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Nutrition and Performance in Sport

Christophe Hausswirth

Chapter 3. Nutrition and lifestyle

Topic 12. Sleep and alertness

Eve Tiollier, Amélie Fosse, Christophe Hausswirth, Axel Heulin, Yann Le Meur, Véronique Rousseau et École Lenôtre

Texte intégral

Questions and answers

Key points
Sleep is favoured by a readily digestible, light dinner, containing carbohydrates rather than proteins.
When not consumed during training, carbohydrates promote somnolence – unlike proteins, which promote wakefulness – although their effect is not as strong as that of stimulants.
On the contrary, during exercise, consuming an energy drink maintains a good state of alertness and ensures effective technical movements.

Can a lack of sleep affect physical performance?

1The impact of a lack of sleep on physical performance depends on several factors. For exercise, the factors at stake are the level of intensity of the exercise, whether it is a one-off or a repeated performance, and how important technical/psychomotor and alertness/concentration components are in performance. The determinant parameters in sleep disturbance are its duration and whether it is chronic or not and, to a lesser degree if it is partial, the moment at which it occurs (beginning or end of the night). Possible effects of lack of sleep are summarized in the table below.

Table 1. Potential effects of lack of sleep

If you weigh 50 kg

Examples of sports


Low intensity, low alertness

Sailing, amateur cycling, self-determined sports

↑ Mistakes

Moderate intensity, high concentration

Team sports, racquet sports

↓ Decision-making

High intensity

3000-m running, 400-m swimming


Aerobic and anaerobic efforts

Combat sports, swimming

↓ Power

Anaerobic efforts

Sprint, power sports


Repeated anaerobic efforts

Jumping, bodybuilding

↑ Fatigue

Which foods can help you to fall asleep?

2Most research into dietary adaptations related to sleep have tried to increase the availability of tryptophan, which is the precursor to the neuromediator involved in sleep, serotonin. However, very few foods as such have been the subject of scientific studies investigating their capacity to promote sleep. Therefore, we should keep in mind the effect of consuming high glycaemic index carbohydrates. Results show that eating a high-carbohydrate meal decreases the time you take to fall asleep. The timing of this meal also appears to be important. The beneficial effects are greater if the meal is taken four hours before going to bed, rather than one hour.

3In other studies, tryptophan was given directly, in the form of a supplement. However, it is worth noting that the best food source of tryptophan is milk, and that carbohydrate consumption creates a favourable hormonal environment for its entry into the brain (where it can be used for serotonin synthesis). In contrast, eating proteins (meat, fish, eggs) reduces the availability of serotonin in the brain and favours the synthesis of other neurotransmitters such as dopamine and noradrenalin, which are stimulatory neuromediators.

4Other foods which are thought to have relaxing effects are plants such as valerian, hops, lemon, hawthorn, passionflower, etc. Among these, the one that has been most researched is valerian. However, the results obtained have been contradictory up to now, and therefore we cannot definitively confirm that this plant has beneficial properties for sleep. However, if consumed as an infusion, these plants can help promote sleep through two effects: firstly, a behavioural effect, when it is part of the bedtime ritual, and secondly, through its action on core body temperature. Drinking a hot beverage decreases the core temperature, which is required for good sleep. From this point of view, a glass of sweetened hot milk combines three conditions promoting sleep: tryptophan intake (milk), favourable hormonal context (carbohydrates) and decrease in internal temperature (hot beverage).

What foods should be avoided?

5Above all, stimultants such as coffee, tea, cola drinks and energy drinks such as Red Bull should be avoided. In those most sensitive, caffeine doses greater than 100 mg can delay and perturb sleep. Drinking alcohol at night is also not recommended. Although its anxiolytic effect promotes dropping off, alcohol affects sleep quality during the second part of the night, and prolongs the light sleep phase during which you are more likely to wake up. Alcohol also stimulates diuresis and increases the need to get up during the night to urinate. Finally, alcohol is linked to increased snoring and sleep apnoea.

6Hearty dinners, which increase body temperature, do not create a climate favourable to sleep either. Finally, consuming large quantities of proteins (meat, fish, eggs) as part of the evening meal does not make sleep easy, as it has a negative effect on serotonin synthesis, as mentioned above. This effect, although it was validated at a neurochemical level, remains to be proven at the behavioural level.

Can a weight-loss diet affect sleep?

