animals caused bladder cancer. Though still prohibited in the United States, cyclamate remains legal in 55 other countries including Canada, where it is a component of Sweet’N Low.

Safety standards and concerns

All artificial sweeteners sold in the United States must undergo rigorous safety testing to gain FDA approval. In addition, the FDA maintains guidelines to inform consumers about safe consumption levels. The FDA has established a safe level of consumption for diet sodas containing aspartame, acesulfame K, and sucralose. This level, known as the Acceptable Daily Intakes (ADI), is the maximum amount considered to be safe for daily consumption. It is assigned after extensive testing and set at an amount 100 times lower than that found to be safe in animal studies. The ADIs for artificial sweeteners per 12 ounces of diet soda are as follows, based on the amount of sweetener typically found in each soda:

• 18—19 cans of diet cola containing aspartame
• 30—32 cans of diet lemon-lime soda containing acesulfame K
• 6 cans of diet cola containing sucralose

Although no ADI has been set for soda containing saccharin, for single-serving packets the ADI is 9—12 packets. To date, no ADI has been set for stevia. The amount of saccharin, aspartame, sucralose, and acesulfame K found in a variety of popular diet sodas is shown in “Amounts of Sweeteners in Popular Sodas.”

Determining the amount of low-calorie sweeteners in products other than diet soda, such as snacks, baked goods, and breakfast cereals, can be difficult. While the labels for these products must note that the sweeteners are present, they often do not say how many milligrams of sweetener is in each serving. People who would like to limit their intake of low-calorie sweeteners can do so by avoiding products that list low-calorie sweeteners near the beginning of the ingredients list, as well as those that contain more than one type of low-calorie sweetener.

Despite safety assurances from the FDA, the sweeteners found in diet sodas have been blamed for a wide variety of health concerns, ranging from headaches, allergies, and digestive problems to cancer and neurological disorders. The public’s uncertainty surrounding the safety of low-calorie sweeteners is complicated by the fact that sweeteners have been studied primarily in animals, and the long-term effects of their use in humans are not completely known. As a result, there has been an explosion in the number of Web sites, forums, and advocacy groups dedicated to exploring the safety of artificial sweeteners, often with contradictory and confusing information. There is, however, new research in humans that has begun to show some links between diet soda and various health conditions.

New research

Studies on the health effects of drinking diet soda have examined connections to a variety of conditions and indicators of health. In many cases, the results have been especially relevant to people who already have Type 2 diabetes or are at risk of developing it. Some of the research is also highly relevant to people with Type 1 diabetes.

Type 2 diabetes risk. A large national study completed in 2007 showed that people who drank one or more servings of diet soda each day had a risk of developing Type 2 diabetes 67% greater than those who did not drink diet soda. The researchers who conducted the study noted that these findings do not indicate that drinking diet soda causes diabetes. Although no clear role for diet soda in the development of diabetes was found in the study, the researchers suggested that drinking sugar-free soda might have an indirect effect on diabetes risk by leading to weight gain or by affecting the action of insulin. (The possible effects of diet soda on weight gain are discussed below.)

Kidney disease. A study presented in 2009 found an association between drinking diet soda and impaired kidney function. Of the 3,000 women in the study, including 730 with diabetes, those who drank at least two diet sodas daily experienced twice the rate of kidney function decline. This result was consistent after controlling for factors such as age, caloric intake, weight, and diabetes status.

Metabolic syndrome. Two recent large studies showed that drinking one or more servings of diet soda per day was associated with a 35% greater risk of developing metabolic syndrome. As in the study showing an elevated risk of Type 2 diabetes, the researchers did not find any evidence of cause and effect between drinking diet soda and metabolic syndrome, and they did not know what role artificially sweetened sodas might play in the development of this condition.

Weight maintenance. Much of the controversy surrounding low-calorie sweeteners focuses on whether they are truly beneficial for weight control in people with or without diabetes. Some researchers believe that drinking diet soda may in fact stimulate appetite and increase cravings for carbohydrate, leading to weight gain and possibly setting the stage for Type 2 diabetes and metabolic syndrome. Another theory is that people who drink diet soda could gain weight by eating more high-calorie foods since they believe they are “saving” calories by drinking diet rather than regular soda.

However, these theories have not been proven, and they are contradicted by other studies showing that people who drink diet soda consume, on average, 15% fewer calories than those who drink regular soda and are more successful at long-term weight maintenance.

Sweetener specifics

Very little is known about the ways in which different low-calorie sweeteners might affect blood glucose control and weight management. Some research has shown that saccharin, aspartame, and acesulfame K may all increase appetite, though the findings are not conclusive. Studies are also beginning to suggest that each sweetener could produce unique effects in the body.

Aspartame has long been among the most controversial of artificial sweeteners, and there is continuing debate – both in the scientific community and among consumers – about its safety, as well as its effectiveness in producing and sustaining weight loss. Although very few studies have examined the role of aspartame in blood glucose control, a recent one found that people with diabetes who drank one or more servings of aspartame-sweetened soda a day tended to have a higher HbA1c level (an indicator of long-term blood glucose control) than those who didn’t.

Another study showed that sucralose – but not aspartame – stimulated the release of a hormone in the digestive tract known as GLP-1. This hormone helps the body regulate signals of hunger and fullness, or satiety, affecting appetite. Thus, it may be possible that the various artificial sweeteners in diet sodas affect hunger and satiety in very different ways.

Much attention has been given recently to stevia, one of the newer sweeteners used in soft drinks. Stevia is unique among low-calorie sweeteners in claiming that it may help regulate blood glucose. Although some studies have shown a favorable effect of stevia on blood glucose control as well as on blood pressure, overall results have been inconclusive. While the highly purified stevia extracts now being sold in beverages and single-serving packets appear to have a very low potential for toxicity or adverse reactions, stevia in its natural form may cause headaches, dizziness, and diarrhea in some people. Consuming large amounts of whole-leaf or less-purified extracts of stevia may also cause interactions with insulin or with blood pressure medicines. People who take these drugs should therefore be cautious when consuming such stevia products (currently sold only as dietary supplements) and probably limit their intake to modest amounts.

Reducing your intake

Because the low-calorie sweeteners used in diet soda and other reduced-calorie products may influence weight, blood glucose control, and kidney function in ways we do not yet fully understand, consumers with diabetes or prediabetes may want to consider limiting their consumption. More research will undoubtedly be conducted to explore the role of low-calorie sweeteners in weight control, development of Type 2 diabetes, and diabetes management, possibly leading to revised safety guidelines.

In the meantime, people with diabetes need not feel they are left with water, fruit juice, or regular soda as their only cold-drink options. Here are some suggestions for creating flavorful but low-calorie drinks that contain little or no artificial sweeteners:

• Dilute your favorite diet soda with seltzer to decrease the amount of artificial sweetener you consume.
• Add small amounts of fruit juice or cider to plain water or seltzer for a lightly flavored drink.
• Try flavored seltzer garnished with a wedge of lemon, lime, or orange.
• Add slightly crushed fresh mint to iced herbal tea.
• For a refreshing drink, place 1 cup of peeled, seeded cucumber and 1/4 cup of honeydew melon in a juicer, blender, or food processor and purée.