Are Bras Healthy?

Recently, a reader asked me about whether bras are healthy, given that hunter-gatherer women obviously didn't wear them.  I have to confess that, being male, I've never even thought about the issue.  But I am always up for a challenge and did some research.

First, I was surprised to see a book out, "Dressed to Kill", that presupposes a link between bras and breast cancer.  Of course, there are books on any subject - aliens, tarot cards, etc. - and a book by itself does mean something is credible.  But from the abstract of the book and some other sources, the theory struck me as very intriguing.

The best summary of all evidence I found is here.  Another summary is here, and the author addresses things from an evolutionary perspective.  He mentions that women evolved under conditions where there was natural breast movement throughout normal daily activities.  The movement could be equated to a daily "massage" for the breasts.  This would agree with recent research that shows for women diagnosed with breast cancer, breast massage increases the activity of natural killer cells.

The bottom line is that there is currently no cut-and-dry evidence that bras are related to breast cancer.  However, viewing the issue from an evolutionary perspective certainly suggests that daily, natural breast movement is healthy, and that bras may restrict this.