Allulose

Allulose is a rare sugar that tastes and bakes much like ordinary sugar but carries almost no calories and blunts the blood-sugar spike after a meal. It also prompts the gut to release glucagon-like peptide-1 (GLP-1), the hormone weight-loss drugs mimic — but far less than a prescription drug delivers, so it is a good sugar substitute, not a "natural Ozempic".

For baking or cooking where you need sugar's bulk, allulose is the best-evidenced substitute, if you can get it and afford it. Keep a single serving under about 0.4 g per kilogram of body weight (about 28 g for a 70-kg adult) to spare your gut.

What it is

Allulose is a rare sugar: a natural sugar whose slightly different shape changes how the body handles it. It has about 0.4 kcal per gram, against sugar's 4. Roughly 70% is absorbed and passed unchanged in urine, and the rest reaches the colon and resists fermentation, which is why the US Food and Drug Administration (FDA) counts it as almost calorie-free and leaves it out of "added sugars" on labels.^[1]

It is "generally recognised as safe" in the US but not authorised in the EU, where the European Food Safety Authority could not establish safety on the dossier it was sent.^[2] That is a gap in the submitted evidence, not a finding of harm.

What it does to blood sugar

Pooled across twelve trials, taking allulose before a meal moderately lowers the glucose and insulin rise afterwards, especially with carb-heavy meals. It doesn't change long-term blood sugar (HbA1c), fasting glucose, blood fats or body composition.^[3]

The GLP-1 story, sized properly

In 18 lean young adults, 25 g of allulose delivered by tube into the stomach triggered a gut release of GLP-1, alongside two other fullness hormones.^[4] In rats and mice, that release signals fullness to the brain through the vagus nerve, and cutting the nerve or removing the GLP-1 receptor blunts allulose's anti-obesity and glucose effects.^[5] The nerve step hasn't been shown in people, and the hormone signal is tiny beside a prescription GLP-1 drug.

Claims that allulose is a "longevity mimetic" rest on fat cells in a dish and lifespan in worms.

The limit is your gut

Severe diarrhoea appeared at 0.5 g per kilogram of body weight in a single dose. The researchers recommend staying under 0.4 g/kg in one sitting and 0.9 g/kg across a day — about 28 g and 63 g for a 70-kg adult.^[6] Loose stools and gas are the most common limit.

Mouth bacteria can't turn allulose into enamel-dissolving acid, so it spares your teeth the way sugar doesn't.^[7]

Tagatose, its cousin

Tagatose is another rare sugar, with about 1.5 kcal per gram. In pooled small trials it improved long-term blood sugar by about a quarter of a percentage point, with no effect on blood fats.^[8] Its only known downside is the gut: in one pilot, ten of twelve people reported stomach side effects.

What to do

Use allulose for baking if cost and availability allow; otherwise a little ordinary sugar within a Mediterranean-style diet is fine.
Stay under about 0.4 g/kg per sitting.
Don't take it as a weight-loss or longevity supplement. Its value is replacing sugar.

For calorie-free sweetness in drinks, see stevia; the full comparison is on Sugar substitutes.