After switching to a vegetarian diet, one Nutrition Diva listener noticed an improvement in PMS symptoms. Follow along as Nutrition Diva follows the trail of evidence.
“PMS has always been a huge issue for me but last month—for the first time in my life—it wasn’t. In the last month, I’d also stopped eating meat, due to environmental concerns. I’ve never heard of meat causing mood swings but is it possible that the hormones in meat could contribute to hormone imbalances?”
Chau’s question is a great example of how the scientific process works. It starts with an observation: Chau noticed an improvement in her PMS symptoms. She then detected a correlation: The improvement in her symptoms coincided with the elimination of meat from her diet. This led her to form a perfectly valid hypothesis: Perhaps hormones in meat were contributing to her hormone-related symptoms?
Unfortunately, all too many people would stop their inquiry right there and start promoting this as an established fact: Hormones in meat cause PMS! But that is not where the scientific process stops! The next step is to start looking for data that either confirm or rule out your hypothesis. So, thanks for sending your question, Chau. I’m glad to help take this thought process to the next level.
Do Hormones in Meat Affect Your Hormone Levels?
Animals that are raised for meat are sometimes treated with steroid hormones, including testosterone, estrogen, and progesterone. These are used to promote their growth and shorten the time it takes them to reach maturity.
See also: Hormones in Food
You can also buy meat that is raised without the use of any hormones. Interestingly, however, the amounts of steroid hormones in untreated and hormone-treated beef are virtually identical. It’s just that the animals that aren’t treated take a bit longer to mature. More to the point, the amount of hormones you ingest when you eat meat is miniscule compared to the hormones produced by your own body.
I was unable to find any evidence that the hormones in meat have any effect on a woman’s hormone levels. Of course, the absence of evidence is not evidence of absence! But I did find a study involving young men, in which there was no relationship between how much meat they ate and their testosterone or estrogen levels. Although the data are limited, given my understanding of the biology involved, it seems unlikely to me that hormones in meat you eat have any direct hormonal effects in your body. However, what you eat can affect your hormone levels in other, less direct ways.
How Diet Affects Hormones
Vegetarians usually have lower estrogen levels than non-vegetarians, and one study found that women who followed a traditional Mediterranean diet, which usually involves eating less animal protein, had lower levels of circulating estrogen. Both of these diets also tend to be higher in fiber, which tends to reduce circulating estrogen.
People who don’t eat meat are also very likely to include more soy in their diets, and we know that soy products affect hormone function, usually in beneficial ways. In fact, one study noted a connection between higher soy intake and reduced PMS!
In addition, vegetarians and those who follow a Mediterranean diet pattern both tend to be leaner than those who eat a more typical meat-centric diet—and we know that body fat affects hormone levels.
Having more body fat is linked to higher estrogen levels. If a change in diet causes you to lose or gain weight, it could affect your hormone levels—not because of the hormones that are or aren’t in your food but because of the change in your body fat percentage.
So, although the hormones in meat may not be a factor, there are still a variety of ways in which your dietary choices can affect your hormone profiles. But PMS is not thought to be caused by elevated hormone levels.