Recombinant Bovine Somatotropin vs Caramel Color IV: which is worse?

What is Recombinant Bovine Somatotropin?

Recombinant bovine somatotropin (rBST) is the synthetic version of bovine growth hormone (BST), naturally produced by the pituitary gland in cattle. The recombinant version is produced using genetically engineered bacteria and is injected into dairy cows to increase milk production by 10-15%. Brand name: Posilac.

What is Caramel Color IV?

Caramel Color IV (Class IV caramel, E150d) is a food coloring made by heating sugar with both ammonium and sulfite compounds. This production method creates a unique set of reactive byproducts, notably 4-methylimidazole (4-MEI), which has been linked to cancer in animal studies. It is the most widely used caramel coloring in beverages like Coca-Cola and Pepsi.

Documented risks

Recombinant Bovine Somatotropin: See recombinant-bovine-growth-hormone-rbgh for full detail. Key concerns: rBST elevates IGF-1 in milk; elevated blood IGF-1 is associated with breast, prostate, and colorectal cancer risk in epidemiological studies. Animal welfare: increased mastitis (up to 25-50% higher rates), lameness, and antibiotic use. The Codex Alimentarius Commission declined to endorse rBST safety MRLs in a historic 33-29 vote. Health Canada rejected rBST approval in 1999 after finding it caused significant animal health problems requiring increased antibiotic use.

Caramel Color IV: The primary concern with Caramel Color IV is 4-methylimidazole (4-MEI), a byproduct of the ammonia-sulfite caramel production process. The National Toxicology Program (NTP) found that 4-MEI caused lung cancer in male and female mice at high doses in 2-year bioassay studies, leading to California listing 4-MEI as a known carcinogen under Proposition 65 in 2011. The Prop 65 safe harbor level is 29 micrograms 4-MEI per day (the level that would cause 1 additional cancer per 100,000 people over a 70-year lifetime). CSPI testing in 2011-2012 found Coca-Cola and Pepsi sold in California contained 4-MEI levels that, at typical consumption rates, would exceed this threshold — triggering voluntary reformulation by both companies to reduce 4-MEI in their US products. The FDA reviewed 4-MEI and concluded that typical exposure levels 'are not a safety concern.' EFSA's evaluation found the NTP findings concerning but noted the margin of safety at typical European exposure levels. The cancer mechanism in mice involves high doses that may not extrapolate to typical human cola consumption.