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Nutrition and Performance in Sport

Christophe Hausswirth

Chapter 3. Nutrition and lifestyle

Topic 14. Dietary supplements

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

Texte intégral

Questions and answers

Key points
When nutritional intake cannot be covered appropriately through food (for example, if the athlete is travelling in a country where only a limited number of foods are available) or when an athlete suffers from a particular deficiency, vitamin or mineral supplements may be recommended.
Supplements can be classified in four groups, as follows: group A (authorized and of scientifically proven efficacy) to group D (forbidden by the World Anti-Doping Aagency, WADA).
Various minerals, vitamins and amino acids are contained in our daily diet and it is preferable to concentrate on having a balanced diet before considering taking supplements.

What distinguishes supplements from ergogenic products?

1A supplement may be medically prescribed, at a physiological dose, to compensate for a deficiency or to artificially increase the body’s stores (for instance of iron, magnesium, etc.). The doses of some supplements are supra-physiological.

2An ergogenic product is a food, a macronutrient or micronutrient which is likely to enhance physical and/or physiological performance.

What vitamins and minerals are necessary when training and to maintain health?

3The duration of daily training, often exceeding 4 hours, associated with very intense exercise, puts the body to the test. To maintain health and sporting performance, it is particularly important to ensure an adequate intake of energy, but also of iron, copper, manganese, selenium, zinc and vitamins A, B6, B12, C and E. These elements should be provided by a varied diet, based mostly on nutrient-rich foods such as vegetables, fruit, broad beans, seeds, lean meats, fish, dairy products and unsaturated fats. Scientific studies show that up to 70% of athletes achieve the recommended intake of vitamins and minerals through their diet by eating varied foods. Thus, the only athletes who present a risk of insufficient micronutrient intake are:

  • those who restrict their diet to lose weight;

  • those whose diet is monotonous, without variety, and who mostly eat foods with a low nutritional density.

How should a deficiency be corrected?

4When nutritional intake cannot be covered appropriately through food (for example, if the athlete is travelling in a country where a limited number of foods are available), or when an athlete suffers from a particular deficiency, vitamin or mineral supplements may be recommended. In general, a broad-spectrum multivitamin and mineral supplement is the best choice when compensating for situations where food is restricted. In contrast, targeted nutritional supplements may be necessary to compensate for a confirmed deficiency (for instance, of iron).

Are the various supplements and sports foods classified (by group) based on the scientific evidence of their effect on athletes’ health and performance, and to identify banned substances?

5The international classification adopted in most countries is as follows (Australian Institute of Sport [AIS] and American College of Sports Medicine [ACSM]):

6 Group A: supplements and sports foods for which effects have been demonstrated through scientific studies

7This group comprises energy sources or foods/supplements which are useful and provide appropriate nutrients for the athlete’s diet, or which have been proven to have positive effects on performance when they are used within the framework of a specific protocol and in a particular sporting situation. This means that they may not be valid for all sports and all athletes. These nutritional components are generally present in the diet.

8The following are Group A substances:

  • bicarbonate and citrate

  • caffeine

  • calcium

  • magnesium

  • creatine

  • iron

  • electrolytes compensating for exercise-induced losses (see Fact sheet No. 10 Hydration, p. 342)

  • multivitamins and minerals

  • energy bars and gels

  • sports drinks (see Fact sheet No. 10 Hydration, p. 342)

  • whey proteins.

9 Group B: supplements and sports foods for which scientific evidence of their effect on performance is controversial or is based on preliminary results

10This group of foods/supplements has been the focus of specific attention, sometimes involving testing in populations of athletes. Preliminary results may suggest beneficial effects on performance, but these may not be unanimously approved.

11Group B includes the following:

  • antioxidant vitamins, C and E

  • colostrums

  • β-alanine

  • glutamine

  • melatonin

  • ribose

  • probiotics (see Fact sheet No. 8 Immunity, p. 317)

  • quercetin

  • beetroot juice

  • fish oil.

12 Group C: supplements and sports foods for which limited scientific evidence is available that they have beneficial effects

13This group contains most of the supplements and sports foods available to athletes. Although some athletes use them, their efficacy does not appear sufficient to be useful and indeed, some of these substances have been shown to have a negative impact on sporting performance.

