Somatotropin, Milk and Cancer Risk – A Primer on How Activists Scare Consumers

Terry Etherton

Anti-biotech activists continue their drum beat of: danger, danger, don’t drink milk because it has hormones, hormones….you will get cancer! The propaganda they have shoveled out linking milk insulin-like growth factor I (IGF-I – a naturally occurring protein hormone found in ALL milk) to an increased risk of cancer is an astonishing piece of nonsense. However, no problem – activist groups have never concerned themselves about basing their scare tactics on scientific facts. It saves time to just make it up!

Activist Story Telling about Milk IGF-I and Cancer

A short version of the propaganda put out by anti-biotech activist groups is that treatment of cows with recombinant bovine somatotropin (rbST) increases milk levels of IGF-I. This is followed by information conveying that too much IGF-I in humans is associated with increased rates of colon, breast and prostate cancer. Another allegation these groups put forth is that definitive studies demonstrating the lack of absorption of milk rbST or IGF-I following oral administration have not been conducted. This is intended to convey the concept that the intact IGF-I molecule, which would be biologically active in humans, just might be absorbed into the circulation. The obvious message is that if you drink milk you will absorb IGF-I into your circulation and increase risk of cancer.

Now, to the truth!

The Science Evidence Base about Milk IGF-I and Cancer

Cows’ milk contains many hormones, including somatotropin (ST) and IGF-I. This is normal. Human milk contains hormones, and colostrum is loaded with hormones, both protein and steroid. The amount of IGF-I in cow’s milk is a fraction of total protein found in milk. It represents one-tenth of one millionth of total milk protein. Negligible quantities of milk IGF-I are absorbed by the human gut as intact proteins. To have any biological activity in humans, IGF-I has to be absorbed intact. This doesn’t happen to any significant extent; however, even if this occurred it would not pose a problem. Why? The amount of IGF-I in milk pales compared to the quantity humans make daily.

The amount of IGF-I secreted daily in the saliva and from digestive tract secretions in humans is equivalent to the amount of IGF-I found in 95 quarts of milk! Remarkable, isn’t it? The activists don’t talk about this because it defeats their argument. If they are concerned about IGF-I in milk being linked to cancer, then why are they NOT concerned about IGF-I that we humans make and secrete? On a quantitative basis, levels of milk IGF-I are a “drop in the bucket” compared to that produced daily in saliva and the digestive tract of humans.

Where’s All the Money Going?

So, the public discussion goes about the safety of rbST. Activists on one side and the truth-based science, on the other.

Activists don’t want to solve the problem, to find a middle ground. They need us in animal agriculture because they can’t stir up the pot unless there are targets and objectives to attack. They promote their “cause” while falsely attacking animal agriculture. To be relevant, they have to keep the business of activism going. Attacks bring visibility to their effort, and, oh yes, donations. Thus, another part of the smoke and mirrors of anti-ag activist attacks is revealed. There are enormous sums of money being collected by the activist’s groups that attack agriculture and biotechnology. Wonder what they do with all the money…don’t suppose some is being used for lavish salaries – wouldn’t that be interesting?

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