Does this Milk Cause Cancer?

Does this Milk Cause Cancer? about undefined

Milk supposedly “does a body good.” My response to that is it depends on the milk. Some milk contains a controversial ingredient with compelling evidence linking it to various types of cancer.1

Even worse, this ingredient is not always listed on the label. Here’s the story…

You’ve likely seen the “rBGH-free” labels on milk, but do you know what those letters actually mean?

It stands for recombinant bovine growth hormone (rBGH). In a nutshell, rBGH is a lab-made, genetically modified bovine, or cow, growth hormone.

Natural vs. synthetic rBGH

About 60 years ago, scientists discovered a way to boost milk production by injecting cows with growth hormone from bovine pituitary glands. That’s the natural form of the hormone.

Soon, they went to the lab to find a shortcut-- a cheaper alternative. Their discovery resulted in Monsanto’s production of rBGH and rBST, with the trade name of Posilac.

Recombinant bovine growth hormone (rBGH) and recombinant bovine somatotropin (rBST) are one and the same-- same hormone, two different names.

Monsanto makes these growth hormones in labs by genetically engineering DNA. The DNA engineering is why it’s called “recombinant.”

In other words, rBGH is a genetically engineered hormone that’s injected into cows to increase milk production, just as the natural form was.1

rBGH stimulates cows’ milk production by boosting another hormone called insulin-like growth factor (IGF-1). This is the hormone linked to cancer—more on that in a minute.

FDA-approved, yet highly controversial 

Despite concern by scientists and government officials, the FDA approved rBGH in 1993. Since then, they’ve turned a blind eye to consumers, physicians, scientists, and food safety experts who have asked that they at least mandate labeling of rBGH foods.

Meanwhile, the United Nations’ Codex Alimentarius, which sets international food standards, refused to approve rBGH three times to date.2

The European Union, Japan, Canada, and Australia have all banned rBGH completely.

Opponents contend that milk from treated cows contains higher rBGH hormone levels.

A 2019 Emory University study found 20 times higher rBGH levels in conventional milk than in non-rBGH milk. (Note: some bovine growth hormone is present naturally, so all milk contains at least a trace of it.)

Still, the FDA counters that growth hormones are not absorbed by humans. In other words, they have no effect on you.

Other groups, including Health Canada, disagree. That’s because the FDA required no long-term toxicology studies on rBGH and opponents argue that the FDA is overlooking the facts.

For example, both European Union and Canadian regulators assert that the FDA completely ignored one study showing that IGF-1 can survive digestion and enter your intestines and blood stream.3

Today, some producers use “rBGH-free” labels, but they’re required to print a disclaimer stating the FDA finds no difference between milk with rBGH and milk without it.

Linked directly to cancer  

Many studies show that IGF-1 hormone does in fact survive digestion. What’s more, there’s plenty of evidence that shows IGF-1 aids in the growth and survival of cancer cells.4,5

For instance, excess IGF-1 correlates to higher rates of colon,6 breast, and prostate7 cancers. It’s also connected to pancreatic, lung,8 and endometrial cancers.

Researchers believe that IGF-1 promotes cancer by inhibiting apoptosis and triggering cell proliferation.9

Stimulates cancer cell growth  

Research published in the journal Medical Hypotheses shows how IGF-1 stimulates growth of human breast cancer cells.10 This is especially true for pre-menopausal women with high blood levels of IGF-1.11

Three meta-analyses showed that IGF-1 increased breast cancer risk, but only among pre-menopausal women.12,13,14

Scientists suspect that there may be “cross-talk” between IGF-1 and the estrogen receptor in breast cancer cells, given estrogen’s role in cancer.15

A couple of studies show no relationship between dairy consumption and breast cancer. But these variances may be due to the type of dairy consumed or measured. Or even differences between high-fat and low-fat milk. So far, the reason for the variations is not clear.

Researchers have extensively studied the role of IGF-1 in prostate cancer. Lower IGF-1 levels correlate to reduced proliferation of cancer cells.16 And higher levels render cancer potentially more invasive.17

Many studies show a link between IGF-1 and colorectal cancer.18,19,20 High levels of IGF-1 are also linked to head and neck squamous cell carcinoma.21 Both IGF-1 and its binding protein, IGFBP-3, may also increase lung cancer risk.22

Toxic hormones are bad for animals too!  

Cows don’t get a free pass from rBGH health problems either. A meta-analysis23 shows that injecting cows with rBGH causes increased risk of:

  • Lameness (increase: 55 percent)
  • Infertility (increase: 40 percent)
  • Mastitis (increase: 25 percent)

The increase in mastitis is especially troubling. That’s because antibiotics are the treatment for this type of infection. And antibiotic overuse is sparking new strains of “superbugs” which have been linked to deadly human infections.

For the cleanest, healthiest dairy... go organic  

Skip conventional milk and other conventional dairy products like ice cream, yogurt, butter, candy bars, and so on. Better safe than sorry, as they say.

On the plus side, consumer pressure has led to more rBGH-free options in the marketplace.

You’ll find two versions of rBGH-free products – organic and conventional. Read labels. Organic brands will say “organic.” Organic standards prohibit the use of any synthetic hormones in either dairy or beef.

Conventional rBGH-free brands will say “rBGH-free” or “rBST-free,” or sometimes “no artificial hormones.”

Speaking of artificial hormones, rBGH isn’t the only hormone used in our foods. Hormones like gonadotropin (GnRH), progesterone, and prostaglandins are common in dairy. Beef cattle also get steroid hormones to promote growth.

So, just because a product says it’s rBGH-free doesn’t mean it won’t contain a cocktail of other lab-grown hormones.

