Issue #204 May 22, 2014
Welcome to KnowYourThyroid.
Today, Dr. Josh Axe is going to talk about cruciferous vegetables. I hear a lot about how you should eat these vegetables because they are so good for you and help stop cancer. On the other hand, you have a thyroid problem they say you shouldn’t eat them because they slow your thyroid function down. So, what should you do? Dr. Josh will explain.
Cruciferous Vegetables: Cancer Killer or Thyroid Killer?
by Dr. Josh Axe and Eric Zielinski
Are you getting enough cruciferous vegetables in your diet? For most people, the answer is no. But I want to encourage you to focus on getting more of these nutrient dense super foods in your diet on a daily basis.
Cruciferous vegetables are unique because they are rich in sulfur containing compounds called glucosinolates which support detoxification and indole-3-carbinol which greatly reduces the risk of breast, colon and lung cancer.
Here is list of the cruciferous vegetables:
- Bok Choy
- Brussel Sprouts
- Collard Greens
- Mustard greens
Cruciferous Vegetables Studies
Ever since a landmark study from 1996, cruciferous veggies have been a hot topic in cancer prevention research. The article – published in the journal Cancer, Epidemiology, Biomarkers & Prevention – reviewed 94 studies and found that consumption of these veggies indicated a decreased risk of both primary and secondary cancers.
Of the 94 research trials evaluated, 70% of cabbage studies showed an decreased relationship with cancer risk. Other notables include cauliflower, broccoli, and brussel sprouts studies that reported 67%, 56% and 29% relationship with decreased cancer risk, respectively.
Not surprisingly, the authors of the study concluded that,
A high consumption of cruciferous vegetables is associated with a decreased risk of cancer. This association appears to be most consistent for lung, stomach, colon, and rectal cancer and least consistent for prostatic, endometrial, and ovarian cancer.
Glucosinolates Kill Cancer
According to the National Cancer Institute, the secret behind the cancer-killing ability of cruciferous veggies is that they are rich in glucosinolates – a large group of sulfur-containing compounds.
These powerhouse chemicals are known to break down during the chewing and digestion process into biologically active compounds that prevent cancer cells growth, which are referred to as indoles, thiocyanates and isothiocyanates.
Having been discovered to prevent cancer growth in rats and mice, indoles and isothiocyanates are heralded to protect against cancer of the bladder, breast, colon, liver, lung, and stomach.
Research suggests that this happens because glucosinolates stimulate what are known as Phase II enzymes, the body’s natural antioxidant system. In essence, glucosinolates trigger the liver to produce detoxifying enzymes that block free-radical attack on your DNA. It has also been reported that glucosinolates:
- Are anti-inflammatory
- Contain antibacterial and antiviral properties
- Inactivate carcinogens
- Reprogram cancer cells to die-off
- Prevent tumor formation and metastasis
Glucosinolates act as natural pesticides in plant cells and, when they are consumed by humans, are utilized for DNA repair and help prevent cancer by slowing cancer cell growth.
According to Jon Michnovicz, MD, PhD, the President of the Foundation for Preventive Oncology, Inc., “Studies have shown that if you make cabbage into a paste and rub in on the backs of laboratory animals, you can prevent tumors from developing.”
In addition to animal studies, Dr. Michnovicz reports that several studies on cruciferous vegetables have been conducted on people and many of these cancer-fighting properties have been confirmed.
Cruciferous Vegetables Thyroid Side Effects
One of the most common questions I get from patients is “does eating cruciferous vegetables cause thyroid problems?”
According to the research, it would take a large amount of cruciferous vegetables to cause hypothyroidism and it appears that there is only a risk if someone also has an iodine deficiency.
One study in humans found that the consumption of 5oz a day of cooked brussels sprouts for four weeks had no adverse effects on thyroid function.
So my advice if you have a thyroid issue is to consume cruciferous vegetables that have been cooked and keep them to about 1-2 servings daily.
Cruciferous Vegetable Recipes
Do you want more cruciferous vegetables in your diet? Then try these recipes:
Finally, amongst the many known benefits of cruciferous vegetables they rank as the most nutrient dense foods on the planet as seen in this chart from worldshealthiestfoods.org.
- Dole Nutrition Institute. How do glucosinolates in vegetables protect me from cancer? Available at: http://www.sharecare.com/health/antioxidants/glucosinolates_protect_cancer
- Giovannucci E, Rimm EB, Liu Y, Stampfer MJ, Willett WC. A prospective study of cruciferous vegetables and prostate cancer. Cancer Epidemiology, Biomarkers & Prevention 2003; 12(12): 1403-1409
- Hecht SS. Inhibition of carcinogenesis by isothiocyanates. Drug Metabolism Reviews 2000; 32(3-4): 395-411.
- Johnson IT. Glucosinolates: Bioavailability and importance to health. Int J Vitam Nutr Res 2002; 72(1): 26-31.
- Murillo G, Mehta RG. Cruciferous vegetables and cancer prevention. Nutrition and Cancer 2001; 41(1-2): 17-28.
- National Cancer Institute. Cruciferous Vegetables and Cancer Prevention. Available at: http://www.cancer.gov/cancertopics/factsheet/diet/cruciferous-vegetables
- Verhoeven DT. Epidemiological studies on brassica vegetables and cancer risk. Cancer Epidemiol Biomarkers Prev 1996; 5(9): 733-48.
- Yang G, Gao YT, Shu XO, et al. Isothiocyanate exposure, glutathione S-transferase polymorphisms, and colorectal cancer risk. American Journal of Clinical Nutrition 2010; 91(3): 704-711.
- Yeager S. The doctors book of food remedies: The latest findings on the power of food. Rodale. New York. 2007. p 127.
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