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Sulforaphane in Broccoli Shows Promise for Diabetes

Published: January 16, 2019

Broccoli is rich in fiber and ranks low on the glycemic index, which is why it is generally considered a good choice for people with type 2 diabetes. But broccoli also provides sulforaphane, an interesting compound that might hold promise as an anti-diabetic supplement. Broccoli sprouts have been found to be a particularly concentrated source of sulforaphane.


According to the Centers for Disease Control and Prevention, more than 100 million people in the United States have diabetes or pre-diabetes, and as many as two out of five Americans are expected to develop type 2 diabetes in their lifetime.

Type 2 diabetes, the most common type of diabetes, typically develops around middle age, often in people who are obese or overweight. Their body may become resistant to insulin, which controls the level of glucose in the blood, or they pancreas may stop producing enough insulin.

People with diabetes are often prescribed a drug called metformin, which helps to lower blood glucose. However, metformin is not suitable for some people, and scientists are continuously looking for new substances that could help people with diabetes control their condition.

Sulforaphane as a Potential Anti-Diabetic Substance

In an intriguing study published in the journal Science Translational Medicine, a group of scientists from the Lund University Diabetes Center in Sweden began their search for a new diabetes supplement by using a computer model to sort through a database of 3,800 substances to find a promising compound. Of all the substances that were screened, sulforaphane seemed to be the best candidate.

Sulforaphane is a breakdown product of glucoraphanin, a glucosinolate that naturally occurs in cruciferous vegetables like broccoli and kale, and their sprouts.

Previously, glucoraphanin-rich foods such as broccoli sprouts have been researched for their potential anti-cancer properties, with promising results. And, there is some evidence that broccoli sprouts may also kill H. pylori, harmful bacteria that can cause peptic ulcers.

Sulforaphane Shows Anti-Diabetic Action in Cultured Cells and Animals

After identifying sulforaphane, the researchers from the Lund University Diabetes Center tested the effects of sulforaphane in an in vitro setting, and discovered that sulforaphane was capable of inhibiting glucose production in cultured cells. They then went on to test the effects of sulforaphane on rats and mice with diet-induced diabetes, and found that a high-sulforaphane extract improved glucose tolerance in rodents on high-fat and high-fructose diets.

"We tested removing sulforaphane from the extract and the effect disappeared", said Anders Rosengren, MD, PhD, the principal investigator, so it seems sulforaphane was indeed the active compound that produced the positive effects [1]

Broccoli Sprout Powder Shows Potential in a Clinical Trial

Eager to find out whether sulforaphane powder made from broccoli sprouts would also work on humans, Dr. Rosengren's team also set up a clinical trial for which they recruited around 100 people with type 2 diabetes. All study participants were of Scandinavian ethnicity, and almost all of them were taking metformin.

Sixty of the patients who completed the study had well-regulated type 2 diabetes, while thirty-seven had dysregulated diabetes which is characterized by higher fasting blood glucose levels. Of the patients with dysregulated diabetes, 20 were non-obese and 17 were obese.

Half of the study participants were randomly assigned to take a daily dose of sulforaphane powder every morning for 12 weeks, in addition to their usual medication, while the other half received a placebo.

According to a news release by the Lund University, which sponsored the study, a daily dose of sulforaphane is equivalent to the sulforaphane you would get by eating 4 to 5 kilograms (9 to 11 pounds) of broccoli [1]. Broccoli sprouts are a much more concentrated source, providing 20 to 50 times the sulforaphane content of mature broccoli [2].

The findings: The study participants with dysregulated type 2 diabetes who took the broccoli sprout extract experienced a significant decrease in their fasting blood glucose, while those with well-regulated diabetes did not. In addition, obese study participants with dysregulated type 2 diabetes experienced a significant drop in their HbA1c levels.

HbA1C, or A1c, is a form of hemoglobin that is measured to get an overall picture of your average blood sugar levels over the last two to three months. According to the American Diabetes Association, the results of an HbA1c test can give you a good idea of how well your diabetes treatment plan is working [3].

The Bottom Line

So, should you start taking sulforaphane pills or eating broccoli sprouts or broccoli if you have diabetes?

"High doses of [broccoli sprout extract] cannot yet be recommended to patients as a drug treatment", say Dr. Rosengren and his co-authors in their report, which was published in 2017, and point out that further studies are still needed.

What's more, the amount of sulforaphane used in this study was so high that you would have to eat huge amounts of broccoli to reach the same levels, which is certainly neither advisable nor healthy.

That said, even if the amount of sulforaphane provided by a normal, healthy serving of broccoli or broccoli sprouts is too small to have the benefits observed in Dr. Rosengren's team's study, there are many other reasons why you should eat your broccoli: broccoli is low in calories, high in fiber, and it ranks low on the Glycemic Index (GI), all of which makes it a great choice for people with type 2 diabetes.

Beyond that, eating broccoli has been associated with many health benefits, and incorporating this nutritious Brassica vegetable into your diet can give your health an added boost. Broccoli is also a versatile ingredient, and even the tough broccoli stems can be used, so there's virtually zero food waste.

When using broccoli, it is good to keep in mind that high temperatures can destroy myrosinase, an enzyme that is needed to form sulforaphane from its precursor, glucoraphanin. Indeed, in vivo studies comparing the effects of raw vs cooked broccoli show that cooked broccoli provides significantly less sulforaphane than its raw counterpart.

Finally, some health food stores and online retailers carry freeze-dried broccoli powder which can be added to everything from green smoothies and soups to omelets and savory muffins.

Freeze-drying does not destroy myrosinase, so provided that the broccoli or broccoli sprouts have not been exposed to high temperatures at any point during the production process, you should get plenty of sulforaphane from that green superfood powder.

Recommended Reading
Diabetes Book

Dr. Joel Fuhrman, M.D., is one of America's leading experts on preventive medicine and a New York Times bestselling author. In "The End of Diabetes", he describes his breakthrough program designed to prevent and reverse diabetes—without drugs. A must-have for anyone with pre-diabetes or type 2 diabetes, this highly acclaimed, science-based book is available through Amazon.