Understanding Bovine Growth Hormones: Natural vs. Synthetic
To understand which milk has growth hormones in it, it's crucial to distinguish between two key types: naturally occurring bovine somatotropin (bST) and the synthetic version, recombinant bovine somatotropin (rBST or rBGH).
Natural Bovine Somatotropin (bST)
Every cow's pituitary gland naturally produces bST. This protein hormone is essential for regulating the cow's growth and is responsible for milk production during lactation. The presence of bST in milk is therefore natural and unavoidable for any milk sourced from cows. The hormone is species-specific, meaning it only affects cattle, and it is largely broken down and rendered inactive during human digestion.
Recombinant Bovine Somatotropin (rBST)
Some conventional dairy farmers use rBST, a synthetic version of the natural bST, to boost milk production in their herds. The FDA approved its use in the United States in 1993, deeming it safe for human consumption based on scientific findings. However, its use is banned in many other countries, including Canada and the European Union, primarily due to animal welfare concerns. Cows treated with rBST have a higher risk of developing udder infections (mastitis), which can necessitate increased antibiotic use. This raises concerns about potential antibiotic resistance, though its effect on human health from milk is not conclusive.
Conventional vs. Organic Milk: Labeling and Production
When navigating the dairy aisle, understanding the difference in farming practices is key to choosing milk based on your preferences.
Conventional Milk
Conventional milk comes from dairy cows that may or may not have been treated with rBST. The use of rBST has declined significantly in recent years due to consumer demand. To provide clarity, many dairy companies voluntarily label their milk as "rBST-free," "rBGH-free," or "no artificial hormones". The FDA requires a disclaimer on these labels, stating that no significant difference has been shown between milk from treated and untreated cows.
Organic Milk
For those who want to avoid synthetic hormones entirely, USDA-certified organic milk is the definitive choice. Organic standards strictly prohibit the use of rBST or any other synthetic growth hormones. It's important to remember, however, that organic milk will still contain the naturally occurring bST, as it is a normal part of a cow's biology. A study conducted by Emory University found that organic milk has significantly lower levels of bovine growth hormones compared to conventional milk, suggesting a link to the synthetic hormone use. Organic milk is also free from routine antibiotic treatments and comes from cows with outdoor access, which may appeal to those with animal welfare concerns.
Plant-Based Milks and Growth Hormones
For individuals seeking to avoid bovine hormones altogether, plant-based milk alternatives offer a definitive solution. Options like almond, soy, oat, and coconut milk are derived from plants and, as such, contain no bovine growth hormones or any other animal hormones.
Comparison Table: Dairy vs. Plant-Based Milk Hormones
| Feature | Conventional Dairy Milk | Organic Dairy Milk | Plant-Based Milks |
|---|---|---|---|
| Natural Bovine Growth Hormones (bST) | Yes | Yes | No |
| Synthetic Growth Hormones (rBGH/rBST) | Permitted, but often labeled 'free' | Prohibited by USDA standards | No |
| Antibiotics | Used for treating illness; levels regulated | Prohibited routinely; sick cow milk is discarded | No |
| Other Hormones (e.g., Estrogen) | Natural presence; higher in milk from pregnant cows | Natural presence; levels similar to conventional milk | No bovine hormones, some contain phytoestrogens (e.g., soy) |
Are Growth Hormones in Milk a Health Concern for Humans?
Decades of research and evaluation by leading health organizations have concluded that milk from rBST-treated cows is safe for human consumption. The primary reasons cited are:
- Digestion renders them inactive: Both natural bST and synthetic rBST are large protein hormones. When consumed, they are broken down by the human digestive system, just like any other protein, and are rendered biologically inactive.
- Species-specific effects: Bovine growth hormones are not designed to affect human physiology. In early clinical trials, large injections of bovine growth hormone in children with growth hormone deficiency had no effect, while human growth hormone injections were effective.
- Pasteurization reduces levels: The pasteurization process, which heats milk to eliminate pathogens, destroys up to 90% of the bovine growth hormone present.
The IGF-1 Controversy
One area of concern that has received significant attention is insulin-like growth factor 1 (IGF-1). Cows treated with rBST have been shown to have slightly elevated levels of IGF-1 in their milk. Some studies have suggested a link between higher blood levels of IGF-1 and an increased risk of certain cancers, such as breast, colon, and prostate cancer. However, major health organizations, including the American Cancer Society, note that the evidence is inconclusive and that IGF-1 is naturally present in both cows' and humans' milk, with human blood levels being much higher than what is found in milk. The American Cancer Society has no formal position on the use of rBGH.
Conclusion
All dairy milk naturally contains the growth hormone bST, a normal and harmless component of cow's milk. The primary concern for many consumers is the synthetic hormone rBST (rBGH), which is sometimes used in conventional dairy farming. To avoid synthetic growth hormones, look for milk explicitly labeled as "rBST-free" or choose USDA-certified organic milk, which prohibits its use. Plant-based milks are also a good option for avoiding all bovine hormones. Ultimately, the choice depends on your personal comfort level with conventional dairy farming practices and an understanding of the extensive research conducted on the safety of milk from rBST-treated cows. Regardless of your choice, milk and its alternatives remain an excellent source of important nutrients.
For more detailed information on the safety of dairy products and rBST, consult reliable health resources, such as the American Cancer Society: Recombinant Bovine Growth Hormone (rBGH) I rBST.
