Diet and sleep in athletes and archers: Eroglu 2024

A Turkish cross-sectional study compared what 115 national-level athletes had eaten the day before with how they had slept that night. The athletes came from five sports: 58 swimmers, 18 taekwondo athletes, 17 archers, 11 canoeists and 11 volleyball players, with a mean age of 19.7. On average they slept 7.5 hours, and on the Richards-Campbell Sleep Questionnaire (RCSQ) 29 of the 115, or 25.2%, counted as poor sleepers (a score below 50).

The good sleepers had eaten more: 2,170.52 kilocalories against 1,746.35, 1.63 grams of protein per kilogram of body mass against 1.27, and 1,356.99 mg of tryptophan against 1,032.75. Relative to body mass, though, energy intake did not differ significantly (31.89 against 26.74 kilocalories per kilogram). Carbohydrate, fat, magnesium, caffeine, water and the glycaemic index of the last meal did not differ significantly between the two groups.

For the archers the paper reports only sleep, not diet. The 17 archers slept 7.58 hours on average, with a total RCSQ score of 66.70, the highest of the five sports, although the differences in the total were not significant. On the item for perceived sleep quality they had the highest value (82.94), while the canoeists were the only group significantly below the other sports.

Of the 124 athletes recruited in May and June 2023, during the regular training season, 115 remained once incomplete questionnaires were removed; anyone under 18 or with a diagnosed sleep disorder was excluded. To count as elite it was enough to belong to a national or professional team or to hold a national ranking. Data were collected on the morning of a weekday training day: a 24-hour dietary recall, aided by household cups and spoons and analysed with the Turkish BeBiS 8.1 software, and the RCSQ for the night just gone.

The RCSQ has five items rated on a 0 to 100 millimetre line (depth of sleep, time to fall asleep, awakenings, time to get back to sleep, perceived quality) and a sixth on noise that does not count towards the total. Body mass and body fat were measured with a bioimpedance scale. The groups, good against poor sleepers and the five sports, were compared by analysis of variance.

A single day of recalled diet and a single night of self-reported sleep are a fragile basis: a 24-hour recall describes a person's usual diet poorly, and sleep was measured only by questionnaire, with no instruments. The study is cross-sectional and cannot say whether people sleep better because they eat more or whether, for instance, athletes who train a certain way eat and sleep differently; stress and psychological factors were not measured, as the authors acknowledge.

Some figures do not add up: the abstract gives 28.6% poor sleepers, the results 25.2%; 37 women out of 115 is 32%, not the 24.7% stated; tryptophan is given in grams in the abstract and in milligrams in the table; and the standard deviation for water in the whole sample (4,557.73 ml) is not compatible with those of the two groups. With a mean age of 19.7 and a standard deviation of 3.6, there is also some doubt about the exclusion of under-18s. Finally, the 17 archers are a small subgroup, and none of their dietary data is reported separately.

For anyone who shoots, the study says little that is specific. The 17 archers in the sample slept more than seven and a half hours on average and rated their sleep as good, on a par with or better than athletes in the other sports; that is a snapshot of one Turkish national-level group in season, not a rule. The link between how much people eat and how they sleep was measured across all sports together, and in that mixed group the good sleepers had taken in more energy, more protein and more tryptophan.

The finding that applies to everyone is energy: on average the athletes took in 30.59 kilocalories per kilogram of body mass a day, below the 40 to 70 that the authors give as the requirement for athletes training at moderate intensity or high volume. For an archer who spends many hours on the range it is a reminder that eating too little can go with poorer sleep, but the study does not show that eating more improves sleep.