Thread: Sugar Alcohols, Glycerine and Low-Carbohydrate Diets

Read this over at netrition awhile ago and thought someone here might find it interesting.


Low-carbohydrate diets require a lot of reading... label reading. Labels can be very deceptive when it comes to hiding serving size, but it is pretty hard to hide carbohydrates right? After all, it's right there, total carbohydrates per serving! But if you look carefully, many times you will notice something on the ingredient list that is not included in the total caloric breakdown or carbohydrate count on the packaging. Typically, these omitted grams will be from sugar alcohols (or glycerine a.k.a. glycerin or glycerol). Sugar alcohol!? But the label says sugar free... well, under FDA guidelines (Title 21 Part 101 – Food Labeling) a product can be loaded with sugar alcohols and still proudly proclaim itself “sugar free!” Furthermore, the FDA guidelines permit the product manufacturer to mention that sugar alcohols promote dental health and hygiene (obviously unlike the tooth-rotting associated with sugar). Is a "sugar alcohol" really a sugar? Seems like the FDA does not consider these “sugars” to be full sugars. Is this a problem?

Many people claimed it was. “Bar-addicts” were noticing that it was harder for them to get into ketosis or to lose weight and immediately the cry went up that it was these “hi-tech” ingredients like glycerine and sugar alcohols that were disrupting the process. So, was this the case? Were companies deliberately mislabeling their products? I do not think I will ever be able to answer that question satisfactorily, except to say that it is very difficult to classify the caloric impact of sugar alcohols and glycerine as coming from a carbohydrate or a fat. Probably for this very reason, for a long time carbohydrates from sugar alcohols and glycerine were not included on the label in a direct manner. This is now changing. Most manufacturers are now listing the carbohydrate and calories coming from sugar alcohols and glycerine. This means that some brands of protein bars and other foods you may have been used to thinking of as having a certain carbohydrate or calorie content had to be relabeled.

The formulation of the product did not change. All that changed was the guidelines the company used to publish the nutritional information. So, if you had been fine eating a certain protein bar and now, looking down, see that instead of 3 grams of carbohydrates that label now says 20 grams but has a comment that this included glycerine or sugar alcohols, do not get alarmed. Sugar alcohols and glycerine make labels seem a lot worse than they really are. Sugar alcohols have, typically, half the calories of normal carbohydrates on a gram per gram basis. Likewise, glycerine, which is a tri-hydric alcohol, has only 4.3 calories per gram, a bit more than normal carbohydrates but less than half the calories of fat. So both of these alcohols are deceptively hard to count on a label. Both of these alcohols have almost no impact on insulin levels unlike normal carbohydrates, which makes them a good low-carbohydrate food additive.

The biological mechanics of low-carbohydrate dieting is that the body switches over from one metabolic pathway in the Krebs cycle where it burns glucose and begins to use ketone bodies for fuel – which the body can metabolize and use for energy, albeit in a less efficient manner hence the weight loss. The switch from glucose to ketone metabolism occurs when the body's stores of glycogen are depleted, particularly the glycogen stored in the liver. Muscle holds glycogen wrapped tightly with water molecules, but it is not muscle glycogen levels that influence ketosis; it is the liver’s “index” of glycogen that matters. This is why athletes can benefit from temporary intake of carbohydrates immediately after a workout and still lose fat (the body - post workout - stores glycogen preferentially in the muscles, not the liver hence the body’s index is not disrupted). This is a simplification of a very complex (and cool) metabolic process in your body, but it is crucial to understanding the impact of different foods on the body with regards to low carbohydrate dieting.

Most people have a sweet tooth, which is like a terminal disease to someone on a low carbohydrate diet. To make up for this, the food industry uses artificial sweetening agents in their products to let the consumer get the best of both worlds. One of these artificial sweetener “families” is the sugar alcohols, which are chemically alcohol molecules but are created from sugar. They are rated compared to sugar as far as sweetness. The sugar alcohols we use in the U.S. include Mannitol, Sorbitol, Xylitol, and Maltitol (also listed as Maltitol Syrup). Another common additive in low-carbohydrate or reduced calorie food is glycerine, which is also sweet but commonly used for its moisturizing effect on food texture; glycerine is commonly used for this purpose in most protein bars so that the bars stay moist and chewy.

Maltitol is the sugar alcohol you are most likely to be consuming. Maltitol is roughly as sweet as sugar (about ninety percent) and is used in a wide variety of products including chewing gum, chocolates, reduced calorie baked goods and sugar free ice cream. Maltitol has only 2.1 calories per gram whereas normal carbohydrates have 4 calories per gram. This means that Maltitol is, gram for gram, almost as sweet as sugar with a little more than half the calories. Maltitol is commonly used in Europe, where studies have shown it to be safe and established no limits on its usage. Currently, the American Food & Drug Administration (FDA) is reviewing Maltitol manufacturers’ petition to grant it Generally Recognized As Safe (GRAS) status.

