RM: Last week you said we would talk about some new information on breast cancer prevention and exercise. Let’s start there this week.

JH:Ok.You know how we talk so much in our book about exercise and its beneficial effects on virtually every organ system in the body as shown by rigorous scientific research in recent years?

RM: Absolutely. During our research for our book we were both surprised by how much research has shown that. Exercise is no longer about “going out for a little walk” to relieve stress or get outside; it’s not a “nice to do” any longer, but a “must do”. In particular, we mentioned that studies have shown that the proper amount of regular exercise may prevent a recurrence of breast cancer in a woman who has been successfully treated.

JH: That’s exactly where I’m going, and there’s even more now.A recent issue of the NCI Cancer Bulletin, which comes out weekly from the National Cancer Institute, put the spotlight on the entire issue of the role of exercise in breast cancer prevention (October 21, 2008; Volume 5, Number 21). More and more research studies indicate that the levels of hormones in the body can be modified by physical activity. Since one of the major theories of breast cancer is that its development is closely related to, and may be caused by, the total amount of estrogen and progesterone a woman is exposed to over her lifetime, knowing that a woman can reduce these hormone levels through exercise is very important information.

RM: In other words, you’re saying that doing regular exercise – by reducing the hormone levels in the body – may be able to actually prevent breast cancer?

JH: That’s the working theory. And there are some good studies to back this up. In one study, known as the “California Teacher’s Study” in which over 133,000 current and retired California teachers and administrators have been enrolled since 1995, the researchers found that the risk of invasive breast cancer (specifically estrogen receptor-negative breast cancer) was inversely related to the amount of strenuous exercise the women had done throughout their lives.

RM: Meaning that the women who did more exercise had a lower risk of invasive breast cancer than those women who didn’t? And how much “strenuous” exercise are we talking about here?

JH: Specifically, the researchers found that those women who had done 5 hours per week of strenuous exercise from the time they were in high school until their current age (around 54 yo), had a significantly lower risk than women who had done ½ hour or less of strenuous exercise over the same time period.

RM: That’s impressive. Are there more studies to back that up?

JH: Yes. The National Institutes of Health (NIH) and the American Association of Retired Persons (AARP) are doing a similar study known as “The Diet and Health Study” that began in 1995. These researchers looked at the amount of physical exercise done by participating women (between the ages of 50 and 71) at the study’s beginning, and found the same thing: that higher levels of physical activity seemed to decrease the risk of estrogen receptor-negative (ER-negative) breast cancer.

RM: I have two questions about these findings. First, a simple explanation. Breast tumors are categorized based on whether or not they have estrogen receptors; those that do have them are known as ER-positive tumors, and those that don’t are called ER-negative.

My first question is: does the fact that exercise reduced the risk of ER-negative breast cancer, rather than other types, make a difference?

JH: Good question. Yes. Here’s why. There are drugs currently in use that can help prevent the formation of ER-positive breast tumors; these drugs are tamoxifen (Novaldex) and raloxifene (Evista). However, there are no drugs available that prevent ER-negative breast tumors. Knowing that physical activity may do that is crucially important.

RM: Very impressive that we may soon be able to help prevent both types of breast cancer.

My second question: You say that the theory is that it is the amount of physical exercise done over a woman’s entire lifetime that may be important in breast cancer prevention. That sounds to me like you’re implying that the earlier she starts doing regular exercise in her life, the less likely she may be to get it. Is that right?

JH: Bingo. (You’re SO smart; glad you are my coauthor! LOL) Remember the Nurse’s Health Study II (NHSII) that you talk a lot about in the book in regard to the use of hormone therapy at menopause?

RM: How could I forget?!

JH: Well, researchers in that study looked at the amount of lifetime regular activity done, from the age of 12 yo and up, in nearly 65,000 premenopausal women, and found a 23 % reduced risk for premenopausal breast cancer in those women who had regularly exercised. Specifically, the higher the levels of physical activity between the ages of 12 and 22, the lower the risk. The researchers think that may have something to do with adolescence being the period of breast development, a time when the breast tissue is most susceptible to hormones and other influences.

RM: So, to all our readers: Get your daughter, granddaughters, nieces and girlfriends’ daughters out there regularly exercising!!

JH: Absolutely. But also a caution to our readers: just because you may not have been physically active when you were younger doesn’t mean it’s too late for you to reap the benefits of exercise now. Researchers from the NCI, and we, strongly believe that becoming regularly physically active at any age is beneficial, especially since we are all living longer.

RM: So don’t forget to take that long walk after dinner on Turkey Day!

JH: And everyday, for that matter. Or at least 5 days a week.

RM: I thought we were going to talk about the importance of abdominal fat this week, but I guess we’re giving our readers/friends a break before Thanksgiving, right?

JH: Yes. We’ll get to that topic right after the Holiday. In the meantime, please read (or reread) our blog from November 5, “The Danger Season.” You’ll see why we’re recommending it again when you read it.

Both: Have a safe and healthy Thanksgiving!!