Table 1.

Effective situations for supplement use.

Situations	Notes
1. Some nutrients are deficient due to characteristics of the diet.	Athletes can become nutrient-deficient for several reasons, such as weight loss, food allergy, intolerance (e.g., lactose or gluten) (25), food preference, and dietary styles (e.g., vegan or vegetarian) (26). In these situations, supplements can be effective for preventing or countering expected deficiencies.
2. Having meals is difficult due to a disease process.	Respiratory disease (mainly upper respiratory tract diseases) is reported as the most common disease in athletes (27). The incidence rate of respiratory disease in elite athlete populations has been reported to be higher compared to that of the general population (28). The higher incident rate in elite athletes can be connected to a reduction in immune system functioning by high-intensity exercise (29–31) or overseas expeditions (32–34). For a summary, see the latest review (35). Furthermore, studies have confirmed that appetite (36) and food intake were reduced during disease (37). The HPSC group is concerned that athletes, who tend to be more active than the general population, are more prone to severe sickness.
3. Accessibility to quality foods is difficult during athletic travel.	Many elite athletes experience situations in which they travel abroad for practice and competition. If the habitual foods and the food hygiene of the places where they stay are not organized, deficiencies of nutrients or even illness and infections may occur due to the limited availability of food options (38). Thus, the HPSC group believes that it is important to investigate the food environment of athletics venues and prepare supplements that can be effective for the maintenance of athletes’ conditions before traveling abroad.
4. Preparing food can be restricted by external situations such as disasters or outbreaks of infection.	In countries where disasters (e.g., tsunami or earthquake) frequently occur, the pathway to preparing foods is often shut down. Similarly, due to infections such as COVID-19, certain geographic areas can be locked down, closing off entire food pathways. For example, Japan frequently experiences disasters in a given year. When food pathways are closed in Japan, carbohydrate-based foods are provided to refugees (39) mainly in the form of rescue energy intake (40). This situation can negatively impact an athlete's body composition (41), as nutrients other than carbohydrates are needed to prevent deconditioning. Compared to conventional foods, supplements as a stockpile may be more useful in this situation since supplements usually have less water content and less chance of food spoilage (42).
5. Having a meal before, during, and after exercise is difficult.	When meal timing is restricted due to the characteristics of the sport, supplement use may be more beneficial than meals. For example, athletes engaged in snow sports spend most of their time on mountains for practices and competitions. In this scenario, supplement use is useful as it facilitates easy and convenient acquisition of necessary nutrients and components. In addition, studies have confirmed that appetite was reduced after both aerobic (43–46) and resistance (47, 48) exercises. To promote recovery between practices or competitions, supplements that have faster digestibility (49) are more effective for selectively obtaining target nutrients compared to meals. Yet, at the same time, the reduction in appetite recovers to that of resting baseline within 60-min after exercise (44, 47, 50). Thus, the “meal first” strategy, which can provide multiple nutrients to a body simultaneously, is recommended if prompt recovery is not necessary.
6. Achieving targeted intake of components to enhance performance is not practical.	Achieving the targeted intake of performance-enhancing components [e.g., caffeine, creatine, nitrate, β-alanine, and sodium bicarbonate (13)] may be difficult only from meals or whole foods. For example, several systematic reviews have reported that consuming 3 mg/kg weight of caffeine at least 60-min before exercise is beneficial to enhance performance (51–53). If the weight of athlete is 80 kg, the targeted intake of caffeine should be 240 mg equaling about 400 ml of coffee. However, finishing 400 ml coffee 60 min before exercise is not an easy way to obtain the benefit of caffeine. While this depends on the weight of the individual and one's food preferences, using supplements could be more convenient compared to coffee in this scenario.