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Little Tweak = Big Sweet

Sarah Mellors's picture

The recent dieting craze – particularly the carb-cutting trend - has created a huge increase in the demand for artificial sweeteners.  According to a 2004 study “as many as 180 million Americans routinely eat and drink sugar-free products such as desserts and artificially sweetened sodas” (1).  As one of countless subscribers to the carb-cutting, low-calorie philosophy, I decided to explore exactly what constitutes artificial sweeteners.  In my explorations, I came across some surprising findings about the chemical composition of various artificial sweeteners and how the body processes them. I focused my research on three sweeteners in particular: Sucralose, which is in the most popular artificial sweetener, Aspartame, which is in the artificial sweeteners, Sweet ‘N Low and Equal, and a new incredibly sweet sweetener called Neotame.  Initially, I expected all these different artificial sweeteners to be chemically dissimilar from less sweet substances; however, further research proved otherwise.

Apparently depending on the chemical composition of the sweeteners they can be anywhere between 160 and 13,000 times sweeter than sugar.  Remarkably tiny changes in the molecular structure of these chemicals produce huge variations in their level of sweetness.  Sucralose, which is in Splenda, is 600 times sweeter than sugar.  Splenda is advertised as being “made from sugar” so it “tastes like sugar”; however, this claim is misleading.  To make it calorie-free its composition is changed so it’s no longer sugar.  During this process, three of the hydroxyl groups in the sucrose (sugar) molecule are replaced with three chlorine atoms (2).  This small change in composition produces a substance that our intestines cannot absorb properly.  Because our bodies eliminate artificial sweeteners without taking in the calories, it appears as though these products are calorie-free even though they just are not being metabolized (3).  It’s remarkable that such a small change in the structure of sugar molecules produces an extremely sweet, indigestible substance.

Similarly, the great effect of small structural changes on a chemical’s properties is demonstrated in the relationship between Aspartame and Neotame.  Aspartame is made from the amino acids aspartic acid and phenylalanine.  Interestingly, aspartame cannot be exposed to heat.  The sources I looked at did not specify why exactly this is but based on our discussions in class I am going to assume that heat causes the aspartame molecules to break down and consequently to lose their sweetness.  Aspartame’s use as a sweetener has sparked much controversy because when broken down by the body it produces formaldehyde, which “is classified by the World Health Organization as a probable human carcinogen” (4).  It is still unknown exactly what the effect of Aspartame is on humans in the long-term though various studies have shown contradictory results about its relationship to cancer (5).  

The artificial sweetener Neotame is derived from Aspartame but is much sweeter.  Neotame is an astonishing 7,000 to 13,000 times sweeter than sugar.  Neotame’s chemical composition is like that of Aspartame except that when consumed by humans the peptide bond between phenylalanine and aspartic acid does not break so it is safe for consumption by people with phenylkenoturia (PKU), a rare genetic disorder where people lack the enzyme to break down phenylalanine (3).  It is remarkable that such a tiny change in the structure of aspartame not only produces a far sweeter product, but also makes it safe for people with PKU to eat. 


The fact that small changes in the chemical composition of these molecules produces much sweeter products, although surprising to the lay reader, actually falls perfectly in line with what we already know about macromolecules.  In class we discussed how minute changes in the composition of proteins allow them to perform different functions in the body.  Likewise, tiny changes in DNA structure produce billions of unique individuals.  Thus, it comes as no surprise that small changes in the composition of these artificial sweeteners produces a wide variance in their level of sweetness.

Exploring the relationship between sucrose and sucralose and aspartame and neotame has elucidated how artificial sweeteners are created.  However, the fact that these small structural changes produce great difference in sweetness also relates to the idea that little can be known about the effect of these substances on humans who consume them in large doses.  Although sucralose is made from sucrose, it is metabolized is differently than sugar so it can be expected that its health impact is unlike sugar as well.  Further research will have to be done to answer the controversial question of whether artificial sweeteners are safe, but for now at least we can understand how these substances are made and why they taste so sweet.





World Wide Web Sources

1. An article entitled “Are Artificial Sweeteners Safe?” from the WebMd homepage

2. A thorough article entitled “Sugar Substitutes and the Potential Danger of Splenda” from the Women to women homepage

3. A useful article entitled “Are Artificial Sweeteners Safe?” from Harvard Health Publications

4. A technical article from Chemical & Engineering News entitled “Artificial Sweeteners”

5. A cancer fact sheet from the National Cancer Institute called “Artificial Sweeteners and Cancer: Questions and Answers”