Scientific Facts About Sugars and Other Sweeteners

Sugars are simple carbohydrates containing one sugar unit (monosaccharides, such as glucose and fructose) or two sugar units (disaccharides, such as sucrose and trehalose).

Quick facts:

• Most sugars contain about 4 Calories, but tagatose contains only about 2 Calories per gram.
• Glucose, sucrose, trehalose and lactose can significantly raise blood glucose levels, but fructose and tagatose raise it very little.
• There seems to be no evidence that sugar consumption by itself results in greater weight gain than consumption of the same calorie worth of other nutrients. Many people tend to consume more calories when they eat sugary than non-sugary foods, though. 
• There is insufficient evidence about the association between moderate sugar consumption and diabetes.
• The risk of dental caries seems to depend more on the genetic predisposition and lack of exposure to fluoride than on the amount or type of sugar consumed.

The above claims base on results of many systematic reviews of studies you can find on Nutrients Review.

Glucose is a simple sugar, which naturally occurs mainly in fruits. You cannot live without glucose, but you do not need to consume it in order to be healthy, because glucose can be produced in your body from other nutrients, such as fats and proteins.

Glucose is also a part of most other sugars. Most carbohydrates, including starch, are digested or metabolized into glucose. 

Possible benefits

Glucose (on food labels: dextrose or just "sugar") is quickly absorbed, so it can be used as a quick source of energy as an ingredient in sport drinks or energy gels. It is also the most appropriate sugar to correct low blood sugar levels (hypoglycemia).

Possible harms

In people with diabetes mellitus, glucose from foods raises the blood glucose levels the most among all sugars.

There is insufficient evidence about harmful effects of moderate glucose consumption on weight gain or diabetes mellitus in healthy individuals.

Fructose is similar to glucose but is absorbed slower. In your liver, fructose is converted into glucose. There has been a lot of discussion about how fructose is metabolized in your body differently than glucose, but this does not seem to have much practical importance for healthy people.

Possible benefits

Fructose is sweeter than glucose and sucrose, so you can use it less to achieve the same sweetness and thus consume less calories.

Fructose has a low glycemic index, which means that it increases blood glucose levels less than glucose, so it is considered an appropriate sweetener for diabetics. 

Fructose is absorbed slower than glucose, so by mixing fructose and glucose in a sport drink, you can get a more sustainable source of energy.

Possible harms

There is no convincing evidence about the association between fructose consumption and weight gain that would be greater than the one from glucose or sucrose.

In some individuals, large amounts of fructose (>50 grams per day) can increase the blood triglyceride levels.

In individuals with fructose malabsorption (which is relatively common), consumption of even small amounts of glucose, for example 5 grams, can trigger abdominal bloating, excessive gas, nausea and diarrhea. Foods highest in fructose are apples, pears, mangoes, agave, honey and beverages with high fructose corn syrup (HFCS).

In individuals with a rare genetic disorder fructose intolerance, even very small amounts of glucose (less than 1 gram) can cause severe abdominal pain and nausea and larger amounts can be life-threatening.

High-Fructose Corn Syrup (HFCS)

HFCS is a liquid sugar, which is semi-artificially produced from corn syrup. It is mainly used in soft drinks, such as cola. It contains 55% fructose, so it is not much different from sucrose which contains 50% fructose. In HFCS, fructose and glucose are split, while in sucrose they are bond together, though.

According to one review of studies in Physiological Reviews, there is no evidence of any harmful effect of HFCS that would be greater than those of sucrose.

Tagatose is a semi-artificial sugar similar to glucose; it is produced from whey. It is poorly absorbed and provides only about 2 Calories per gram. Currently, it is used mainly in Japan and South Korea.

It is a little less sweet than sucrose.

When taken in large amounts (>10-15 g per meal), it can cause bloating.

Tagatose has a low glycemic index (GI = 3), so raises blood sugar levels much less than glucose and sucrose.

Sucrose or table sugar is composed of glucose and fructose.

Possible benefits

Sucrose raises blood sugar in individuals with diabetes less than glucose.

Possible harms

There is insufficient evidence about harmful effects of sucrose in otherwise healthy individuals.

In individuals with a genetic disorder called sucrase-maltase deficiency, sucrose can trgger diarrhea. 

Trehalose is a sugar very similar to sucrose but it is less sweet; it is semi-artificially produced from corn starch.

