What Is Sulforaphane?

Sulforaphane is a natural plant compound derived from cruciferous vegetables, such as broccoli and Brussels sprouts. It is known for its antioxidant, antimicrobial, and anti-inflammatory properties. As such, some research has looked at its potential health benefits, such as cancer prevention and heart and brain health.

Sulforaphane in cruciferous vegetables occurs in a stored, inactive form as glucoraphanin. Glucoraphanin is converted to sulforaphane's active form by the enzyme myrosinase. This activation is triggered by chopping or chewing but can also be produced in the gut by certain bacteria.

This article explains sulforaphane's uses, benefits, and side effects. It also covers proper dosage and precautions.

Uses of Sulforaphane

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or doctor. No supplement is intended to treat, cure, or prevent disease.

Researchers have studied sulforaphane for its potential health effects on various conditions, including cancer prevention, blood sugar, heart disease, and autism.

Cancer

Sulforaphane has chemoprotective properties. That means it inhibits carcinogens (cancer-causing substances) from binding to DNA. In addition, it is anti-inflammatory, which is beneficial for cancer prevention because inflammation can play a role in some types of tumor formation. Because of these characteristics, some researchers have evaluated the possible role of sulforaphane in cancer treatment and prevention.

One randomized, double-blinded study, published in 2020, looked at 40 adults in palliative chemotherapy with pancreatic cancer. The researchers reported that, though not statistically significant, the survival rate was higher in the treatment group during the first six months after intake compared to those in the placebo group. In addition, supplementation did not severely impact their self-care and overall abilities.

Another study published in 2014 reported on the effects of sulforaphane supplementation in 20 people with recurrent prostate cancer. The study did not reveal statistically significant results. However, they found that sulforaphane treatment was safe with no adverse side effects.

Research published in 2019 studied the effects of sulforaphane supplementation on prostate cancer progression. Researchers put 49 subjects into two groups: a control group given soup made with standard broccoli and a test group that received soup containing broccoli with enhanced concentrations of glucoraphanin, respectively.

After 12 months of eating a portion of broccoli soup each week, people in the test group had a dose-dependent reduction in prostate cancer progression.

In addition, a 2016 study looked at the association between cruciferous vegetable intake and specific tumor biomarkers. Researchers evaluated 54 people scheduled for breast biopsies after abnormal mammogram findings.

They found that total cruciferous vegetable intake was associated with decreased cell growth in breast tissue. However, other compounds in broccoli may have contributed to these findings.

Autism

Sulforaphane's role in regulating genes and its antioxidant properties has prompted some research on the nutrient's potential therapeutic role in autism.

In 2014 a placebo-controlled, double-blind, randomized study examined sulforaphane treatment in 40 males between 13 and 27 with moderate to severe autism spectrum disorder (ASD). Participants received sulforaphane or a placebo for 18 weeks.

After 18 weeks, participants receiving sulforaphane experienced minimal change compared to those receiving the placebo. However, the experiment group showed substantial improvements in behavior, communication, and social interaction. In addition, after stopping sulforaphane supplementation, total scores returned to levels closer to those before supplementation.

Another study, published in 2018, looked at autism treated with sulforaphane from broccoli. Fifteen children with ASD and related neurodevelopmental disorders participated in the 12-week study.

The researchers looked at behavior and social responsiveness to sulforaphane supplementation. After the 12 weeks, both behavior and social responsiveness improved; however, only the change in the social responsiveness was significant.

Cardiovascular Disease

Because oxidative stress and inflammation are markers in cardiovascular disease, and sulforaphanes have antioxidant and anti-inflammatory properties, researchers have looked at their potential role in protecting against heart disease.

A 2015 paper reviewed how sulforaphane might be protective against cardiovascular disease. Clinical studies and animal experiments demonstrated that sulforaphane is potentially protective against heart diseases, including hypertension and atherosclerosis.

Evidence for this use is limited. Therefore, more research is needed.

Diabetes

Sulforaphane's role in maintaining healthy cells and genes has prompted some researchers to look at its potential role in insulin resistance (when your body doesn't respond normally to the hormone insulin) and diabetes.

A 2012 randomized, double-blind study examined the effects of broccoli sprouts on insulin resistance in people with type 2 diabetes. Researchers analyzed glucose and insulin levels in 63 people who received placebo or broccoli sprout powder for four weeks. Results showed a significant decrease in serum insulin concentration and resistance in those receiving 10 grams per day of broccoli sprouts.