7The mechanisms controlling alertness and sleep cycles are closely linked to those involved in regulating energy metabolism. The interaction between reduced energy intake and sleep works both ways.

8On the one hand, energy restriction leads to sleep disorders, particularly by increasing the time it takes to fall asleep and decreasing the duration of slow-wave sleep (which is the phase of sleep during which physical recovery takes place). These disorders are linked to the effects of calorie restriction on thermoregulation. On the other hand, during a lowcalorie diet, the shorter duration of sleep (5.5 rather than 8.5 h) affects the quality of body mass reduction, increasing the reduction in lean mass and decreasing fat reduction.

Does the composition of a meal (carbohydrate-to-protein ratio) affect alertness?

9The level of alertness follows a “natural” cycle every 24 hours. This cyclic pattern can include significant variations in alertness, especially due to the effect of a meal. Thus, two hours after eating a breakfast rich in carbohydrates, reaction times are clearly slower than if the breakfast was rich in proteins. This difference between proteins and carbohydrates was also observed over a longer period. During a boat-race lasting about 30 hours (from one morning at 9 a.m. to the day after 4 p.m.), individuals who consumed carbohydrate-enriched food were more tired than those who ate proteinenriched food. This difference appeared as early as the beginning of the night and continued throughout the following day. Another study investigated the consumption of foods rich in carbohydrates, compared to mixed food, over a 24-hour period. A carbohydrate-rich diet was associated with a higher level of somnolence and an irrepressible desire to sleep, particularly when alertness is naturally at a very low level (between 12 noon and 4 p.m., and between 12 midnight and 4 a.m.).

10These results lead to two main conclusions:

  • consuming carbohydrates favours somnolence, unlike proteins, which contribute to alertness, although their effect is not as powerful as that of stimulants;

  • the negative effect of carbohydrates on alertness appears greater when the individual is sleep-deprived or when these foods are eaten at night (when alertness levels are naturally low).

Does this mean that consuming a sports drink during exercise can hamper alertness?

11On the contrary, the effect of carbohydrates is completely different during exercise involving significant energy expenditure. Ingesting a sweet drink during exercise decreases perceived fatigue and enhances psychomotor performance. In practice, this results in more efficient technique. During an effort similar to a football match, for instance, having a sports drink rather than a placebo drink increased dribbling efficiency and shot precision. In addition, consuming carbohydrates during a long or repeated exercise prevents hypoglycaemia, which diminishes alertness. Therefore, consuming a sports drink during exercise maintains a good mental attitude after exercise. This was also shown in a study where those who ingested a sweet drink had the same reaction time in tests performed before and after a 90 minute race.

Does hydration status affect mental performance?

12From a loss of 1% in body weight, dehydration affects cognitive performances. Research on the topic showed that dehydration caused by heat and physical exercise leads to an increase in perceived fatigue, reaction times and number of mistakes made, as well as decreasing short-term memory. By the same token, it has a drastic impact on the technical component of various disciplines.

Do foods containing caffeine have advantages for athletes?

13Caffeine is commonly consumed to enhance performance in a sporting environment. And yet, sensitivity to caffeine varies extensively from one individual to another. Because of this, the effects – which may be beneficial or harmful – are greater in those who are most sensitive.

14The scientific data reveal that consuming 3−1 of caffeine has a favourable effect on performance in endurance sports, racquet sports, team sports and during intense exercise lasting between 1 and 60 minutes. However, it is not beneficial at all for one-off exercises involving strength and power production. The other beneficial effect of caffeine is its capacity to restore alertness which may be reduced due to lack of sleep.

15However, these positive effects of caffeine should be balanced against its potentially deleterious effects. In sensitive individuals, doses greater than 100 mg can postpone sleep. Caffeine can also reduce the total duration of sleep and modify its structure: sleep becomes lighter, with shorter slow, deep sleep phases. Paradoxically, this can increase fatigue on the following day and, thus, encourage resorting to the use of caffeine, resulting in a vicious cycle. The maximal blood concentration of caffeine is reached about one hour after its ingestion, and its half-life is about four hours. Thus, four hours after consuming caffeine, half of it still remains in blood; and eight hours later, a quarter. Caffeine is eliminated more slowly in women taking the pill and in people who have consumed alcohol.

16Caffeine also has other negative effects, such as its diuretic properties, which are unfavourable to maintaining hydration status. It can also increase anxiety in sensitive people. Because of these effects, it is important to weigh up the pros and cons before resorting to this type of product.

