Radishes are low-calorie root vegetables that pack a surprisingly dense mix of vitamins, minerals, and protective plant compounds. A one-cup serving of raw sliced radishes contains just 19 calories while delivering meaningful amounts of vitamin C, potassium, folate, and fiber.
Vitamins and Minerals per Serving
One cup of raw sliced radishes (about 116 grams) provides roughly 17 mg of vitamin C, which covers nearly 20% of the daily recommended intake for most adults. Vitamin C is essential for building collagen (the protein that holds skin, tendons, and blood vessels together) and for supporting immune function. Because vitamin C degrades with heat, eating radishes raw gives you the most benefit.
That same cup also contains about 270 mg of potassium, a mineral that helps regulate blood pressure and fluid balance. For context, a medium banana has around 420 mg, so a cup of radish slices gets you roughly two-thirds of the way there for a fraction of the calories. You’ll also get 29 mcg of folate, a B vitamin your body uses to make DNA and red blood cells. Folate is especially important during pregnancy, and radishes offer a modest contribution toward the 400 mcg daily target.
Radishes contain smaller amounts of calcium, magnesium, phosphorus, and trace minerals like zinc and manganese. None of these appear in standout quantities on their own, but they add up when radishes are part of a varied diet rich in vegetables.
Fiber and Calorie Profile
With about 1.9 grams of dietary fiber per cup, radishes contribute to digestive regularity and help feed the beneficial bacteria in your gut. That fiber is split between soluble and insoluble types. Soluble fiber slows digestion and can help moderate blood sugar spikes after a meal, while insoluble fiber adds bulk that keeps things moving through your intestines.
At under 19 calories per cup, radishes are one of the lowest-calorie vegetables you can eat. Their high water content (around 95%) makes them filling relative to their calorie count, which is why they show up frequently in weight-management meal plans. A half-cup serving, which is closer to what you might toss into a salad, comes in at about 9 calories and 1 gram of fiber.
Glucosinolates and Isothiocyanates
Beyond standard vitamins and minerals, radishes contain a group of sulfur-based compounds called glucosinolates. These are the same class of protective chemicals found in broccoli, cabbage, and other cruciferous vegetables. When you bite into or chop a radish, an enzyme called myrosinase breaks the glucosinolates down into isothiocyanates, which are the compounds responsible for that sharp, peppery bite.
Isothiocyanates have documented antibacterial and antioxidant activity. Radishes produce specific types, including raphasatin and sulforaphene, that have attracted research interest for potential anti-inflammatory and anticancer properties. The conversion happens most efficiently in raw radishes, since cooking can deactivate the myrosinase enzyme. This is one reason raw radishes taste spicier than cooked ones, and it’s also why you get more of these protective compounds when you eat them fresh.
Red Radishes vs. Daikon
The small red table radish you see in most grocery stores and the long white daikon popular in East Asian cooking share the same core nutrients: vitamin C, fiber, and folate. Daikon radishes are considerably larger, so a typical serving by weight delivers more of those nutrients in absolute terms. Daikon also has a milder flavor, which makes it easier to eat in larger quantities, whether raw, pickled, or simmered in soups.
Red radishes tend to be more concentrated in certain pigment-related antioxidants, particularly anthocyanins, which give the skin its red-to-purple color. These pigments function as antioxidants in the body, helping neutralize unstable molecules that can damage cells. If you eat a variety of radish types, you’ll get a broader range of these plant compounds than you would from sticking with just one.
A Note on Thyroid Health
Radishes contain goitrogens, naturally occurring chemicals found in many cruciferous vegetables. Goitrogens can interfere with your thyroid’s ability to absorb and use iodine, which is a key ingredient in thyroid hormone production. In very large quantities, goitrogens can contribute to an enlarged thyroid (goiter) or worsen an already underactive thyroid.
For most people, the amounts present in a normal diet pose no concern. If you have hypothyroidism or an iodine deficiency, a few practical steps reduce any risk: eat radishes in moderate portions rather than enormous quantities, cook them when possible (heat reduces goitrogen activity), and make sure your diet includes adequate iodine and selenium, both of which support healthy thyroid function.