New Study: Broccoli Sprout Extract Lowers Glucose Production

By Thomas A. Bowman PhD

A new study published last week in Science Translational Medicine1 shows a significant effect of broccoli seed extract and its active antioxidant – sulforaphane – on liver glucose production.* The study found a common decrease in glucose production in all research study segments: in liver cells, in rodents, and in human subjects.*

Broccoli sprouts → Glucoraphanin and Myrosinase → Sulforaphane

Broccoli consumption (and especially broccoli seed extract consumption) increases production of a bioactive substance called sulforaphane. Bacteria in the intestine metabolize glucoraphanin (an inert precursor) to produce bioactive sulforaphane. Additionally, broccoli sprouts contain myrosinase, which, when released by chewing, metabolizes glucoraphanin into sulforaphane. Extensive studies on sulforaphane include its effects in reducing chemical damage and free radical damage from liver oxidant stress. There are also studies on its effects on reducing inflammation and fat in the liver.*

Sulforaphane → KEAP1 shape → Free NRF2 → Antioxidant Response

The mechanism of the antioxidant effects of sulforaphane stems from its potent ability to change the molecular shape of a liver protein, KEAP1, which releases another protein, NRF2. Free NRF2 is then able to activate the nuclear DNA region called the antioxidant response element.2 An active antioxidant response element produces antioxidant enzymes, like glutathione. These antioxidants protect the liver from damage caused by oxidative stress. Protection from oxidative stress is an important liver-related health concern because the liver is one of the most metabolically active organs.*

Sulforaphane → Enzymes → Glucose Production

After determining the glucose lowering effect of sulforaphane, the study1 also examined the mechanism of this glucose lowering. Sulforaphane appears to have its effects on glucose separate from insulin, without any change in insulin signaling in the liver or the uptake of glucose into muscle caused by insulin. The study confirmed in mice and humans that insulin sensitivity and glucose uptake were not significantly different with sulforaphane. However, similar to the in vitro results, in mice and in humans, broccoli seed extract consumption decreased new glucose production. The mechanistic link, based on this study, appears to involve sulforaphane (likely through KEAP1 and NRF2) decreasing production of enzymes that produce glucose.

The researchers found a reduction in excess glucose production only in rodents on a very high-fat diet.1 Similarly, in the 97 human subjects that completed the study, consumption of broccoli seed extract decreased excess glucose production only in very overweight subjects with high glucose production at baseline. The researchers explained that the reason that sulforaphane only decreased glucose production in the more overweight individuals is due to a decrease in NRF2 in those overweight individuals. Therefore, overweight individuals may need even more than a normal amount of broccoli seed.*

In conclusion, this new study1 highlights the importance of sulforaphane from broccoli in liver health beyond its known antioxidant effects. Additionally, a new mechanism has been revealed involving sulforaphane, KEAP1, NRF2 and liver glucose production. This is the first clinical study to examine these effects in human subjects. Given the importance of liver health in our growing overweight population, we should consider the benefits of sulforaphane from broccoli and broccoli supplements.*

  1. Axelsson AS, Tubbs E, Mecham B, et al. Sulforaphane reduces hepatic glucose production and improves glucose control in patients with type 2 diabetes. Science translational medicine. 2017;9(394).
  2. Dinkova-Kostova AT, Fahey JW, Kostov RV, Kensler TW. KEAP1 and done? Targeting the NRF2 pathway with sulforaphane. Trends in Food Science & Technology. 2017.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.