Sugar Alcohols

“Sugar-free, low sugar, zero sugar”. These are marketing claims seen on many packaged foods such as yoghurt, lollies, chewing gum, biscuits and diet foods promoted as “health” foods due to their low sugar content. The question is how can these foods have a sweet taste and yet contain little or no sugar and no artificial sweeteners? In a market that is more health savvy, sugar alcohols such as xylitol, sorbitol and mannitol are commonly being used in foods to replace sugar and artificial sweeteners.

Sugar alcohols tend to have a similar taste providing a similar sweetness to sugar while avoiding the bitter aftertaste and potential health risks that are associated with artificial sweeteners. They also tend to have less impact than sugar on blood glucose levels. Sound wonderful? This article takes a critical look at sugar alcohols to see if they are actually as good as they are made out to be or if they are just another “green-wash” in a market flooded with pseudo-health foods.

Also known as polyols, sugar alcohols are a type of carbohydrate formed from an alcohol portion and a sugar portion. Despite the name sugar alcohols don’t contain ethanol and so you won’t become intoxicated from consumption. Sugar alcohols tend to be less sweet and also contain between ½ to 1/3 less calories than sugar (2 or 3 calories compared to 4 with sugar). Apart from their sweet taste, sugar alcohols also help to bulk out foods, provide texture and “mouth feel” to products such as chewing gum. While they occur naturally in fruits and vegetables, most sugar alcohols used in food production are commercially produced from glucose, sucrose or starch.

It is important to remember however, that sugar alcohols don’t necessarily act like sugar in the body. Sugar alcohol absorption from the small intestine into the blood stream is incomplete resulting in a reduced rise in blood glucose when compared to sugar. For this reason they are popular in foods products targeted to the diet, low carb and diabetes market.

A minor problem arises when foods containing sugar alcohols claim to be “sugar-free” or “low-sugar”. While technically correct, consumers may assume that the food will therefore have little or no impact on blood sugars. As discussed above, sugar alcohols reduce the energy density of foods and therefore have less impact on blood sugars however, there is still some impact which diabetics need to take into account. It is considered safe to assume that sugar alcohols will have approximately half the impact of sugar on blood sugar levels 1.

Due to the incomplete digestion and absorption, a portion of the sugar alcohol remains in the gut. This can lead to fermentation by bacteria in the intestine and issues such as bloating and excess. Additionally, sugar alcohols hold a lot of water in the bowel and for this reason they may cause diarrhoea. Manufacturers state that this effect is usually an initial response and that increased tolerance usually comes with repeat consumption. However, with some consumers, digestive issues may be an ongoing issue.

An important factor that needs to be taken into account is the total daily consumption of sugar alcohols. Over a day it is likely to be the total quantity consumed that impacting on blood sugar levels and the digestive system with greater quantities more likely to cause side effects. The American Diabetic Association advises a warning “may cause diarrhoea: on quantities higher than 50g/day for sorbitol and 20g/day for mannitol 2.

Broken into categories based on chemical structure, there are 3 types of polyols: sorbitol, mannitol, xylitol are derived from monosaccharides, isomalt, lactitol and maltitol are disaccharide derived and hydrogenated starch hydrolysates (HSH) are derived from polysaccharides. Outlined below are the details of a few commonly used sugar alcohols.

Sorbitol is made from corn syrup and only has half the sweetness of sugar. Sorbitol is less likely to cause intestinal upset than mannitol however is not recommend for diabetics as it is not readily excreted and high levels can contribute to microvasculature damage. Ironically, it is often found in “sugar-free” gums and candy recommended to diabetics. Sorbitol can also cause laxative effects.

Frequently used in chewing gums and hard candy Mannitol is extracted from seaweed for use in food prodution. Less sweet than sugar, more is required to match the relative sweetness of sugar. Mannitol is most likely to cause bloating and have a laxative effect and as such a label warning is often seen to that effect.

Xylitol is a sugar alcohol made from a part of birch trees that has been used safely since the 1960s. Despite researching this ingredient, at this stage there are no negative reports of xylitol in humans. In fact the opposite seems to be true with positive effects on tooth decay reduction. Unlike sugar, Sugar alcohols are not acted upon by bacteria in the mouth. Xylitol has been found to inhibit oral bacteria, and is often used in sugarless mints and chewing gums for this reason. Research has shown that regular chewing of gum containing xylitol showed up to 60% reduction in tooth decay when compared to controls. The other positive report for diabetics is reduced blood sugar and insulin responses to xylitol consumption when compared to sugar.

One area for concern with regard to xylitol is its use with animals, specifically at this stage dogs. A recent report in the Journal of the American Veterinary Medical Association (JAVMA) reported that sugar-free dog treats containing xylitol have caused liver failure and in a small number of instances death 3. Based on this report, it is advisable for pet owners to avoid giving their dogs’ xylitol containing treats.

Foods containing sugar alcohols are increasingly available due to the trend in diet, low carb and diabetic foods. Based on the research completed to write this article sugar alcohols are not without issue. Consumers, particularly diabetics need to keep in mind total daily consumption of sugar alcohols and those experiencing ongoing digestive upset would do well to completely eliminate them from their diets. Of course, sugar alcohols are definitely out for dogs and possibly other pets as well.

Finally, while sugar may be responsible or partially so for many of modern society’s health complaints, it is a natural substance that we have been consuming for thousands of years. While we eat far too much of it, sugar is part of our evolutionary history. On the other hand sugar alcohols have only been used in recent times. The effects of long term use, beneficial or otherwise are not known. As such, moderation is recommended when including sugar alcohols as part of your diet.

Ananda Mahony ND is a naturopath and holistic skin specialist. Her practice focuses on the treatment of skin conditions and Food As Medicine. Ananda also owns Vitale Natural Skin & Body Care, a natural & organic skin care store in Paddington. www.vitalenatural.com.au
References:
1 American Diabetes Association. Nutrition principles and recommendations in diabetes-Position Statement. Diabetes Care, Jan.2004.

2 Powers M. American Dietetic Association Guide to Eating Right When You Have Diabetes. Hoboken, NJ: John Wiley & Sons; 2003:130,139

3. Stevens KL. 2007. Dog Watch. Sugar-free treats: a danger? Xylitol, a naturally occurring sugar substitute, isn't safe for your dog. Be careful of feeding him snacks that might contain it. Viewed at http://www.highbeam.com/doc/1G1-160229900.html on 10th February 2007.