Are Xylitol, Sorbitol, and Other Sugar Alcohols Safe Replacements For Sugar?

In the last article of this series I discussed artificial sweeteners, and gave you my take on whether you should include them in your diet. This week, I want to talk about sugar alcohols, which are another popular low-calorie sugar substitute.

Xylitol is the most popular and most extensively researched, so I’ll focus my discussion on it, but the general takeaway of this article applies to other sugar alcohols as well, such as sorbitol and erythritol.

Xylitol and sorbitol are commonly used as sugar replacements, but are they safe? Here’s what you need to know!

What exactly are sugar alcohols?

Sugar alcohols are a type of ‘low-digestible carbohydrate,’ a category that also includes fiber and resistant starch. Sugar alcohols occur naturally in many fruits and are also known as ‘polyols,’ which you may recognize as a FODMAP. Unlike artificial sweeteners, sugar alcohols aren’t completely calorie-free, because we are able to digest and absorb them to some extent. The absorption rate varies among sugar alcohols, from about 50% for xylitol to almost 80% for sorbitol, depending on the individual. Erythritol is almost completely absorbed, but is not digested, so it provides almost no calories. 

Compared with artificial sweeteners, sugar alcohols have very few safety and toxicity studies, and are generally accepted as safe. In one long-term human study, 35 participants consumed xylitol as their primary dietary sweetener for two years, and no adverse effects other than GI distress were observed, and GI symptoms dissipated after the first couple months. The amount of xylitol consumed during this trial regularly exceeded 100g per day, often going over 200g per day, depending on the participant.

Metabolic effects of sugar alcohols

Sugar alcohols are a popular choice for weight loss due to their reduced calorie content, and for diabetics due to their low glycemic index. There’s not nearly as much research on the metabolic effects of sugar alcohols as there is on artificial sweeteners, but the evidence we have suggests that sugar alcohols are at least harmless, and possibly beneficial.

For the most part, sugar alcohols cause no appreciable changes in blood glucose or insulin in humans, and sorbitol and xylitol have not been found to raise blood glucose following consumption. In diabetic rats, 5 weeks of xylitol supplementation (as 10% of their drinking water) reduced body weight, blood glucose, and serum lipids, and increased glucose tolerance compared with controls. Two other rat studies also found that xylitol-supplemented rats gained less weight and fat mass compared with control rats, and had improved glucose tolerance. 

Because sweetness does not predict caloric value in sugar alcohols, one might expect that they would cause the same ‘metabolic confusion’ that is seen with noncaloric artificial sweeteners. Unfortunately there isn’t enough evidence to form a conclusion about this, but my feeling based on what I’ve read is that this isn’t a significant issue for sugar alcohols.

For one, sugar alcohols aren’t ‘intense sweeteners’ like artificial sweeteners, which are hundreds of times sweeter than sugar. In fact, many are less sweet than sugar. Also, sugar alcohols do provide some calories, so there’s not as much of a discrepancy between the caloric load your body expects and the caloric load it actually gets.

Does xylitol prevent tooth decay?

The most well-known health benefit of xylitol is easily its effect on dental health, and evidence for xylitol’s ability to prevent tooth decay is pretty robust. A couple trials have found xylitol to be more effective at preventing cavities than fluoride, and benefits of xylitol consumption have even been observed in children whose mothers chewed xylitol-containing gum. Unsurprisingly, the most drastic effects are observed when xylitol replaces sucrose in either the diet or in chewing gum, but significant reductions in cavities have been observed when xylitol is simply added on top of a normal diet as well. 

Although some effects of xylitol are undoubtedly due to nonspecific factors such as increased saliva production or the replacement of sugar, it does appear to have specific properties that support dental health. Xylitol is not fermentable by common plaque-forming oral bacteria like sugar is, so it doesn’t provide a food source. Additionally, xylitol actively inhibits the growth of these bacteria. It also forms complexes with calcium, which may aid in remineralization.

Sugar alcohols and digestive health

While sugar alcohols appear to be safe and potentially therapeutic, they are also notorious for causing digestive distress. Because sugar alcohols are FODMAPs and are largely indigestible, they can cause diarrhea by pulling excess water into the large intestine. The fermentation of sugar alcohols by gut bacteria can also cause gas and bloating, and sugar alcohols may decrease fat absorption from other foods. However, most evidence indicates that people can adapt to regular sugar alcohol consumption, and the adverse GI effects reported in studies tend to fade after the first month or two.

Erythritol is probably the best-tolerated sugar alcohol, and a few human trials have found that if the amount of erythritol is gradually increased and doses are spread throughout the day, many people can tolerate large amounts (up to1g/kg of body weight) of erythritol without GI distress. The average tolerance for xylitol and sorbitol is lower; most study subjects could tolerate about 30g per day without a problem, but significant adaptation was necessary to increase xylitol content in the diet. 

