Evidence on DIM and Estrogen Levels
There is insufficient evidence to support that diindolylmethane (DIM) significantly lowers overall estrogen levels, though it may alter estrogen metabolism pathways. 1
What is DIM?
DIM (3'-diindolylmethane) is a phytonutrient derived from cruciferous vegetables that is commonly used as a dietary supplement in complementary and alternative medicine. It is the primary in vivo product of indole-3-carbinol, another compound found in cruciferous vegetables.
Effects on Estrogen Metabolism
The most recent and comprehensive research on DIM shows that it affects estrogen metabolism rather than simply lowering total estrogen levels:
A 2024 study examining premenopausal women found that DIM supplementation resulted in significant differences in the concentrations of almost all urinary estrogens and estrogen metabolites compared to non-users 1
DIM appears to alter the ratio of estrogen metabolites, particularly increasing the 2-hydroxyestrone:16-hydroxyestrone ratio 1
This shift in metabolism pathways may change the overall estrogenic activity in the body, but does not necessarily reduce total estrogen levels
Clinical Implications
When considering DIM supplementation:
In postmenopausal women using transdermal estradiol patches, concurrent DIM use significantly altered their urinary estrogen profiles 2
These alterations may potentially decrease the overall estrogenic impact of hormone therapy on clinical endpoints such as symptom improvement and bone mineral density 2
A phase I dose-escalation study in men with prostate cancer found that BR-DIM (a specific formulation of DIM) was well-tolerated up to 225 mg twice daily, with minimal toxicity 3
Limitations of Current Evidence
The evidence regarding DIM's effects on estrogen levels has several important limitations:
Most studies focus on estrogen metabolite ratios rather than absolute estrogen levels
There is a lack of large, randomized controlled trials specifically designed to assess DIM's impact on total estrogen levels
The clinical significance of the observed changes in estrogen metabolism remains unclear
A 2007 review concluded that there was insufficient evidence to suggest DIM provides enhanced clinical benefits over its precursor, indole-3-carbinol (I3C) 4
Conclusion
While DIM supplementation appears to alter estrogen metabolism pathways, particularly by increasing the 2-hydroxyestrone:16-hydroxyestrone ratio, there is insufficient evidence to support claims that it significantly lowers overall estrogen levels. The clinical significance of these metabolic changes requires further investigation through well-designed clinical trials.
Individuals considering DIM supplementation should be aware that it may interact with hormone therapies and potentially affect their efficacy 2. Healthcare providers should inquire about DIM supplement use in patients receiving hormone therapy.