Digestive enzymes can break casein down into peptides that have some biological activity in cells and in laboratory animals though conclusive causal effects on humans have not been established.^[1]

Although research has shown high rates of use of complementary and alternative therapies for children with autism, including gluten and/or casein exclusion diets, as of 2008^[update] there was a lack of evidence that these diets had any effect.^[2]

If opioid peptides breach the intestinal barrier, typically linked to permeability and constrained biosynthesis of dipeptidyl peptidase-4 (DPP4), they can attach to opioid receptors. Elucidation requires a systemic framework that acknowledges that public-health effects of food-derived opioids are complex with varying genetic susceptibility and confounding factors, together with system-wide interactions and feedbacks.^[3]

β-Casomorphins 1–3 edit

• Structure: H-Tyr-Pro-Phe-OH
• Chemical formula: C₂₃H₂₇N₃O₅
• Molecular weight: 425.48 g/mol

Bovine β-casomorphins 1–4 edit

• Structure: H-Tyr-Pro-Phe-Pro-OH
• Chemical formula: C₂₈H₃₅N₄O₆
• Molecular weight: 522.61 g/mol

Bovine β-casomorphin 1–4, amide edit

• Structure: H-Tyr-Pro-Phe-Pro-NH₂
• Chemical formula: C₂₈H₃₅N₅O₅
• Molecular weight: 521.6 g/mol

Also known as morphiceptin

Bovine β-casomorphin 5 edit

• Structure: H-Tyr-Pro-Phe-Pro-Gly-OH
• Chemical formula: C₃₀H₃₇N₅O₇
• Molecular weight: 594.66 g/mol

Bovine β-casomorphin 7 edit

• Structure: H-Tyr-Pro-Phe-Pro-Gly-Pro-Ile-OH
• Chemical formula: C₄₁H₅₅N₇O₉
• Molecular weight: 789.9 g/mol

Bovine β-casomorphin 8 edit

• Structure: H-Tyr-Pro-Phe-Pro-Gly-Pro-Ile-Pro-OH
• Chemical formula: C₄₆H₆₂N₈O₁₀
• Molecular weight: 887.00 g/mol

(Note: There is also a form of bovine β-casomorphin 8 that has histidine instead of proline in position 8, depending on whether it is derived from A1 (His) or A2 (Pro) beta-casein.)