14Group C includes the following elements:

  • branched-chain amino acids

  • carnitine

  • coenzyme Q10

  • cordyceps

  • cytochrome C

  • ginseng

  • inosine

  • pyruvate

  • medium-chain triglycerides

  • hydrogen peroxide

  • vanadium

  • chromium picolinate.

15 Group D: supplements and sports foods which are illegal to use and are dangerous

16All substances classed in this group are banned by the World Anti-Doping Agency (WADA). There is a high risk that these substances may contaminate other products, which could lead to a positive anti-doping test (see​fr).

17The following elements are classed in Group D:

  • androstenedione

  • 19-norandostenedione

  • DHEA 19-norandostenedione

  • ephedra

  • strychnine

  • herbal supplements containing testosterone (Tribulus terrestris)

  • glycerol

  • methylhexanamine (MHA).

■ Bicarbonate and citrate

18During intense exercise of short duration, the muscles produce various acids, including lactic acid, which are both beneficial (they can be used as energy substrates) and harmful (they affect muscle function). In the same way as excess acid in the stomach can be neutralized by taking bicarbonate, buffering components taken before an event (specifically, between one and two hours before the event) can counteract the negative effects of lactic acid. Because of this, bicarbonate supplements are widely used by athletes in events lasting a few minutes (one to seven minutes) and resulting in fatigue. However, few athletes adapt their intake of these supplements to their body weight (maximum 300−1), even though when taken in excess they present a real risk of causing gastrointestinal problems. Continuous supplementation is not recommended because it increases the risks of undesirable effects.

19Citrate also efficiently buffers lactic acid and could be an interesting alternative to bicarbonate as it generates fewer gastric problems. A limited number of studies recently showed that β-alanine supplements can also increase the muscles’ buffering capacity, but its long-term safety has yet to be proven.

20Sporting situations where these supplements are often used:

  • when athletes practise intense activities lasting between one and seven minutes;

  • in team sports or intense exercise lasting more than one hour (beneficial effects have recently been shown);

  • when athletes perform very intense intermittent exercises.

21Bicarbonate and citrate in food:

  • through the mineral and organic components it contains, food influences the body’s acid-base balance. Thus, foods rich in organic acids have a higher buffering capacity. The acid-base imbalance is caused by some nutrients leading to the production of acidic or alkaline components. For example, eating too much animal protein increases acidosis. Vegetable proteins, in contrast, are frequently consumed in the form of foods rich in components likely to increase the body’s pH. Therefore, any vegetable intake helps to neutralize the acidity produced in the body and through exercise. Fruit is very alkalinizing, whereas vegetables, mushrooms and pulses have a different buffering power depending on their origin (for example, button mushrooms are very alkaline);

  • in addition, many drinks contain bicarbonates. These drinks, often sparkling, should particularly be consumed after exercise, to enhance recovery by increasing blood pH.

■ Whey proteins

22Whey proteins are attracting increasing interest for use during the recovery phase or during the muscle reconstruction phase. This interest stems from experimental evidence that milk proteins (casein and/or whey) are an important source of nitrogen-containing components. These proteins are apparently more effective than soy proteins in promoting protein synthesis during the early recovery phase after performing strength exercises. When consumed after a bodybuilding exercise, whey proteins increase and prolong muscle hypertrophy. This prolongation should lead to greater muscle mass gain when whey proteins, rather than casein, are taken within the framework of a bodybuilding session. After prolonged exercise, the consumption (as a recovery drink) of lowfat milk is therefore recommended, not only for rehydration, but also because it promotes glycogen resynthesis in the muscle.

23Sporting situations where whey proteins are often used:

  • when athletes include a significant proportion of bodybuilding in their training;

  • for endurance athletes who undertake prolonged exercise.

24Food sources of whey proteins:

25cow’s milk and dairy products are important sources of amino acids, lipids, vitamins and minerals. Milk proteins are distinguished based on those present in the micellar fraction (mainly casein) and those found in the soluble fraction (termed whey proteins). A litre of cow’s milk contains about 30 g of total proteins (of which about 80% casein and 20% whey proteins). As a source of protein, it is preferable to drink semi-skimmed or skimmed cow’s milk, and to avoid soy milk.

