Table A1.
Studies conducted to assess the effect of dairy products on sleep.
| Study (Year) | Enrolled Subjects | Study Design | Country | Independent Variable | Dependent Variable | Results |
|---|---|---|---|---|---|---|
| Valtonen et al. (2005) [12] | Study 1: 59 females and 11 males (mean age = 81 ± 9 years, range = unclear); Study 2: 64 females and 17 males (mean age = 82.8 ± 8.1 years, range = unclear) | Study 1: Randomized controlled trial (RCT) (2-arms); Study 2: RCT (3-arms) | Finland | “Study 1: Group I: night milk (experimental) for 8 weeks and normal commercial milk (placebo) for 8 weeks, with a washout period of 1 week; Group II: normal daytime milk for 8 weeks, then switched to night milk after the washout period; Study 2: Group III: night milk for 8 weeks and normal daytime milk for another 8 weeks, with a washout period of 1 week; Group IV: normal milk for 8 weeks and night milk for another 8 weeks, with a washout period of 1 week. Group V: normal daytime milk throughout the experiment (control)” | Study 1: sleep quality, number of restless nights reported by nurses, Mini-Mental State Exam (MMSE) score; Study 2: sleep quality, daytime activity reported by caregivers | Study 1: decreased number of restless nights in Group I in Period 2 (normal milk), decreased sleep quality and number of restless nights in Group II in Period 2 (night milk); Study 2: increased sleep quality in Group III in Period 2 (normal milk). No effect of night milk. Increased sleep quality, morning activity and evening activity in Group IV in Period 2 (night milk). Slight increase in sleep quality In Group V in Period 2 (control). |
| Steinberg et al. (1992) [13] | 57 infants | RCT (4-arms) | USA | Experimental formulae (EF): +0 (892 μmol/L tryptophan), +1 (1192 μmol/L tryptophan), +2 (1513 μmol/L tryptophan), +3 (1808 μmol/L tryptophan) | Sleep latency, quiet sleep, active rapid eye movement (REM) sleep (observation) | Shorter sleep latency in those fed with the higher tryptophan-containing formula. |
| Brezinova et al. (1972) [14] | Younger group: six males and four females (mean age = 22 years, range = 20–30); older group: three males and five females (mean age = 55 years, range = 42–66) | RCT (2-arms) | Edinburgh | 32 g Horlicks solution with 250 mL of hot milk or control (inert yellow capsule) | Electroencephalography (EEG) | Younger group: diminished restlessness during sleep in Horlicks-administered group; older group: longer total sleep duration and fewer instances of awakening in the Horlicks group. |
| Southwell et al. (1972) [15] | Four male students (age: unclear) | RCT (2-arms) | London | No drink (control), 350 mL of warm water, or 350 mL of warm milk plus Horlicks | Movements during sleep | Horlicks consumption reduced the number of small movements during sleep |
| Jalilolghadr et al. (2011) [16] | Children (8–12 yrs; n = 8) | Experimental study | Sydney | High glycemic index (GI) drink (200 mg low fat cow’s milk with 50 g Glucodin powder) vs. low GI drink (200 mg full cream cow’s milk with 50 g honey) each for one day | PSG | The mean total arousal index in the first half of the night after the consumption of the high GI drink was greater than that of the low GI drink. (12.9 ± 4.6 vs. 9.9 ± 2.2, p = 0.03). Non-rapid eye movement (NREM) arousal index in the first half of night after the consuming the high GI drink was also higher than that of the low GI drink (12.7 ± 4.8 vs. 9.6 ± 2.3, p = 0.04). |
| Tatone-Tokuda F et al. (2012) [17] | Children (6 years old: n = 1106; 7 years old: n = 1015) | Quebec Longitudinal Study of Child Development (QLSCD) (longitudinal study: 1998–2010) | Canada | Proportion who had consumed a dairy product | Categorical sleep pattern characteristics (“short-persistent⁄increasing” sleep pattern, “10-h persistent,” “11-h persistent” patterns. | Girls who had a “short-persistent⁄increasing” sleep pattern consumed milk products significantly less often (≤once per day) and soft drinks significantly more often (≥once per day) than girls with “10-h persistent” or “11-h persistent” patterns. In boys or girls; milk products or soft drinks (in boys) at the 0.05 level (data not shown). |
| Aparicio S et al. (2007) [18] | Healthy infants (12–20 weeks of age; n-18) consuming artificial milk before the study | Experimental study (double-blind) | Spain (Balearic Island) | 1. Control week: each infant received commercial infant milk throughout the 24 h of the day (1.5 g tryptophan/100 g protein). 2. Other control week (inverse): control milk from 18.00 to 06.00 h, and tryptophan-enriched milk (3.4 g tryptophan/100 g protein) from 06.00 to 18.00 h. 3. The experimental week the infants received control milk during light time (from 06.00 to 18.00 h) and tryptophan enriched milk during dark time (from 18.00 to 06.00 h)” |
Sleep time; sleep efficacy; sleep bouts; immobility on activity recording | Slept longer, better sleep efficiency, more immobility during the experimental week. |
