Is There Growth Hormone in Raw Milk? Unpacking the Science

December 28, 2025 •

4 min read

Raw milk, like all animal products, contains naturally occurring hormones, including a small amount of bovine growth hormone (bGH). This natural occurrence is a physiological reality for any lactating mammal and is distinct from the artificial, synthetic hormones sometimes used in dairy farming. This article explores the science behind hormones in raw milk and their impact on human consumption.

Quick Summary

The presence of growth hormone in raw milk is natural, but its biological effects on humans are minimal due to species-specificity and digestion. The confusion often arises from the use of synthetic rBGH in some cows, though this, too, is rendered inactive when consumed. Both raw and pasteurized milk contain negligible amounts of hormones relevant to humans.

Key Points

Raw milk contains natural bovine growth hormone (bGH): All milk from mammals, including cows, contains naturally occurring hormones as part of its physiological composition.
Bovine growth hormone is species-specific: bGH is not biologically active in humans, meaning it does not affect human growth or hormonal systems.
Digestion inactivates bGH: When consumed, bGH is broken down into inactive amino acids by the human digestive system, effectively neutralizing any potential hormonal effect.
rBGH is a synthetic version, also inactive in humans: The controversial synthetic hormone rBGH, used to increase milk production in some cows, is also not orally active in humans and is digested similarly.
IGF-1 levels from milk are negligible: While milk contains Insulin-like Growth Factor 1 (IGF-1), its concentration is low compared to the body's own production, and its absorption is minimal and insignificant.
Pasteurization reduces but doesn't eliminate hormones: The heat treatment of pasteurization can denature some hormones, but the effect is minimal given the already low levels in raw milk.
Primary health risk of raw milk is bacterial contamination: The main health concern regarding raw milk is not its hormone content but the potential presence of harmful bacteria like E. coli and Salmonella.
"Hormone-free" milk labels refer to rBGH: Labels such as 'rBGH-free' or 'from cows not treated with rBST' indicate the absence of the synthetic hormone, not natural ones.

The Natural Presence of Hormones in Milk

Every mammal produces a variety of hormones naturally, and these are passed into their milk. For cows, this includes bovine growth hormone (bGH), a natural protein produced in the pituitary gland that is essential for the animal's growth and milk production. The same principle applies to human breast milk, which also contains species-specific hormones crucial for an infant's development. It's a fundamental part of mammalian physiology, not a contamination or an added substance. The concentration of bGH in cow's milk is minuscule and not biologically active in humans.

Raw Milk vs. Pasteurized Milk Hormones

For those wondering if the processing of milk affects its hormonal content, the answer is complex. Pasteurized milk is heated to eliminate pathogens, and this process can further denature some hormones, including bGH. However, the initial concentration in raw milk is so low that this difference is largely insignificant from a human health perspective. Another hormone, insulin-like growth factor-1 (IGF-1), is more heat-resistant and is found in both raw and pasteurized milk, but its levels are also negligible compared to what the human body naturally produces.

The Controversial Case of rBGH

The public concern about hormones in milk often stems from the use of recombinant bovine growth hormone (rBGH) or recombinant bovine somatotropin (rBST). This is a synthetic version of bGH that was historically given to some dairy cows to increase milk production. While its use is now banned in many countries, and many US dairy producers label their products as rBGH-free, it's important to understand the distinctions:

Natural bGH: Species-specific, present in all milk, biologically inactive in humans.
Synthetic rBGH: Artificially produced, mimics bGH, also biologically inactive in humans due to oral digestion.

Studies conducted by the FDA and other health organizations have consistently affirmed that milk from cows treated with rBGH is safe for human consumption because the synthetic hormone is not orally active in humans.

Digestion: The Body's Defense Mechanism

One of the most important factors in this discussion is the human digestive system. Hormones like bGH and rBGH are protein-based and, when ingested, are broken down into their component amino acids by digestive enzymes. These amino acids are then used by the body for various functions, just like the protein from any other food source. This effectively neutralizes any potential hormonal activity, preventing it from entering the bloodstream as an active hormone.

Insulin-Like Growth Factor 1 (IGF-1)

While bGH is not active in humans, the conversation around IGF-1 is slightly different. IGF-1 is found in both bovine and human milk and plays a role in growth and regeneration. However, the concentration of IGF-1 in milk is extremely low compared to the levels that the human liver already produces. Furthermore, studies have shown that any oral absorption of IGF-1 from milk has a negligible effect on overall human IGF-1 levels. Some research suggests that the presence of casein in milk might help protect a small amount of IGF-1 from digestion, but the biological significance of this is not considered meaningful for adults.

Comparison of Hormones in Raw, Pasteurized, and rBGH-Treated Milk

To clarify the differences, here is a comparison of hormone levels and activity across different milk types:


Feature	Raw Milk	Pasteurized Milk	Milk from rBGH-Treated Cows
Natural bGH Content	Contains minute, natural levels.	Contains minute, natural levels; some may be denatured by heat.	Contains minute, natural levels.
Synthetic rBGH	No synthetic hormones used.	No synthetic hormones used.	Contains synthetic rBGH.
rBGH Impact on Humans	None.	None.	None; orally inactive and digested.
IGF-1 Content	Contains natural IGF-1.	Contains natural IGF-1, which is more heat-resistant.	Contains slightly elevated IGF-1 levels.
IGF-1 Impact on Humans	Minimal; levels are negligible compared to human production.	Minimal; levels are negligible compared to human production.	Minimal; any increase is within normal human ranges and the hormone is mostly digested.
Overall Health Risk	Minimal from hormonal standpoint; primary risk is pathogens inherent to raw milk.	Minimal from hormonal standpoint; primary risk is contaminants if pasteurization fails.	Minimal from hormonal standpoint; minimal impact on human health.

Conclusion: Raw Milk and Growth Hormone

In summary, raw milk does contain growth hormone, but it is the naturally occurring bovine growth hormone (bGH) that is specific to cows. This hormone is biologically inactive in humans and is broken down during digestion, rendering it harmless. Concerns over growth hormones are often conflated with the now-rarely-used synthetic version, rBGH, which is also considered safe for human consumption by health authorities. While raw milk advocates praise its nutritional integrity, the presence of growth hormone is not a significant health issue for human consumers. The primary health risk associated with consuming raw milk remains bacterial contamination, a risk eliminated through pasteurization. For individuals concerned about any hormonal intake, choosing milk from producers who do not use rBGH (often labeled) is an option, although the impact on human health is widely considered to be negligible across the board.

Frequently Asked Questions

Yes, bGH is a naturally occurring protein hormone present in all cow's milk, both raw and pasteurized, as it is a natural component of a cow's physiology.

No. The bovine growth hormone is species-specific and biologically inactive in humans. Furthermore, it is a protein that is broken down and digested by the human body before it can have any effect.

Natural bGH is produced by the cow itself, while rBGH (recombinant bovine growth hormone) is a synthetic, lab-produced version. Both are inactive in humans when ingested.

The use of rBGH has declined significantly, and it is banned in many countries. Many dairy producers choose not to use it, and products from these cows are often labeled as such.

The amount of IGF-1 in milk is negligible compared to the amount your own body produces. Health authorities agree that the minimal amount of IGF-1 absorbed from milk has no significant impact on human health.

Pasteurization can denature some heat-sensitive hormones like bGH, but many others, including the more stable IGF-1, remain. However, the total effect of these hormones on humans remains insignificant.

No food from animal or plant sources is completely hormone-free. When a milk product is labeled as "hormone-free," it refers to the absence of added synthetic hormones like rBGH, not naturally occurring ones.