Fact check: Does eating too much cheese give you nightmares?

1. Why the July 2025 paper reignited the “cheese causes nightmares” story

The July 2025 study reported that dairy products were the second most prevalent food group implicated in affecting dreams, including disturbing and bizarre dreams, and it found a robust association between nightmares and lactose intolerance, which has driven renewed public attention ^[1]. That paper’s prominence stems from its recent date and the specificity of its claim linking a metabolic trait—lactose intolerance—to nightmare frequency, implying that physiological reactions to dairy might plausibly alter sleep architecture or sleep-related cognition. The paper strengthens an association signal, but association is not proof of causation; alternative explanations such as reporting bias, comorbid conditions, and timing of dairy intake were not fully disentangled ^[1].

2. Earlier reviews offer a contrasting picture focused on sleep quality, not nightmares

Systematic and narrative reviews from 2023 and 2024 examined dairy’s relationship to sleep more broadly and emphasized potential sleep-promoting effects of dairy, including mechanisms like tryptophan and melatonin precursors, without documenting an increase in nightmares ^{[3] [2]}. These reviews synthesized population studies and mechanistic data to argue that dairy intake may improve some sleep parameters, which complicates the simple headline that cheese causes bad dreams. The divergence between reviews and the 2025 study suggests heterogeneity by outcome (sleep quality vs dream content) and by population, indicating the need to interpret each claim within the specific endpoints and methods used ^{[3] [2]}.

3. How lactose intolerance emerges as a plausible biological moderator

The 2025 paper’s finding linking nightmares with lactose intolerance introduces a biologically plausible moderator: unabsorbed lactose can cause gastrointestinal distress, systemic inflammation, or sleep fragmentation, each of which can increase dream recall or the intensity of dreams ^[1]. This shifts the focus from cheese per se to individual digestive responses; people without lactose malabsorption may not experience nightmare-related effects, while intolerant individuals could be more vulnerable. The implication is actionable: reducing lactose exposure or using lactase-treated dairy might mitigate reported dream disturbances for susceptible people, though randomized trials testing this intervention are not reported in the available materials ^[1].

4. Methodological gaps that limit causal claims and inflate headlines

The body of evidence presented contains observational designs, heterogeneous outcomes, and reliance on self-reported dream alterations, which leave several confounders unaddressed: timing and quantity of cheese intake, concurrent alcohol or caffeine use, psychiatric comorbidity, and recall or selection biases ^{[3] [4] [1]}. Earlier reviews caution that mechanistic pathways are speculative and population studies often mix children, adolescents, and adults with differing diets and metabolic profiles ^{[3] [2]}. These methodological limitations mean headlines claiming cheese “gives” nightmares overstate what the data support; the most defensible claim is an association in specific subgroups under particular circumstances ^{[1] [3]}.

5. Competing interpretations and possible agendas to watch

Different stakeholders may emphasize contrasting findings: food-sensitivity researchers and advocates for dietary personalization may highlight the July 2025 association with lactose intolerance, while dairy industry–friendly narratives or metabolic-sleep researchers may stress sleep-promoting effects of dairy reported in reviews ^{[1] [2] [3]}. Each party can legitimately cite parts of the literature, but readers should note agenda risks—commercial interests could underplay negative associations, and advocacy groups might overgeneralize subgroup findings. Balanced interpretation requires acknowledging both the 2025 association signal and earlier mechanistic and population-level studies showing neutral or beneficial sleep effects ^{[1] [3]}.

6. Practical takeaways and research priorities for definitive answers

For individuals experiencing vivid or disturbing dreams after eating cheese, the evidence supports a pragmatic trial: reduce or eliminate lactose-containing dairy before bedtime, try lactose-free options, or track timing and quantity to see if symptoms abate, reflecting the lactose-intolerance hypothesis ^[1]. Research priorities include randomized crossover trials testing lactose-free versus lactose-containing dairy on dream content and objective sleep measures, mechanistic studies on gut-derived inflammation and REM sleep, and stratified analyses by lactose absorption phenotypes. Only such targeted studies will move the literature from association to causal understanding ^{[1] [3] [2]}.