Does Unhomogenised Milk Have Hormones Naturally?

December 23, 2025 •

3 min read

All milk, whether conventional, organic, or unhomogenised, naturally contains small amounts of various hormones. Specifically, the mechanical process of homogenisation has no impact on the milk's inherent hormone profile.

Quick Summary

All milk naturally contains hormones, regardless of whether it is homogenised. This mechanical process only affects the fat particles, not the hormone content. Levels of hormones like estrogen and progesterone are influenced by the cow's pregnancy status and overall health, while the human body typically breaks down most ingested bovine hormones during digestion.

Key Points

Natural Origin: All milk, regardless of whether it's homogenised, contains naturally occurring hormones from the cow.
Homogenisation's Role: The mechanical homogenisation process only breaks down fat globules for a uniform texture; it does not remove or alter the hormonal content of milk.
Pregnancy's Impact: Hormone levels like estrogen and progesterone are higher in milk from pregnant cows, which is common in modern dairy farming.
Fat and Hormones: Fat-soluble hormones concentrate in the fat portion of milk, meaning whole milk (unhomogenised or homogenised) contains higher levels of these hormones than lower-fat options.
Human Absorption: The human digestive system is highly effective at breaking down most bovine hormones, limiting their biological impact on adults.
Health Concerns: While research is ongoing and some studies have shown correlations, major regulatory bodies like the FDA state that IGF-1 from dairy poses no increased health risk for consumers.

The Natural Presence of Hormones in All Milk

Contrary to some popular beliefs, the presence of hormones in milk is a completely natural phenomenon. Just as human breast milk contains hormones for infant development, cow's milk contains a variety of hormones that support the growth of a calf. The critical point to understand is that all dairy milk, including unhomogenised, organic, and conventional versions, will contain a native hormonal profile. Homogenisation is a separate process entirely focused on texture and stability, not chemical composition.

Types of Naturally Occurring Bovine Hormones

The hormonal composition of milk includes a mix of steroid and protein-based compounds. The concentration of these hormones varies based on several factors, including the cow's breed, diet, and most significantly, its stage of lactation and pregnancy.

Steroid Hormones: These are fat-soluble and include reproductive hormones like progesterone, estrogen (e.g., estrone and estradiol), and androgens. Their levels can increase substantially in milk from pregnant cows.
Protein Hormones: These are water-soluble and consist of growth-related factors. Key examples include Insulin-like Growth Factor-1 (IGF-1), prolactin, and bovine somatotropin (bST).

Does Homogenisation Affect Hormone Levels?

No, homogenisation does not affect the natural hormone levels in milk. This mechanical process has one primary function: to break down the milk's fat globules into smaller, uniformly sized particles so they remain suspended rather than separating as a cream layer. It does not remove, add, or alter the chemical makeup of the hormonal compounds present in the milk. Any differences in hormone concentration between unhomogenised and homogenised milk are a consequence of the starting milk's fat content, not the process itself. Steroid hormones are concentrated in the fat portion, so full-fat milk will naturally contain more of them than skimmed milk, regardless of homogenisation.

The Role of rBGH and IGF-1

Concerns about milk hormones often stem from the use of recombinant bovine growth hormone (rBGH), a synthetic hormone used by some dairy farmers in the U.S. (its use is banned in the EU and Canada) to boost milk production.

rBGH and IGF-1: Cows treated with rBGH produce higher levels of the naturally occurring hormone IGF-1. Milk from these treated cows therefore has elevated IGF-1 concentrations compared to untreated cows.
Digestion and Absorption: The human body's digestive system, however, breaks down most protein-based hormones like bST and IGF-1. While some studies have explored a potential link between milk IGF-1 and health issues like cancer, the scientific consensus generally indicates the risk from dietary intake is negligible for adults due to low absorption and overall endogenous production.

Unhomogenised vs. Homogenised Milk: A Comparison


Feature	Unhomogenised Milk	Homogenised Milk
Fat Distribution	Cream rises to the top over time as fat globules remain large and intact.	Fat globules are broken down and evenly dispersed, resulting in a consistent texture.
Hormone Level	Contains natural hormones, with fat-soluble steroids concentrated in the cream layer.	Contains the same level of natural hormones as the starting milk. Fat content dictates concentration.
Processing	Only pasteurisation (for safety) is applied, or it may be sold as raw milk in some regions.	Undergoes a mechanical process (homogenisation) in addition to pasteurisation.
Digestibility	Some anecdotal claims suggest easier digestion for certain individuals due to intact fat structure, though scientific evidence is limited.	Claims of reduced digestibility exist, but studies suggest protein may be digested more rapidly due to smaller fat globules.
Taste	Often described as having a richer, creamier taste due to the concentrated cream at the top.	Has a uniform, consistent flavor throughout due to the even fat distribution.

Conclusion

All milk, including unhomogenised milk, contains naturally occurring hormones. The presence of these hormones is a biological constant across all mammalian milk, and the homogenisation process does not affect their levels. The concentration of certain fat-soluble hormones like estrogen and progesterone is linked to the milk's fat content and the cow's physiological state, especially pregnancy. Although high levels of ingested dietary hormones have raised some health concerns, especially regarding certain cancers and potential effects on children, most evidence suggests the digestive process largely inactivates these bovine hormones in adults. The primary difference between unhomogenised and homogenised milk is textural, concerning fat distribution, not a fundamental difference in hormonal content. Ultimately, for those concerned about hormones, opting for milk from cows not treated with rBGH and monitoring fat content can be more relevant considerations than the homogenisation process itself.

For more detailed scientific discussions on hormones in dairy, review the extensive analysis provided by the U.S. National Institutes of Health.

Frequently Asked Questions

No, homogenisation is a mechanical process that doesn't remove hormones. Any difference in hormone concentration is due to the fat content, as some hormones are fat-soluble. Since unhomogenised milk is typically full-fat, it may contain higher levels of these specific hormones than lower-fat versions, but this is a function of fat, not the homogenisation process.

Pasteurisation is a heating process used to kill harmful bacteria and ensure milk is safe for consumption. Homogenisation is a mechanical process that breaks down and disperses fat particles to prevent a cream layer from separating, improving texture and consistency.

Scientific consensus suggests that the amounts of naturally occurring bovine hormones are very low and are mostly broken down during digestion, posing little to no risk for adults. However, some studies have raised questions, especially concerning sensitive populations like children, prompting ongoing research.

Yes, organic milk also contains naturally occurring hormones, as they are a biological component of all cow's milk. However, USDA organic standards prohibit the use of supplemental growth hormones like rBGH, so organic milk will not contain added synthetic hormones.

IGF-1, or Insulin-like Growth Factor-1, is a naturally occurring protein hormone present in milk. While high levels in milk from rBGH-treated cows have raised concerns, the FDA and other experts conclude that little to no active IGF-1 is absorbed during human digestion.

It is not possible to find completely hormone-free milk from any mammal. All milk naturally contains hormones. However, you can choose milk that comes from cows not treated with supplemental hormones like rBGH, which is often labelled on the packaging.

Modern dairy farming practices often involve keeping cows in a cycle of near-constant pregnancy to maximise milk production, which naturally continues throughout most of gestation. The milk from these cows, particularly during the later stages of pregnancy, has higher levels of certain hormones like estrogen and progesterone.