Radishes: Roots, Leaves, Nutrients, and Potential Health Benefits
Types of Radishes
Radishes are a tasty and nutritious food. All parts of the radish plant are edible. The most commonly eaten part is the root, however. The roots have a variety of colours, including red, pink, purple, white, yellow, green, and black. Most have a white interior, but some have a coloured flesh. They have a peppery taste, which ranges from hot to mild, and add a crunchy texture to salads. The coloured forms give salads a very attractive appearance.
Radishes are classified into two categories—summer ones and winter ones. The term "radish" usually refers to the summer varieties, which are the most common type in North America. Winter radishes, such as the Daikon, are popular as well. They are eaten raw and are also pickled, baked, and added to stir-fries.
Summer and winter radishes have the same scientific name—Raphanus sativus—despite the different colours and shapes of the roots.
An Edible and Useful Plant
The entire radish plant is edible and can be eaten raw. The roots are usually crisp and moist. Although the leaves are often discarded, they can be used as a nutritious salad green. The peppery radish seeds add a spicy taste to meals. The seed capsules, commonly known as “pods”, can be eaten too, and so can the flowers. Some people like to steam or boil radish roots and leaves or add them to soups and stews. Radishes can also be microwaved, roasted, and pickled.
An oil is extracted from some radish seeds. While this generally isn't used as a culinary oil due to its very strong taste, it's still useful. It's added to some cosmetics as a moisturizer. It's also being investigated for its potential to act as a biofuel.
Nutrients in Radishes
Radishes contain many vital nutrients. The roots are a good source of vitamin C. One cup of raw radish slices provides about 29% of our daily vitamin C requirement, depending on the variety of radish. It’s important to remember that Vitamin C is a water-soluble nutrient and escapes from the roots into the surrounding water if they're boiled.
Radishes are also a good source of folate (a B complex vitamin), vitamin B6, riboflavin (vitamin B2), potassium, calcium, magnesium, copper, manganese, and fibre. Like vitamin C, the B vitamins are water soluble. Radishes are almost fat-free and are low in calories. Like all plants, they contain no cholesterol.
Radishes can be much larger and heavier than those found in grocery stores. Some varieties can be as large as baseballs or even bigger.
Potential Health Benefits of the Roots
Radishes belong to the family of flowering plants called the Brassicaceae, sometimes known as the Cruciferae. The family includes many healthy vegetables, including:
- Brussels sprouts
Like many other members of their family, radishes contain chemicals called glucosinolates. These chemicals in turn contain sulphur and give the roots their pungent taste. An enzyme called myrosinase is present inside radish cells, separated from the glucosinates. When the roots are chewed or cut, the myrosinase is released and reacts with the glucosinolates, producing other compounds such as isothiocyanates and indoles. Research suggests that these new compounds might reduce the risk of cancer development.
Scientists are continuing to explore the potential health benefits of radish plants and their relatives. Nutritionists recommend that we eat lots of vegetables, including cruciferous vegetables like radishes. They provide many essential nutrients and may have the added benefit of reducing the risk of some types of cancer.
The Night of the Radishes is an annual competition in the city of Oaxaca in Mexico. Large radishes are carved and used to create sculptures. Prizes are awarded for the best creations. The event is generally held on December 23rd.
Growing and Storing Summer Radishes
Growing radishes is fun and easy. Freshly picked roots are the most nutritious kind. The popular red, globe-shaped or oval radishes that are commonly found in stores and planted in gardens grow best in spring and in late summer/early fall when they are planted outside. These are “summer” radishes.
Despite their name, summer radishes don’t grow well in the hottest part of the year. If they’re being grown during the summer months they'll need to be planted in partial shade. Too much hot sun will cause the plants to bolt (grow tall and produce seeds instead of growing leaves and building up their roots). The roots of a radish plant that has bolted develop an unpleasant taste.
If you’ve bought summer radishes from a farmers market or grocery store and you want to store them in your home, remove the leaves and eat them so that they don’t draw nutrients from the roots. The roots will keep for about two weeks in a refrigerator.
Eating the Leaves
The leaves of a radish plant are often thrown away or put on a compost heap, which is a shame. They are good to eat, especially when they're young, small, and fresh. Like other raw greens, they are a good source of beta-carotene (a vitamin A precursor), vitamin C, potassium, and other nutrients.
My favourite leaves are the ones that I get at a local farmers market in the summer. I add them to salads and sandwiches. Some people use them in smoothies, soups, stews, and omelettes. The larger and older leaves can sometimes produce a prickly sensation in the mouth. Cooking them eliminates this sensation, however.
Planting the Seeds and Harvesting
The soil for planting radish seeds needs no further preparation than is usually required for growing plants. It should be fertilized and have stones and pebbles removed. Lumps of soil should be broken up. The seeds should be planted about half an inch deep in the soil and about one inch apart from each other in their row. Rows should be separated by about eight inches. The plants will need to be thinned at some point after the seeds have germinated. Radishes don’t grow well when they’re crowded. The plants need to be kept well watered as they grow.
