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Benefits, side effects, and food sources of sulforaphane

Sulforaphane is a natural plant compound found in many cruciferous vegetables like broccoli. This article reviews sulforaphane, including its benefits, possible side effects, and food sources.

This article is based on scientific evidence, written by experts, and fact-checked by experts.
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Sulforaphane: Benefits, side effects, and food sources
Last updated on March 14, 2023, and last reviewed by an expert on December 18, 2021.

Sulforaphane is a natural plant compound found in many cruciferous vegetables like broccoli, cabbage, cauliflower, and kale.

Sulforaphane: Benefits, side effects, and food sources

It has been linked to health benefits, such as improved heart health and digestion.

This article reviews sulforaphane, including its benefits, possible side effects, and food sources.

In this article

What is sulforaphane?

Sulforaphane is a sulfur-rich compound found in cruciferous vegetables like broccoli, bok choy, and cabbage. It has been shown to provide powerful health benefits.

In these foods, it’s in the inactive form glucoraphanin that belongs to the glucosinolate family of plant compounds.

Sulforaphane is activated when glucoraphanin comes into contact with myrosinase, a family of enzymes that play a role in the defense response of plants.

Myrosinase enzymes are only released and activated when a plant is damaged. Therefore, cruciferous vegetables must be cut, chopped, or chewed to release myrosinase and activate sulforaphane.

Raw vegetables have the highest levels of sulforaphane. One study found that raw broccoli had ten times more sulforaphane than cooked broccoli.

Steaming vegetables for one to three minutes may be the best way to optimize sulforaphane levels when cooking.

It’s best to cook the vegetables below 284˚F (140˚C), as exceeding this temperature results in a loss of glucosinolates like glucoraphanin.

For this reason, it’s best to avoid boiling or microwaving cruciferous vegetables. Instead, eat them raw or lightly steamed to maximize their sulforaphane content.

Summary: Sulforaphane is a naturally occurring compound in cruciferous vegetables like broccoli, cabbage, and kale. It’s activated only when vegetables are chopped or chewed. The highest levels of sulforaphane are found in raw vegetables.

Potential benefits of sulforaphane

Animal, test-tube, and human studies have indicated that sulforaphane may offer several health benefits.

Sulforaphane may have anticancer effects

Cancer is a potentially fatal disease characterized by the uncontrolled growth of cells.

Sulforaphane has been shown to have anti-cancer properties in many test-tube and animal studies, reducing both the size and number of various types of cancer cells.

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Sulforaphane may also prevent cancer cell growth by releasing antioxidant and detoxification enzymes that protect against carcinogens — substances that cause cancer.

Keep in mind that these studies use a concentrated form of sulforaphane, so it’s unclear whether the amounts found in fresh foods have the same effect.

What’s more, it’s still unclear whether sulforaphane could be used in a clinical setting to lower cancer risk and reduce cancer growth in humans.

That said, population studies have linked a higher dietary intake of cruciferous vegetables like broccoli with a significantly reduced risk of cancer.

Researchers believe that compounds in these vegetables — including sulforaphane — are responsible for the potential anticancer properties.

Sulforaphane may support heart health

Both test-tube and animal studies show that sulforaphane may boost heart health in many ways.

For instance, sulforaphane may benefit heart health by reducing inflammation. Inflammation may lead to narrowing of your arteries — a major cause of heart disease.

Research in rats also indicates that sulforaphane may reduce high blood pressure, which may prevent heart disease.

Despite these promising findings, more research is needed to determine whether sulforaphane could improve heart health in humans.

Sulforaphane may prevent diabetes

Type 2 diabetes is a chronic disease affecting millions of people worldwide.

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Those with type 2 diabetes can’t effectively transport sugar from their blood to their cells, making it difficult to maintain healthy blood sugar levels.

A 12-week study in 97 people with type 2 diabetes examined how consuming broccoli sprout extract — equivalent to 150 µmol of sulforaphane — daily affected blood sugar levels.

The study found that sulforaphane effectively reduced fasting blood sugar levels by 6.5% and improved hemoglobin A1c, a marker of long-term blood sugar control. These effects were particularly strong in participants who were obese with poor diabetes control.

Sulforaphane’s beneficial effect on blood sugar levels is supported by animal studies as well.

Other health benefits of sulforaphane

Studies show that sulforaphane may have other health benefits as well:

It’s important to note that most of these studies were performed on isolated human cells or animals.

Thus, further research is needed to confirm whether sulforaphane would have the same effects in humans.

Summary: Sulforaphane has been associated with various health benefits and may beneficially affect cancer, heart disease, diabetes, and digestion. More high-quality research is needed to understand the extent of these effects in humans.

Side effects and safety concerns of sulforaphane

Consuming sulforaphane in amounts found in cruciferous vegetables is considered safe with few — if any — side effects.

Suggested read: 14 evidence-based health benefits of broccoli

Additionally, sulforaphane supplements are available for purchase at health food stores and online retailers.

These supplements are typically made from broccoli or broccoli sprout extract and are generally concentrated, containing more sulforaphane than what’s naturally found in food.

Glucoraphanin — the precursor to sulforaphane — supplements are also available combined with myrosinase for activation. These are marketed as a way of increasing sulforaphane production in your body.

While there are no daily intake recommendations for sulforaphane, most available supplement brands suggest taking around 400 mcg per day — typically equalling 1–2 capsules.

Mild side effects have been associated with sulforaphane supplements, such as an increase in gas, constipation, and diarrhea.

Despite their growing popularity, more research is needed to determine the ideal dose, safety, and effectiveness of sulforaphane supplements in humans.

Summary: Sulforaphane appears to be safe with few to no side effects. Sulforaphane supplements are available on the market as well. Their safety and effectiveness in humans are still unknown.

Sulforaphane food sources

Sulforaphane can be obtained naturally from a range of cruciferous vegetables. These vegetables not only provide sulforaphane but also many other important vitamins, minerals, and antioxidants.

To increase your intake of sulforaphane, include more of the following vegetables in your diet:

It’s important to cut the vegetables before you eat them and chew them well to activate sulforaphane from its inactive form, glucoraphanin.

To optimize your intake of sulforaphane, eat vegetables raw or cooked at temperatures below 284˚F (140˚C).

To further boost your intake, add mustard seeds or mustard powder to your meals. These ingredients are rich in dietary myrosinase, which can help increase the availability of sulforaphane, particularly in cooked vegetables.

Summary: Sulforaphane can be found in cruciferous vegetables like broccoli, kale, cabbage, and watercress. To maximize your sulforaphane intake, eat vegetables raw or cooked at low temperatures with a sprinkle of mustard seeds or mustard powder.


Sulforaphane is found in cruciferous vegetables like broccoli, cauliflower, and kale. It may offer anticancer, antidiabetes, and other benefits.

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Still, most research has been done on animals and isolated cells. Thus, more high-quality human studies are needed to better understand sulforaphane’s possible health benefits.

Adding more sulforaphane to your diet by incorporating more cruciferous vegetables into your meals is a nutritious and tasty way to boost your health.

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