Nothing strikes fear or anger deep in the hearts of women quite like breast cancer. And with good reason.
According to breastcancer.org, one in eight American women will develop invasive breast cancer at some point in their lives. With the exception of skin cancer, breast cancer is the most commonly diagnosed cancer in U.S. women.
While breast cancer death rates have been steadily declining every year since 1990, more women die from breast cancer than any other from of cancer, besides lung cancer. Given this, it’s little wonder than women and researchers alike are devoted to finding ways to not only treat or detect it, but how to prevent breast cancer from occurring in the first place.
The Antioxidant Promise
One of the more promising areas of breast cancer prevention lies in nutrition. Several studies have turned their attention to antioxidants, namely vitamin A, beta-carotene, vitamin C, lycopene and even selenium.
One of the most common explanations for why antioxidants could help prevent against cancer has to do with free radicals. Antioxidants prevent free radical damage, which in turns prevents cellular damage. Cellular damage, over time, can damage DNA.
When the damage is extensive and irreversible, it may lead to cancer. The hypothesis is that since antioxidants prevent free radical damage, they can decrease oxidative stress and damage to DNA, and therefore help prevent breast cancer. 
Many studies have looked at antioxidant intake from either diet or supplements and their effect on breast cancer risk. However, the results have been inconsistent.
In an attempt to clear up these inconsistencies, Canadian researchers looked at the preventative effects of antioxidants from both diet and supplement use on women between the ages of 20 and 76.
Antioxidant Use and Breast Cancer Prevention
The reviewed data was collected by the National Enhanced Cancer Surveillance System, a multi-component, collaborative project of Health Canada and the provincial cancer registries in Canada. Participants included more than 21,000 Canadians with one of 19 types of cancer, including more than 2,300 cases of breast cancer, and more than 5,000 people who were cancer-free.
Each person filled out a questionnaire, which was designed to gather detailed information about potential cancer risk factors, such as smoking, age, marital status, ethnicity, height, weight, exercise level, alcohol consumption and menstrual/reproductive history. It also included a 69-item food frequency component, as well as information on type and length of vitamin and mineral supplementation.
It was these latter two items that researchers honed in on. They assessed the total weekly intake levels, including those of a variety of antioxidants, namely:
- Vitamin C
- Vitamin E
They also determined the frequency and length of supplement use for 10 nutrients, including:
- Vitamin A
- Vitamin C
- Vitamin E
- B-complex vitamins
Length was determined as less than a year, one to two years, three to five years, six to nine years, 10 to 19 years or 20-plus years. Frequency was determined as never, not regularly or fairly regularly.
Additionally, researchers looked at several other breast cancer risk factors, such as:
- Physical activity and frequency
- Hormonal status
After all the information was gathered, there were 866 premenopausal women with breast cancer, 1,496 postmenopausal women with breast cancer, and 2,462 cancer-free women.
They found that regardless of hormonal status or high level of intake, there was no significant association between antioxidant intake from dietary sources and a reduced risk of breast cancer. However, supplementation was a different story.
Researchers found that premenopausal women who had taken zinc for 10 years or longer had a statistically significant reduction in breast cancer risk.
And when it came to postmenopausal women, there was a statistically significant reduction in breast cancer risk for those women who took multivitamins, beta-carotene, vitamin C, vitamin E and/or zinc for 10 years or longer.
However, in both cases, the association was nullified if supplementation was less than 10 years.
Before making their conclusions, researchers were quick to point out several limiting factors in their study. First is the idea of recall bias, as people don’t always accurately remember their diet, or may even misrepresent their eating habits.
Additionally, researchers were unable to gather specific supplement dosage information when it came to vitamin and mineral use.
Lastly, and most concerning, they were not able to get family history nor birth control or hormone replacement use for all of the participants. This is a pretty big gap to overlook.
Based on this, researchers concluded, “Supplementation of 10 years or longer of certain antioxidants such as beta-carotene, vitamin C, vitamin E, and zinc may reduce the risk of breast cancer.”
Start a Supplement Program Today
While there are some pretty glaring gaps in the data collection, one thing is clear: Long-term antioxidant supplementation appears to play a role in breast cancer prevention. Therefore, if you are 35 years old or older, don’t wait to start a consistent antioxidant program.
Be sure to take zinc, as well as a good-quality multivitamin. For added protection, you can take an antioxidant supplement that includes beta-carotene and vitamins C and E. Follow dosage suggestions on the labels.
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 Thomson CA, et al. Plasma and dietary carotenoids are associated with reduced oxidative stress in women previously treated for breast cancer. Cancer Epidemiol Biomarkers Prev. 2007;16:2,008-15.
 Pan, SY et al. Antioxidants and breast cancer risk – A population-based case-control study in Canada. BMC Cancer. 2011 Aug 24;11(1):372. [Epub ahead of print.]