Technically speaking, sugar alcohols are linear poly-alcohols, as opposed to table sugar (and other sugars) which are cyclic poly-alcohols. The structure of the sugar molecules probably means next to nothing to most of you, but the bottom line is that the form of the molecules affects the ability of the body's enzymes to oxidize or "burn" the molecule. So gram per gram, these sugar alcohols generally have fewer calories than the formal sugars (those cyclic poly-alcohol creatures). This already makes them an obvious candidate to replace “real sugars” in food since they are roughly as sweet as sugar (the exact comparison ranges from fifty to one hundred percent depending on the molecule being considered).

Another tricky thing about these molecules is how the body can process them. It cannot process them very well. The molecules are slowly and incompletely absorbed in the small intestine and taken into the blood stream to produce energy. This process does not involve very much insulin, which means that these sugars are very “gentle” on the low-carbohydrate dieter who must avoid tremendous insulin surges (diabetics, of course, are well aware of the effects of diet on their insulin levels) because insulin, a potent storage hormone, will quickly increase the glycogen stores of the body, disrupting ketosis and ending the diet, at least temporarily. This breakdown normally happens at three in the morning, hunched like a wild animal over a box of cookies, mad eyed, feral, growling and shoveling chocolate chips into your mouth with both hands. Or maybe that’s just me...

This poor absorption of sugar alcohol in the small intestine, while potentially a boon for dieting, can also be a problem when consumed to excess, particularly with products derived from lactose (Lactitol). This means that over-indulgence in sugar alcohols (which is possible given the wide range of sugar free or low carbohydrate candies and chocolate bars on the market) can have a laxative effect or lead to a very unhappy digestive system. Taken in moderation, this does not appear to be a problem, with the one exception appearing to be Lactitol which has bothered just about everyone I know who had even a modest amount. Fortunately, most companies are phasing this ingredient out or retailers have stopped carrying product lines using significant amounts of this sweetener.

Glycerine needs to be mentioned here as well. Glycerine is commonly found in most protein bars. The glycerine molecule attracts and holds water like crazy. Glycerine is therefore added to a product to keep the texture of the food moist. Glycerine is included as a carbohydrate on most nutritional labels even though it is really a by-product of the metabolism of fat. However, glycerine does not affect insulin levels or blood glucose. This means that while it has calories, it will not negatively impact the body in ways that will disrupt ketosis. You should still count the calories you are consuming from this product, since even a low carbohydrate diet needs some calorie control, but you do not need to worry about disrupting ketosis because there is no evidence that glycerine effects either insulin or blood sugar, which is the way that normal carbohydrates disrupt ketosis.

So where does this leave the end consumer who does not give a damn whether a molecule can stand on its head and juggle flaming swords as long as it tastes good and they can still lose weight consuming it. The truth is that sugar alcohols do have calories, albeit less than real sugar, and have very little impact on the body’s insulin levels. Could they potentially disrupt ketosis? Yes, particularly in the initial phases where absolute glycogen depletion is the goal and as little as 15-30 grams of carbohydrates can prevent ketosis from occurring. In the beginning, it would be wise to avoid any products containing sugar alcohol, but then again, this induction period is usually not more than 4 days. After the initial plunge into ketosis, the body can accommodate an increased intake of carbohydrates. I would recommend being aware of your sugar alcohol intake and counting at least half of every gram you consume towards your daily carbohydrate limit. A stick or two of gum is not going to be a problem, but three bars a day each containing 15 grams of sugar alcohol can quickly add up.

***editing ad*** Polydextrose, sometimes referred to by the trade name Litesse, provides about 1 calorie per gram and is considered dietary fiber. It is a water-soluble polymer of dextrose containing minor amounts of sorbitol and citric acid. Polydextrose can also have a laxative effect if consumed in large quantities (more than 15 grams).

Sugar alcohols (and glycerine) are a “comfort food” for a low-carbohydrate dieter; people who are extremely concerned with weight loss or bodybuilders should remember that, especially on a low carbohydrate diet, the choice of calories and food sources is crucial. If you permit yourself 50 grams of carbohydrates a day, are you better off eating complex carbohydrates spread out over the day or eating an equal amount of calories from fake chocolate sweetened with a sugar alcohol? I do not mean to outright compare the two food sources, because the sugar alcohols have fewer calories (usually) than normal carbohydrates and a different impact on your blood sugar. I just want to make the point that sugar alcohols, as presented in many “comfort foods” are still empty calories, albeit less empty calories than the sugar they replace. You still need to be aware of the calories associated with your sugar alcohol and glycerine intake.

Do not treat sugar alcohols or glycerine as a free food without any potential for disrupting weight loss! Both of these products contain calories. It is just that these calories are not disruptive to insulin levels or blood sugar. However, if you are committed to the long-term low-carbohydrate lifestyle, it is inevitable that you will want to indulge yourself. When that time comes, lock up the children and small animals, and pick an artificially-sweetened low-carbohydrate candy over that bag of crunchy M&Ms (Mmmmm... M&Ms... ).

Sugar alcohols provide some excellent benefits to the low carb dieter and diabetic. As always, use in moderation for best results

Bump!