Is Zucchini Low FODMAP?
For years, zucchini was considered a “safe” vegetable for those eating low FODMAP. And many books and online sources still list zucchini as low FODMAP. But other sources suggest limiting zucchini. So, what gives? Is zucchini a high or low FODMAP food?
Zucchini is low FODMAP in servings of one-fourth to one-third cup. Zucchini has both excess fructose and fructans. At larger servings, zucchini exceeds low FODMAP guidelines in both categories. At one-half cup (sliced or chopped) zucchini becomes medium to high FODMAP for fructose and fructans.
In this post, we’ll look at the FODMAP content of zucchini. We’ll also discuss how zucchini compares to yellow squash. Zucchini is typically considered a green vegetable, but there are yellow varieties of zucchini that can be confused with other yellow summer squashes. So, we’ll take a short dive into that, too.
FODMAPs in Zucchini
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When it comes to FODMAPS in squash, the primary concerns are excess fructose, fructans and polyols. Currently, there are only two identified FODMAPs in zucchini, fructose and fructans.
Since zucchini doesn’t taste sweet, you may be surprised that it has fructose. But zucchini, like all squashes, is technically a fruit. So the presence of fructose isn’t that surprising.
The fructose content in zucchini is well-documented, but there’s less data on fructans in zucchini.
Fructose Content of Zucchini
Summer squashes like zucchini lack the notable sweetness of winter varieties like butternut squash and pumpkins. The sweetness of winter squashes doesn’t come from fructose, but rather from a high sucrose content. Zucchini has much less sucrose, so it doesn’t taste sweet, even though zucchini has a fair amount of fructose.
When it comes to FODMAPs, it’s not the amount of fructose in a food that matters as much as the ratio of fructose to glucose. If a food has more fructose than glucose, or “excess fructose,” then it may qualify as high FODMAP.
Currently, a food that has more than .40 grams of excess fructose is classified high FODMAP. However, if another FODMAP is present in the food, that number drops to .15 grams.1 Since zucchini also contains fructans, we use the lower number when deciding if there’s enough excess fructose in zucchini to qualify as high FODMAP.
The table below shows the glucose, fructose and excess fructose content for different serving sizes of zucchini.
Glucose, Fructose and Excess Fructose in Zucchini
| Serving Size | Weight (ounces) | Glucose (grams) | Fructose (grams) | Excess Fructose (grams) |
|---|---|---|---|---|
| 1 small | 4.16 | 1.26 | 1.63 | .37 |
| 1 medium | 6.91 | 2.10 | 2.70 | .60 |
| 1 large | 11.39 | 3.46 | 4.46 | 1.0 |
| 1 cup, chopped | N/A | 1.33 | 1.71 | .38 |
| 1 cup, sliced | N/A | 1.21 | 1.56 | .35 |
As the table shows, zucchini has enough excess fructose to be classified as high FODMAP. You would need to reduce serving size to about half a small zucchini or a third of a cup of sliced or chopped zucchini to bring the excess fructose level below those recommended by low FODMAP researchers.
Fructan Content in Zucchini
While the fructose content of zucchini is well-established, the data on fructan content is less clear.
In a study that analyzed low FODMAP lists from different countries, zucchini appeared on five of the lists. Four of these reported that zucchini is low FODMAP. The fifth, from FODMAP researchers at Monash University, found that zucchini is medium FODMAP, testing for medium levels of fructans.3
Another study looked specifically at fructan content of common fruits and vegetables, including zucchini. This study found that 100 grams of raw zucchini (the standard measure used in food analysis) contains .8 grams of fructans. However, after the zucchini was steamed, the fructan content increased to 1.0 grams.4
This last study raises questions about how cooking alters the FODMAP content of foods. The current belief is that cooking doesn’t significantly change the FODMAPs in food.5 However, studies like this indicate that cooking, either through steaming, boiling or other methods, can alter the FODMAP content of food. In this case, the fructan content increased. For other foods in the same study, steaming decreased the fructan content.
