Questions and Answers About Labeling of Milk Products Containing Recombinant Bovine Somatotropin (rbST)

What are bST and rbST?
Somatotropin is a protein hormone produced in humans and virtually all mammals that is important to support tissue health, maintenance, and growth.  BST refers to the hormone in dairy cows. Recombinant bovine somatotropin (rbST) is a version of the naturally-occurring protein in dairy cows that is produced through biotechnology.  Through this recombinant DNA technology, exact copies of the protein hormone are produced.  All milk, regardless of production method, provides the same nutritional benefits. Some companies and retailers are marketing milk from cows not supplemented with rbST as “not produced with artificial growth hormones.”

Why do farmers use rbST?
rbST is used to supplement the cow’s natural level of somatotropin to allow her to maintain her milk production for a longer period of time. This benefits farmers by improving the productive efficiency of their farms which allows dairy producers to produce milk using fewer natural resources.

Is rbST safe?
Yes. The Food and Drug Administration (FDA) approved the use of rbST (sometimes referred to as rbGH) in November 1993.  FDA approved the product because it had determined after a thorough review that rbST is safe and effective for dairy cows, that the milk from rbST-supplemented cows is safe for humans, and that production and use of the product does not have a negative impact on the environment.  In 2000, FDA upheld its original conclusion that milk from cows supplemented with rbST is safe for human consumption.  FDA’s determination has been supported by numerous scientific and regulatory bodies including the Joint Food and Agricultural Organization/World Health Organization Expert Committee on Food Additives (JECFA), an international panel of experts in the fields of toxicology and chemistry of animal drug residues; the Commission of the European Communities; and the National Institutes of Health.

Aren’t hormone levels increased in milk from rbST-supplemented cows?
Hormones are present in all milk, including human breast milk.  While the protein hormones help cows produce milk, they are not active when consumed by humans.  Studies on cows have repeatedly shown that use of rbST does not significantly increase levels of hormones in milk. A recent study published in the Journal of the American Dietetic Association looked at the quality, nutritional value and hormone composition of milk purchased at retail stores that were labeled according to farm-management practice—organic, processor-certified as not from cows supplemented with rbST, or conventional.  The study found that the type of label was not related to any meaningful differences in nutritional value, quality, or hormone composition.  The hormones measured were bovine somatotropin, insulin-like growth factor-1, progesterone and estradiol.  The authors conclude that “it is important for food and nutrition professionals to know that conventional, rbST-free and organic milk are compositionally similar so they can serve as a key resource to consumers who are making milk purchase (and consumption) decisions in a marketplace where there are misleading milk label claims.”

Is there any way to differentiate between naturally occurring bST and rbST in milk through testing?
No. According to the FDA, there is no way to differentiate between them.  FDA guidance indicates that companies making production claims regarding rbST should be able to demonstrate that all milk-derived ingredients in the product are from cows not supplemented with rbST.  It is up to individual states, however, to determine whether a label is misleading and what documentation is necessary to ensure compliance. 

Are dairy products containing rbST required by FDA to be labeled?
No.  Because FDA found that there was no significant difference between milk from supplemented and unsupplemented cows, it did not have the authority under the Federal Food, Drug and Cosmetic Act to require such labeling.  The fact that label claims are not related to any meaningful difference in the milk’s composition is supported by the research published in the Journal of the American Dietetic Association.

Can industry voluntarily label their products to let consumers know that they do not use milk from cows supplemented with rbST?
Yes, provided any statements made are truthful and not misleading.  In particular, such labeling cannot imply any difference in safety or quality over competing milk products.  In February 1994, FDA issued a guidance document stating that because natural bST is present in milk, no milk is “bST-free,” and the term “rbST free” may imply a difference in composition between milk from supplemented and unsupplemented cows.  FDA said such misleading implications could best be avoided by the use of accompanying information that puts the statement in proper context.  For example, the statement “from cows not supplemented with rbST” could be followed by “No significant difference has been shown between milk derived from rbST-supplemented and non-rbST supplemented cows.”  

Should I continue to drink milk?
Yes, regardless of the labeling as to the method of production, milk is an excellent source of many essential nutrients, including protein and calcium. 


J. Vicini, T. Etherton, P. Kris-Etherton, J. Ballam, S. Denham, R. Staub, D. Goildstein, R. Cady, M. McGrath, M. Lucy.  Survey of Retail Milk Composition as Affected by Label Claims Regarding Farm-Management Practices.  J. Am. Diet Assoc., 2008, vol. 108, no. 7, pp 1198-1203.

Evaluation of Certain Veterinary Drug Residues in Food.  Fiftieth report of the Joint FAO/WHO Expert Committee on Food Additives.  World Health Organization. 1999.

CVM Update, Center for Veterinary Medicine, April 21, 2000.

Interim Guidance on the Voluntary Labeling of Milk and Milk Products From Cows That Have Not Been Treated With Recombinant Bovine Somatotropin.  Federal Register, February 10, 1994.

Veterinary Medicinal Products Containing Bovine Somatotropin.  Commission of the European Communities, February 1, 1993.

Bovine Growth Hormone: Human Food Safety Evaluation, by Judith C. Juskevich and C. Greg Guyer, Science, New Series, Vol. 249, No. 4971 (Aug. 24, 1990) pp 874-884.