Why brussel sprouts are good for you! About Indole-3-Carbinol

Women's Health | June 16, 2017 | Author: Naturopath

women's health

Why brussel sprouts are good for you! About Indole-3-Carbinol

Bad news – our parents were right. Eating our Brussels sprouts is one of the best ways to get healthy and stay that way.

Here's why:

Indole-3-carbinol (I3C) is a chemical found in brassica vegetables such as cauliflower, broccoli, mustard greens and the infamous brussels sprouts. I3C is released when these vegetables are chopped and chewed. It is then converted in the stomach into several different compounds, the well-researched of which is diindolylmethane (DIM). I3C was identified by scientists who were researching why people who ate a diet rich in brassica vegetables were less likely to suffer from cancer – it appears that I3C may have many liver supporting, anti-cancer, antioxidant, and oestrogen-balancing properties.

And here's how it can work for you:

Indole-3-Carbinol and Liver Detoxification

indole liver detoxYou've probably heard of going on a “detox” to cleanse your body of toxins – this means you're helping your liver to do its job. Almost all medications, hormones, toxins, drugs and carcinogens are metabolised by the liver. This makes them into less harmful substances that the body can eliminate. This process uses two metabolic pathways – Phase I and Phase II. The first phase prepares the harmful substances for Phase II, which then converts them into water-soluble substances that can be easily eliminated from the body.

When either Phase I or Phase II are over-active or under-active, toxins can be released into the body and cause issues like headaches, mood swings, fatigue, weight gain, acne, or nausea. Indole-3-carbinol has been shown to boost the activity of both phases to speed up toxin elimination, prevent damage from carcinogens, and protect the body from damage.

What does this actually mean?

Eating more brassica veggies is the great way to kick off a spring detox, recover from a big night, start a new skin care regime, or support your body as you quit coffee or cigarettes. Keep your diet rich in these veggies to support your liver and protect your body from toxins in the long-term.

How I3C Balances Oestrogen

The effect of I3C on the liver goes beyond detox pathways. Put your science-hats back on for a moment, but we'll keep it simple:

indole hot flushesOnce oestrogen has done its job, it needs to be excreted from the body. The liver naturally breaks it down into one of two substances: it can be converted into 16-a-hydroxyesterone (16OHE1) or to 2-hydroxyesterone (2OHE1). Having high levels of 16OHE1 has been shown to cause all kinds of oestrogen-related conditions and to stimulate the spread of oestrogen-dependant cancer cells, while 2OHE1 appears to be relatively safe.

Here's where our favourite brassica veggies come in – indole-3-carbinol shifts the metabolism of oestrogen towards the safer 2OHE1 metabolite. In short: I3C helps to move unwanted oestrogen out of the body, which may help to combat symptoms of oestrogen excess.

This oestrogen balancing role is particularly beneficial in conditions related to oestrogen dominance:

  • Menopause where I3C may help to reduce hot flushes [1].
  • Endometriosis [2].
  • Oestrogen-related cancers including breast cancer and ovarian cancer [3].
  • Cervical dysplasia, or abnormal pre-malignant cells on the cervix [2].

Therapeutic Potential for I-3-C in Cancer & Chemoprotection

indole cell deathYep, time for more science – when any cell divides, it passes through many stages before it divides again. Some of these stages act as “check-points” to make sure that the DNA within the cell is intact. If the DNA is damaged and irreparable, the cell undergoes apoptosis or “cell death” so that it doesn't replicate and create a mutant cell. A defect in these pathways may be responsible for the development of mutations leading to tumours and cancer.

Laboratory research has suggested that I3C may step in at these check-points and signal the defective cell or cancer cell to undergo apoptosis [4] [5]. I3C and DIM may also prevent cancer by helping the liver to detoxify carcinogens, and by acting as an antioxidant to protect DNA from damage in healthy cells [6].

Research trials on I3C in cancer are still quite new, and researchers use huge doses of isolated indole-3-carbinol extracts that are highly concentrated. It's still unclear whether it is safe to take a concentrated I3C or DIM supplement in very high doses, so the potential for I3C to “cure” cancer is still very speculative [7]. However, the evidence suggests that it's perfectly safe to eat a diet rich in brassica vegetables and it may help to prevent the development of many cancers [11]. Plus these veggies could also help to protect the body during chemotherapy [8]!

I3C in Type-2 Diabetes

indole diabetesI3C and its side-kick, DIM, may act as antioxidants to protect the body from damage caused by high blood glucose and insulin in type-2 diabetes (T2DM). 

Laboratory research suggests it's possible that IC3 could act similarly to metformin, a T2DM drug, but DIM could even further improve carbohydrate metabolism to keep blood sugar steady and stop the liver from converting sugar into cholesterol [9] [3].

This research is still in its early stages, but there's no harm in boosting your carbohydrate-heavy meals with lots of cruciferous veggies to support your blood sugar levels.

Which foods contain the most indole-3-carbinol?

