Are There Growth Hormones in Milk?

Recently, we received a reader comment asking which brands of milk contain growth hormones. To answer this question, we reached out to Dr. Ann Macrina, Research/Teaching Associate at Penn State University. Dr. Macrina previously answered questions about hormones in milk.

What can you tell us about growth hormones in milk?

Dr. Ann Macrina:

First, let me say that all living things – plants, animals, people – produce various hormones, including growth hormone naturally. Milk therefore also contains growth hormone that cows naturally produce.  This hormone, also known as somatotropin or bST, can be found in milk in small quantities.

How do you find out what brands of milk are produced by cows that were treated with bST?

Dr. Ann Macrina:

Some milk processors label their milk as “not from cows treated with bST.” They have requested that the dairy farmers in their co-op refrain from treating their cows with bST. However, there currently is no method to validate this claim. Some brands of milk do not have this claim on their label, and the milk may or may not have come from cows that were treated with bST. Absence of the claim on the label does not indicate that the cows received bST treatment.

*Note: The use, sale or import of rbST is not allowed in Canada. Milk produced on Canadian farms was therefore produced without using the artificial growth hormone.

What is life like on a dairy farm? Teresa of Tiaras & Tantrums shares her experience touring a working dairy farm.

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Milk bottles” by m01229 is licensed under CC BY 2.0.

*Updated 6.1.16*