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Sulforaphane is a phytonutrient found in cruciferous vegetables like broccoli, cabbage and Brussels sprouts and—in higher doses—supplements. While it’s currently being studied for its wide range of potential health benefits, including its role in cancer protection, improved blood sugar control and neuroprotection, more human clinical trials are needed to fully understand its effects.
Read on to learn more about sulforaphane, its potential benefits and side effects, how to get more of it and expert recommendations on who should consider taking it as a supplement.
What Is Sulforaphane?
Sulforaphane is a compound that comes from cruciferous vegetables like broccoli, kale and Brussels sprouts. Interestingly, the sulforaphane in cruciferous vegetables is inactive until these vegetables are cut or chewed. When cruciferous vegetables are cut, chewed or chopped, a precursor to sulforaphane, known as glucoraphanin, comes in contact with the enzyme myrosinase, forming sulforaphane.
While sulforaphane comes from many common vegetables, it’s available in higher doses as a supplement derived from broccoli seed and sprout extract.
Sulforaphane Benefits
Sulforaphane may offer a range of potential health benefits, including cancer protection, suppression of inflammation, blood sugar regulation, immune system response and protection against neurodegenerative diseases.
“Some studies indicate that sulforaphane may have a positive impact on metabolic health by improving insulin sensitivity and reducing the risk of type 2 diabetes,” says Sam Schleiger, a functional medicine registered dietitian and women’s health specialist based in Milwaukee.
In a small study of 97 people with type 2 diabetes, those who took 150 micromoles of sulforaphane in the form of concentrated broccoli sprout extract daily for 12 weeks had significantly lower hemoglobin A1C (HbA1c), a measure of blood sugar over time, compared to those taking a placebo. Participants with obesity and dysregulated type 2 diabetes—meaning their HbA1C was over 50 millimoles per mole (6.7%) at the start of the study—also experienced significantly decreased fasting blood sugar compared to placebo.[1]
One of sulforaphane’s most promising benefits is its anti-cancer activity. Studies suggest sulforaphane may help treat certain cancers, including prostate, breast and pancreatic cancer and melanoma. However, most research examining sulforaphane’s role in cancer treatment has been conducted in vitro (done via a test tube) and in animals. A review of eight human trials found promising but inconsistent results.[2]
And while animal studies investigating sulforaphane’s benefits in protecting against neurodegenerative diseases like Alzheimer’s and Parkinson’s, neuroinflammation and traumatic brain injury recovery show promising results, human clinical trials are needed to confirm these benefits.
Sulforaphane Side Effects
“While sulforaphane is generally considered safe when consumed through dietary sources, high doses from supplements may lead to gastrointestinal discomfort,” says Ella Davar, a registered dietitian focused on longevity and gut health expert based in Miami and New York City.
People taking certain medications for high blood pressure (including furosemide and verapamil) and certain non-steroidal anti-inflammatories (NSAIDs) (like ketoprofen) should consult their health care provider before taking sulforaphane supplements, as they can change the way the body processes these medications.
Additionally, people taking the seizure medication Tegretol should talk with their doctor before taking sulforaphane supplements, as animal studies suggest it may alter the effectiveness of this medication, says Lisa Andrews, a registered dietitian nutritionist at the Bodybuilding Reviews and owner of Sound Bites Nutrition in Cincinnati.
How Much Sulforaphane Per Day Is Safe?
While eating a lot of cruciferous vegetables may result in excess gas, bloating or digestive discomfort for some due to their high fiber content, it’s not likely to lead to overconsumption of sulforaphane.
There is no established recommended dose or upper limit for sulforaphane from supplements. However, studies examining the safety of broccoli sprout extract have found that sulforaphane doses between 50 to 400 micromoles, or 9 to 71 grams, are well tolerated and generally without side effects.[2]
“Not everyone needs sulforaphane in high doses, but most people would probably benefit from getting more of this powerful nutrient on a more regular basis, and the easiest way to do that is through diet,” says Kaytee Hadley, a registered dietitian specializing in treating irritable bowel syndrome (IBS) in Richmond, Virginia.
What Foods Are High in Sulforaphane?
While sulforaphane can be obtained from all cruciferous vegetables like kale, cauliflower or kohlrabi, broccoli is by far the best source, says Jessica Shapiro, a registered dietitian at Montefiore Einstein Advanced Care, based in New York. Broccoli sprouts, which are the small seedings of broccoli plants, are the richest source of glucosinolates, providing 10 to 100 times more sulforaphane than mature plants, she adds.
Hadley recommends growing broccoli sprouts in a glass jar on the kitchen countertop for an easy way to get more sulforaphane.
The best food sources of sulforaphane are cruciferous vegetables, including:
- Broccoli
- Broccoli sprouts
- Kale
- Bokchoy
- White and red cabbage
- Brussels sprouts
- Turnips
- Cauliflower
- Radish
- Chinese cabbage
Note that heat destroys the enzyme that converts glucoraphanin to sulforaphane, so cooked vegetables contain less of this beneficial compound than raw vegetables. Consume cruciferous vegetables raw or lightly steamed to get the most sulforaphane.
Are Sulforaphane Supplements Healthy?
Obtaining sulforaphane through a balanced diet rich in cruciferous vegetables is preferable to taking supplements, says Davar. Supplements lack many of the other beneficial compounds found in whole foods, she adds.
“While supplements provide a concentrated form of sulforaphane, obtaining it through a varied diet that includes cruciferous vegetables is generally considered a healthy practice,” agrees Schleiger. “Whole foods provide a mix of beneficial compounds and nutrients that may work synergistically.”
That being said, “if you have difficulty incorporating an adequate amount of cruciferous vegetables into your diet, supplements could be a convenient way to ensure you receive a consistent dose of sulforaphane,” adds Schleiger.