The role of cooking in reducing (or possibly increasing) FODMAPs needs a lot more research. Until that happens, you’ll just have to test your tolerance for cooked versions of specific foods. And, you may need to try different cooking methods, too. As I wrote in my post on parsnips, there’s some evidence that boiling and steaming foods lead to very different changes in fructan content.
Now that we know zucchini is high FODMAP at many serving sizes, you may be wondering about yellow squash. This, along with zucchini, are what most people envision when they think of summer squash (though there are certainly other summer squashes, like pattypans).
Short Guide to Summer Squash
While we typically think of zucchini as a green vegetable, there are yellow varieties of zucchini. I thought a short discussion on the difference between yellow zucchini and yellow squash might be helpful.
Yellow zucchini have the same shape as green zucchini and have the green “cap” at the top where the fruit was attached to the stem. Nutritionally, there’s no difference between green and yellow zucchini.
There are two types of elongated yellow squashes that look a bit like zucchini.6 Most of us are familiar with the crookneck yellow squash. This is easy to spot, since the neck of the squash makes a curved shape. This is the type of yellow squash most commonly sold in grocery stores, at least in my area of the country.
Another type of yellow squash is yellow straightneck squash. This looks more like yellow zucchini because the neck doesn’t have a distinct curve.
But straightneck yellow squash does have a shape distinct from zucchini. Straightneck squash is full on the bottom, but thins in the middle, before growing a bit larger around the neck (or stem end) of the squash. Also, unlike zucchini, which typically has a round bottom, straightneck squash is more likely to be pointed on the end opposite the neck.
Nutritionally, there are slight differences between zucchini and yellow squash. I wasn’t able to find data for straightneck squash, but the following section describes some differences between zucchini and yellow crookneck squash.
Is Yellow Squash Low FODMAP?
Yellow squash, sometimes called crookneck squash is closely related to zucchini; both are members of the C. pepo variety of squash. It’s logical, then, to assume they share characteristics. That said, data on crookneck squash is limited.
For example, I wasn’t able to find information on fructan content in yellow squash. I think it’s safe to assume yellow squash contains some fructans, just like zucchini. But I wasn’t able to find any publicly available data just on yellow squash. If you’re sensitive to fructans, you’ll need to test your tolerance for yellow squash.
As for fructose content, the fructose levels in yellow squash are quite a bit higher than that of zucchini.
For example, one cup of sliced yellow squash contains 2.02 grams of fructose, compared to 1.52 grams for zucchini. The glucose content is 1.56.7 So, yellow squash has a greater amount of excess fructose than zucchini. If you’re sensitive to fructose, you’ll need to watch your portion size when it comes to these summer squashes.
Is Zucchini a Low FODMAP Food?
The conclusion here is that zucchini can be a low FODMAP food, if you limit your serving size to less than one-half cup. At servings larger than that, zucchini contains excess fructose and likely contains fructans higher than recommended levels. This is probably true for yellow crookneck squash, too.
As mentioned, you may want to try different cooking methods when testing your tolerance for zucchini. It’s possible that different ways of cooking can change the FODMAP content of food. A lot more research needs to be done here, so until then, you’ll have to experiment on your own.
And remember that everyone’s tolerance level is different. Just because zucchini may contain fructans doesn’t necessarily mean you won’t be able to eat it. For example, I have fructan sensitivity, but only to very high levels of fructans.
I can’t eat raw onions, which have some of the highest fructan levels. But I can eat many foods that have lower fructan levels, including zucchini. If I had blindly followed low FODMAP guidelines, I would’ve cut a lot of foods from my diet unnecessarily.
Remember, the low FODMAP system isn’t supposed to be overly restrictive, even if it often feels that way. There’s a lot of variation within the FODMAP categories, especially fructans. You really do need to test your tolerance levels for different foods, not just different FODMAPs.
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.
