Does All Dairy Contain Hormones? Separating Fact from Fiction

January 2, 2026 •

3 min read

According to the Food and Drug Administration (FDA), all milk, whether organic or conventional, contains naturally occurring hormones, which are proteins found in all animals and plants. This fact often leads to consumer confusion and concern regarding the question, "Does all dairy contain hormones?". The answer involves distinguishing between these natural compounds and the controversial synthetic growth hormones sometimes used in conventional farming.

Quick Summary

All milk naturally contains trace amounts of hormones, a normal part of a cow's biology. The controversy surrounds artificial growth hormones like rBST, which are declining in use and banned in some regions.

Key Points

Natural vs. Synthetic: All dairy contains naturally occurring hormones like bST, while synthetic rBST is a controversial man-made alternative used by some conventional farmers.
Digestion Deactivates Hormones: The human body digests and breaks down bovine hormones, rendering them inactive and harmless during consumption.
rBST Use is Declining: Strong consumer demand for rBST-free products has led most major dairy brands to voluntarily stop using the synthetic growth hormone.
Labeling is Your Guide: The majority of milk sold in stores, both conventional and organic, is now labeled as 'rBST-free', making it easy to identify.
Organic is rBST-Free by Law: USDA organic standards prohibit the use of synthetic growth hormones like rBST, ensuring that organic milk is always free of them.
IGF-1 Controversy: While some studies have raised concerns about higher IGF-1 levels in rBST-treated milk, major health organizations do not find it a significant human health risk.

The Inevitable Presence of Natural Hormones

Every mammal, including humans and cows, produces hormones to regulate essential bodily functions such as growth and reproduction. Therefore, the simple presence of hormones in dairy is not the core issue, as it is a natural biological process. The primary natural hormone in question is bovine somatotropin (bST), a protein hormone that helps regulate normal growth and milk production in cows. When humans consume cow's milk, these naturally occurring bovine hormones are not recognized by the human body and are digested like any other protein, effectively rendering them biologically inactive. Pasteurization, the heat treatment used to kill bacteria in milk, further degrades and denatures up to 90% of the bST protein. Other naturally present hormones in milk include tiny amounts of estrogens, progesterone, and androgens.

The Story of Synthetic Hormones: rBGH/rBST

The real debate for many consumers centers on synthetic, or man-made, hormones. The most well-known of these is recombinant bovine growth hormone (rBGH), also known as recombinant bovine somatotropin (rBST). This synthetic version of the cow's natural bST protein was designed to boost milk production. While approved by the FDA for use in the US in 1993, rBST is banned in many countries, including Canada and the European Union, often due to animal welfare concerns. Consumer opposition in the US has led many dairy producers to voluntarily avoid rBST, with most US milk now coming from untreated cows.

Understanding the Health Implications for Humans

Concerns about rBST-treated milk often involve potential increases in insulin-like growth factor-1 (IGF-1), which is naturally present in both cow and human milk. Some studies suggest high IGF-1 levels might link to increased cancer risks, though the connection between consuming rBST milk and elevated human IGF-1 is inconclusive and needs more research. The American Cancer Society has no formal stance on rBST use. Increased antibiotic use due to conditions like mastitis in rBST-treated cows is another concern, though dairy is tested for antibiotic residue.

Comparing Conventional, Organic, and Plant-Based Milk

Choosing milk involves understanding types. The table below highlights key differences regarding hormone content.


Feature	Conventional Dairy	Organic Dairy	Plant-Based Milks (Soy, Almond, Oat)
Natural Hormones	Contains natural bovine hormones.	Contains natural bovine hormones.	Hormone-free (no animal hormones).
Synthetic Hormones (rBST)	May be from cows treated with rBST, though most dairy is now rBST-free.	Prohibited by USDA organic standards; must be rBST-free.	Hormone-free (no animal hormones).
IGF-1 Levels	Potentially slightly elevated, but absorbed IGF-1 is controversial.	Normal levels for lactating cows.	No animal-based IGF-1.
Antibiotics	May be used to treat sick cows, but milk is tested for residue.	Prohibited; strict animal welfare standards apply.	N/A.
Sourcing	Farms can vary widely in size and practices.	USDA-certified farms adhering to specific animal care standards.	Sourced from plants, production varies by brand.

Making Informed Choices About Dairy

Consumers concerned about synthetic hormones have many options. Many conventional and organic dairy products are labeled "rBST-free". These products still contain natural hormones. Plant-based alternatives are an option for avoiding all animal-based hormones.

Choose Certified Organic: USDA organic milk is guaranteed to be from cows not treated with synthetic growth hormones.
Look for Labels: Most milk brands use "rBST-free" labels due to consumer demand.
Consider Plant-Based Alternatives: For complete avoidance of animal hormones, plant-based milks are available.

Conclusion

All dairy naturally contains hormones as part of mammalian biology. The main concern is synthetic hormones like rBST, whose use is decreasing due to consumer preference and labeling. While health studies on synthetic hormones are inconclusive, major health bodies deem milk from rBST-treated cows safe. Consumers can choose based on their preference for natural vs. synthetic treatments, or opt for plant-based options to avoid animal hormones entirely.

Visit the FDA's website for more information on milk safety.

Frequently Asked Questions

Natural hormones, like bovine somatotropin (bST), are produced by the cow itself as a normal biological function. Synthetic hormones, like rBST, are man-made versions used to boost milk production.

Yes, organic milk contains naturally occurring hormones, as it comes from a lactating mammal. However, USDA organic regulations prohibit the use of synthetic growth hormones like rBST.

According to the FDA and other major health organizations, milk from cows treated with rBST is safe for human consumption. The bovine hormones are digested and do not affect humans.

Look for dairy products with labels stating 'rBST-free' or 'no artificial growth hormones.' You can also choose USDA-certified organic products or plant-based milk alternatives.

Pasteurization can destroy a significant percentage of protein hormones like bST. However, naturally occurring steroid hormones are less affected by heat, though their levels are already very low.

Concerns often focus on IGF-1 levels, with some studies suggesting potential links to certain cancers, though this evidence is inconclusive. Other issues relate to animal welfare associated with rBST use.

Plant-based milks like soy, almond, and oat are free from animal-based hormones. Some, like soy milk, contain phytoestrogens, which are plant compounds with weak hormonal effects, but they are not the same as animal hormones.