Does Dairy Cause Breast Cancer?

Dairy is a common target of nutritional fear mongering. It’s also one of the most highly politicized nutrition topics in the United States. Pro-dairy groups will tell you that you must eat dairy for good health. Anti-dairy groups will tell you that you must avoid dairy for good health. Who’s right?

The truth? Somewhere in the middle.

This is because the connection between dairy and health is not black and white. Dairy may be helpful for reducing risk of some health threats, yet it may be implicated in increasing the risk of other diseases. If someone issues a blanket statement about dairy and health, they simply are not telling the truth. The science on dairy and health does not support that dairy is always good, or always bad.

Can dairy and breast cancer be studied accurately?

Unfortunately, the gold standard of research – a double-blinded, placebo-controlled trial – isn’t available for dairy and breast cancer. It’s nearly impossible to randomly assign people to consume dairy or not consume dairy, have them stick to this dietary regimen faithfully, and follow them for the decades required to see how many people in each group get breast cancer.

Never mind that you can’t “blind” people to the intervention. If someone is assigned to drink milk, they know it. There isn’t a good placebo – or a non-dairy milk – that would fool anyone into thinking they are drinking milk when they aren’t. Ditto for cheese and yogurt. So it’s unlikely that we’ll get this type of evidence anytime soon.

Fortunately, there are dozens and dozens of observational studies on dairy and breast cancer. And while no single observational study can prove cause and effect, when we have a lot of these studies to consider, we can look for a pattern.

A great example is smoking and lung cancer. Even though we don’t have a controlled clinical trial on smoking and lung cancer, the observational studies all point the same way.

And about breast cancer?

How do dairy and breast cancer stack up? It turns out that dairy is, if anything, slightly protective against breast cancer. One large meta-analysis – a type of study that combines data from previous studies on the topic – found that women with the most dairy in their diets had about a 15% reduced risk of breast cancer.

However, other large observational studies and research reviews have found that dairy is neither protective against, nor increases the risk of, breast cancer. In essence, it is neutral.

To sum it all up, if dairy foods truly had a strong connection with breast cancer, the results of all of this observational research would consistently point in that direction. This isn’t what we see, which means there probably isn’t a strong connection between dairy and breast cancer risk, one way or the other.

The Take Home Message?

If breast cancer is your concern, dairy is pretty much a non-issue. If you enjoy dairy, have dairy. If you don’t like dairy, don’t have dairy. You may have other reasons for wanting to avoid dairy, but don’t let someone sway your decision by convincing you that dairy causes breast cancer.

Advertisements