Animal studies have also shown positive results. For example, a 2017 study published in Diabetes evaluated whether dietary glucoraphanin improved obesity and insulin resistance in mice. Researchers placed mice in one of four groups: normal food, food with 0.3% glucoraphanin, a high-fat diet, or a high-fat diet with 0.3% glucoraphanin.

After 14 weeks, the normal food with glucoraphanin group did not have altered blood glucose. However, compared to a control group, the high-fat diet with glucoraphanin group had significantly lower fasting blood glucose.

Since the study included mice, it's unclear if researchers could replicate the results in humans.

Other

In addition to the above, people also use sulforaphane for other health conditions, though there are few quality human studies on these topics. These include: 

• Constipation
• Sun damage to the skin
• Osteoporosis
• Neurological diseases
• Obesity

What Are the Side Effects of Sulforaphane?

Your healthcare provider may recommend sulforaphane to reduce your risk of cancer, heart disease, or diabetes. However, consuming a supplement like sulforaphane may have potential side effects. These may be common or severe.

Common Side Effects

Sulforaphane is safe when consumed in plant forms, such as kale or broccoli. In supplement form, sulforaphane has minor, if any, side effects. The main side effects include digestive problems, such as gas and a bad aftertaste. (Broccoli in particular is likely to cause gas.)

Severe Side Effects

Some animal research indicates that high doses of sulforaphane could cause the following side effects associated with toxicity:

• Sedation
• Hypothermia (low body temperature)
• Impaired motor coordination
• Decreased skeletal muscle strength
• Death

Though sulforaphane seems to be well tolerated with minimal side effects, there is insufficient quality research to know if it is safe to take by mouth as a medicine, especially in high doses and for long periods.

Precautions

Sulforaphane is safe during pregnancy and breastfeeding when eaten in whole food form, such as broccoli. However, whether it's safe when taken as a supplement during pregnancy and breastfeeding is unknown. Therefore, you should avoid taking the supplement if you are pregnant or breastfeeding or consult with a healthcare provider first.

In addition, sulforaphane may interfere with some anti-seizure medications, including Tegretol (carbamazepine).

Dosage: How Much Sulforaphane Should I Take?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage are appropriate for your individual needs. 

There are no daily intake recommendations for sulforaphane, and supplement brands vary widely in how much they suggest taking.

Although there is a wide availability of sulforaphane in supplemental form, more research is needed to determine the ideal dose, safety, and effectiveness. So, be sure to speak with a healthcare provider to determine an appropriate amount in your situation.

What Happens If I Take Too Much Sulforaphane?

While there is no established upper limit for sulforaphane, some research has found evidence of toxicity at higher doses (150–300 mg/kg). Talk to a healthcare provider before taking a sulforaphane supplement to avoid toxicity. If you consume a high amount or more than what is recommended by your healthcare provider, you may want to go to the emergency room.

How To Store Sulforaphane

Store sulforaphane in a cool, dry place (not the bathroom, which can get warm and steamy). Keep sulforaphane away from direct sunlight. Discard after one year or as indicated on the packaging.

Sources of Sulforaphane and What To Look For

Sulforaphane is widely available through cruciferous food sources. In addition, you can also take it as a supplement.

Food Sources of Sulforaphane

Cruciferous vegetables are well known for their sulforaphane content, including:

• Broccoli
• Broccoli sprouts
• Kale
• Cauliflower
• Brussels sprouts
• Cabbage
• Bok choy
• Watercress
• Collard greens
• Mustard greens

Sulforaphane Supplements

Sulforaphane supplements are available in various forms, including:

• Tablets
• Capsules
• Powder
• Liquid

They are often made from broccoli, broccoli seeds, or broccoli sprouts extract. Some sulforaphane supplement manufacturers also advertise their products as combined with myrosinase enzymes for enhanced absorption.

Summary

Sulforaphane is a nutrient found in cruciferous vegetables and supplements. It is known for its antioxidant, antimicrobial, and anti-inflammatory properties. Some people take sulforaphane for health reasons, including to lower their risk of cancer, heart disease, and diabetes, and to treat moderate to severe autism symptoms. There is some evidence to support those uses, but the research is limited.