Why milk makes coffee antioxidants stick around
Molecular mechanism of the interactions between coffee polyphenols and milk proteins
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Coffee polyphenols are approximately twice as soluble in proline solution as in water.
Most assume water is the best solvent for plant compounds, but here, an amino acid in milk outperforms water—challenging assumptions about solubility in biological systems.
Practical Takeaways
If you like milk in your coffee, don’t worry—you’re not losing antioxidants; you might be helping them stay active longer in your drink.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Coffee polyphenols are approximately twice as soluble in proline solution as in water.
Most assume water is the best solvent for plant compounds, but here, an amino acid in milk outperforms water—challenging assumptions about solubility in biological systems.
Practical Takeaways
If you like milk in your coffee, don’t worry—you’re not losing antioxidants; you might be helping them stay active longer in your drink.
Publication
Journal
Food Research International
Year
2025
Authors
Kazuki Horita, Tomoshi Kameda, Hiroshi Suga, Atsushi Hirano
Related Content
Claims (5)
When you add milk to your coffee, the protein in the milk (casein) latches onto the healthy compounds in coffee, making it harder for your body to absorb them—so you get 30% to 60% less of their benefit.
Coffee compounds called polyphenols dissolve better in environments full of a substance called proline than in plain water, which suggests they like to stick together with proline.
A natural compound in coffee and fruits called caffeic acid sticks to a specific part of milk proteins because they both like to avoid water — kind of like oil clinging to oil.
When you add milk to coffee, the proteins in the milk might help keep the healthy compounds in coffee from breaking down too quickly — but scientists weren’t sure exactly how this works.
When coffee compounds meet milk proteins, the glow they produce gets stronger if the milk proteins have more of a specific building block called proline — so proline seems to help them stick together better.