Hormones and pus in cow’s milk

Cow’s milk contains many components that the dairy industry doesn’t advertise because they know it would put people off.


A cow is milked for the first seven months of her nine-month pregnancy and milking then resumes after each birth. To keep her milk supply up, she is then inseminated again and so the cycle continues. It means a cow is usually milked for 10 out of each 12 months and her milk is full of natural hormones.

In a typical glass of milk or bite of cheese, there are 35 hormones (Grosvenor et al., 1993). These include sex and growth hormones driving a calf’s development but in adult humans, they have been linked to the development of cancer (Malekinejad and Rezabakhsh, 2015; Melnik and Schmitz, 2017).

Drinking cow’s milk not only delivers growth hormones into your body, it also increases your own body’s production of these (Melnik, 2021). A recent study investigated milk intake in adults and how it affects one of these hormones (IGF-1) and it found that milk-drinking significantly increases its levels (Romo Ventura et al., 2020).

On the other hand, vegans have lower levels of IGF-1. One study comparing IFG-1 levels in British women found that compared with meat-eaters and vegetarians, vegan women had 13 per cent lower levels of IGF-1 (Allen et al., 2002). Another study, this time in men, found that IGF-1 levels in vegan men were nine per cent lower (Allen et al., 2000). This difference was considered enough to significantly lower the risk of prostate cancer. The intake of animal protein was linked to the higher IGF-1 levels and diet explained most of the differences between groups.

Mothers drinking cow’s milk have larger babies, children consuming it grow faster, young milk-drinking people have more acne, high milk intake is also thought to play a role in type 2 diabetes and some types of cancer – such as prostate, breast and liver (Melnik, 2021).


Mastitis is a painful bacterial infection of the udder which affects 26-36 out of each 100 dairy cows every year (Cattle Health and Welfare Group, 2020). When a cow is suffering from mastitis, her body produces large numbers of white blood cells which fight the infection in the udder. Many of these cells, together with damaged and dead cells from the udder, then become a part of her milk – they are called somatic cells. The greater the infection, the higher the number of these somatic cells in the milk (AHDB Dairy, 2020). If these cells weren’t mixed into milk, they would have the appearance of pus, which is essentially what they are.

The level of somatic cells at around 100,000 per millilitre or less is normal, 200,000 indicates that the cow is highly likely to be suffering from mastitis, 300,000 and more means that the cow is suffering from a serious infection (AHDB Dairy, 2020). Under UK and EU regulations, milk with a somatic cell count up to 400,000 per millilitre may be sold for human consumption.



AHDB Dairy. 2020. Somatic Cell Count, an indicator of milk quality. Available from: https://ahdb.org.uk/somatic-cell-count-milk-quality-indicator [Accessed 16 December 2021]

Allen NE, Appleby PN, Davey GK et al. 2000. Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. British Journal of Cancer. 83 (1) 95-97.

Allen NE, Appleby PN, Davey GK et al. 2002. The associations of diet with serum insulin-like growth factor I and its main binding proteins in 292 women meat-eaters, vegetarians, and vegans. Cancer Epidemiology Biomarkers and Prevention. 11 (11) 1441-1448.

Cattle Health and Welfare Group. 2020. Fifth Report of the GB Cattle Health & Welfare Group. Available from: https://projectblue.blob.core.windows.net/media/Default/Beef%20&%20Lamb/CHAWG2020-Report5_3613_171120_WEB.pdf [Accessed 16 December 2021]

Grosvenor CE, Picciano MF, Baumrucker CR. 1993. Hormones and growth factors in milk. Endocrine Reviews. 14 (6) 710-28.

Malekinejad H, Rezabakhsh A. 2015. Hormones in Dairy Foods and Their Impact on Public Health – A Narrative Review Article. Iranian Journal of Public Health. 44 (6) 742-58.

Melnik BC. 2021. Lifetime Impact of Cow’s Milk on Overactivation of mTORC1: From Fetal to Childhood Overgrowth, Acne, Diabetes, Cancers, and Neurodegeneration. Biomolecules. 11 (3) 404.

Melnik BC, Schmitz G. 2017. Milk’s Role as an Epigenetic Regulator in Health and Disease. Diseases. 5 (1) 12.

Romo Ventura E, Konigorski S, Rohrmann S et al. 2020. Association of dietary intake of milk and dairy products with blood concentrations of insulin-like growth factor 1 (IGF-1) in Bavarian adults. European Journal of Nutrition. 59 (4) 1413-1420.


How to change your diet

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All about dairy

Find all the above and more in Viva!’s ground-breaking resources:

An eye-opening guide Why You Don’t Need Dairy– presenting information on health, animals and the environment in an easy-to-read format.

A practical guide on how to cut dairy out of your diet and all you need to know to live a healthy and delicious dairy-free life: Everyone’s Going Dairy-Free

If you want to know more about dairy and your health and explore what scientific studies have to say, see the in-depth report White Lies


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