A few studies indicate that sugar alcohols may have a prebiotic effect. This isn’t too surprising, considering the prebiotic effects of other low-digestible carbohydrates such as fiber and resistant starch. Animal studies have found that xylitol causes a shift from gram-negative to gram-positive bacteria, with fewer Bacteroides and increased levels of Bifidobacteria. A similar shift has been observed in humans, even after a single dose of xylitol. Additionally, the shifts observed allowed for more efficient use of the sugar alcohols by gut bacteria, which largely explains the reduction in GI symptoms after a few months of regular consumption.

In addition to the potential metabolic, dental, and prebiotic benefits already discussed, xylitol shows promise for preventing age-related decline in bone and skin health. One interesting study found that 10% xylitol supplementation over 20 months increased collagen synthesis in the skin of aged rats, resulting in thicker skin. Preliminary rat studies have also shown that xylitol can increase bone volume and mineral content and protect against bone loss. 

Overall, sugar alcohols appear to be safer than artificial sweeteners with several potentially therapeutic effects. Although the metabolic and weight loss benefits of sugar alcohols haven’t been studied as extensively, I would recommend sugar alcohols over artificial sweeteners to anyone who needs a low-calorie sweetener, although I wouldn’t recommend that anyone consume huge amounts of them. I’ll also be interested to see additional research on their ability to alter the gut microbiome and disrupt biofilms, because this could make sugar alcohols a useful tool for certain patients.

At this point, there don’t seem to be any major problems with sugar alcohols, so if it’s something you’re interested in, I would experiment with your own tolerance and see how they affect you. However, people with gut issues should be cautious.

Please call 734-726-0153 to schedule a free consultation and evaluation. At Digestive Health Ann Arbor we are known for providing professional and compassionate care. We strive to guide people towards a comprehensive and holistic healing strategy. Restoring your body to health will restore the quality of your life.

 

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The Unbiased Truth About Artificial Sweeteners

Artificial sweeteners continue to be a controversial public health issue, and the research keeps coming. In fact, a new study on artificial sweeteners and weight loss was just published on Monday, and the FDA approved a new artificial sweetener (advantame) last Wednesday.

On one hand, many people are adamantly opposed to the use of artificial sweeteners because of the purported link with increased risk for cancer and other diseases. But on the other hand, artificial sweeteners are becoming increasingly popular as people try to reduce calorie consumption and lose weight.

There’s too much research out there to cover comprehensively in a blog article, but I’ll try to cover the basics: will artificial sweeteners give you cancer or other diseases? Do they actually help with weight loss, or do they hurt? And ultimately, should you be eating them?

Cancer

Artificial sweeteners were first tied to cancer risk in the 1970’s after a study showed that a combination of saccharin and cyclamate (another early artificial sweetener) caused bladder cancer in lab rats. The mechanism behind these effects was later found to be specific to rats and not generalizable to other animals or humans (in these rats, comparable doses of vitamin C can also cause bladder cancer), and further studies demonstrated that neither sweetener is carcinogenic.

However, this study cast a shadow of doubt over artificial sweeteners, and thanks in part to the media’s penchant for blowing things way out of proportion, the reputation of artificial sweeteners has never recovered.

A later study suggested a link between aspartame consumption and brain tumors. The authors based this hypothesis on the fact that both brain cancer and aspartame consumption had increased since 1980 – despite not knowing whether the people getting brain tumors actually consumed artificial sweeteners – and on a rat study where aspartame supplemented diets led to the formation of brain tumors.

This association has been more or less dismissed by the research community because three case-control studies have found no association between brain tumors and aspartame consumption, and subsequent animal studies haven’t been able to replicate the aspartame-induced brain tumors found in the original rat study.

Artificial sweeteners have also been implicated in the development of lymphoma and leukemia, and one observational study found a weak link between artificial sweetener consumption and development of non-Hodgkin lymphoma and multiple myeloma in men, but not in women. The study authors concluded that due to the inconsistency in their results, there isn’t likely a causal link, although it can’t be ruled out.

Artificial sweeteners have also been tested for associations with other cancers, including breast, pancreatic, stomach, colon, and endometrium, with no correlations found. Based on the evidence, I don’t think artificial sweeteners are a huge risk factor for cancer, although the possibility can’t be ruled out and caution is warranted.

Diabetes, Heart Disease, and Metabolic Syndrome

Artificial sweeteners have also been increasingly tied to increased risk for developing metabolic syndrome and related diseases such as diabetes and cardiovascular disease. Numerous observational studies have attempted to parse out a consistent association with disease risk, but for every study that has linked artificial sweetener consumption with metabolic syndrome, heart disease, or diabetes, there’s another that has found no association.

This inconsistency shouldn’t come as a surprise, given the inherent limitations of observational evidence, but because there’s little to no clinical evidence in humans to test these hypotheses, the effect of artificial sweeteners on risk for these diseases remains inconclusive.

Pre-term Delivery

There has been concern in recent years over a potential link between artificial sweetener consumption and pre-term delivery, prompted by two observational studies published in 2010 and 2012. These studies have significant limitations: the associations are small and not linearly dose-dependent; not all artificially-sweetened beverages were accounted for; and women who consume more artificially sweetened drinks also tend to smoke more, have higher BMI, and lower socioeconomic status. All told, the risk seems small, but I would advise pregnant women to avoid artificial sweeteners just to be on the safe side.