Trehalose is Generally Recognized as Safe (GRAS) in the United States and also approved and commonly used in Japan, Taiwan and South Korea.

Possible benefits

Trehalose has a lower potential to cause dental caries than sucrose.

Possible harms

In individuals with a rare genetic disorder trehalase deficiency, trehalase can trigger diarrhea.

Lactose is present in milk products, mainly in milk, yogurt and ice cream, in much smaller amount in cheese and is not found in butter.

Lactose can be added as a sweetener to beer (milk stout, cream stout, sweet stout) and various food products, such as protein powder.

Possible benefits

Lactose is a source of energy.

Possible harms

In individuals with lactose intolerance, which is common, a large amount of milk (usually more than 1 glass), or commercial protein powder can cause bloating and diarrhea.

In bottle-fed infants, lactose can promote dental caries.

Sorbitol is a "sugar alcohol" or polyol. It is a poorly digestible carbohydrate, naturally occurring in grapes, prunes and cherries, or semi-artificially produced from glucose syrup and used in "low-calorie" or "no-sugar" food products, such as chewing gum and soft drinks.

It has about 2.5 Calories per gram.

Possible benefits

Sorbitol has a low glycemic index, so it can be suitable for diabetics.

Possible harms

When consumed in large amounts by healthy individuals or in small amounts by individuals with fructose malabsorption, sorbitol can cause abdominal bloating or diarrhea.

Other polyols similar to sorbitol are isomalt, maltitol, mannitol and xylitol.

Erythritol, unlike other polyols, contains almost no calories and does not raise blood glucose levels after meals, so it is suitable for diabetics.

Glycerol (edible glycerin) is classified as polyol, but is much more similar to sugars than to polyols: it is about as sweet as glucose and has about 4 Calories per gram, like other common sugars. Natural vegetable glycerin is obtained from vegetable oils (palm, coconut or soybean oil) and natural animal glycerine from animal fats, such as beef tallow. Glycerin can be also semi-synthetically produced from cane or corn sugar syrup. No harmful effects are known.

Non-sugar sweeteners are not carbohydrates, do not contain calories and do not raise blood sugar levels.

Acesulfame K is available as a commercial product with a brand name Sunett or as added sweetener in soft drinks, frozen deserts and bakery. It is up to 200 times as sweet as sucrose.

According to The Joint Expert Committee on Food Additives (JECFA), the scientific advisory body to the World Health Organization and the Food and Agriculture Organization of the United Nations, acesulfame K is safe to use as a sweetener.

According to the U.S. Food and Drug Administration (FDA), the Acceptable Daily Intake (ADI) for acesulfam K for adults is 15 mg/kg/day (~1 g/day for a 70 kg/155 lb person).

Aspartame (commercial products: Equal, NutraSweet) is chemically a methyl ester of the amino acids aspartic acid and phenylalanine. It is about 200 times as sweet as sucrose.

Aspartame is safe to use according to the Food and Drug Administration (FDA) in the United States and European Food Safety Authority (EFSA).

Individuals with a genetic disorder phenylketonuria need to avoid aspartame, since it is metabolized into phenylalanine.

The Acceptable Daily Intake (ADI) for sucralose for adults is 50 mg/kg/day (3.5 g/day for a 70 kg/155 lb person).

Saccharin (commercial products: Sweet'N Low, Sugar Twin) is an artificial sweetener; chemically it is benzoic sulfimide. It is up to 400 times as sweet as sucrose.

Based on studies in rats, saccharin was once classified as a possible human carcinogen, but later studies have not confirmed that saccharine would cause bladder or any other cancer in humans.

The Acceptable Daily Intake (ADI) for saccharin for adults is 15 mg/kg/day (~1 g/day for a 70 kg/155 lb person).

Stevia (commercial products: Truvia, PureVia, SweetLeaf) is a very sweet natural sweetener extracted from the leaves of the plant Stevia rebaudiana. It is up to 300 times as sweet as sucrose.

Pure stevia contains no calories, but the commercial stevia products can be mixed with maltodextrin and can contain about 2 Calories per gram.

The Acceptable Daily Intake (ADI) for stevia for adults is 4 mg/kg/day (280 mg/day for a 70 kg/155 lb person).

Sucralose (a commercial product: Splenda) is artificial sweetener produced by chlorination of sucrose. It is up to 1,000 times as sweet as sucrose.

There is no evidence about any harmful effects of sucralose. Regular consumption of sucralose can make you consume more sugar, though.