Do High-Fat Diets Cause Cancer

Sorting through conflicting information
Kathryn E. Vinson, MS, CCRC

Do high-fat diets cause cancer? We all know that how we eat and what we eat have tremendous impacts on our health; however, the extent of those effects and the precise influences of those factors are harder to pinpoint where cancer is concerned. The problem with saying “food X causes cancer” is that it is unethical to conduct a trial when you feel that the item you are testing is hazardous.  With these limitations, often the best that we can do is say that something is “linked” to a higher or lower chance of developing a certain disease.

Fat has gotten a bad rap for a lot of years.  It is important for us to realize that we need fat (lipids) in our diets for some very important reasons.  Lipids are vital components of cell walls in all animals.  Also, many hormones are synthesized from cholesterol – such as estrogen and testosterone.  Not all fats are bad and are actually needed to be healthy.

Some interesting studies have come out recently that link diet to breast and prostate cancer risks.  Let’s visit about these studies today and what they mean for us.

Prostate Cancer and High Fat Diets

The correlation between high fat diets and prostate cancer has been seen for many years.  One of the key pieces of data in this link has been the relatively low incidence of prostate cancer in men of Asian descent, with the traditionally low-fat diet seen in many Asian cultures. In January, a team of researchers from Beth Israel Deaconess Medical Center released information from a study targeting certain genes called PML and PTEN in mouse models of prostate cancer. They found that in both mouse models and in human cell cultures, when the PML gene was lacking, a protein was activated that caused the body to produce copious amounts of fat.  In fact, the metastatic tumors that were produced were full of fat. The researchers feel that this data shows a possible increased risk of more aggressive metastatic disease in men that consume a high fat diet.

Breast Cancer and BMI

Over the years, it has been well known that a risk factor in developing post-menopausal breast cancer is being overweight; however, this correlation has not been greatly studied in pre-menopausal breast cancer patients.  The fact that the average age of a breast cancer diagnosis is 62 years, helps us to understand the lack of study.  In June, a group of researchers from the University of North Carolina, utilizing retrospective data from multiple previous studies, were able to link higher BMIs with lower risk of breast cancer in pre-menopausal women.  Further analysis of the data shows that this seemingly protective factor of a higher BMI was only apparent in women with hormone receptor positive breast cancer; no change was seen in triple-negative breast cancer.

Before you go out and buy a bucket of KFC, remember that this shows correlation – not causation.  We cannot say that a higher BMI is the reason some women were protected, or a lower BMI is the reason that some women developed breast cancer.  The results of this study give researchers new avenues to pursue in why cancer develops in some people and not in others.  Remember above when I told you that we need lipids for the production of estrogen?  The researchers believe that the estrogen produced by adipose (fat) tissue may help to down-regulate the estrogen production in the ovaries of pre-menopausal women, thus having an effect on the development of cancer.

So, what is the take away message here? One place we hear that high fat is bad, the other place we hear that a high BMI can be good.  My honest opinion is that moderation is the answer.  Do your best to live a healthy lifestyle – a healthy diet and a good exercise regimen are always a good idea.  But don’t beat yourself up over that cookie.


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