What Is Horseradish?

You're probably most familiar with horseradish as a spicy condiment often served with steak or a roast beef sandwich. It's often used in sauces and dressings to give them a "kick" of heat.

Horseradish isn't just valued for being flavorful, though. The pungent root is believed to have some medicinal value as well. For this reason, it's sometimes taken as a supplement or intentionally increased in the diet to yield its many health benefits.

If you've ever cooked with horseradish or chopped it up to use as a condiment, you know that cutting or crushing it releases the pungent odor it's known for.

When the root is damaged, it releases mustard oils, which are made of natural compounds called glucosinolates. Glucosinolates are known to have a variety of biological functions, and that's where the medicinal value of horseradish comes in.

What Horseradish Is

Horseradish is a root vegetable and a member of the Brassicaceae family, better known as the mustard family. Other common vegetables from this family include:

• Broccoli
• Cauliflower
• Cabbage
• Brussel sprouts
• Mustard greens
• Wasabi
• Kale

They're also known as cruciferous vegetables. The horseradish plant is most often grown for its tapered root, which is large and white.

What Is Horseradish Used For?

It's rich in several important nutrients, including:

• Calcium
• Dietary fiber
• Folate
• Manganese
• Magnesium
• Potassium
• Vitamin C
• Zinc

Purported health benefits of horseradish go back thousands of years. But are they supported by science? And is it safe to use horseradish medicinally? You can find claims online—some supported by medical science and some not—that horseradish can:

• Prevent cancer
• Strengthen your immune system
• Treat urinary tract infections
• Treat sinus infections
• Relieve pain and inflammation
• Regulate your blood pressure
• Aid in digestion
• Improve the health of your teeth
• Improve your metabolism

As with most supplements, there's not much evidence to back the claims that are out there. However, some preliminary evidence supports some of the purported uses. Probably the best-researched aspect of horseradish is a component of the plant called sinigrin.

Sinigrin: What We Know

A review of the medical literature published in a 2016 edition of the journal Molecules lists several pieces of evidence that sinigrin may, in fact:

• Slow the spread of cancer, especially in the liver, through multiple mechanisms at the cellular level
• Lessen inflammation and improve atherosclerosis (chronic inflammatory disease) by blocking or altering pro-inflammatory components of the immune system, including TNF-α, interleukine-6, nitric oxide, COX-2, and prostaglandin E2
• Act as an antibiotic agent, especially against E. coli bacteria
• Act as an anti-fungal agent
• Act as an antioxidant, preventing the formation of potentially disease-inducing free radicals
• Speed wound healing, when used topically

However, the review's authors state that while the early evidence is compelling, not nearly enough work has been done on the effects of sinigrin. They urge further studies to delve into how sinigrin behaves in the body, its mechanisms of action, and possible therapeutic benefits.

Several studies published after that review have added to the body of literature suggesting medicinal uses of sinigrin.

A 2017 study published in the World Journal of Gastroenterology suggests that the antioxidant activity of sinigrin may be useful as a dietary approach to treating fatty liver.

Also, a 2017 paper in the Journal of Applied Toxicology advances the theory of sinigrin's anti-cancer activity with promising results on urinary bladder tumors in rats.

Evidence Based Complementary and Alternative Medicine also published a study providing further evidence that the horseradish root has an anti-inflammatory effect through its actions on specialized cells in the immune system. This study involved human immune cells.

A study in Biomedicine and Pharmacotherapy goes deeper into the cellular mechanisms of action to explain why sinigrin lowers inflammation.

Possible Side Effects

Horseradish comes with several possible side effects, which you should watch for if you're taking it medicinally. Potential side effects of horseradish include:

• Irritation to the digestive tract of children under 4 years old
• Irritation to the digestive tract of people with stomach or intestinal ulcers, inflammatory bowel disease, infections in the digestive tract, or other digestive diseases
• Increased urine flow, which can be a problem for some people with kidney disorders
• Worsening hypothyroidism (underactive thyroid gland)

Horseradish and Hypothyroidism

The vegetables of the Brassicaceae family are classified as goitrogens, which means they can impair thyroid function, especially if they're eaten raw and in large amounts.

They're perfectly fine for people with normal thyroid function to consume, but those with thyroid disease need to be careful with these vegetables, especially at medicinal levels.

If you have any of the above conditions, or conditions related to them, use extra caution with horseradish and be alert to any increases in symptoms that could be attributed to it.

Horseradish and Pregnancy

Horseradish is a rich source of folate, also known as folic acid. Just about anyone who's contemplated pregnancy has heard that a diet high in folic acid can help prevent a serious birth defect.

However, that doesn't mean horseradish is safe to consume when you're pregnant. That's because of the mustard oil the plant contains—the same component that makes it smell so strong when you cut it.

It may also be passed through breastmilk in levels high enough to be dangerous to your baby, so it's not recommended for breastfeeding mothers.

Keep in mind this is with large amounts, like what you'd take using horseradish medicinally. Don't panic if you put a little on your prime rib last week—just know it's not something to eat in large quantities while it can be passed on to your baby.

Possible Negative Drug Interaction: Levothyroxine

Levothyroxine is a synthetic form of thyroid hormone that's widely used to treat hypothyroidism. Because horseradish (and other vegetables in the Brassicaceae family) may decrease thyroid function, it's suspected of decreasing the effects of this medication.

If you take levothyroxine and are interested in using horseradish medicinally, be sure to talk to your healthcare provider/health provider and pharmacist about the possible interaction.

Dosage and Preparation

So far, we don't have enough information on horseradish's potential benefits to have established doses for any health conditions.

If you're using the root medicinally, be sure to follow the directions on product labels and talk to a medical professional about how much you should take based on your medical history.

What to Look For

You can buy horseradish as supplements in capsule form and as tinctures and tonics.

Dosages of these preparations are likely higher in concentration than you would receive from just increasing horseradish in your diet naturally. (You could also buy raw horseradish, which looks similar to the ginger root.)

A Word From Verywell

Horseradish is "natural," but it's important to remember that "all natural" things can have potentially deleterious effects. Any substance that alters how your body functions, including supplements, can be considered a drug and you should treat them like you would pharmaceuticals.

Be sure to let your healthcare provider or healthcare professional know about supplements you're taking. That way, they can help you watch out for side effects, drug interactions, or any other potential problems.

Your pharmacist can help you watch for drug interactions, as well, so use them as a resource.