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WSJ reports: Milk collected at night makes mice sleepy

Got Night Milk? A Possible Treatment for Anxiety, Insomnia

Our Review Summary

Starting with the headline of the article, so-called “night milk” (cow’s milk collected at night) is touted as a possible treatment for anxiety and insomnia. This is certainly the type of headline that grabs one’s attention. The claim is difficult to support, however, due to the inherent limitations of the underlying study. The article’s main shortcoming is that it mischaracterizes the quality of evidence presented by the study. Our concern is that the story misreports the comparisons that were made in the study. Contrary to what the article reports, night milk is never directly compared against day milk in the study. Nor is it ever directly compared against diapezam. To its credit, the article does a very good job in correctly recognizing that the underlying study only concerns animals and thus cannot be generalized to humans without further research.


Why This Matters

The CDC states that, “getting sufficient sleep is not a luxury – it is a necessity – and should be thought of as a ‘vital sign’ of good health.” Further, more than one quarter of Americans claim to not get enough sleep and around 10% suffer from chronic insomnia. The sleep-promoting and anxiety-reducing effects of night milk are worth studying because the findings may suggest its potential as a natural aid for sleep and anxiety related disturbances.


Does the story adequately discuss the costs of the intervention?


Although the cost of night milk is not discussed directly, the reader is given a hyperlink to the company website of Milchkristalle GmbH, a producer of night milk, where the price of night milk may be found. (Though we find it strange that a hyperlink of night milk should direct the reader to a specific company selling a night milk product.)

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

The reader is left to ponder statements such as “mice that got night milk were significantly less active…” But how much less active?

The story does make a good faith effort to report some number-based outcomes from the study. It says, for example, “Balance and coordination were measured by the number of falls from a rotating bar during a 20-minute period: Mice fed night milk on average fell four to five times, about twice as often as mice given day milk. Diazepam-treated controls fell about nine times, while the water-fed controls fell twice.” But then again, it’s not exactly made clear how this result relates to the outcomes that readers are interested in such as sleep or anxiety. We’ll reluctantly rate this Not Satisfactory.

Does the story adequately explain/quantify the harms of the intervention?

Not Applicable

Drinking milk is common enough that it hardly warrants an explanation of the associated harms.

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

The story earns points for declaring up front that the study was conducted in animals and including a caveat at the end that the study can’t be generalized to humans. This is an excellent practice that helps counterbalance some significant concerns we had with other aspects of the piece.

Specifically, the statements

… the study found that milk collected at night, or night milk, had enhanced sedative effects in mice compared with milk produced during the day.


Night milk significantly decreased the rodents’ physical activity, balance and coordination and increased sleep time compared with day milk, the research showed.

are misguided. The underlying study never directly compares night milk to day milk. Rather, the treatment arms of 1) day milk at three doses, 2) night milk at three doses, and 3) diazepem are each compared to the treatment arm corresponding to the control group, which consists of mice who only received distilled water.

We think the confusion may stem from the fact that the study also reports one-way ANOVA results. (Just fancy statistics jargon for comparing treatment effects between multiple groups.) A significant ANOVA result allows one to conclude that not all of the treatment arms are the same, i.e. there exists at least a pair of comparisons amongst the treatment arms that are significantly different from each other. ANOVA used in this way simply tests an omnibus hypothesis that is not very interesting in its own right, in that it is not a procedure that identifies which two experimental arms are different.

We acknowledge that the study itself is not clear on this point, making it difficult for journalists to analyze the results. Inclusion of an independent source might have helped with the evaluation.

Does the story commit disease-mongering?


No disease-mongering going on here.

Does the story use independent sources and identify conflicts of interest?

Not Satisfactory

No independent sources are solicited. The only link included to an outside “source” is to the company that sells night milk.

Does the story compare the new approach with existing alternatives?


The article states

Mice fed night milk were more inclined to explore open spaces, an indication of reduced anxiety that was comparable to the effects from consuming diazepam

The design of the study, however, does not support this claim because a direct comparison is never made between night milk and diazepam. Since we’ve already addressed this issue above, however, we’ll give the story credit here.

Does the story establish the availability of the treatment/test/product/procedure?


The article makes an effort to establish the availability of night milk by providing a hyperlink to a company that sells night milk. But the website obviously caters to German customers and seems like it could be a headache for US consumers to navigate. And we couldn’t find any other online sources of night milk besides this company that would be more accessible.

Does the story establish the true novelty of the approach?

Not Satisfactory

The article does not establish the context of the study adequately, making it hard to judge the novelty of using night milk to treat anxiety and insomnia. Is this the first such study to be conducted? This is where an independent expert could’ve helped out.

Does the story appear to rely solely or largely on a news release?

Not Applicable

We couldn’t find a news release to compare with the story. But since no independent sources are quoted, we can’t be sure the story didn’t rely on a news release. We’ll rate this Not Applicable.

Total Score: 4 of 8 Satisfactory


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