Concerns about the negative health effects of sugar have sparked the development of a plethora of sugar alternatives. Manufacturers claim their products, which are often positioned as "natural," can help enhance weight loss, ward off diabetes and prevent tooth decay. Some are well known while others remain relatively obscure in the United States despite widespread acceptance and use in other parts of the world. But just how natural are these sugar alternatives? And how safe are they?
Sugar, of course, is a natural product. It's derived from a grass, Saccharum officinale, commonly known as sugarcane. Sucrose from sugarcane provides about 4 calories per gram; this translates to approximately 15 calories per teaspoon. Sucrose has a moderately high glycemic index of around 65,1 compared with glucose, which has a GI rank of 100.
Most currently available alternative sweeteners may be categorized into two broad categories: intense sweeteners, which can be used by consumers in much the same ways as sugar, and polyols, which primarily are used as bulk ingredients in commercial products.
Intense sweeteners are typically many times sweeter than natural sugar—some as much as 8,000 times sweeter. Popular sweeteners in this category include aspartame (NutraSweet) and sucralose (Splenda), as well as the less-known stevioside (a compound from the herb Stevia rebaudiana, commonly known as stevia).
Intense sweeteners lower the calorie content of foods when they are substituted for sugar. Some experts argue that instead of helping to enhance weight loss, however, intense sweeteners may actually increase consumers' appetite for sweet foods, promoting overeating and weight gain. In fact, studies suggest that both the brain and the pancreas respond differently to intense sweeteners than they do to natural sugars.2 Some theorize that sweetness unaccompanied by calories can send the body ambiguous signals that confuse its regulatory mechanisms, leading to a loss of appetite control.2 A recent review of studies on sweetness and satiety concluded that in general, intense sweeteners do not work as appetite suppressants and do not necessarily enhance weight loss.2
Sucralose. Marketed under the brand name Splenda, sucralose is used by consumers much the same way as sugar in baking, cooking and as a tabletop sweetener. It is also a common ingredient in prepared snacks and beverages. Sucralose is about 600 times sweeter than sugar but has virtually no calories.
Most animal studies have concluded that sucralose has low toxicity,3,4 and sucralose was approved by the U.S. Food and Drug Administration for use as a sweetener in 1998. Studies in animals and humans show that most sucralose ingested in a single dose is not absorbed, so it passes through the body relatively unchanged.3,5 Two minor urinary metabolites (accounting for about 2 percent to 3 percent of an oral dose) have been detected in humans as well as a variety of test animals.3,5
A human tolerance study showed that sucralose had no effect on plasma insulin; another study demonstrated that sucralose did not stimulate insulin secretion, and did not affect the ability of sucrose to stimulate insulin production. 3 These results suggest that sucralose does not cause the blood-sugar spikes seen in some sweeteners. A small placebo-controlled clinical trial conducted in 2003 also concluded that consumption of sucralose for three months at doses of 7.5 mg per kg of body weight each day (three times the researchers' estimated maximum daily intake among high-level consumers of alternative sweeteners, such as diabetics) had no effect on glucose metabolism in people with type 2 diabetes.6
Sucralose critics point out, however, that long-term human safety data is still lacking, and a number of post-approval adverse events associated with sucralose have raised additional questions. Case reports of migraines occurring after ingestion of sucralose suggest that like aspartame, sucralose may act as a migraine trigger for some people.7,8
Sucralose proponents assert that it is a natural ingredient because it is made from sugar. In fact, while natural cane sugar is the starting material, the chlorination process it undergoes to produce sucralose is anything but natural. The complex, multi-step chemical manufacturing process results in the production of a chlorinated molecule that critics claim is akin to a pesticide.
Stevioside. Stevioside comes from the stevia leaf (Stevia rebaudiana), a sweet-tasting herb native to South America. Stevioside is up to 300 times sweeter than sucrose, with a slightly bitter aftertaste. It is approved as a sweetener and enjoys widespread use in some Asian and South American countries, including Brazil, Japan and China. In the United States, stevia and stevioside are sold as dietary supplements.
An extensive review of the literature concluded that stevia and stevioside are safe for consumption as sweeteners by healthy consumers as well as diabetics, phenylketonurics and obese individuals.9 According to the evidence, acute and subacute toxicity studies to date suggest that stevia and stevioside have very low toxicity, and no allergic reactions have been reported.9 The researchers calculated an acceptable daily intake for stevioside of 7.9 mg per kg of body weight.9 Controversy about the safety of stevia and stevioside persists, however. Concern primarily revolves around steviol, a metabolite of stevioside that has demonstrated weak mutagenic effects in some assays.9 Results of studies designed to assess whether or not steviol is actually absorbed by the body have been mixed.9,10
Lo han kuo. While still relatively unknown in the United States, lo han kuo (Siratia grosvenori) is a fruit with a long history of use as a food, traditional medicine and sweetening agent in China. The sweet compounds in lo han, called mogrosides, are 250 to 400 times sweeter than sucrose.13,14 These compounds appear to resist human digestive degradation and to lack both calories and glycemic properties.14,15
Standard toxicity studies conducted by the Japanese Ministry of Health, Labor and Welfare concluded that lo han has extremely low toxicity in rats, 13,14 although long-term safety studies and pharmacological data in humans are lacking.
