Antibiotic use is associated with an increased risk of breast cancer, according to a study, and the more antibiotics used the more the risk of breast cancer increased.

The study of more than 10,000 women found that women who took antibiotics for more than 500 days--or had more than 25 prescriptions--over an average period of 17 years had more than twice the risk of breast cancer as women who had not taken any antibiotics. Even women who had between one and 25 prescriptions over the same time period were about 1.5 times more likely to get breast cancer.

The results do not necessarily mean that antibiotics cause breast cancer; it could also mean that the something about the women who are using antibiotics is increasing the risk. For instance, they may be biologically predisposed to breast cancer by a hormonal imbalance that is increasing their risk for infections and prompting their antibiotic use.

The authors suggested a few other possible explanations for the observed association between antibiotic use and increased breast cancer risk including:

• Antibiotics can affect bacteria in the intestine, which may impact how certain foods that might prevent cancer are broken down in the body

• Antibiotics may effect the body's immune response and response to inflammation, which could also be related to the development of cancer

• Women with frequent infections may be generally less healthy as those without such infections, and may therefore be more likely to get breast cancer

A study conducted in Finland in 2000 also found an association between antibiotics and breast cancer, and prompted the current study.

In an accompanying JAMA editorial, it is noted that the finding is particularly worrisome as exposure to antibiotics is so prevalent, and often not necessary. Therefore, the risk could be substantial and largely preventable. They also raise the question of whether the use of antibiotics is a risk factor for other cancers, and point to a need for further research to address this concern.

More than 200,000 U.S. women are diagnosed with breast cancer each year and 40,000 die from the disease, making it the second leading cause of cancer deaths among women.

Journal of the American Medical Association February 18, 2004;291(7):827-35

Dr. Mercola's Comments:

Antibiotics can significantly alter the balance of bacteria in your intestine by indiscriminately killing beneficial bacteria. This means that not only are the bad (pathogenic) bacteria killed, but the good bacteria that are essential to health and an integral part of your immune system, are also diminished. Antibiotics frequently allow harmful bacteria to proliferate and repopulate barren areas of the intestinal tract. Over time, repeated use of these medicines can ripen conditions for the overgrowth of harmful organisms that are unaffected by medications and are able to regenerate once treatment has ceased. Even drinking chlorinated water can negatively impact the balance of good and bad bacteria in your gut, leading to any number of health problems, so you can imagine the impact that the repeated use of antibiotics can have. If Americans were eating truly healthy diets it would generally be possible to maintain a healthy bacterial balance in the gut. However, our typical diets are so dependent on sugars and grains that promote the bad bacteria, and antibiotic use is so pervasive, that nearly everyone can benefit from probiotics, as nearly everyone has a ratio of good to bad bacteria in their gut that favors the bad bacteria. This is why, even though I routinely advise patients against too many dietary supplements, I highly recommend and now offer Probiotics, the purest and most highly effective probiotic that I have found. This high potency formula helps to repopulate your intestinal tract with over 26 billion beneficial microorganisms per serving! Of course, if you want to achieve optimal results you must use Probiotics Plus in conjunction with a healthy diet, which means increasing your intake of metabolically appropriate vegetables and decreasing your intake of sugar and carbohydrates. Related Articles: Good Bacteria Work Even When They are Dead When To Take Good Bacteria When On Antibiotics Antibiotics May Improve Heart Disease Finally, U.S. Doctors Cut Use of Antibiotics Finally, Fewer Antibiotics for Children Antibiotics Kill Your Body's Good Bacteria, Too, Leading to Serious Health Risks Most Ear Infections Clear Up Without Antibiotics