| Yamamura et al. (2009) [19] | 29 healthy elderly subjects (aged 60–81 years) | RCT with double-blind, cross-over design | Japan | Fermented milk vs. artificial milk (placebo) | Sleep efficacy; sleep latency; waking episodes; waking after sleep onset (WASO) based on actigraphy | There was no significant difference between the groups. Sleep efficiency had improved significantly from the baseline period in those receiving the fermented milk (p = 0.03). The number of awakening episodes decreased significantly from the baseline period in the fermented milk group (p = 0.007). |
| Misra et al. (2015) [20] | 56 toddlers (Age: 14–24 months) | A double-blind RCT (between subjects) design | Malaysia | Low GI (23) milk or high GI (65) milk for a period of 3.5 days | Sleep-onset latency (SOL), total sleep time (TST), WASO, sleep efficiency (SE). | “There were no significant differences between the two GI groups for SOL, TST, WASO, and SE. There was no need for any added sugars to improve the sleep patterns of this age group. The LGI formulations are preferable, as these tend to be higher in dietary fiber and lower in refined sugars and starches.” |
| Markus et al. (2005) [21] | Healthy college students with (n = 14) or without (n = 14) mild sleep complaints | A double-blind, placebo-controlled study | Netherlands | Tryptophan-rich alpha-lactalbumin (A-LAC) tryptophan-low placebo protein | The Stanford Sleepiness Scale, The Psychmotor Vigilance task, electroencephalographic recordings, concentrations of plasma tryptophan to other large neutral amino acids (Trp:LNAA) | The mean plasma Trp:LNAA was higher after the A-LAC diet condition than after the placebo diet condition (but not significantly). All subjects were less sleepy in the morning after evening intake of A-LAC than after placebo intake (but not significantly). Evening consumption of tryptophan-rich A-LAC may improve early morning performance indirectly through enhanced available brain tryptophan levels and subsequent sleep improvement. |
| Sato-Mito et al. (2011) [22] | 3304 female dietetics students (Age: 18–20 years) | Cross-sectional survey | Japan | Midpoint of sleep | A validated 16-page self-administered diet history questionnaire (DHQ). | The late midpoint of sleep was significantly negatively associated with the percentage of energy derived from proteins and carbohydrates, and the energy-adjusted intake of cholesterol, potassium, calcium, magnesium, iron, zinc, vitamin A, vitamin D, thiamin, riboflavin, vitamin B6, folate, rice, vegetables, pulses, eggs, and milk and milk products. |
| Grandner et al. (2014) [23] | The 2007–2008 National Health and Nutrition Examination Survey (NHANES) (n = 4552) | Cross-sectional survey | USA | The 2007–2008 National Health and Nutrition Examination Survey (NHANES)” | “Sleep symptoms (difficulty falling asleep, difficulty maintaining sleep, non-restorative sleep, and daytime sleepiness)” |
Low calcium intake was associated with difficulty falling asleep and a greater duration of non-restorative sleep. |
| Takada et al. (2017) [24] | 94 medical students | Double-blind, placebo-controlled trial | Japan | Lactobacillus casei strain Shirota (LcS) or non-fermented placebo milk (a daily dose of 100 mL) for 8 weeks prior to and 3 weeks after the examination (under psychological stress) | Overnight single-channel electroencephalography (EEG) recordings, subjective sleep and anxiety reporting. | There was a significant positive effect of LcS treatment on subjective assessment of sleepiness on waking and sleep duration. Sleep latency measured by EEG increased as the exam approached in the placebo group but was significantly suppressed in the LcS group. The percentage of stage 3 non-REM (N3) sleep decreased in the placebo group as the exam approached, whereas it was maintained in the LcS group throughout the trial. |
| Kitano et al. (2014) [25] | 421 community-dwelling older people aged ≥65 years (mean age: 74.9 ± 5.5 years; male: 43.7%) | Cross-sectional survey | Japan | The Pittsburgh Sleep Quality Index | Dairy consumption of habitual intake of milk, yogurt, and cheese; the Physical Activity Scale for the Elderly | The combination of engaging in leisure-time physical activity (LTPA) and consuming milk or cheese is necessary as a prescription to improve latency to sleep onset for older adults suffering from DIS. |
RCT: randomized controlled trial, MMSE: Mini-Mental State Examination, EF: experimental formulae, REM: rapid eye movement, EEG: electroencephalography, GI: glycemic index, NREM: non-rapid eye movement, WASO: waking after sleep onset, SOL: sleep onset latency, TST: total sleep time, SE: sleep efficiency, Trp: tryptophan, A-LAC: alpha-lactalbumin, DHQ: Diet History Questionnaire, NHANES: National Health and Nutrition Examination Survey, LcS: Lactobacillus casei strain Shirota, LTPA: leisure-time physical activity.