Polyols include erythritol and xylitol, both of which are increasingly popular ingredients in low-calorie, low-carb snacks. Polyols contain an average of about 2 calories per gram. Not all polyols are as sweet as sugar. Erythritol, for example, is only 60 percent to 80 percent as sweet. Among other potential benefits, these sugar alcohols are touted as low-calorie, tooth-friendly ingredients with a much lower glycemic index than sucrose and other sugars. Polyols cause gastrointestinal upset in some people, however, and tend also to have laxative effects, which some have attributed to colon-hydrating properties.1 Other polyols include sorbitol, isomalt and mannitol.
Erythritol. Erythritol is a sugar alcohol used in a variety of baked goods, sweets and other foods, and has enjoyed popularity in Japan since the 1990s. Erythritol occurs naturally in a variety of foods and beverages, including grapes, pears, watermelons and mushrooms, as well as cheese, wine, beer, sake and soy sauce. Per capita consumption of erythritol in the United States from its natural occurrence in food is estimated to be about 80 mg per person per day, or 1.3 mg per kg of body weight per day.16 The sweetener is commercially produced via enzymatic hydrolysis, a process by which enzymes break down wheat or corn starch to yield glucose, which is then fermented with food-grade yeasts and purified.
Studies show that while up to 90 percent of ingested erythritol may be absorbed by the small intestine, it is not systemically metabolized and is largely excreted unchanged in the urine.17,18 While all polyols have the potential to cause some gastrointestinal upset, a recent study suggests erythritol may be less likely to do so than xylitol.19 In this small, controlled study in humans, gastrointestinal responses to erythritol taken in single oral doses of 0.4 or 0.8 g per kg of body weight per day were comparable to those with sucrose.20 Studies to date show plasma glucose and insulin concentrations are unaffected by erythritol.20,21
Xylitol. Research supports the use of xylitol in chewing gums designed to promote dental health,22,23,24 and the FDA permits xylitol-containing chewing gums to carry a dental health claim. Xylitol is often touted as natural because it is found in small quantities in a variety of fruits, grains, vegetables and mushrooms. Commercially available xylitol, however, is chemically synthesized via a hydrogenation process, primarily utilizing birch wood as a starting material.
Xylitol appears more likely to cause gastrointestinal upset than sucrose or erythritol. A recent double-blind, placebo-controlled, randomized clinical study in young adults compared gastrointestinal responses to consumption of 45 g of sucrose; 20 g, 35 g and 50 g of xylitol; and 20 g, 35 g and 50 g of erythritol taken as a single dose in water.19 Sixty-four participants completed the study. Compared with the subjects who consumed 45 g of sucrose, those who consumed 50 g of xylitol reported a significant increase in nausea, bloating, intestinal rumbling, colic, watery feces and total bowel-movement frequency. Consumption of 35 g of xylitol also increased frequency of bowel movements resulting in passage of watery feces. In contrast, participants who took 50 g of erythritol reported significant increases only in nausea and intestinal rumbling.19
While humans may be able to tolerate relatively large quantities of xylitol with little more than gastrointestinal upset, small amounts of the substance have proven quite dangerous for dogs. In August 2006, the Animal Poison Control Center run by the American Society for the Prevention of Cruelty to Animals issued a warning of an increase in canine poisonings related to consumption of xylitol-containing baked goods, candies and chewing gum.25 Dogs that consume significant amounts of xylitol-sweetened foods (more than 100 mg per kg of body weight) can experience a sudden drop in blood sugar resulting in depression, loss of coordination and seizures within 30 minutes of ingestion.26 There also appears to be a strong link between high doses of xylitol (500-1,000 mg per kg of body weight) and the development of liver failure in dogs.27 According to one case report, a standard poodle died after eating five or six xylitol-sweetened cookies.28 Even small quantities of the compound can be dangerous for dogs, so dogs ingesting any amount of xylitol should receive immediate veterinary attention.
Regardless of their relative safety, research to date suggests that alternative sweeteners don't necessarily help people lose weight. Xylitol and sucralose, while derived from materials found in nature, are highly chemically processed products that are not quite as natural as manufacturers would like consumers to believe. Overall, the jury is still out on the long-term health effects of most alternative sweeteners.
Evelyn Leigh is a freelance writer and natural health advocate based in Boulder, Colo.
Natural Foods Merchandiser volume XXVIII/number 11/p. 40,42
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