Why do I run out to buy milk for my morning café au lait even in a blizzard?

Hello. I am Midori Maruoka, a medical writer.

I am a huge fan of café au lait.
When I open the fridge in the morning and realize, 'Oh no! I'm out of milk!', I quickly throw on my down jacket and run to the local Lawson, even if it's a blizzard. (Though, it is only a two-minute walk...)

If it were bread or eggs, I would just think, 'I guess I'll skip it today.' I feel it's a bit of a waste to go out of my way to shop during the precious morning hours before working from home. There is also the simple reason that it's just a hassle (laughs).

However, milk is different. The desire to 'have a café au lait!' far outweighs the hassle.

For me, café au lait might be like a small ritual to flip the switch for work.

At one point, I suddenly wondered: Why do I want a café au lait that much? Since I only have about two cups, it's not really caffeine withdrawal symptoms.

I thought perhaps there might be a reason related to the components of milk, so I decided to look it up in English research papers (PubMed).

Recent basic research suggests that a substance called casomorphin-10, a type of peptide derived from milk, may be involved in neurotransmission and biological rhythms. (However, this research was conducted at the cellular level, and it does not mean that a direct effect on daily life has been confirmed.)

Still, it felt a bit interesting to think that there might be a scientific background to my morning ritual.

I headed to Lawson in a blizzard not just for the taste, but because I was looking for a switch to change my mindset... Thinking about it that way, it makes sense.

Recently, I've been using an electric milk frother to enjoy a fluffy café au lait.

As a nurse, I usually write medical articles that emphasize evidence.
Peeking into daily little questions through research papers is quite an exciting time.

A series where I verify daily oddities using English research papers.
I'm thinking of verifying my cat's behavior next time.

[References]
Fukunaga, M., Watanabe, S., Orihara, K., & Yamamoto, N. (2025). Casomorphine-10 (CM-10) Peptide Orchestrates Circadian and Neurodevelopmental Gene Clusters via δ-Opioid Receptor Signaling: Insights from Transcriptome Analysis with δ-Opioid Receptor-Expressing HEK293 Cells. Life, 15(10), 1636.
https://pubmed.ncbi.nlm.nih.gov/41157308/

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