Does Diet Matter After Breast Cancer?

Most breast cancer survivors want to know what they should be eating after treatment.  Unfortunately, when they ask their oncologists about what diet they should follow after treatment the answers generally range from “eat what you want” to “just eat more fruits and veggies.” 

I know because this is what you have told me over the many years that I have seen patients as an integrative oncologist.  And I have heard it directly from my oncology colleagues.  Some just don’t think nutrition is all that important and others are as confused by the research as you are.

Well, as you might have guessed, there is more to the nutrition recommendation than just eat more fruits and veggies.  In fact, there is a LOT more you need to know.  Part of the confusion comes from docs not really knowing the results of the trials that have been done and the quality of those trials.  While there has been some research on nutrition in breast cancer survivors, it is difficult to draw firm conclusions from the largest (and most expensive) trials. 

I have gotten additional training in integrative oncology and have spent a lot of time researching nutrition in breast cancer survivors so that I can help you answer this all-important question.  But let me be clear about one thing that may frustrate you…there is no ONE single diet that is right for everyone.  Which contributes to the confusion over what to recommend to breast cancer survivors.  So let’s get to the research.

First I want to go over some of the basic diets that you have probably heard of and that some of you have been trying to follow because you were told they were the “best diets”.  Surprisingly enough there have only been a few that have been studied in breast cancer survivors. This probably goes back to the difficulty in conducting nutritional studies in general which I talk about in another post.  But we are going to work with the information we have.

The low-fat diet was thought to be the “best” diet for several decades but really this conclusion was not based on strong evidence.  But we do have some information on low-fat diets specifically in breast cancer survivors. 

The WINS study (which was the Womens Intervention Nutrition Study) is probably the most quoted breast cancer and diet study.  Here the researchers concluded that a low-fat diet led to a lower risk of breast cancer recurrence.  The trouble with that conclusion is that the low-fat group also lost weight during the study.  So we really can’t say if it was the low-fat diet or the weight loss that led to their lower risk.  If you don’t know it yet, weight loss if you are overweight will dramatically reduce your risk of a breast cancer recurrence.

The Nurses Health Study which was another huge study concluded that there was no benefit to a low-fat diet.  And a third study was the WHEL study (Women’s Healthy Eating and Living) which looked at low-fat plus lots of fruits and veggies as well as additional fiber.  There wasn’t any real benefit to this diet either but an interesting fact came out of this study.  This particular diet did lower circulating levels of estrogen…  But so did a high fiber alone diet—meaning without the low-fat part.

Knowing this about low-fat diets is important because a) this is likely what some docs will recommend and b) low-fat diets are not a lot of fun to be on.  Fat tastes good.  And remember, foods that are labeled “low-fat” are likely to be processed foods with carbs added to replace the fat.

What about one of my favorites, the Mediterranean diet?  The main difference between a Mediterranean diet and a low-fat diet is that low-fat usually means less than 15-20% of calories from fat and the Mediterranean diet allows 30 to 40% fat.  Which makes food a lot tastier. 

A recent meta-analysis which combines a bunch of studies did not show that the Mediterranean diet influenced breast cancer outcomes if you included diets that allowed for a moderate amount of red wine intake.  Yes, I hear the sighs now.  The red wine might slightly increase the risk of recurrence.  In another review of studies that looked at the Mediterranean diet without red wine, there was a beneficial effect on breast cancer survival.  Was red wine the difference?  We can’t really say for these particular studies.

So most docs who bother to give you a nutrition recommendation at all are going to mention either a low-fat diet or the Mediterranean diet.  Both of these diets can be considered “healthy” but there is much more to the story when we think about what is the right diet for your particular situation.

That is why I have included a nutrition assessment in my program, THRIVE Beyond Breast Cancer.  A member of the program can put in some specific health information and the assessment will tell them which diet is likely to be best for them.  No one size fits all.