Weight Loss

For most people, the primary motivation for consuming artificial sweeteners is a desire to reduce calorie consumption and lose weight. But do artificial sweeteners actually help achieve that goal? Yet again, the evidence is mixed. Many observational studies have found a positive association between artificial sweetener intake and obesity, but in this situation, reverse-causality is particularly likely.

In other words, while it’s possible that artificial sweeteners contributed to weight gain in these studies, it’s also possible that people who are overweight are more likely to choose diet beverages and other artificially sweetened foods in an effort to lose weight. We also have a decent number of clinical trials testing the weight loss effects of artificial sweeteners in humans, although many are too short-term to have much practical significance.

In one study, overweight subjects were given supplements of either sucrose or artificial sweeteners for 10 weeks. At the end of the trial period, subjects in the artificial sweetener group on average had experienced a reduction in weight, fat mass, and blood pressure, while subjects in the sucrose group gained weight and had increased blood pressure.

A study just published this week on weight loss and artificial sweeteners was surprisingly positive: over a 12-week period, participants who were instructed to drink 24 ounces of artificially sweetened beverages every day actually lost more weight than participants who were instructed to drink 24 ounces of water daily. (It’s worth noting that this study was fully funded by The American Beverage Association.) Other trials have also shown successful calorie reduction and weight loss in participants who consumed artificial sweeteners (usually in the form of beverages).

Based on this evidence, it seems that artificial sweeteners can be helpful for weight loss in some circumstances, at least over the short term. However, due to the limited nature of these studies and the evidence I’ll present next, I hesitate to draw any conclusions.

Do Artificial Sweeteners ‘Confuse’ The Body?

For most of human history, sweeteners were inextricably tied to caloric density. If our sweet taste receptors evolved primarily to help us identify calorie-rich food sources, how will our bodies respond when our taste receptors are consistently bombarded with sweetness, but with no concomitant calorie surge?

Animal models certainly indicate that artificial sweeteners can impair the innate ability to regulate caloric intake. Rats who are fed with artificial sweeteners consistently gain more weight than rats who are fed with glucose or sucrose. Additionally, the rats don’t tend to lose the excess weight, even after their diets are switched back to glucose or sucrose to re-establish the calorie-predictive nature of sweet taste.

Interestingly, rats who were given stevia solutions gained significantly more weight than the glucose-fed rats, and similar amounts of weight to the saccharin-fed rats. Rats fed with artificial sweeteners also develop an impaired ability to respond to sugar-containing foods. In one study, rats who had been fed artificial sweeteners were unable to compensate for the calorie content of a sugar preload by eating less chow afterwards, while rats who had been fed sugar-containing food compensated almost perfectly for the extra calories in the preload by eating less chow.

Rats that have been conditioned with saccharin also display a reduced thermic effect in response to consumption of a caloric sugar-containing meal, as well as higher blood glucose, compared with rats who had been conditioned with glucose. Additionally, saccharin-fed rats secreted less GLP-1 (which is implicated in satiety and glucose homeostasis) when given a sugar-containing test meal.

Unfortunately, although the animal evidence is fairly robust, evidence in humans is limited. However, two interesting studies that used MRI to measure brain responses to sucrose solutions indicate that artificial sweeteners may alter the brain’s response to sweet tastes in humans. In one study, people who regularly consume artificially sweetened drinks had higher reward responses to both saccharin and sucrose compared with people who don’t consume artificial sweeteners.

Additionally, people who don’t consume artificial sweeteners had different brain responses to the saccharin and sucrose, while those who regularly consume artificial sweeteners responded the same to both sweeteners. Another study found that the amygdala’s response to sucrose consumption was inversely related to artificial sweetener use. (The amygdala is part of the brain that is involved with taste-nutrient conditioning.)

Should You Be Eating Artificial Sweeteners?

My conclusion might seem a little anticlimactic after all that information, but the point I’d like to drive home is that artificial sweeteners are extremely new to the human diet, and for modern, industrial foods, the operating principle should always be “guilty until proven innocent.” We’ve conducted what are essentially population-wide experiments with the introduction of other industrial foods (such as high omega-6 vegetable oils) because the initial evidence seemed promising, and we can see how well that worked out.

Despite some successful short-term weight loss studies, I don’t think the potential therapeutic effects of artificial sweeteners have been demonstrated clearly enough thus far to warrant widespread consumption, especially given the conflicting links with disease risk and the questionable influence on appetite regulation and weight control. Ultimately, while artificial sweeteners are perhaps not as scary as some might believe, I don’t recommend including them in your diet.

Please call 734-726-0153 to schedule a free consultation and evaluation. At Digestive Health Ann Arbor we are known for providing professional and compassionate care. We strive to guide people towards a comprehensive and holistic healing strategy. Restoring your body to health will restore the quality of your life.

http://chriskresser.com/the-unbiased-truth-about-artificial-sweeteners