Is Watermelon High Fructose?

One of the things that inspired me to eat low FODMAP is my inability to properly digest many fruits. I realized early on that I have fructose malabsorption. I’d known for years that I’m lactose intolerant, but I’d never heard of fructose malabsorption.

Once I identified fructose as a problem, I started studying this FODMAP in more detail. I learned that up to a third of the world’s population may be afflicted with fructose malabsorption.¹ So, I started writing posts that focus specifically on fructose. This post is part of that series, focusing on fructose in watermelon.

Watermelon is high in fructose, based on accepted guidelines for a low fructose diet. Ten watermelon balls have about 4 grams of fructose, while a typical watermelon wedge contains over 9 grams of fructose. Both of these exceed the suggested amount of 3 grams of fructose per serving.

In this post, we’ll look at the fructose content of watermelon at different serving sizes. It’s possible to stay within some low fructose guidelines here, if you watch your portion sizes. We’ll also look at how watermelon compares to other popular melons and whether those may be lower fructose alternatives.

Fructose in Watermelon

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Before we get started, we need to understand what high fructose means and how it differs from high FODMAP. Generally, there are two ways to define whether a food is high fructose: based on fructose content and based on fructose percentage.

In the first case, a food is classified as high fructose if it contains more than 3 grams of fructose in a standard serving.² For fruits and vegetables, the generally accepted serving size is half a cup. For liquids, such as fruit juice, a typical serving is 8 ounces.

In the second case, a food is classified as high fructose if fructose makes up more than 50% of the total naturally occurring sugars in the food. Again, we use typical serving sizes when making these measurements.³

In contrast, a high FODMAP food is one that exceeds a specific fructose-to-glucose ratio. So, it’s not the amount of fructose that determines if a food is high FODMAP. Instead, the FODMAP classification is based on the amount of fructose in relation to the amount of glucose. Generally, if the amount of “excess fructose” in a food is .40 grams or more, the food is classified as high FODMAP.⁴

Now that we know how to determine if a food is high fructose, let’s look at the fructose content of watermelon. The following table shows the amount of fructose in fresh watermelon at different serving sizes.

Fructose in Watermelon (grams per serving)

Serving	Weight (ounces)	Fructose (grams)
1 wedge	10	9.6
10 balls	4.3	4.1
1/2 cup, diced	N/A	2.5

As shown in the table, watermelon is high fructose at most serving sizes. However, if you reduce the serving size to half a cup of diced watermelon, then the amount of fructose is within acceptable guidelines.

It’s difficult to find criteria for the low fructose (also known as the fructose restricted) diet. The best sources I found suggest limiting total fructose intake to between 10 and 15 grams a day.^6,7 So, if you’re monitoring total fructose content, you can fit small servings of watermelon into your eating plan.

Remember, though, there’s another way to measure fructose content. The following table lists the total sugar content of watermelon for the same serving sizes used earlier. The final column of the table shows fructose as a percent of total sugar content. If a food is more than 50% fructose at a particular serving size, it’s considered high fructose.

Fructose as Percent Total Sugar Content of Watermelon

Serving	Weight (ounces)	Glucose (grams)	Sucrose (grams)	Fructose (grams)	Total Sugar (grams)	Percent Fructose
1 wedge	10	4.5	3.5	9.6	17.6	54.5
10 balls	4.3	1.9	1.5	4.1	7.5	54.6
1/2 c, diced	N/A	1.2	.92	2.5	4.6	54.3

As shown in this table, watermelon is high fructose when the percent total sugar method is used. Fructose percent varies slightly based on serving size, but generally, fructose accounts for 55% of the sugar in watermelon. This exceeds the 50% threshold, making watermelon a high fructose food at all serving sizes.

If you monitor your overall fructose intake, you may be able to eat a half cup of watermelon, as it contains less than 3 grams of fructose. However, if you need to more closely monitor the fructose ratio of your foods, then watermelon may be off the menu for you.

As I wrote in another post, the fruit’s high fructose-to-glucose ratio is one reason watermelon is classified high FODMAP. In addition, watermelon also contains excess fructans and high amounts of polyols. If fructans and polyols don’t bother you, then you’re probably reacting to fructose if you have trouble digesting watermelon.

