Xylitol: Can a sugar be good for your skin?

Everybody knows that sweet stuff is bad for you. Excessive consumption of sugar in its various form (sucrose, high fructose corn syrup, glucose, or fructose) has been associated with increased risk of health problems, such as obesity, type II diabetes, heart disease, tooth decay and others. Furthermore, high levels of blood sugar (glucose), whether due to overconsumption and/or impaired carbohydrate metabolism, appear to accelerate aging (including skin aging) via the process of glycation and crosslinking.

Even the supposedly innocuous non-caloric sugar substitutes are not "without sin". In particular, research indicates that non-caloric artificial sweeteners may still contribute to weight gain by indirectly affecting the settings of the appetite regulation center in the brain.

In this context, you would be tempted to think that anything sweet is bad (or at best useless) for your health in general and your skin in particular. And you would be wrong -- there appears to be at least one sweet exception, xylitol.

Admittedly, some experts do not consider xylitol to be a sugar. Technically, xylitol is a so-called sugar alcohol, a compound closely related to typical sugars. However, in the body, xylitol is converted to sugar (glucose) and related metabolites. Also, xylitol is approximately as sweet as table sugar (sucrose). It is also a natural substance: xylitol occurs in foods (e.g. plums) and also is produced by the body as an intermediate step of normal metabolism.

Therefore, for practical purposes (and in the opinion of many experts) xylitol is a sugar. More importantly, in many respects xylitol is better than common sugars. Xylitol carries only about half as many calories per gram as regular sugar. Also, it is absorbed slowly and has a relatively small effect on blood glucose levels. As a result, it is much less likely to contribute to weight gain or impair carbohydrate metabolism. In fact, xylitol is one of the most widely used sugar substitutes for diabetics. As opposed to most other sugars, xylitol does not promote tooth decay and may even suppress the formation of dental plaque. A Finnish study found that xylitol improved bone density in rats - not a proof for humans but a fruitful direction of research nonetheless. Another study in rats indicated that xylitol might improve the body's ability to fight bacterial infections by increasing the activity of neutrophils, a type of while blood cells.

Xylitol has a very good safety profile in humans. It has been safely used in food industry for decades, especially in products for diabetics. However, since xylitol is not completely absorbed during digestion, the doses exceeding about 50 g a day may cause diarrhea in some people (especially if the intake is increased abruptly). Notably, xylitol may cause low blood sugar in dogs (but not in humans) and should not be given to pets.

Well, enough of that general health information! What can xylitol do for your skin? The research in that direction is still scarce but the developments so far are intriguing.

In a 2000 Finnish study, published in the journal Life Sciences, Dr Knuuttila and co-workers found that short-term (three month) supplementation with xylitol increased skin collagen synthesis in rats. They also found that xylitol reduced the glycation (a.k.a. glycosilation) of skin collagen, which is an important mechanism of skin aging. In another study, published in the journal Gerontology in 2005, the same group of researchers investigated the effect of long-term dietary xylitol on the skin content of collagen in rats. They found that dietary xylitol prevented both the age-related decline in collagen synthesis and the age-related increase in the collagen degradation. Other studies showed the ability of xylitol to increase stability of certain proteins by reinforcing their 3-dimensional structure. This effect might play a role in the reported effects of xylitol on skin collagen.

What does this all mean in practical terms for skin-conscious individuals? A couple of encouraging laboratory studies in rats is a far cry from conclusive human clinical trials. If xylitol were a new drug, using it in people based on such modest evidence would be entirely inappropriate. Furthermore, without clinical trials, it is unclear what xylitol dosage (if any) would produce skin benefits in humans.

On the other hand, xylitol is a well-known, natural food ingredient with a long history of safe use in humans over a wide range of intakes. If used appropriately, it is likely to yield some health benefits (at least when it replaces sugar in one's diet), whether it improves the skin or not.

For those who do not wish to wait for human studies, one approach could be the following. Replace some of the items in your diet that contain sugar with equivalent ones containing xylitol. These could include chewing gum, mints, candy, table sugar & other sweeteners, and even chocolate. (Yes, they make chocolate with xylitol instead of sugar.) It would be prudent to build up the intake gradually and stay well below 50 grams of xylitol per day. Whether you receive any skin benefits or not, your teeth and the rest of your body are likely to benefit from the reduced consumption of sugar.

Finally, I am anticipating the question: If oral xylitol may be good for the skin, why not put some in a cream and apply topically? Unfortunately, as of the time of this writing, there are no studies of xylitol as a skin care ingredient, not even in rats. Therefore, we do not know whether it works topically, and even if it did, what concentrations and vehicles would be optimal. Furthermore, while the safety of xylitol in diet has been well established, it remains to be determined whether its topical use is free of negative side effects.