Rhubarb (organic?)

Rhubarb (Rheum rhabarbarum) should be eaten cooked. Eating large quantities of raw rhubarb may be dangerous in certain circumstances.

Culinary uses:

Rhubarb tastes tart and refreshing. The stalks can be cut, cooked, and eaten, peeled or unpeeled. Cooking vegetables is usually not ideal as it tends to result in valuable nutrients being lost. However, raw rhubarb contains high amounts of oxalic acid, meaning that it deprives the body of important minerals such as calcium, magnesium, and iron. This can be dangerous under certain circumstances, especially for children and people with biliary and kidney diseases.

You should not eat rhubarb leaves because they contain a lot of oxalic acid.

Rhubarb tends to be considered a fruit because of its use in desserts and sweet recipes, but it is actually a vegetable. Rhubarb jams and compotes are some of the most popular dishes made from rhubarb, alongside cakes and muffins. Rhubarb can also be pressed into juice or made into ice cream. Another option are rhubarb chutneys, which are tangy and delicious. Although rhubarb is rarely eaten as a vegetable, you can boil the flower buds like broccoli and cauliflower.¹

You can reduce the amount of oxalic acid in rhubarb by selecting certain types (e.g., Holstein Bloodred rhubarb) or by neutralizing the acid by adding certain spices and other ingredients. Ingredients that can neutralize rhubarb stalks include lemon juice, wild celery stalks, nutmeg, cloves, cinnamon, and bay leaf. These spices also go well with rhubarb’s flavor. On the other hand, traditional English rhubarb marmalades are flavored with ginger, orange, and arnica.² If you combine young stems with thicker stems, which are older and more acidic, if may be worthwhile to peel the skin. This is because it contains more oxalic acid.³

The oxalic acid in rhubarb reacts with aluminum and other metals. This means that you should avoid cooking rhubarb in aluminum pots or wrapping it in aluminum foil.² We recommend cooking rhubarb in heat-resistant glass or ceramic dishes and storing it in acid-resistant plastic containers.³ Pour away the cooking water; do not drink it.

Purchasing — where to shop?

Rhubarb stalks are usually sold with the flower heads and leaves removed. During rhubarb season (April to June in the northern hemisphere), rhubarb can be found at all major supermarkets, including Walmart, Whole Foods Markets, Kroger, and Safeway (United States); Extra Foods, Metro, and Freshmart (Canada); Asda, Sainsbury’s, Tesco, Aldi, and Lidl (Great Britain); Woolworths, Coles, Aldi, and Harris Farm (Australia). We recommend opting for organic rhubarb, or if possible buying rhubarb at fresh food markets or directly from farms. This will ensure that your rhubarb is organic.

You should not eat rhubarb leaves, even if you have bought organic rhubarb. All of the green parts of rhubarb are poisonous because of their oxalic acid content. The oxalic acid contained in the stalks is relatively harmless if the rhubarb is harvested before mid to late June (in the northern hemisphere). After June, the amount of oxalic acid in the plant reaches dangerous levels.²

Finding wild:

Unlike in Asia, rhubarb is rarely found in the wild in Europe.⁴ See the section “Danger of confusion” below.

Storing:

Ideally, rhubarb should be processed immediately after purchasing. If you want to keep the stems fresh for a few days, wrap them in a damp cloth and store in a cool place. Rhubarb can also be frozen while fresh. It will keep for about a year frozen.⁵

Nutrients — nutritional information — calories:

Rhubarb is low in calories (21 cal/100 g) and contains a variety of healthy nutrients including potassium, iron, vitamin K, vitamin C, and fiber (see the nutritional tables below).⁶ At 29 µg/100 g, rhubarb contains considerable amounts of vitamin K, which is similar to the amount of vitamin K found in raw celery and alfalfa, and a little higher than the amount of vitamin K found in snow peas, sauerkraut, and peas. Kiwi, celery root, and asparagus all contain approximately 40 µg/100 g of vitamin K, a higher amount than rhubarb. Some foods are extraordinarily rich in vitamin K, including broccoli (100 µg/100 g), spinach (approx. 483 µg/100 g), and kale (approx. 705 µg/100 g). If you eat a natural balanced vegan diet, you will definitely meet your vitamin K needs.

Fruit acids are important for giving rhubarb its flavor, especially malic, citric, and oxalic acid. Rhubarb with red stems contains less fruit acids than rhubarb with green stems. Rhubarb stems contain an average of 460 milligrams of oxalic acid per 100 grams⁷, and rhubarb leaves contain even more than this.⁴

Health benefits — effects:

Although rhubarb contains oxalic acid, it is healthy if it is cooked, peeled, and eaten in moderation. The plant can help purify your blood and regulate your intestines, which is why it is recommended as part of detoxification programs.³ Rhubarb is not recommended for small children or people with certain health problems (see below).

