Vail Science of Food column: Breaking down bovine growth hormone |

Vail Science of Food column: Breaking down bovine growth hormone

Lisa Julian, Ph.D.
Science of Food
Major side effects in cows treated with recombinant bovine growth hormone include reproductive problems, lameness and a condition called mastitis, when the cow’s udder becomes infected and inflamed. Mastitis can also occur when a cow is over-milked, a common practice among large dairy farms, whether they are organic or not.
Getty Images/iStockphoto | iStockphoto

Editor’s note: This is the third in a monthly series of columns about the benefits of eating organic food.

What does it mean to buy “certified organic”? Let me first start off by explaining the general standards set forth by the U.S. Department of Agriculture that define the “certified organic” label.

Organic growers, farmers and food producers are prohibited from using genetically modified organisms (GMOs), antibiotics and synthetic hormones (in meat and poultry) and require 100 percent organic feed for livestock. Processed and packaged food products sold with the USDA certified organic seal must contain at least 95 percent of these aforementioned organically grown ingredients.

This means that if the farm is not organic, then dairy cows can be treated with antibiotics or growth hormones or may be eating genetically modified food or food containing pesticides. If you consume dairy products from cows that are eating pesticides in their food, then these chemicals can be transferred to you upon consumption.

“You are what what you eat eats,” as author and food advocate Michael Pollan so succinctly describes. I refer you to the past two columns in this series to learn more about why the widespread use of antibiotics and synthetic pesticides is harmful to human health. Here, I will focus on how the use of growth hormones in dairy products.

Growth hormones

Growth hormones are given to dairy cows to increase milk production. Bovine growth hormone (BGH), and specifically the recombinant version (rBGH), also known as bovine somatotropin (rbST), has been used widely on dairy farms since its approval in 1993.

The actual drug administered to cows is similar to the hormone they naturally produce, but it has been genetically engineered so that it can be produced in large amounts and sold for profit. It was first developed by Monsanto under the name Posilac and is one of the top-selling animal pharmaceuticals in the United States. It works by slowing the death of mammary cells, and the result is an increase in milk production.

Use of synthetic growth hormones in meat and poultry is banned in Europe, Canada and many other countries, due to the potential harm they cause to both humans and cows. Major side effects in cows treated with recombinant bovine growth hormone include reproductive problems, lameness and a condition called mastitis, when the cow’s udder becomes infected and inflamed.

Mastitis can also occur when a cow is over-milked, a common practice among large dairy farms, whether they are organic or not. But the cows raised on non-organic farms are often given antibiotics to treat the infection, creating a viscous cycle of pharmaceutical use in modern dairy farming.

Hormones and cancer

Potential harm to human health comes not necessarily from the presence of residual bovine growth hormone itself. The harm comes from an increase in another hormone called insulin-like growth factor, or IGF-1. As it says in its name, IGF-1 is a growth factor; it is a very important protein that signals the body to turn on cell growth. It plays a role in normal growth and development, but it can also drive cancer growth.

Scientific evidence has already linked elevated IGF-1 levels to cancer, especially cancers of the prostate, breast, testicular and colon tissues. Edward Giovannucci, associate professor at the Harvard Medical School, has been studying the link between diet, hormones and cancer for decades. He led a large human study published in 2001 correlating IGF-1 and colon cancer, following more than 32,000 nurses for a six-year period of time.

“When IGF-1 is added to dishes of cells growing in the laboratory, the cells flourish like flowers blooming in spring,” Giovannucci said. IGF-1 is a key player in regulating cell growth.

Since cancer is a disease of the cell with uncontrolled and rapidly proliferating cell growth as the fundamental driver, it makes clear sense that IGF-1 would influence cancer. More specifically, we know that IGF-1 works in part by inhibiting a process in the body called apoptosis. In brief, apoptosis is a mechanism in the body to eliminate cells when the body knows the cell is damaged, a so-called “cell-suicide.” It is a fundamental pathway that is required for your body to effectively kill cancer cells.

Nearly 10 years ago, when I was working as a research scientist at the biotech company Amgen, we (along with many other drug companies) were creating pharmaceutical drug candidates, now patented, to initiate this very mechanism of apoptosis as a treatment for cancer. If you initiate cell-suicide, then cancer cells die faster, this being the therapeutic rationale for targeting apoptosis with a pharmaceutical drug. In contrast, if you shut if off, as IGF-1 does, then the cells can grow faster or live longer.

What to buy

The FDA does not require that milk from cows treated with bovine growth hormone be labeled as such, and this has been an ongoing and highly controversial political public health issue. Unless the milk is labeled organic or hormone-free, your milk may be coming from cows treated with this bioengineered growth hormone.

IGF-1 hormone is measurably raised in cows treated with recombinant bovine growth hormone, and this is transferred to the milk. Bovine growth hormone is degraded during the pasteurization process, but IGF-1 is not, and there are some studies that show elevated levels of IGF-1 in adults who consume milk from cows treated with growth hormone. These findings suggest the possibility that IGF-1 can be absorbed by the human gastrointestinal tract and can enter the bloodstream, thereby raising circulating levels of IGF-1.

Look for the “certified organic” label on milk, butter, cheese, yogurt and ice cream, as this will provide some assurance of the requirements listed above. Although enforcement of the strict organic regulations set forth by the USDA can be problematic, it is a good place to start, especially when buying at large supermarkets. If possible, seek out smaller farms in your community at local farmers’ markets during growing season. You may be able to find organic foods at cheaper prices, even without the actual governmental label, from these smaller farms, owned and operated by trustworthy farmers.

Considering that the use of growth hormones in dairy farming is a relatively recent practice and knowing how it reacts in the body with a potential to fuel cancer growth, I would in no way consider this safe for humans. Even the American Cancer Society agrees that “more research is needed to address these possible health concerns.”

There is too much human and molecular evidence that links synthetic growth hormones to an increased risk of cancer, and it is a current risk to public health to continue the use of growth hormones in our food supply. Knowing this, isn’t it worth buying organic dairy as an active step toward cancer prevention for you and for our society as a whole?

Lisa Julian, Ph.D., has a passion for organic chemistry — the “molecules of life” — and its application to food and health. She’s the owner of Elevated Yoga & Holistic Health in Frisco and teaches science and nutrition at the University of Colorado Denver and Colorado Mountain College. She can be reached at 970-401-2071 and For more information about services offered at her studio, visit

Support Local Journalism

Start a dialogue, stay on topic and be civil.
If you don't follow the rules, your comment may be deleted.

User Legend: iconModerator iconTrusted User