DIM Versus I3C:

The Following From The Townsend Newsletter 8/1/2001
And Has Not Been Updated
DIM Versus I3C Effect On Estrogen Metabolism

Cruciferous vegetable phytonutrients include natural substances whose supplemental use has great potential for the prevention of human cancer. The additional discovery that the cruciferous indoles, diindolyl-methane (DIM) and Indole-3-Carbinol (I3C), also promote healthy estrogen metabolism has expanded their usefulness as dietary supplements for many estrogen-related conditions. Beyond cancer prevention, effective uses of absorbable DIM have included benefits for perimenopausal women, in premenstrual syndrome (PMS), in endometriosis, and in cervical dysplasia. Also benefited from supplementation are women on estrogen replacement (HRT), as well as men with estrogen-related conditions including prostate hypertrophy. In choosing dietary supplement formulations containing DIM or I3C, it is important to understand basic differences in their phytochemical characteristics and interaction potential. These differences have important implications as to their relative safety for long-term use.

Introduction To The Cruciferous, Indole Phytonutrients

Cruciferous vegetables (broccoli, cabbage, cauliflower, Brussels sprouts, bok choy) are in the news as powerful sources of cancer-preventive phytonutrition. A recent study of Seattle men showed that three or more servings of cruciferous vegetables a week can reduce prostate cancer risk almost by half.

The following Information was originally written on 8/1/2001, and does not include later findings.

Significant amounts of DIM are found in cruciferous plants following crushing. This is unlike I3C which, due to its unstable nature, is only transiently present, primarily during digestion. I3C is the natural precursor to DIM, which is formed from a "condensation reaction" in which one I3C molecule combines with another. The resulting DIM is a "di-indole" or double molecule formed from two I3C molecules. Release of active DIM is facilitated by enzymes in the plant and is also due to the action of gastric acid on I3C released during digestion. Pure forms of these natural substances derived from plant-based precursors are now available as dietary supplements. The choice of precursor I3C, or active DIM as a supplement requires an understanding of their relative merits and safety as phytonutrients. This review will compare and contrast the important differences between DIM and I3C.

DIM And I3C Have Different Physical And Phytochemical Characteristics

Based on well known physical characteristics, DIM is very stable in water and acid but highly insoluble. I3C is soluble but highly reactive, resulting in over 20 condensation products, including DIM, after I3C is exposed to stomach acid. When I3C is kept dissolved in water, or buffered in weakly acidic solutions, a greater conversion to DIM occurs. DIM requires a special dietary supplement formulation to provide for improved solubility and complete gastrointestinal absorption. 13C requires careful storage, avoiding heat, moisture and light to slow its rapid breakdown on the shelf. Taken as a dietary supplement, 13C requires gastric acid for conversion to active products. I3C is more irritating to the stomach than DIM, due to its chemical reactivity. I3C is much more sensitive to interaction with components of food, especially vitamin C, which limit its conversion into DIM and other condensation products. Conversion from I3C into DIM not only requires a precise acidity it requires time. This conversion may proceed slowly, requiring more than a typical intestinal transit time to be complete.

A compelling study favoring the use of DIM over I3C demonstrated the fact that following an oral dose of I3C in humans only DIM and no I3C was found circulating in the bloodstream of test subjects. This finding confirms that I3C disappears after entry into our stomachs, and since a highly sensitive detection method was used, no direct benefits can be attributed to absorbed I3C. Based on this study it is also documented that over 90% of an oral dose of I3C goes unaccounted for in the form of non-DIM "condensation products" of uncertain structure, uptake and activity.

Benefits For Healthy Estrogen Metabolism

The history of supplemental use of cruciferous vegetable phytonutrients begins over 20 years ago with research showing that either broccoli, pure DIM, or pure I3C prevented chemically induced breast cancer in animals. In the last 10 years it has been discovered that supplemental use of both DIM and I3C is associated with a beneficial shift in estrogen metabolism. Both specially formulated DIM and I3C, used as dietary supplements, have been shown to reliably increase the 2-hydroxylation of estrogen, increasing the 2/16 ratio of estrogen metabolites. This ratio (also known as the "good to bad" balance of estrogen has now been shown to be a predictor of future breast cancer in a prospective study of 5,000 Italian women. In this study, the future risk of developing breast cancer over a 4 year period was reduced in the premenopausal women who demonstrated the highest 2/16 ratio. In a second study, a favorable ratio of higher 2/16 was also seen in benign conditions compared to breast cancer cases which had lower ratios.

A patented formulation of absorbable DIM, has been shown to result in a significant increase in the 2/16 ratio at one tenth of the dose using I3C. Supplemental I3C at 300 or 400 mg/day is required by women to significantly increase the ratio. Animal studies have clearly shown that it is DIM and not I3C that is the active promoter of greater 2-hydroxylation of estrogen which is associated with a cancer-resistant estrogen metabolism.

Apart from therapeutic potential, dietary supplement use of DIM and I3C relates to hormonal balance and symptoms of "estrogen dominance." Supplemental use requires consideration of long term safety. The reactivity, instability, and observed side effects from I3C raise questions and concerns about its safety in comparison to DIM.


Dim And I3C Information: Ben Kim, M.D. - I3C

Dim And I3C Information: Michael A. Zeligs, M.D. - The Cruciferous Choice

Dim And I3C Information: Michael A. Zeligs, M.D. - Dim And I3c

Dim And I3C Information: The Analyst 3/3/2009 - Dim And I3c

Dim And I3C Information: DIM Lowers Potential Of Cancer Cell Metastasis


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