Taken with meals
Fructaid Glucose Isomerase Capsules
An enzyme that converts fructose to glucose in the gut, for people whose bloating follows fruit, honey and sweet drinks.
- Format
- Capsule
- Type
- Digestive enzyme
- Cost
- $0.44 a day
- Customer rating
- 4.3 out of 5 from 609 ratings from Amazon
What customers consistently report
- Eating fruit again without the bloating and cramps
- A clear difference when taken before, and none when forgotten
- Covering fructans in onion and garlic for some users
Those are the themes that recur across the reviews. Moderate review confidence — 4.3 from 609 Amazon ratings.
Why it might work
Fructose is absorbed by a transporter that is easily overwhelmed; what is not absorbed reaches the colon and ferments, which is fructose malabsorption. Xylose isomerase converts fructose into glucose, which is absorbed by a different, high-capacity route. Taken just before fruit or sweetened food, the enzyme changes the sugar before it can reach the bacteria. It does not act on lactose or on the galactooligosaccharides in beans.
What the research supports
Ingredient-level evidence from one good trial. A double-blind, placebo-controlled crossover study gave people with confirmed fructose malabsorption oral xylose isomerase (the same enzyme as glucose isomerase) with a fructose solution: breath hydrogen fell significantly, showing the fructose was absorbed rather than fermented, and nausea and abdominal pain improved against placebo. The enzyme is not absorbed and acts only on the food. No trial of the Fructaid brand was found.
What the label discloses
The listed ingredient is glucose isomerase enzyme; the activity units per capsule are not stated on the listing. The brand states the product is gluten-free and lactose-free. No third-party testing certificate or allergen statement appears on the listing.
Who this tends to suit
We match this product to people reporting symptoms that follow particular foods, bloating, gas, general abdominal discomfort and loose stools. It fits someone whose priority is handling meals or day-to-day comfort. Whether it is the best fit for you depends on the rest of your answers — what you have already tried, what format you will take, and anything that has to be ruled out.
Where it may not fit
The label supports gluten-free, dairy-free and no added sweeteners. A capsule only works if you will take it as often as the label directs.
Side effects and what to be aware of
It only helps if fructose malabsorption is actually the problem, which a breath test can confirm; for bloating from other causes it does nothing. The dose is one to four capsules a few minutes before the food, and at $0.44 a capsule a fruit-heavy day adds up. Reviewers call it life-changing and expensive in the same breath.
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Others we researched for the same job
These sit in the same role as Fructaid Glucose Isomerase Capsules — taken with meals — so they are the sensible things to weigh it against.
See all the products we have researched →
Related reading
Background on how this type of product works, read from the trial evidence.