Nutrition 101 Video Series: The Lowdown on Low-Calorie Sweeteners

This is the fourth installment of our video series in partnership with Osmosis, a group that focuses on health science education, highlighting the basics of several nutrition topics. The Nutrition 101 series also includes videos on dietary fats, carbohydrates, sugars and hydration.

Most people love sweet foods. Originally, sweetness was nature’s way of identifying energy-dense foods that were safe to eat. This was particularly important throughout the long history of our species when food was scarce. But times have changed and nowadays, sweetness is mostly associated with the sugars added to foods and drinks. Unfortunately, many people consume too many calories from these sorts of added sugars. Over time, consuming more calories than the body needs can contribute to the onset of chronic diseases like obesity, type 2 diabetes mellitus, hypertension, or cardiovascular disease. Low-calorie sweeteners can satisfy our taste buds while reducing the calories we eat from sugar.

The good news is that randomized controlled trials have shown that replacing full-calorie foods and beverages with low-calorie sweetened versions can lead to modest weight loss, as long as the individual doesn’t overindulge on additional calories from other sources say, by ordering dessert because they had a diet soda with dinner. Low-calorie sweeteners don’t raise blood glucose or insulin levels, so they can help people with diabetes control their blood sugar and reduce the amount of total sugars they consume each day.

Some low- and no-calorie sweeteners like stevia and monk fruit extracts come from plants. Others, like aspartame, sucralose, and acesulfame potassium are man-made. It’s important to note that all of them are sweeter than sugar, which means that only tiny amounts are needed to equal the sweetness of sugar. As a result, low-calorie sweeteners are often blended with carbohydrates like dextrose and maltodextrin or the sugar alcohol erythritol when they’re found in tabletop packets. This makes the overall volume similar to a packet of sugar, so that it’s easier to measure and pour. That’s why packets of low-calorie sweeteners and sugar are about equal in size.

Aspartame, which is about 200 times sweeter than sugar, is composed of two amino acids, aspartic acid, phenylalanine and a molecule of methanol. When we consume aspartame, it’s rapidly broken down in the small intestine into these three components – all of which are naturally found in much higher quantities in other foods that we eat every day. Like sugar, aspartame contains four calories per gram, but due to its sweetness, only a very tiny amount is needed to replace sugar. As a result, it doesn’t contribute a substantial number of calories to our diet.

Sucralose is about 600 times sweeter than sugar and is made from the disaccharide sucrose, commonly known as table sugar, by replacing three of its hydroxyl groups with chlorine atoms. This structure prevents digestive enzymes from fully breaking it down, so only a small amount is metabolized and it doesn’t contribute any calories. In fact, about 85 percent of the sucralose we consume is not absorbed, and the small amount that is absorbed is rapidly excreted in the urine.

Acesulfame potassium, sometimes called Ace-K, is a potassium salt that’s 200 times sweeter than sugar. It’s usually added to foods and beverages in combination with other low-calorie sweeteners. Ace-K is absorbed in the small intestine but it’s not broken down before being excreted in the urine, so it also doesn’t provide any calories. Although it contains potassium, it contributes very little of this nutrient to our diets, since only tiny amounts of Ace-K are found in foods and beverages.

Stevia sweeteners are derived from the stevia plant, which is native to South America, and are about 200 times sweeter than sugar. Stevia sweeteners are made by extracting sweet compounds called steviol glycosides, from the leaves of the stevia plant and purifying them to remove some of the bitter compounds found in the crude extract. Some steviol glycosides are also made through processes like fermentation, which allows sweeter and less bitter glycosides to be produced on a larger scale. Glycosides are monosaccharides, like glucose, which are bound to another molecule by a glycosidic bond. Steviol glycosides all have a common basic backbone called steviol. They include compounds like stevioside and many different forms of rebaudiosides, the most common of which is rebaudioside A or Reb A. Purified steviol glycosides remain intact through the upper gastrointestinal tract and don’t get absorbed, which means that they do not contribute any calories to our diet. When they get to the colon, our gut microbiota cleave off the glucose molecules and use them as an energy source. The remaining steviol backbone is then absorbed via the portal vein, metabolized by the liver, and excreted in urine.

Monk fruit sweeteners come from the Siraitia grosvenorii Swingle fruit, or monk fruit, which is a plant native to southern China, and they’re about 250 times sweeter than sugar. Juice from monk fruit is extracted for its mogrosides, the compounds that give the ripe fruit its sweetness. They’re a combination of a compound called a mogrol, and glucose units or glycosides. Like steviol glycosides, monk fruit sweeteners undergo only minimal systemic absorption. But the glycosidic attachments of the mogrosides can be digested by the gut microbiota, leaving the basic mogrol backbone, which is then excreted.

All of these low-calorie sweeteners have been studied extensively to determine their safety and to establish levels of Acceptable Daily Intake, also known as an ADI. The ADI represents the amount of a compound in foods or beverages that could be ingested every day, over a lifetime, without health risks. To calculate the ADI, the first step is to study the effects of the compound in animals – like a rat or mouse. To be sure that the animal model testing is relevant, scientists conduct human clinical trials to confirm that there are no major differences in metabolism between the animal models and people. Testing is then done in the appropriate animal models and includes studies to ensure that there are no effects on pregnancy, growth or development, or any indication of side effects, including with high intakes every day until old age. From these results, a No Observed Adverse Effect Level or NOAEL is determined. The NOAEL is then divided by 100 to arrive at the ADI. In other words, the ADI is an extremely conservative number to make sure that there’s no chance of harm. On average, the amount of low-calorie sweeteners we consume each day is well below the ADI, even for people with a really sweet tooth.

Now here’s a quick recap: Most people enjoy a sweet treat, but unfortunately, many people eat more added sugar than is recommended, sometimes at the expense of nutrient-dense foods they need. Low-calorie sweeteners can help reduce the number of calories we eat from sugar without having to sacrifice sweet taste. Each low-calorie sweetener has a distinct structure and metabolic pathway, and they all provide a unique level of sweetness as compared to sugar. Extensive research has shown that they are safe in the amounts expected to be consumed, can help with weight loss and weight maintenance, and they can be an option for people trying to control their blood sugar.