Level A: strong evidence
Creatine monohydrate: the most researched supplement in the history of sport. It increases PCr resynthesis, improving performance in explosive efforts and short-duration strength work. 3 to 5 g/day is enough. Safe for healthy adults.
Caffeine: 3 to 6 mg/kg, 30 to 60 minutes before exercise. It reduces perceived effort, improves alertness and can increase endurance and strength performance by 1 to 3%. Tolerance builds with continuous use. One or two "caffeine holidays" per week preserve the ergogenic effect.
Beta-alanine: buffers lactic acid in the muscles during efforts of 1 to 4 minutes. Dose: 3.2 to 6.4 g/day, split up to reduce the tingling (paresthesia), a common and harmless side effect.
Level B: moderate evidence
Nitrate (beetroot juice): converts into nitric oxide in the body, reducing the oxygen cost of exercise. The effect is more pronounced in recreational athletes than in elite athletes. Dose: ~500 ml of concentrated beetroot juice, 2 to 3 h before the race.
Vitamin D: deficiency (below 30 ng/mL) is associated with a higher risk of stress injuries and immunosuppression. Athletes who train indoors or live at high latitudes have a higher prevalence of deficiency. Dosage based on a blood test.
Level C or no evidence
BCAAs, HMB, glutamine, L-carnitine, CLA and the vast majority of thermogenic "fat burners" have no convincing evidence of benefit for athletes who already consume adequate protein. The money spent on these products would be better invested in quality food.
The starting point for reading supplement evidence is the ABCD framework of the Australian Institute of Sport (AIS), also aligned with the IOC. Group A (strong evidence for specific situations) holds the few ergogenics with solid backing: caffeine, creatine, beta-alanine, dietary nitrate, sodium bicarbonate and glycerol, plus sports foods and some medical supplements such as iron and vitamin D. If a product does not appear in that group, skepticism is the most honest stance.
Creatine monohydrate is the most studied supplement in the category, with more than a thousand papers published since the 1990s according to the ISSN position stand (Kreider, 2017). The suggested maintenance dose is 3 to 5 g per day after muscle saturation. The effect is consistent in short, intense efforts and in strength, not in long-duration endurance.
Caffeine came off the WADA prohibited list in 2004 and became the most used legal ergogenic aid in elite sport. The meta-analysis by Southward (2018) estimated an average improvement of about 2 to 3% in time trial time with doses of 3 to 6 mg/kg taken about an hour before. Nitrate from beetroot juice, in turn, reduces the oxygen cost of submaximal effort by around 3 to 5% (same VO2 per watt), and vitamin D is worth monitoring because the pooled prevalence of insufficiency reaches 56% among athletes (Farrokhyar, 2015), with a documented impact on bone health.
The takeaway
The ABCD framework of the Australian Institute of Sport does a good job of separating the wheat from the chaff: of the hundreds of products sold as ergogenics, only caffeine, creatine, beta-alanine, nitrate, sodium bicarbonate, glycerol, iron and vitamin D have real backing, Group A. Everything else (BCAA, HMB, glutamine, L-carnitine, CLA, the trendy thermogenics) lives in Group C, with no evidence to justify the price. Creatine alone has accumulated more than a thousand studies since the 1990s and remains the most studied supplement in sport, with 3 to 5 g/day being enough to maintain the effect. Before opening your wallet for the next nicely labeled tub, it is worth asking: is this product in Group A, or only in the advertising? The right answer saves money and sometimes saves you a positive anti-doping test.
