At the recent American Association for Cancer Research annual meeting, new evidence highlighted the importance of cruciferous vegetables for breast cancer protection
The cruciferous vegetable family:
|Broccoli rabe||Kale||Turnip greens|
|Brussels sprouts||Mustard greens|
The cruciferous family is unique among vegetables because of their glucosinolate content – glucosinolates give cruciferous vegetables their characteristic spicy or bitter tastes; when the plant cell walls are broken by blending, chopping, or chewing, an enzyme called myrosinase converts glucosinolates to isothiocyanates (ITCs) – compounds with potent anti-cancer effects, including:1
- Anti-inflammatory effects – ITCs have been found to decrease the secretion of inflammatory molecules.
- Anti-angiogenic effects – isothiocyanates can inhibit the development of new blood vessels to limit tumor growth.
- Detoxification of carcinogens – Some carcinogens must be converted to their active form before they can bind DNA to cause carcinogenic changes – isothiocyanates can block this transformation.
- Preventing DNA damage – Isothiocyanates also increase the production of our body’s natural detoxification enzymes, which protect DNA against damage from carcinogens and free radicals.
- Stopping cell division in cells whose DNA has been damaged
- Promoting programmed cell death in cancerous cells
- Anti-estrogenic activity – Exposure to estrogen is known to increase breast cancer risk; estrogens can alter gene expression, promoting cell proliferation breast tissue. ITCs have been shown to inhibit the expression of estrogen-responsive genes.
- Shifting hormone metabolism – Eating cruciferous vegetables regularly helps the body to shift hormone metabolism, reducing the cancer-promoting potency of estrogen and other hormones.
Eating cruciferous vegetables produces measurable isothiocyanates in breast tissue2, and observational studies show that women who eat more cruciferous vegetables are less likely to be diagnosed with breast cancer: In a Chinese study, women who regularly ate one serving per day of cruciferous vegetables had a 50% reduced risk of breast cancer.3 A 17% decrease in breast cancer risk was found in a European study for consuming cruciferous vegetables at least once a week.4
What about women who already have cancer? Is it too late for cruciferous vegetables to improve their prognosis?
We know that childhood and adolescence are the most crucial times for environmental stimuli to affect breast cancer risk, but changes made during adulthood and even after diagnosis still have the potential to create positive changes in the body.
The study kept track of cruciferous vegetable intake in Chinese women with breast cancer for the first 3 years after diagnosis, and followed the women for a total of 5 years. They found dose-response effects – this means that the more cruciferous vegetables women ate, the less likely they were to experience breast cancer recurrence or die from breast cancer. When the women were grouped into four quartiles of cruciferous vegetable consumption, in the highest quartile had a 62% decrease in risk of death and 35% reduced risk of recurrence compared to the lowest quartile.5
This data supports a previous report from the Women’s Healthy Eating and Living (WHEL) study. Breast cancer survivors who reported higher than median cruciferous vegetable intake and were in the top third of total vegetable intake had a 52% reduced risk of recurrence – especially powerful since the average intakes were quite low – 3.1 and 0.5 servings/day of total and cruciferous vegetables, respectively.6
Don’t forget: cruciferous vegetables must be chopped, crushed, or chewed well for maximum benefit!
The myrosinase enzyme is physically separated from the glucosinolates in the intact vegetables, but when the plant cells are broken, the chemical reaction can occur and ITCs can be formed. The more you chop before cooking (or chew if you are eating the vegetables raw), the better. Some ITC benefit may be lost with boiling or steaming, so we get the maximum benefit from eating cruciferous vegetables raw – however, gut bacteria also have the myrosinase enzyme, so additional ITC production may occur in cooked cruciferous vegetables after we eat them. Also, we can increase ITC production from cooked cruciferous vegetables by having some shredded raw cruciferous vegetables such as cabbage, kale, collards or arugula in a salad in the same meal to supply the myrosinase enzyme, which the body can use during the digestive process.
1. Higdon J, Delage B, Williams D, et al. Cruciferous vegetables and human cancer risk: epidemiologic evidence and mechanistic basis. Pharmacol Res 2007;55:224-236.
2. Cornblatt BS, Ye L, Dinkova-Kostova AT, et al. Preclinical and clinical evaluation of sulforaphane for chemoprevention in the breast. Carcinogenesis 2007;28:1485-1490.
3. Zhang CX, Ho SC, Chen YM, et al. Greater vegetable and fruit intake is associated with a lower risk of breast cancer among Chinese women. Int J Cancer 2009;125:181-188.
4. Bosetti C, Filomeno M, Riso P, et al. Cruciferous vegetables and cancer risk in a network of case-control studies. Ann Oncol 2012.
5. Nechuta SJ, Lu W, Cai H, et al: Cruciferous Vegetable Intake After Diagnosis of Breast Cancer and Survival: a Report From the Shanghai Breast Cancer Survival Study. Abstract #LB-322. In Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4. Chicago, Il; 2012.
6. Thomson CA, Rock CL, Thompson PA, et al. Vegetable intake is associated with reduced breast cancer recurrence in tamoxifen users: a secondary analysis from the Women's Healthy Eating and Living Study. Breast Cancer Res Treat 2011;125:519-527.