It's October, so you know what that means—Breast Cancer Awareness month. It's usually time for me to get grumpy because of all of the "pink-washing" that goes on, so I'm just going to post a link to this website and be done with it: Think Before You Pink
There was also an excellent blog post written over at ScienceBasedMedicine.org about a month ago by Dr. David Gorski, who is a surgeon specializing in breast cancer. He talks about the dangers of forgoing conventional treatments and instead using alternative medicine, and also talks a little bit about how some people prey on the fears that women (and men) have about cancer. Read it here: Link
Speaking of preying on people's fears, during this month you are also likely to hear a lot about diets that prevent breast cancer and even diets that "cure" breast cancer. Is there any evidence for any of these? Let's find out!
One of the more well known diets that is out there claiming a "cure" for breast cancer is the "Alkaline Diet," and it was promoted/discussed on The Oprah Winfrey Show. This diet and it's perpetrators have already been excoriated over at The Skeptic's Dictionary here, but I feel like these words from Gabe Mirkin, M.D. are worth repeating:
"Anyone who tells you that certain foods or supplements make your stomach or blood acidic does not understand nutrition. You should not believe that it matters whether foods are acidic or alkaline, because no foods change the acidity of anything in your body except your urine. Your stomach is so acidic that no food can change its acidity. Citrus fruits, vinegar, and vitamins such as ascorbic acid or folic acid do not change the acidity of your stomach or your bloodstream. An entire bottle of calcium pills or antacids would not change the acidity of your stomach for more than a few minutes. All foods that leave your stomach are acidic. Then they enter your intestines where secretions from your pancreas neutralize the stomach acids. So no matter what you eat, the food in the stomach is acidic and the food in the intestines is alkaline. You cannot change the acidity of any part of your body except your urine. Your bloodstream and organs control acidity in a very narrow range. Anything that changed acidity in your body would make you very sick and could even kill you." (emphasis mine)
Keep in mind that this alkaline diet is promoted for a lot of other ailments, keep in mind that the "One diet to rule them all" theory is also usually a big red flag.
What about diet for prevention of cancer?
Honestly I would love nothing more to be able to say "eat more of this and you will never get cancer, breast or otherwise," but since I try to be the best scientist I can be (and I also have scruples), I can't tell you that. One of the problem is that there are many people that still do not understand that correlation does not equal causation. It also doesn't help, in my humble opinion, that you can see a headline like "Foods that Fight Cancer" pop up on the American Institute for Cancer Research's website. Fortunately they are willing to immediately counter with "there is no one food that can prevent cancer," but it still makes me cringe because I know not everyone is going to ignore the headline.
So, apparently there is data that eating more plants is associated with a lower risk of cancer—but it's just an association based on observational studies, and you remember what I said about observational studies before—you can say "huh, that's interesting" but you can't start pointing out cures. There is apparently data that states that having lower body is associated with a lower risk of cancer, but once again, observational studies are at play here. Are there other reasons to eat a lot of vegetables? Sure, the do ensure that you get micronutrients for your body to function overall correctly and since they have a low caloric density you can fill up on them to limit overeating on other things. Are there other reasons to lose excess body fat? Sure, improved insulin sensitivity for those who are diabetic and pre-diabetic, you can breathe easier if you have lung problems, less wear and tear on your joints, better blood pressure, etc. But you can't point to a particular food, or even a particular diet plan, and say "this will keep me from getting cancer."
More recently there was another diet/breast cancer association reported on—apparently there was a higher risk of breast cancer in those with higher cadmium rich food intake (Link). Unfortunately, once again we are using the notorious unreliable food questionnaire (remember that?) and even the authors of the study cautioned that we really don't know what the association between cadmium consumption and breast cancer is—and they also pointed out that high levels in a person's body might come from other sources like smoking, etc. And they were also quick to point out that cadmium might be found in—you guessed it—plant foods. (I can hear it now, "What am I supposed to do, quit eating?" No, you need to stop making judgments about your food without having evidence to back it up. There isn't enough evidence to tell you to quit vegetables, etc.)
Take home message—it's not going to hurt you to include more vegetables in your diet for a variety of reasons. We don't know enough about cadmium rich foods to start making recommendations. Will eating a certain way keep "the big C" away? Maybe, maybe not.