■ Caffeine

26The main sources of caffeine are leaves, nuts, a certain number of plants, tea, coffee and various cola-based drinks. The low cost of this molecule and the fact that it is perceived as a stimulating product favour its consumption in sporting environments. In general, normal food sources provide between 30 and 100 mg of caffeine. The recent inclusion of caffeine (and guarana) as an ingredient in energy drinks designed for use during exercise can significantly increase the dose of caffeine ingested, which could lead to dehydration. Caffeine was removed from the list of banned substances published by the WADA in January 2004. The effects of caffeine on the human metabolism are relatively complex, because they involve various difficult-to-isolate cellular interactions. Its main effects are to increase fatty acid and glycerol levels, thus stimulating the use of “fat” during exercise. Caffeine also stimulates stress hormones, and induces muscle cell contraction.

27Scientific evidence:

  • caffeine increases athletes’ aerobic capacities in a regular pattern, mobilizing “fats” and sparing glycogen.

  • excess caffeine has a significant diuretic effect and can easily lead to dehydration in athletes.

28Situations where caffeine is frequently used:

  • before and/or during endurance efforts (exercise lasting more than one hour) and in intermittent sports; including team sports;

  • when athletes perform very intense short-duration exercises (lasting less than five minutes).

29Caffeine in food:

30individual reactions to caffeine differ: in some this compound reduces the intensity of headaches; it also increases lipolysis and diuresis. It is found naturally in the daily diet.

■ Antioxidants (for example vitamins C and E)

31These compounds are important in protecting tissues exposed to stress caused by intense or prolonged exercises. However, it has yet to be proved that intense training significantly increases antioxidant needs given that the body naturally develops efficient defences when provided with a balanced diet. Nevertheless, protocols with supplementation have been developed, with typical daily doses of 500 mg vitamin C and 200 mg vitamin E, over a fortnight. The synergistic effects of these two vitamins are very well known: their combination helps to prevent the deleterious effects of free radicals produced during physical exercise (in particular by protecting against cell membrane lesions). However, no published study has shown that they have a beneficial effect in terms of sporting performance in a healthy athlete who eats well and has no dietary deficiencies. The biggest difficulty is therefore to detect populations of athletes who present a risk of deficiency, including those not competing in sports where calorie intake is often restricted (gymnastics, weigh-category sports, etc.).

32Sporting situations where these vitamins are often used:

  • at the beginning of a new training phase when the training load is high or of high intensity;

  • when travelling in a hot environment;

  • when taking part in a training course at altitude.

33It should be noted that excessive supplementation with these two vitamins can lead to a decrease in the body’s natural defence capacities, or even reduce the athletes’ aerobic capacities. High doses of vitamin C (exceeding 1 g/d) have also been shown to reduce the efficacy of the contraceptive pill.

34Food sources of antioxidants:

35our diet contains many natural sources of antioxidants such as vitamins A, C and E, some trace elements (zinc, copper, selenium) and other components of various origins (carotenoids, flavonoids, coenzyme Q10, etc.). Although high-level athletes represent a high-risk population because they often have a low antioxidant status, a balanced diet including fruit and vegetables is often sufficient to maintain an appropriate daily intake.

■ Calcium

36An inadequate calcium intake during adolescence can lead to bone mineral deficiency. To maintain an appropriate calcium balance in women, 1.5 g must be consumed daily, especially when menstruating.

37There is a direct link between calcium intake through food and bone mineralization. Some epidemiological studies established a safety threshold for calcium intake of about 1 g per day. This intake covers the requirements for bone metabolism.

38Interestingly, there is a close correlation between the sports practised and calcium intake. Thus, classing sports based on their energy expenditure and calcium consumption reveals interesting results, whereby the dietary behaviour of athletes competing in some sports (in particular endurance sports) can lead to insufficient calcium consumption.

39In general, female athletes have a lower calcium intake than men.

40Sporting situations where calcium supplementation is often used:

  • for high-risk athletes whose dietary calcium intake is insufficient;

  • for athletes with disordered eating behaviour.

41Food sources of calcium:

42our daily diet contains many calcium sources.