This is another compelling reason to go organic. The same Emory study that found 20 times more growth hormone in rBGH milk also found:

  • Antibiotic residue including two outlawed drugs in 60 percent of conventional milk samples (but none in organic samples). Also amoxicillin exceeding federal limits.24 
  • Pesticide residues of chlorpyrifos (a neurotoxin), atrazine, and permethrin in 26 to 60 percent of conventional samples (depending on the pesticide). But none in the organic samples.

Organic dairy contains no synthetic growth hormones, antibiotics, GMOs, or conventional pesticides. Organic cows consume organic feed, are generally healthier, and are raised more humanely.

So, for the cleanest dairy products with the healthiest nutrient profile, choose organic. This goes for beef, too.

Best regards,

Lee Euler,


  1. (Accessed February 9, 2021)
  2. (Accessed February 9, 2021)
    (Accessed February 9, 2021)
  4. Hartog, H. , Boezen H. M., de Jong M. M., Schaapveld M., Wesseling J., and van der Graaf W. T.. 2013. Prognostic value of insulin‐like growth factor 1 and insulin‐like growth factor binding protein 3 blood levels in breast cancer. Breast 22:1155–1160.
  5. Yakar, S. , Leroith D., and Brodt P.. 2005. The role of the growth hormone/insulin‐like growth factor axis in tumor growth and progression: lessons from animal models. Cytokine Growth Factor Rev. 16(4–5):407–420.
  6. Ma, J. , Pollak M. N., Giovannucci E., Chan J. M., Tao Y., Hennekens C. H., et al. 1999. Prospective study of colorectal cancer risk in men and plasma levels of insulin‐like growth factor (IGF)‐I and IGF‐binding protein‐3. J. Natl Cancer Inst. 91:620–625.
  7. Chan, J. M. , Stampfer M. J., Giovannucci E., Gann P. H., Ma J., Wilkinson P., et al. 1998. Plasma insulin‐like growth factor‐I and prostate cancer risk: a prospective study. Science 279:563–566.
  8. Yu, H. , Spitz M. R., Mistry J., Gu J., Hong W. K., and Wu X.. 1999. Plasma levels of insulin‐like growth factor‐I and lung cancer risk: a case‐control analysis. J. Natl Cancer Inst.20:151–156.
  9.  (Accessed February 9, 2021)
  10. Outwater, J L, A Nicholson and N Barnard. “Dairy products and breast cancer: the IGF-1, estrogen, and bGH hypothesis.” Medical Hypotheses 48, 6 (1997): 453-61. Doi:10.1016/s0306-9877(97)90110-9.
  11. Hankinson, S E et al. “Circulating concentrations of insulin-like growth factor-1 and risk of breast cancer.” Lancet 351, 9113 (1998): 1393-6. Doi:10.1016/S0140-6736(97)10384-1.
  12. Renehan, A. G. , Zwahlen M., Minder C., O'Dwyer S. T., Shalet S. M., and Egger M.. 2004. Insulin‐like growth factor (IGF)‐I, IGF binding protein‐3, and cancer risk: systematic review and meta‐regression analysis. Lancet 363:1346–1353.
  13. Shi, R. , Yu H., McLarty J., and Glass J.. 2004. IGF‐I and breast cancer: a meta‐analysis. Int. J. Cancer 111:418–423.
  14. Sugumar, A. , Liu Y. C., Xia Q., Koh Y. S., and Matsuo K.. 2004. Insulin‐like growth factor (IGF)‐I and IGF‐binding protein 3 and the risk of premenopausal breast cancer: a meta‐analysis of literature. Int. J. Cancer 111:293–297.
  15. Kaaks, R. , Johnson T., Tikk K., Sookthai D., Tjonneland A., Roswall N., et al. 2014. Jun. Insulin‐like growth factor I and risk of breast cancer by age and hormone receptor status‐A prospective study within the EPIC cohort. Int. J. Cancer 134:2683–2690
  16. Pollak, M. , Beamer W., and Zhang J. C.. 1998. Insulin‐like growth factors and prostate cancer. Cancer Metastasis Rev. 17:383–390.
  17. Saikali, Z. , Setya H., Singh G., and Persad S.. 2008. Role of IGF‐1/IGF‐1R in regulation of invasion in DU145 prostate cancer cells. Cancer Cell Int. 8:10.
  18. Ma, J. , Pollak M. N., Giovannucci E., Chan J. M., Tao Y., Hennekens C. H., et al. 1999. Prospective study of colorectal cancer risk in men and plasma levels of insulin‐like growth factor (IGF)‐I and IGF‐binding protein‐3. J. Natl Cancer Inst. 91:620–625.
  19. Nomura, A. M. , Stemmermann G. N., Lee J., and Pollak M. N.. 2003. Serum insulin‐like growth factor I and subsequent risk of colorectal cancer among Japanese‐American men. Am. J. Epidemiol. 158:424–431.
  20. Tripkovic, I. , Tripkovic A., Strnad M., Capkun V., and Zekan L.. 2007. Role of insulin‐like growth factor‐1 in colon cancerogenesis: a case‐control study. Arch. Med. Res. 38:519–525.
  21. Wu, X. , Zhao H., Do K. A., Johnson M. M., Dong Q., Hong W. K., et al. 2004. Serum levels of insulin growth factor (IGF‐I) and IGF‐binding protein predict risk of second primary tumors in patients with head and neck cancer. Clin. Cancer Res. 10(12 Pt 1):3988–3995.
  22. Jaques, G. , Noll K., Wegmann B., Witten S., Kogan E., Radulescu R. T., et al. 1997. Nuclear localization of insulin‐like growth factor binding protein 3 in a lung cancer cell line. Endocrinology 138:1767–1770.
  23. (Accessed February 9, 2021)
    (Accessed February 9, 2021)

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