Only a small percentage of Americans consumes the five daily servings of fruits and vegetables that the government recommends for good health. Even more distressing, the typical American diet is deficient in some of the most healthy foods available: (Brassica) cruciferous vegetables such as broccoli, cauliflower, Brussels sprouts, cabbage, collard/mustard greens, radish, rutabaga, turnip, and kale.
DIM and I3C are specifically referenced in Red Cabbage, Broccoli, and Cauliflower
Nutrient losses to storage and cooking
Studies have shown that even if you eat these vegetables every day, their beneficial glucosinolates may be lost during food storage, or degraded or leached out during food processing. Moreover, cooking cruciferous vegetables tends to inhibit the conversion of much of their glucosinolate content to beneficial compounds. Boiling cruciferous vegetables for 9–15 minutes resulted in an 18–59% decrease in the total glucosinolate content of cruciferous vegetables.2
Cooking methods that use less water, such as steaming or microwaving, may reduce glucosinolate losses. That is why many have looked for additional ways to supplement their dietary intake of these beneficial compounds like Indole 3 Carbinol & DIM.
2. Br J Nutr. 2003 Sep;90(3):687-972