"Natural" is not a synonym for safe. That said, the data on stevia, monk fruit and allulose is relatively clean so far.
The three differ in how sweet they are and in what your body does with them.
Sweetness runs from 400 times sugar down to 0.7 times
| Sweetener | Sweetness vs sugar | Calories (1 g) |
|---|---|---|
| Stevia | 200–400x | 0 kcal |
| Monk fruit | 150–250x | 0 kcal |
| Allulose | 0.7x | 0.4 kcal |
| Sugar | 1x | 4 kcal |
Allulose is the only one less sweet than sugar, so you can use it by volume the way you use sugar. It is also the only one that browns in the oven.
Stevia and monk fruit reach the same sweetness at a four-hundredth of the amount, so a batter made with them comes out short on volume.
Stevia has a daily limit
The acceptable daily intake for steviol glycosides is 4 mg per kg of body weight. At 60 kg that is 240 mg a day.
A can of a stevia-sweetened drink usually holds a few dozen mg, so normal drinking will not get you there.
Monk fruit has no set daily limit. That is not a safety rating. So little is needed for full sweetness that regulators saw no need to set one.
Too much allulose upsets your stomach
Your body absorbs almost no allulose and passes it through. Blood sugar and insulin barely move.
The cost is gas and diarrhea when you take a lot at once. The tolerated amount in one sitting is around 0.4 g per kg of body weight.
Finish a tub of "zero sugar" ice cream or a bag of jelly and you take in allulose or sugar alcohols all at once. The stomach ache is about the amount, not about your body rejecting the ingredient.
Blending cuts the aftertaste
Stevia leaves a bitter, licorice-like aftertaste. Monk fruit leaves a faint fruity note.
That is why products blend two or three of them. One covers what the other leaves behind.
At home, pick by the job
- •Coffee and tea: a drop or two of stevia or monk fruit
- •Baking: allulose, since you need volume and browning
- •Yogurt and fruit: allulose, the closest match to sugar
- •Desserts you eat a lot of at once: half the amount, whichever you use
One tablespoon of sugar is 48 kcal. Switch the sugar in two cups of coffee to stevia and that is 35,000 kcal a year, worth 4.5 kg of body fat. That holds only if nothing else changes.
Sources · JECFA evaluation of steviol glycosides · US FDA GRAS notices (monk fruit, allulose) · Korea's Ministry of Food and Drug Safety sweetener standards