1 cup serving of:                      contains this much indole-3-carbinol:

Garden cress (aka pepper cress)          8.0mg

Brussels sprouts                                   5.6mg

Kale                                                     1.0mg

Watercress                                           1.0mg

Turnips                                     1.0mg

Cabbage, green                                    1.6mg

Cabbage, red                                       1.2mg

Broccoli                                               1.2mg

Kohlrabi                                              1.0mg

Bok choy                                             1.0mg

Cauliflower                                         0.80mg

Source: McNaughtan & Marks [10].

How To Eat Indole-3-Carbinol Foods

indole brocoliChop & chew – indole-3-carbinol is actually derived from the interaction of a compound within brassica vegetables called “glucobrassicin”, and an enzyme that is only released when the vegetables are chopped or chewed. Cooking brassicas will destroy some of the I3C content, but eating them raw has a major down-side – these raw veggies contain high levels of acids that prevent nutrients from being absorbed, compounds that interfere with thyroid hormone production and may contribute to kidney stones [14].

Boiling brassicas for 10 minutes or less is long enough to break down these health hazards while retaining ~80% of the I3C content [12], but because I3C is a water-soluble nutrient it can leak out of the food and into the water. This is fine if you're making a meal where you'll consume the water (like in soup), as that's where the nutrients are! Otherwise, lightly steam or stir-fry your brassicas to get the most I3C (and flavour) out of them. Fermentation is a great way to preserve a huge dose of I3C, but it doesn't eliminate the dangerous compounds [13].

Supplementing with I3C and DIM 

If you can't tolerate brassicas or want to boost your indole-3-carbinol intake to therapeutic levels, both I3C and DIM are available as supplements. Since some I3C is converted to DIM within the stomach, some people prefer to take the end-product, while others prefer to stick to I3C. Taking DIM for 15 weeks or less appears to be safe for most people, but speak to your healthcare provider – or stick to the whole food option!

There may be risks involved in taking I3C at high dosages or long-term, and it can interfere with the effectiveness of other drugs. Supplementation is best undertaken under the care of a nutritionist or naturopath who can monitor your symptoms and prescribe dosages that will be safe and effective for your personal circumstances. If you experience any symptoms of vomiting, nausea, tremors or dizziness, stop taking I3C and contact your healthcare professional immediately.

In conclusion... Eat your Brussels sprouts!


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[2] Hamilton, K. J., et al. (2017) Estrogen hormone biology. Curr Top Dev Biol., 125, 109 – 146. https://www.ncbi.nlm.nih.gov/pubmed/28527569

[3] Marconette, C. N. (2012) Indole-3-Carbinol disrupts estrogen receptor-alpha dependent expression of insulin-like growth factor-1 receptor and insulin receptor substrate-1 and proliferation of human breast cancer cells. Mol Cell Endocrinol., 364, 74 – 84. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3684449/

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[6] Bonnenson, C., Eggleston, I. M. & Hayes, J. D. (2001) Dietary Indoles and Isothiocyanates That Are Generated from Cruciferous Vegetables Can Both Stimulate Apoptosis and Confer Protection against DNA Damage in Human Colon Cell Lines. Epidemiology and Prevention, 61:16. http://cancerres.aacrjournals.org/content/61/16/6120.long

[7] Suzui, M., et al. (2005) Indole-3-carbinol inhibits the growth of human colon carcinoma cells but enhances the tumor multiplicity and volume of azoxymethane-induced rat colon carcinogenesis. Int J Oncol. 27:5, 1391-1399. https://www.ncbi.nlm.nih.gov/pubmed/16211236

[8] Shapiro, T. A., et al. (2001) Chemoprotective glucosinolates and isothiocyanates of broccoli sprouts: metabolism and excretion in humans. Cancer Epidemiol Biomarkers Prev., 10:5, 501 – 508. https://www.ncbi.nlm.nih.gov/pubmed/11352861

[9] Poornima, J. & Mirunalini, S. (2014) Regulation of carbohydrate metabolism by indole-3-carbinol and its metabolite 3,3'-diindolylmethane in high-fat diet-induced C57BL/6J mice. Mol Cell Biochem., 385, 7 – 15. https://www.ncbi.nlm.nih.gov/pubmed/24072613

[10] McNaughton, S. A. & Marks, G. C. (2003) Development of a food composition database for the estimation of dietary intakes of glucosinolates, the biologically active constituents of cruciferous vegetables. Br J Nutr. 90:3, 687-697. https://www.ncbi.nlm.nih.gov/pubmed/13129476

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[13]  Jaiswal, A. K. & Abu-Ghannam, N. (2016) Fermentation-Assisted Extraction of Isothiocyanates from Brassica Vegetable Using Box-Behnken Experimental Design. Foods, 5:4, 75. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5302433/

[14] Shapiro, T. A., et al. (1998) Human metabolism and excretion of cancer chemoprotective glucosinolates and isothiocyanates of cruciferous vegetables. Cancer Epidemiol Biomarkers Prev., 7:12, 1091 – 1100. https://www.ncbi.nlm.nih.gov/pubmed/9865427
[15] Osiecki, H. (2014) The Nutrient Bible (9th ed). Bio Concepts Publishing.

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