rBST, or recombinant bovine somatotropin, is a synthetic form of bovine somatotropin (BST), a growth hormone, used to increase milk yield in dairy cows.

Health considerations

Milk from rBST treated cows may have higher levels of BST and insulin-like growth factor 1 (IGF1) than traditional milk. BST is found in milk from rBST and non-rBST treated cows, as it is a naturally occurring hormone; BST is degraded by the human digestive system. IGF1 is a growth factor that is not destroyed by pasteurization and may be absorbed in the digestive tract. rBST treated cows also typically require more antibiotics than their untreated counterparts.

Keep in mind

rBST use labeling is not mandatory in America, where the hormone is regulated but not prohibited. It is prohibited in Canada due to concerns for animal health.

May be found in

Milk, yogurt, other dairy products


Health Canada
Agricultural Biotechnology
Health Canada

Alternative Spellings and Names

Bovine somatotropin, BGH, bST, recombinant bovine growth hormone, rBGH

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