Replacing sugar with allulose

Let’s step back for a moment. What, exactly, is allulose? It is yet another monosaccharide, but with a twist. You see, the structure of allulose differs from fructose at one of the carbon atoms (c3) where the hydroxl (-OH) group is on the opposite side. Allulose is an epimer of fructose.

Figure. Comparison of fructose and allulose structures. [source]

Although it is functionally classed as a carbohydrate, allulose is mostly absorbed in the small intestine without being converted into energy: at least 90% is excreted by the kidneys without being metabolized.  This means that in a functional sense allulose has 95% fewer calories than sucrose and is why the FDA determined in 2019 that it does not need to be listed under total or added sugar. Interestingly, despite being almost the exact same molecule as fructose, allulose is also a bit less sweet (70% the sweetness of sucrose—what many studies commonly compare to as opposed to fructose, which is less-frequently substituted). An animal study in rats reported that allulose only contributes to 0.3% of the energy deposit in animals. But it gets better. 

It would be enough if allulose didn’t elicit a physiologic response in the way that other carbohydrates do (i.e., increase blood sugar, insulin response, de novo lipogenesis). But allulose may induce a number of other intriguing and beneficial responses. Data from animal studies suggest that compared to fructose and/or glucose, allulose may lower blood glucose, reduce abdominal fat, decrease insulin resistance and fat accumulation in the liver, and prevent or delay the onset of type 2 diabetes. In a recent meta-analysis of human trials, when allulose was given with carbohydrate-containing meals, it was found to decrease postprandial glucose by 10% (noting that the quality of evidence is moderate). I can anecdotally support that when I put allulose into black coffee, my blood glucose goes down. Usually black coffee would be neutral for my blood sugar, so this suggests that allulose is pulling glucose out of my body via my kidneys. In my experience, it also doesn’t leave me with that weird, slightly astringent aftertaste left by many sugar substitutes. Allulose even feels like sucrose if I were to grab a handful of the substance. Let that all sink in for a moment: allulose—slightly less sweet than the taste profile of sucrose, with the mirror image configuration of fructose—does not increase blood glucose, but actually drags glucose with it to excretion. 

But is there a catch regarding its safety? It would be reasonable to question the safety profile of a compound that renally excretes glucose. While there isn’t a study looking at cancer and allulose per se, in order to inductively reason the risk profile that may not yet be reflected in the literature, we can refer to a 2019 meta-analysis study of sodium-glucose co-transporter-2 inhibitors (SGLT-2i) and cancer: SGLT-2i are drugs used in patients with type 2 diabetes and cause glucose to be excreted by the kidneys in amounts far larger than allulose. The study prospectively looked at a cohort of more than 20,000 patients, with randomization over a minimum 12 month period, and it didn’t find an increase in the risk of any cancer—with no risk for bladder cancer, in particular. While this study is about SGLT-2i and not allulose, it is reassuring that a drug that drags A LOT of glucose through the kidney to the bladder found no increase in cancer. 

Allulose-specific literature suggests that the compound does not have many side effects. Animal studies have found no toxicity at high doses (2 g/kg in rats and 4 g/kg in dogs). And while some people experience digestive issues after consuming allulose, they are usually temporary and mild, especially when compared to other sugar substitutes, such as alcohol sugars: A non-randomized study of 30 healthy young participants recommended a maximum single dose of 0.4 g/kg and a maximum total daily intake 0.9 g/kg. This means that an adult who weighs 150 pounds could take up 61.2 grams daily with few side effects (the equivalent of more than 15 packets of sugar). However, consuming more than the recommended amounts of allulose per day may cause side effects such as bloating, gas, diarrhea, and abdominal pain.  The fact that allulose is excreted via the kidneys, meaning it probably spends less time in the gut, is possibly the reason it takes a high dose before we see the gastrointestinal side effects that we see with other substitutes.

At the risk of sounding like the Consumer Reports of sugar alternatives, I favor allulose for the mouthfeel, safety profile, and of course its impact on blood glucose, followed by monk fruit. In my opinion, these are the only two non-“sugar” sweeteners that really taste like sugar. After that I would settle for alcohol sugars like erythritol and xylitol. But this is very much a matter of individual taste. 

Although allulose is not as sweet as sugar, I have found that when my daughter bakes with a 1:1 replacement ratio as called upon by recipes, it is still plenty sweet. In short, allulose provides a reasonable amount of sweetness for my family. One aesthetic caveat is that allulose browns in the baking process so it is best used for darker-colored goods…unless you are like me and don’t mind a brown-colored angel food cake. And—assuming my exposé on allulose has provided enough convincing to give it a go—if you need some inspiration as you embark on recipes with allulose replacement, here is one of my daughter Olivia’s allulose-sweetened cakes to whet your palate.