Rhubarb is a unique vegetable known for its sour stalks.
In Europe and North America, it is often grouped among fruits.
However, in Asia its roots are more commonly used as a medicinal herb.
This article provides a detailed overview of rhubarb, its uses and potential health benefits.
What Is Rhubarb?
Rhubarb is a vegetable known for its sour taste and thick stalks, which are usually cooked with sugar.
The stalks range in color from red to pink to pale green and have a consistency that’s similar to celery.
This is what they look like:
Given that growing rhubarb requires cold winters, it’s found in mountainous and temperate regions around the world, especially in Northeast Asia. It is also a common garden plant in North America and Northern Europe.
Also, there are several varieties.
For cooking, the most commonly used variety is called culinary rhubarb, or garden rhubarb, scientifically known as Rheum x hybridum.
Bottom Line: Rhubarb is a vegetable crop grown for its thick, sour stalks, which are usually eaten after being cooked with sugar.
How Is It Used?
Rhubarb is unusual among vegetables in that it is very sour and slightly sweet.
In fact, some people who have never seen its intact stalks may mistake it for a fruit. Adding to the confusion, rhubarb is officially classified as a fruit by the United States Department of Agriculture (USDA).
Because it’s intensely sour, it’s rarely eaten raw. It is almost always cooked, sweetened with sugar or used as an ingredient.
It wasn’t until the 18th century, when sugar had become cheap and readily available, that rhubarb became popular as a food.
Before that, it was mainly used as a medicinal herb. In fact, its dried roots have been used in traditional Chinese medicine for thousands of years.
Only the stalks are used as food, most commonly in sweet soups, jams, sauces, pies, tarts, crumbles and cocktails. They can also be used to make rhubarb wine.
Sweet rhubarb pies are a traditional dessert in the UK, US and Canada. For this reason, rhubarb is sometimes called “pie plant.”
Bottom Line: Rhubarb is a vegetable that is often categorized as a fruit. Because of its sourness, it’s often used as an ingredient in jams and sweet desserts.
The Nutrient Content of Rhubarb
Rhubarb is not especially rich in essential nutrients, and its calorie content is low.
However, it is a very good source of vitamin K, providing around 26–37% of the RDI in a 3.5-oz (100-gram) serving.
This percentage depends on whether it’s cooked or not.
Like other fruits and vegetables, it’s also high in fiber, providing similar amounts as oranges, apples or celery.
A 3.5-oz (100-gram) serving of cooked rhubarb with added sugar contains:
- Calories: 116.
- Carbs: 31.2 grams.
- Fiber: 2 grams.
- Protein: 0.4 grams.
- Vitamin K1: 26% of the RDI.
- Calcium: 15% of the RDI.
- Vitamin C: 6% of the RDI.
- Potassium: 3% of the RDI.
- Folate: 1% of the RDI.
Although there are decent amounts of calcium in rhubarb, it’s mainly bound to oxalic acid in the form of the antinutrient calcium oxalate. In this form, the body can’t absorb it efficiently.
It is also moderately high in vitamin C, containing 6% of the RDI in a 3.5-oz (100-gram) serving.
Bottom Line: A 3.5-oz (100-gram) serving of cooked rhubarb contains 26% of the RDI for vitamin K. It’s also a good source of fiber. Otherwise, it’s not a significant source of essential nutrients.
Health Benefits of Rhubarb
Studies on the health benefits of rhubarb are limited.
However, a few studies have examined the effects of isolated rhubarb stalk components, such as the fiber.
Lower Cholesterol Levels
Rhubarb stalks are a good source of fiber.
In one controlled study, men with high cholesterol levels ate 27 grams of rhubarb stalk fiber every day for a month.
The researchers found that eating the stalk fiber reduced participants’ circulating cholesterol by 8% and the “bad” LDL cholesterol by 9%.
This beneficial effect is not exclusive to rhubarb fiber. Many other fiber sources are equally effective.
Rhubarb is also a rich source of antioxidant plant compounds.
One study suggests that its total polyphenol content may be even higher than that of kale.
The antioxidant compounds in rhubarb include anthocyanins, which are responsible for rhubarb’s red color and thought to contribute to the health benefits of other colorful fruits and vegetables.
Rhubarb is also high in proanthocyanidins, also known as condensed tannins.
These antioxidants are believed to be responsible for some of the health benefits of fruits, red wine and cocoa.
Bottom Line: Rhubarb is a good source of fiber and antioxidants. Studies show that rhubarb fiber may lower cholesterol, but research on its health benefits is otherwise limited.
Why Does It Taste So Sour?
Rhubarb is probably the most sour-tasting vegetable you can find.
Its acidity is mainly due to its high amounts of malic acid and oxalic acid.
Malic acid is one of the most abundant acids found in plants and contributes to the sour taste of many fruits and vegetables.
Interestingly, growing rhubarb in darkness makes it taste less sour. This method produces a variety known as forced rhubarb, which is grown in spring or late winter.
In addition to forced rhubarb’s milder taste, its stalks are more tender. These desirable properties, as well as the extra work required to grow forced rhubarb, make it more expensive than other varieties.
Bottom Line: Rhubarb is exceptionally sour, making it hard to eat raw or without sugar. The sour taste is mainly due to malic acid and oxalic acid. Forced rhubarb is much less sour than other varieties.
Safety and Side Effects
Rhubarb is among the richest dietary sources of calcium oxalate, the most common form of oxalic acid in plants.
This especially applies to the leaves, but the stalks may also contain high amounts, depending on the variety.
Too much calcium oxalate can lead to hyperoxaluria, a serious condition characterized by the accumulation of calcium oxalate crystals in various organs.
The symptoms are most often associated with the kidneys, where calcium oxalate forms kidney stones. Sustained hyperoxaluria can lead to kidney failure.
Not everyone responds to dietary oxalate in the same way. Some people are genetically predisposed to health problems associated with oxalates.
Vitamin B6 deficiency and a high intake of vitamin C may also increase the risk.
Additionally, growing evidence suggests this problem is worse for those who lack certain beneficial gut bacteria.
Interestingly, some beneficial gut bacteria, such as Oxalobacter formigenes, degrade and neutralize dietary oxalates.
Although reports of rhubarb poisoning are rare, make sure you consume the stalks in moderation and avoid the leaves. Also, consider cooking your rhubarb, since that may reduce its oxalate content by 30–87%.
Bottom Line: Rhubarb may be high in oxalate and should be cooked and eaten in moderation. Make sure to avoid the leaves.
How to Cook With Rhubarb
Rhubarb can be used in a number of ways. It is usually used in jams and sweet desserts, which contain lots of added sugar.
However, it is also easy to use in low-sugar recipes, or even with no added sugar at all. Here are a few examples.
- Rhubarb salad recipes.
- Healthy rhubarb crumble.
- Rhubarb oatmeal.
Bottom Line: Rhubarb is a popular ingredient in crumbles, pies and jams — foods that are usually loaded with sugar. However, with a bit of searching, you can also find rhubarb recipes with little or no added sugar.
Take Home Message
Rhubarb is a unique vegetable that people use in cooking and baking.
Since it may be high in oxalate, you should avoid eating too much of it and try to select stalks from low-oxalate varieties. If you are prone to kidney stones, it might be best to avoid rhubarb altogether.
On the bright side, rhubarb is a good source of antioxidants, vitamin K and fiber.
Additionally, its sour taste makes it a perfect ingredient in jams, crumbles, pies and other sweet desserts.