Practical applications

1. To promote sleep

Composition of dinner (preferably to be eaten 3 to 4 hours before going to bed)

Mistakes to avoid

Follow the basic rules for a good night’s sleep

17 Bedroom temperature between 18 and 20 °C

18 No sources of light or noise in the bedroom

19 A comfortable bed adapted to your needs

2. To promote alertness


20 Outside training hours

21 During exercise

22 Have a sports drink during exercise. It will help to maintain alertness and the technical quality of your performance

23 Make sure you are well hydrated. The colour of your urine is a good indicator

24 Make sure you eat (meal or snack) 4 to 5 hours before exercise

3. Caffeine

What you need to know

25 Sensitivity to caffeine varies greatly between individuals

26 Its concentration peaks about 1 hour after ingestion; 4 hours after ingestion, half of the initial quatity remains in the blood; and 8 hours later, one quarter

27 For athletes, caffeine has advantages and disadvantages. Each athlete must weigh up the pros and cons:

Sports that could benefit from a positive effect

Potential negative effects

Endurance sports
Sports involving intermittent intense exercise (team sports/racquet sports)
Sports involving intense exercise < 1 hour

On sleep:
– reduction in total duration of sleep
– increases light sleep
– reduces deep sleep
On mood:
– increases stress
Diuretic effects:
– unfavourable to a good hydration status

28 Sources

Robusta coffee contains twice the caffeine of Arabica coffee


Gambas and saffron rice with vegetables

Photo credit: Thibaut Ruggeri.

29Serves 2

30Preparation time: 45 minutes

31Cooking time: 30 minutes


33 10 peeled gambas tails

34 1 litre chicken stock

35 1 g saffron stamens

36 50 g peeled carrots

37 50 g courgettes

38 50 g fennel

39 6 cherry tomatoes

40 10 g olive oil

41 Salt, pepper

42Wash and chop the carrots, courgettes and fennel into 3 to 5 mm cubes.

43Boil the saffron in the chicken stock. Add a pinch of salt.

44Cook the vegetables individually in the stock for a few minutes (they should still be crunchy) and drain.

45Chop the onions and sweat in olive oil.

46Add the rice, coat it in oil but make sure it does not brown. Pour in one and a half

47volumes of boiling saffron stock. Add the bouquet garni *.

48* Bouquet garni: (bunch of mixed herbs) parsley, thyme, and bay leaves all wrapped and tied up in a leek leaf.

49Pilaf rice

50 10 g d’huile d’olive

51 50 g d’oignons

52 100 g de riz

53 1 bouquet garni *

54 1 quart de botte de ciboulette

55 Le jus d’un demi-citron

56Cover with a tight-fitting lid and cook for 16 minutes in the oven at 200 °C. Check that it is fully cooked and stir with a fork to separate the rice grains. Add the vegetables.

57Keep warm.

58Season the gambas tails and fry in olive oil. Add the cherry tomatoes.

59Serve the rice and vegetables, the fried gambas tails and the cherry tomatoes in a deep plate. Sprinkle with chopped chives and drizzle with some lemon juice.

60Chef’s note

61This dish is very well balanced. Served with raw vegetables as a starter, with a dairy product and a fruit purée for dessert, it is an ideal dinner to promote sleep.

62Nutritional analysis per person

Energy (Cal)

Carbs (g)



Lipids (g)

Protein (g)



Poached peaches with lemon verbena

Photo credit: Thibaut Ruggeri.

63Serves 6

64Preparation time: 20 minutes

65Cooking time: 1 heure


676 peaches

68 1.1 litres of water

69 500 g sugar

70 30 g fresh lemon verbena

71Cut a cross in the lower part of the fruit.

72Plunge the peaches into boiling water for 1 minute so that you can peel off the skin more easily.

73Mix the water and sugar together and boil for 3 minutes.

74Add the peeled peaches and lemon verbena, simmer gently for about 1 h.

75Allow to cool before storing in the fridge.


77You can serve the fruit with fromage blanc or vanilla ice cream.

78Chef’s note

79This dessert is rich in carbohydrates. It is perfect as part of a meal to be eaten after intense training. In these conditions, it contributes to the replenishment of muscle energy stores, while also promoting sleep. The amount of carbohydrate varies considerably depending on how much syrup is served with the peaches.

80Nutritional analysis per person

Energy (Cal)

Carbs (g)



Lipids (g)

Protein (g)




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