■ Creatine

43Creatine is not an essential element in our diet, but it is found in large amounts in meat and fish. To attain an optimal intake, two scientifically tested methods suggest the following:

  • athletes should consume between 3 and 5 g creatine over four weeks, as the creatine concentration in muscles decreases after 10 to 15 days.

  • alternatively, they should consume about 20 g divided into three doses (morning, lunchtime and evening) over five to seven days and then continue to take 3 to 4 g for 21 days.

44So far, no negative effects of creatine intake have been identified.

45An exogenous creatine intake increases the total work capacity in sports where explosive power is required (team sports, track cycling, swimming or kayak ergometer), but does not always increase maximal strength or aerobic performance. Recent studies indicate that creatine supplementation increases intramuscular glycogen storage. However, creatine can cause body mass gain, between 600 and 1000 g, due to increased water retention; thus, it can be counterproductive in sports where weight is an issue.

46Sporting situations where creatine supplementation is often used:

  • although creatine is used in many sports, evidence for its efficacy was only provided for sports where athletes repeat maximal exercises after short recovery periods;

  • when athletes want to develop their lean mass through resistance work;

  • in intermittent sports (basketball, rugby, football, racquet sports, etc.).

47Overconsumption of creatine can lead to renal and hepatic disorders.

48Food sources of creatine:

49there are various sources of creatine in our daily diet.

■ Iron

50Normally, the body contains between 3 and 5 g of iron as a trace element. About 80% of this iron is active, mainly contained in haemoglobin present in red blood cells. Beyond its role of oxygen carrier in the blood, iron has other important exercise-related functions.

51Athletes should therefore ensure that their daily diet contains appropriate amounts of iron-rich foods. Iron deficiency causes general fatigue and a reduced performance capacity when exercising. Women are a high-risk population because of their increased iron requirements due to blood loss during menstruation, and because they often restrict their food intake. A diet rich in iron will help to reduce the risk of deficiency.

52Sporting situations where iron is often used:

  • when female athletes have their period;

  • when endurance athletes experience general fatigue confirmed by biochemical indicators (low ferritin, low haemoglobin, etc.).

53Intake through food:

54the daily diet contains various sources of iron, but intestinal absorption of this element is closely linked to the body’s requirements, and to dietary composition. For instance, the intestine only absorbs 2 to 10% of the iron contained in vegetables, but between 10 and 35% of the iron from animal sources; in fact: consuming more meat is more effective than taking commercial iron supplements in maintaining iron levels in female athletes.

■ Multivitamins and minerals

55Vitamins are essential biological components which, apart from vitamin D, cannot be synthesized in the body. Vitamins are involved in various essential functions.

56Determining your vitamin status can thus be an important step before seeking supplementation advice.

57Sporting situations where these supplements are often used:

  • when athletes reduce their calorie intake;

  • when athletes compete in weight-category sports and have chosen to restrict their diet to be classed in a lower weight-category;

  • when athletes who limit their food intake for aesthetic reasons present a risk of vitamin deficiency which should be monitored;

  • when athletes must travel for long periods, especially in countries where their usual diet is not commonly available;

  • when athletes cannot vary and diversify their diet;

  • when athletes have several important competitions in a row and have to modify their eating habits.

58Multivitamins and minerals in food:

59Nothing can really prove a need for supplementation. In general, the normal daily diet is enough, as vitamins are present in large amounts in fresh fruit and vegetables, and also in various cereals. Unless you have a major energy imbalance, the water-soluble vitamin B requirements are covered by a full and varied diet.

■ Magnesium:

60Magnesium is involved in at least 300 enzymatic reactions related to energy metabolism, it is therefore essential.

61Active athletes often have an inadequate magnesium intake. A recent survey showed that this is the case for a quarter of high-level female marathon runners. Similar data were found in male athletes, especially for long-duration sports. However, it seems that the most exposed disciplines are those with weight categories (wrestling, judo, etc.) and those where weight is closely linked to success (ballet or gymnastics).

