Here is the headline that caught my eye:
FDA Allows Allulose to be Excluded from Added Sugars
Has the FDA sold out? In 2018 FDA changed nutritional labeling to include a line reporting the amount of added sugars in food products, and now they are letting manufacturers add the rare sugar allulose without listing it as an added sugar. What gives?
First, let's talk about what allulose is. It's a sugar (also known as psicose) that is almost identical to fructose, and it is found in very small quantities in jackfruit, raisins, figs, wheat, and other plants. Chemically, it differs from fructose only in the stereochemistry at one carbon atom. This subtle difference has some important effects. It is only 70% as sweet as fructose, and it is very difficult for the human body to metabolize. As a result, it provides only 0.2 calories per gram (compared to 4 calories per gram for sucrose, glucose, fructose, and other sugars). A perfect sugar replacement, right?
Since it isn't metabolized like most sugars, the FDA decided allulose does not have to be included under "Total sugars" or "Added sugars." But allulose does have to be included under "Total carbohydrates." Total carbohydrates include starches and fibers in addition to sugars, so it seemed sensible to include allulose in this category.
What happens to allulose in the body? A portion (10-25%) can be absorbed into the human body, using the same transport protein that absorbs fructose. Absorbed allulose is excreted in the urine. Unabsorbed allulose remains in the digestive tract until it reaches the colon, where it encounters many species of bacteria that can digest it; the results may be gas, short chain fatty acids that draw water into the colon, and diarrhea if too much allulose is consumed. How much is too much? Studies suggest that most people can tolerate up to 30 grams without adverse effects, and it is further estimated that 90% of the population would not consume more than this amount. The risk would increase if you found a great no-sugar-added candy or ice cream that relies on allulose, and then you were to binge on it.
There are several other rare sugars currently being developed as sugar substitutes. In general, they provide some level of sweetness and have the bulk and physical properties that sugar usually provides. They offer taste and functionality with far fewer calories, and they have the potential to cause problems when they are fermented in the lower digestive tract. The key, as with most foods, is to use them in moderation.