Dangers — intolerances — side effects:

Oxalic acid is found in large quantities in rhubarb and other plants of the buckwheat family (Polygonaceae) such as sorrel. Carambola (starfruit) is also rich in oxalic acid. Similar amounts of oxalic acid are found in wood sorrels, chard, spinach, parsley, cocoa, chocolate, and red beets. Many species of fungi also excrete oxalic acid.

The oxalic acid in rhubarb eats up calcium in the human body and binds iron and magnesium. We excrete oxalic acid via the kidneys. If crystals of oxalic acid and calcium form, kidney or bladder stones may develop. Because of this, we suggest that people with kidney and biliary tract problems be cautious about their rhubarb intake. Children should similarly be cautious because they need a greater daily dose of calcium.⁷ Oxalic acid furthermore makes the intestinal absorption of iron difficult, meaning that foods with a high content of oxalic acid should be avoided.
Given that oxalic acid makes it difficult to absorb iron in the intestine, foods with a high oxalic acid content should be avoided if you are treating iron deficiency.⁸

When breastfeeding mothers consume rhubarb, small amounts of rhubarb pass into the breast milk and have slight laxative effects for the infant.³

Eating rhubarb raw leads to abdominal pain and symptoms of poisoning such as cramps and circulatory problems. However, a lethal dose of rhubarb is rather high, being more than 7 kg raw rhubarb for an adult weighting 60 kg (600 mg per kilo body weight).⁸

Use as a medicinal plant:

The rhubarb that we grow and eat today is a hybrid of the species Rheum rhabarbarum that emerged during the nineteenth century. The roots of the rhubarb you typically find at the supermarket and cook with are not used as a medicinal plant.^9,10

The Chinese rhubarb species Rheum officinale and Rheum palmatum, on the other hand, are used in Chinese medicine as a laxative. The roots of these species of rhubarb contain anthraquinone glycosides, which have laxative effects. Caution: the leaves of these plants are poisonous! These plants are bitter and cooling. Depending on the dosage, their intake promotes digestion, stimulates the uterus, and has a laxative effect.⁹

Description — origin:

The Rheum genus contains about 60 species and is widespread in Asia. Rhubarb originally comes from Central Asia.⁴ Edible rhubarb (Rheum rhabarbarum, also known as garden rhubarb) grows in the wild in Central Asia, from eastern Siberia to Mongolia, and the Chinese provinces.¹¹ Today, rhubarb is grown in all temperate zones of the world. In Europe, rhubarb cultivation primarily occurs in England, the Netherlands, and Germany. However, cultivation has extended to some tropical and subtropical countries.¹²

Cultivation in the garden or as potted plants:

Rhubarb is an uncomplicated plant to grow in the garden. You should ideally plant rhubarb in late autumn or early in the year in a semi-shady location. It thrives well near compost. Holstein Bloodred rubarb and Sutton rhubarb are recommended for growing in the garden. Rhubarb should ideally be harvested sometime before mid to late June so that the oxalic acid content is not too high. From July onwards, rhubarb begins to regenerate. During winter, it disappears into the soil, but sprouts again at the beginning of the year.⁵

You should remove all rhubarb leaves before cooking with rhubarb, even if it is home grown.

Danger of confusion:

It is important not to confuse wild rhubarb with Petasites hybridus, also known as butterbur, which has similar looking leaves. On Wikipedia, there is a warning against making tea from butterbur because the plant contains substances with mutagenic, carcinogenic, and possibly toxic effects on the liver.¹³

General information:

Rhubarb (Rheum) is a genus in the buckwheat family (Polygonaceae). The name rhubarb (Rheum rhabarbarum) is derived from the Latin word rhabarbaum and probably describes a Rheum species cultivated on the coast of the Black Sea. The Romans imported rhubarb roots from unknown barbarian lands. The lands were beyond the Volga River, sometimes known as the Rha River. Imported from barbarians across the Rha, the plant became Rha barbarum and eventually rhabarbarum.^11,16

Chinese rhubarb (Rheum officinale and Rheum palmatum, also known as medicinal rhubarb) thrives in Tibet and China, but is also grown in parts of Europe such as Austria and Germany.³ It is one of the most widely used plants used in traditional Chinese medicine, and has been a valuable commodity since ancient times. In the Middle Ages, dried roots of Chinese rhubarb were exported along the caravan routes. The root was called different names depending on the stopovers, including Turkish, Russian, East Indian, and Chinese rhubarb.¹⁴ Transportation from China took a long time and was expensive. Chinese rhubarb could generally not be found in Europe at this time. Until the nineteenth century, there was a Chinese and then a Russian trade monopoly that prevented Chinese rhubarb from being freely transported to the West.¹⁵ From the eighteenth century onward, the English began to diligently cultivate Chinese medicinal rhubarb.⁹

The food industry uses medicinal rhubarb extract (without its bittering agents) to flavor food and as a tanning agent.

Alternative names:

Rhubarb is also known as garden rhubarb, edible rhubarb, pieplant, and Rheum rhabarbarum.

Literature — sources:

Author: Georgia Wilkinson | 29 Jul 2020