Practical applications

1. Dietary supplements or sports products?

Dietary supplement

Sports product

This term has a legal definition: a dietary supplement is a product intended for ingestion, commercialized in a standard (physiological) dose (capsule, pill, tablet, etc.) that contains a “dietary ingredient” intended to add further nutritional value to (supplement) the diet. In France, these supplements are subject to very specific regulations

Sports drinks, gels, bars. In legal terms, these products are subject to specific regulations which differ from those relating to supplements

2. It should be remembered that performance depends, above all, on various factors

3. Become an informed consumer

Before taking any supplement, there are a few questions you should ask yourself

62 Has this supplement been shown to be effective? (See classification below)

63 Do you think you are lacking in something that could be provided by the supplement?

64 Do the conditions in which this supplement is effective correspond to your situation?


Always consult a nutritional expert (doctor, dietician, scientist)

Be aware of the risks

Positive result on an anti-doping test


Poor performance


■ The supplement may be contaminated by a banned product (deliberately or not)

■ Harmful substance, whatever the dose
■ Excessive dose of an initially harmless product
■ Presence of impurities due to lack of hygiene in the manufacturing plant (lead, broken glass, animal excrement)

■ Consuming excessive quantities of some substances has the opposite effect to that expected, which may damage performance (e.g. antioxidants)

■ The active component indicated on the label may not be present in the product

4. Classification of the different supplements

This can change as scientific knowledge advances

5. Class A in detail

66Supplements for which the efficacy has been proven when used following a given protocol and in particular sporting situations

67This does not mean that they are effective for every sport and all athletes

6. Vitamins, minerals and trace elements

What you need to know

Vitamins, minerals and trace elements are necessary to the optimal functioning of all the mechanisms linked to exercise and therefore to performance

A micronutrient (vitamins, minerals and trace elements) supplement will not improve performance for athletes who do not have any deficiency

Megadoses (several times the Dietary Reference Intake [DRI]) should never be taken. Do not be tempted to take high doses. Firstly, because "more" is not "better", and secondly, because high doses can have deleterious health effects. Keep to doses close to the DRI

A massive intake of one micronutrient can lead to deficiency in another micronutrient (some use the same absorption route)
Taking a micronutrient complex rather than a single micronutrient is recommended

If you take supplements to compensate for a poor diet, you should be aware that it would be infinitely more beneficial to change your eating habits rather than taking a few micronutrients in supplement form

Before contemplating taking supplements, a full nutritional and biological check-up should be performed to assess your micronutrient intake. The opinion of medical specialists should be adhered to

Food sources

68 There are numerous vitamins, minerals and trace elements. All the food groups contribute to meeting the body’s needs


70It is important to have a varied and balanced diet (See Fact sheet No. 11 A Balanced Diet, p. 358)

7 If you do decide to take supplements...

71 Make sure you do a complete nutritional check-up before starting

72 Ask for advice from your medical entourage or, at least, talk about it

73 Choose products with an anti-doping label

74 Buy from safe selling points (famous laboratories be careful with the Internet!)

75 Favour supplements complying with European legislation, which is stricter than in most other countries

76 Stick to the doses prescribed by the doctor or, failing that, recommended on the box

77 Comply with the conditions of use (when, for whom, etc.)

78 Remember that your performances mainly depend on various other factors (training, motivation, skill, etc.)

79 Be aware that what is written on the label does not necessarily reflect what is in the product (absence of active product, presence of unmentionned illicit substances, nutritional allegations may not have been verified), particularly if the product is of undetermined origin


Beetroot and hibiscus flower cocktail

Photo credit: Thibaut Ruggeri.

80Serves 2

81Preparation time: 20 minutes


83 200 ml organic beetroot juice

84 20 g dried hibiscus flowers

85 200 ml water

86 200 ml organic red fruit juice

87Make an infusion: heat up the water and add the hibiscus flowers.

88Allow to cool.

89Add the beetroot juice and the red fruit juice. Mix well to combine.

90Serve chilled.


92You can make the beetroot juice yourself using a juice extractor.

93Wash and peel an organic beetroot. Chop it and put it in the juice extractor to extract the juice.

94Chef’s note

95This drink is rich in polyphenols, which are contained in the beetrood and red berries. This gives it antioxydant properties, and makes it ideal for athletes. In addition, beetroot juice is rich in nitrates, which have a favourable influence on energy consumption during exercise.

96Nutritional analysis per person

Energy (Cal)

Carbs (g)



Lipids (g)

Protein (g)




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