Sure, they look like a potato crossed with a carrot. But what are parsnips, exactly? And can they fit on a low FODMAP eating plan? Maybe. It could depend on the preparation.
Parsnips are low FODMAP at serving sizes of one-fourth to one-half cup mashed. At larger serving sizes, parsnips may contain fructans at levels beyond those suggested by low FODMAP researchers. However, there’s no clear scientific consensus on the fructan content of parsnips.
In this post, we’ll learn more about parsnips, which I think are underappreciated in the United States. We’ll also look at research on the FODMAP content of parsnips. These root vegetables contain fructose, but that’s not much of an issue. Fructans, however, could keep parsnips off your plate.
What Are Parsnips?
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If you’re reading this, you’re likely new to the low FODMAP diet. And perhaps new to the idea of parsnips. At least, that was the case for me when I began eating low FODMAP. I’d had parsnips exactly once in my life. I remembered liking them but knew nothing about them.
Parsnips are a fall and winter root vegetable most closely related to carrots. Both carrots and parsnips belong to the Apiaceae family, which also includes celery and fennel. Herbs and spices like cumin, coriander, dill and parsley are also part of the Apiaceae family.1
Parsnips were grown in ancient Rome, then made their way into the rest of Europe.2 They were widely consumed, at least until potatoes were introduced to Europe in the 1500s.3 Parsnips are sweeter than most root vegetables and were used as a sweetener in Europe before cane sugar became readily available.4
Parsnips can be eaten raw, like carrots, but have a hard, woody center. As such, parsnips are typically cooked before eating. Cooking, particularly roasting, brings out the natural sweetness of parsnips. Nutritionally, parsnips are a good source of potassium, as well as both soluble and insoluble fiber.5
FODMAP Content of Parsnips
Now that we know a bit more about parsnips, let’s talk FODMAPs. Parsnips contain two FODMAPs: fructans and fructose. But, as we’ll see, fructose isn’t what makes parsnips so sweet.
Sugar Content in Parsnips
Like carrots, parsnips have a sweet taste that really shines when they’re cooked. It’s no surprise, then, to learn that parsnips contain fructose.
But the presence of fructose alone isn’t what makes a food high or low FODMAP. Instead, we need to look at the ratio of fructose to glucose. If there’s more fructose than glucose, we say the food has “excess fructose.” The amount of excess fructose determines whether a food is high or low FODMAP.
Fortunately, we have quite a bit of data on the sugar content of parsnips. One recent study found that 100 grams of parsnips (about 3.5 ounces) has .78 grams of glucose and .73 grams of fructose.5 This means parsnips have no excess fructose.
This is confirmed by the food composition database at CSIDCares.org. This organization supports people with congenital sucrase-isomaltase deficiency, a condition that means they can’t digest certain sugars. It’s very important for CSID sufferers to know the exact nature of sugars in foods. CSIDCares maintains a database with a full breakdown of the sugar content in common foods.
The CSID database also reports that parsnips contain no excess fructose. It also shows that much of the sweetness of parsnips comes from sucrose, not fructose. The table below shows the sugar content for raw and cooked parsnips.
Fructose, Glucose and Sucrose Content of Parsnips
|1/2 cup, raw||.35||.56||2.4|
|1/2 cup, creamed/mashed||.26||.42||2.2|
As shown here, the fructose in parsnips shouldn’t be an issue for those following low FODMAP guidelines. However, that may not be the case for fructans. Despite many sources reporting that parsnips are low FODMAP, recent research may prove otherwise.
Fructan Content in Parsnips
When I first started researching the FODMAP content of foods, the most frustrating thing was that most sources simply said whether a food is high or low FODMAP, without giving any detail. They didn’t tell me what kind of FODMAPs might be in a food and in what proportions. This is the case with parsnips.
I consulted several blog posts, some from reputable sources, some from questionable sources. All of them simply state that parsnips are low FODMAP, without any further explanation. Basically, they all parrot what a popular app says, without any additional research.
Well, I did the additional research and guess what? Parsnips have fructans. The amount of fructans varies based on which study you consult, but there’s growing evidence that parsnips may contain fructans in amounts beyond low FODMAP guidelines.
Research on Fructans in Parsnips
I found two quality studies on the fructan content in parsnips. Each study used 100 grams of raw parsnip; this is a common amount used in food analysis.
The first study found that 100 grams of raw parsnip contains .39 grams of fructans, which exceeds the low FODMAP threshold of . 20 grams of fructans per serving.5,6 In contrast, the second study found that 100 grams of raw parsnip contains 1.3 grams of total fructans.7 This far exceeds low FODMAP guidelines.
Curiously, this second study found that the fructan content of parsnips declines dramatically when the parnsips are cooked. In this study, 100 grams of raw parnsips were steamed. After steaming, the fructan content was just .30 grams. This means smaller servings of cooked parsnips may fall within low FODMAP guidelines.
The primary fructan in parsnips is inulin.8 A study from 2020 found that cooking parsnips altered the amount of inulin. In this study, boiling parsnips had little overall effect on inulin levels, while steaming increased the inulin levels significantly.9
These findings call into question the currently accepted idea that cooking doesn’t significantly alter FODMAPs.10 More research needs to be done on this topic, but I’m increasingly finding data from different sources that cooking does indeed affect the FODMAP content of foods.
Are Parsnips FODMAP Friendly?
At present, it appears that cooked parsnips can fit into a low FODMAP eating plan. The fructose in parsnips shouldn’t be an issue for low FODMAPers, even those sensitive to fructose, since there’s more glucose than fructose in parsnips.
However, the jury is still out on fructans in parsnips. If you aren’t sensitive to fructans, then parsnips shouldn’t trouble you. If you are sensitive to fructans, you’ll need to test your tolerance.
And, based on my research, you may want to try cooking parsnips in different ways. Steaming parsnips seems to boost the fructan content more than boiling parsnips. I couldn’t find data on how roasting may alter the fructan content of parsnips. This is unfortunate, since roasting is one of the most common ways to prepare parsnips.
If you want to test whether you can safely add parsnips to your diet, I’d start with a small serving of one-fourth to one-third cup mashed parsnips, made from boiled parsnips. If you’re able to tolerate that, then you may try a few pieces of roasted parsnip next.
Just remember, roasting brings out the sweetness of parsnips in a way that boiling doesn’t. Expect your roasted parsnips to taste different than the boiled version.
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.