Why Do Grapes Cause Gas? (There’s 1 Main Reason)

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There’s something special about grapes that often make them cause gas…

It’s really easy to eat a lot of grapes. They are basically pure sugar after all.

Ultimately, the reason that grapes cause gas is because they are very high in fructose. The only solution is to control your serving size.

If you want to understand why this happens, and how many grapes is a common threshold to producing gas, read on.

What Causes Gas in Fruits?

Flatulence and bloating are not complicated, they’re just things that most people never learn about.

All you need to know is that almost all gas is caused by carbohydrates.

Some carbohydrates either don’t digest at all, or only partially in the stomach and small intestine. They go onto the large intestine where your gut bacteria ferments them.

Fermentation produces gasses, which either build up (bloating) or are released (flatulence).

The 2 main types of carbohydrates that commonly lead to gas are:

  • Fiber
  • FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) – Fructose is considered one of these (a fermentable monosaccharide).

Nutritional Profile of Grapes

Let’s take a quick look at the macronutrient profile of grapes.

The data below is for a 100 gram serving, which is about 20 normal-sized grapes.

  Grapes
Energy (kcal) 69
Protein (g) 0.72
Total Lipid (g) 0.16
Carbohydrate (g) 18.1
Fiber (g) 0.9
Sugars (g) 15.5

There’s 2 things we can note.

First, grapes are actually quite low in fiber compared to many other fruits. Usually it takes a minimum of 10-15 grams of fiber to cause any gas issues, so it’s very unlikely that the fiber in grapes is a significant issue for most.

Second, grapes are almost pure sugar, and most of that is fructose, and we’ll see below.

FODMAPs in Grapes

A team of researchers measured the amount of FDOMAPs in several common foods.

Grapes are quite low in FODMAPs, other than fructose.

The table below shows a breakdown of the carbohydrates in grapes, and omits all the FODMAPs that were not found in detectable amounts. 

Even though this data is also for 100 grams of grapes, it’s a different variety and sample from the USDA nutrition data above, which is why the numbers don’t add up to the exact same total.

Grape, red Vranec
Moisture 74 g
Fructose 8.13 g
Glucose 13.75 g
Sucrose 0.83 g
Total FOS 0.08 g

Glucose is not a FODMAP, it digests very easily.

FOS stands for fructooligosaccharides, which is a specific class of oligosaccharides. It’s technically found in grapes, but a very small amount, so it’s not really an issue.

The only potential issue is that grapes are higher in fructose than every other fruit (of common fruits at least).

How Much Fructose Causes Side Effects?

Fructose intolerance has been studied a lot more in the last few decades, along with FODMAPs in general.

Some people are more sensitive to certain FODMAPs than others, which makes them difficult to study. Depending on sensitivity and the amount consumed, people can experience any of the following symptoms:

  • Belching
  • Bloating
  • Gas
  • Stomach pain
  • Diarrhea

One study of fructose intolerance looked at how many people registered a positive test result showing gas produced from fructose consumption. They found that:

  • 73% of subjects tested positive when consuming 50 grams of fructose
  • 70% tested positive from 30 grams of fructose
  • 39% tested positive from 15 grams of fructose

In other words, most people cannot tolerate a large amount of fructose with no side effects. At the very least, they will likely experience some bloating or flatulence.

Reducing Gas From Grapes

As we just saw, many people show signs of fructose intolerance with just 15 grams of fructose, which is about 200 grams of grapes, or about 40 grapes.

Obviously, some of these people will even experience side effects with a smaller serving size, and you might be one of them.

If you really want to test your limits and reaction to fructose, you can try eating other fruits that are relatively high fructose like:

  • Apple 
  • Blueberries
  • Pears

None have quite as much as grapes, but enough that you can test your tolerances.

About the author

Dale Cudmore

Your friendly neighborhood vegan from Toronto. Chemical engineer turned semi-professional soccer player and freelance nutrition writer. I've been vegan for years and try to make life easier for others by sharing what I've learned.