Understanding Bovine Growth Hormone (bGH) and rBST
Bovine growth hormone (bGH), also known as bovine somatotropin (bST), is a naturally occurring protein hormone in cattle that regulates metabolic processes and stimulates milk production. Recombinant bovine somatotropin (rBST or rBGH) is a genetically engineered version used to increase milk yield. Its use has prompted public concern about potential impacts on human health.
The Science Behind Human Safety
Major health and food safety organizations like the FDA and WHO have long stated that consuming dairy and meat from rBST-treated cows is safe. This is primarily because bGH is a large protein biologically active only in cattle and similar species, meaning it cannot bind to human growth hormone receptors. Furthermore, human digestion breaks down bGH and rBST into inactive fragments, preventing absorption. Pasteurization and cooking also help deactivate the hormone.
The Role of IGF-1
Concerns about rBST often involve Insulin-like Growth Factor-1 (IGF-1), as rBST can increase IGF-1 in cow's milk. Some worry higher IGF-1 intake could pose a health risk, but IGF-1 from milk is largely broken down during digestion and has little biological effect orally. The amount of IGF-1 from milk is also minimal compared to what the human body produces naturally. IGF-1 levels in milk from rBST-treated cows are generally within the normal range found in milk from untreated cows and human breast milk.
Comparing Milk from Treated vs. Untreated Cows
| Feature | Conventional Milk (Potentially rBST-treated) | Organic Milk (No rBST) |
|---|---|---|
| Bovine Growth Hormone (bGH/rBST) | May contain synthetic rBST (though many dairies stopped use voluntarily), along with naturally occurring bGH. | Does not contain synthetic rBST, but has naturally occurring bGH. |
| Insulin-like Growth Factor-1 (IGF-1) | May have slightly higher levels due to rBST, but still within the normal range. | Contains naturally occurring IGF-1. |
| Nutritional Composition | Generally comparable to organic milk nutritionally. | May have a better fatty acid profile due to diet/grazing. |
| Antibiotic Residues | Tested; milk exceeding tolerance is prohibited. Increased mastitis from rBST could potentially increase antibiotic use, though national data shows no increased human exposure risk. | No antibiotics used, thus no residues. |
| Animal Welfare Concerns | rBST linked to increased mastitis and other health issues. | Adheres to stricter animal welfare standards. |
Potential for Increased Antibiotic Resistance
While bGH is not a direct human health risk, rBST use can increase a cow's risk of mastitis, potentially leading to more antibiotic use. This raises concerns about antibiotic resistance, which are monitored by regulatory bodies. Despite concerns, national data indicates a decline in antibiotic residue violations.
Conclusion
Scientific and regulatory bodies agree that bovine growth hormone does not affect humans through milk or meat consumption. It is species-specific, inactive in humans, and broken down by digestion and processing. While rBST slightly increases IGF-1 in milk, the amount and minimal absorption are unlikely to impact human health. Concerns about animal welfare and potential antibiotic use from increased mastitis are valid and have led some countries to ban rBST based on animal health rather than human safety. Consumer choices between conventional and organic milk often involve personal values, agricultural practices, and cost, more than direct human health risks from bGH itself.