Summer radishes are a good plant for children and beginning gardeners to grow since the plants grow rapidly, can be planted in containers, and are usually healthy. They can be eaten as sprouts or left to form mature plants. The roots should be ready to pick in three to six weeks. They shouldn’t be left in the ground for too long or they will become woody and their taste will become hot and bitter.
Winter and Daikon Radishes
The so-called “winter” radishes are planted in mid to late summer and are ready to pick in late fall. They grow more slowly than summer radishes and reach a larger size. Once they are picked, they can be kept in cold storage for several months.
The daikon is a popular type of winter radish. It has long, white roots that are shaped like carrots. (The Sakurajima daikon described below is an exception to this rule.) Daikons are native to Asia but grow well in North America. They need more space to grow than summer radishes because they are larger in size.
Daikon radishes have similar nutritional benefits to summer ones. Also like summer radishes, they are a versatile vegetable that can be prepared in many different ways. In addition to bring served raw, they can be boiled, baked, roasted, stir-fried, grilled, broiled, or pickled. They can be eaten as part of a meal or served in a small quantity as a condiment.
The leaves of daikons are edible. As is the case for other radishes, daikons can be eaten as spouts. The sprouted seeds are fun and quick to produce and give a spicy touch to dishes.
The world's heaviest radish was grown by Manabu Oono (Japan) and weighed 31.1 kg (68 lb 9 oz) on 9 February 2003 at the Sakurajima Radish Contest, Kagoshima, Japan. It had a circumference of 119 cm (46.8 in).— Guinness World Records
Nitric Oxide From Sakurajima Daikons
The Sakurajima daikon is the largest type of radish in the world. Its name is capitalized because it refers to the former island of Sakurajima in Japan. The island is a volcano today.
The large radish may have special benefits for our blood vessels. Researchers from Kagoshima University recently made some interesting discoveries related to the vegetable. They tested the effect of radish extract on endothelial cells from blood vessels of humans and pigs. Endothelial cells line the blood vessels. The researchers used extracts from both the Sakurajima daikon and smaller types of radishes in their experiment.
The Sakurajima daikon extract stimulated more nitric oxide production in the endothelial cells than the extract from the other radishes. This discovery may be significant because nitric oxide triggers the walls of blood vessels to relax, thereby expanding the vessels and reducing blood pressure. The expansion could be helpful in dealing with cardiovascular disease.
In addition, the scientists discovered that the Sakurajima radish contained a plant hormone called trigonelline that appears to trigger beneficial changes in blood vessels, including the production of nitric oxide. Interestingly, trigonelline is found in animals as well as plants. It seems to be a chemical that should be investigated in more detail.
Research in isolated cells and other structures doesn't necessarily apply to those structures when they are inside the body. Still, the results of the research may be important.
Adding the Vegetables to the Diet
Any type or colour of radish is a healthy food and a nutritious addition to a meal, whether it’s grown at home or bought in a store. It's also a good snack. The tangy taste works especially well in salads. Some people prefer to cook radishes in order to reduce their peppery taste. Peeling radishes also reduces their hotness.
One drawback to eating radishes might be their high salicylate concentration. People with salicylate sensitivity may find that they need to limit radishes in their diet, eat them only in peeled or cooked form, or avoid them completely. For other people, though, radishes in a raw, sprouted, pickled, or cooked form can be a great addition to the diet.
Nutrients in radish roots from the USDA (United States Department of Agriculture)
Information about isothiocyanates from the Linus Pauling Institute at Oregon State University
Facts about growing summer and winter radishes from the University of Illinois
Heaviest radish award from Guinness World Records
Compounds in monster radish could tame cardiovascular disease from the phys.org news service
Night of the Radishes information from the BBC
This content is accurate and true to the best of the author’s knowledge and does not substitute for diagnosis, prognosis, treatment, prescription, and/or dietary advice from a licensed health professional. Drugs, supplements, and natural remedies may have dangerous side effects. If pregnant or nursing, consult with a qualified provider on an individual basis. Seek immediate help if you are experiencing a medical emergency.
Questions & Answers
If I plant a radish in the spring, what will happen?
Planting spring radishes in the spring is a good idea, as long as there is no frost around and the soil is soft enough to be dug. Cool weather is fine for planting the seeds. The plants should grow well and produce radishes quickly. Some varieties of spring radishes grow especially well in early spring.
Winter radishes need to be planted in mid to late summer. They take longer to mature than the spring ones, and should be ready by fall.
Radishes are usually grown from seeds. The root can sometimes be coaxed to grow an entire plant. However, the process is said to be moderately difficult.
© 2011 Linda Crampton