You may be wondering, then, if you could substitute other kinds of melon for watermelon. Honestly, there’s not good data on most types of melon. The best available data is for cantaloupe and honeydew. We’ll look briefly at those now.

Fructose Content of Watermelon versus Other Melons

If you can’t eat watermelon due to its high fructose content, you may have luck with two other common melons, honeydew and cantaloupe. The following table summarizes the fructose content and percent fructose for the three melons at a serving size of one diced half-cup.

Fructose as Percent of Sugar Content of Various Melons

Type	Glucose (grams)	Sucrose (grams)	Fructose (grams)	Total Sugar (grams)	Percent Fructose
Watermelon	1.2	.92	2.5	4.6	54.3
Honeydew	2.3	2.1	2.5	6.9	36.2
Cantaloupe	1.2	3.4	1.5	6.1	24.6

As shown in the table, a half cup of diced honeydew contains 2.5 grams of fructose, the same as watermelon.

However, because the ratios of fructose, glucose and sucrose are more balanced in honeydew than in watermelon, fructose accounts for only 36% of total sugar in honeydew. So, if the high percentage of fructose in watermelon is a no-go for you, honeydew may be an option.

But, as I wrote on this post concerning FODMAPs in honeydew, this melon also contains fructans and polyols, specifically sorbitol. If fructans or polyols cause you digestive problems, then your best option for melon is probably cantaloupe.

In contrast to watermelon and honeydew, the primary sugar in cantaloupe is not fructose but sucrose. In fact, cantaloupe contains the lowest amount of fructose of all common types of melon. A half cup of diced cantaloupe contains only 1.5 grams of fructose.

Moreover, cantaloupe contains the lowest percentage of fructose of all three types of melon. About 25% of the sugar in cantaloupe is fructose, compared to over 50% for watermelon.

Even more good news is that fructose is currently the only known FODMAP in cantaloupe. As I discussed in this summary of FODMAPs in melon, researchers have not identified fructans or polyols in cantaloupe. So, if you have multiple FODMAP issues, including fructose, cantaloupe may be a great fruit option for you.

Conclusion: Watermelon is High in Fructose

While smaller, half cup servings of watermelon have less than 3 grams of fructose, the high percentage of fructose in watermelon makes this a high fructose fruit. On average, fructose accounts for about 55% of the total sugar in watermelon, which is more than the 50% threshold associated with the low fructose diet.

If fructose is your only concern, then you can safely fit small servings of both honeydew and cantaloupe into your diet. Each of these contain less than 3 grams of fructose per half cup and also contain less than 50% fructose overall. Be aware that honeydew does contain other FODMAPs, though at seemingly safe levels. As yet, fructose is the only recognized FODMAP in cantaloupe.

Just remember that both the low fructose and low FODMAP diets are meant to treat specific digestive issues. If fructose doesn’t cause you intestinal distress, there’s no reason to limit it, even if you follow the low FODMAP diet for other reasons.

Posts Related to “Is Watermelon High FODMAP?”

I’m slowly building this fructose-focused series. If you’re interested in the fructose content of other popular fruits, check out my post on fructose and bananas.

I do okay with bananas, but my inability to digest even small amounts of apples was the first clue that I have fructose malabsorption. You can read more about that in my post on fructose in apples.

I’ve also written posts on FODMAPs in popular melons. You can learn more about watermelon here, including why it’s generally a terrible choice for low FODMAPers. I’ve also written in detail about honeydew, which can be a better choice, since it seems to contain safe levels of fructose, fructans and polyols.

If you just can’t stomach watermelon, an alternative may be kiwi. An average size green kiwi is low fructose. However, yellow (or golden) kiwi scores higher on the fructose scale. You can learn more about each variety in this post on fructose in kiwi.

About the Author

Amanda Coleman, PhD, studies food culture and teaches a popular Food and Society course. Years of digestive problems led her to live low FODMAP. Now she uses her research and analysis skills to help others understand FODMAP essentials, so they can lead better, healthier lives.