Journal Title (Medline/Pubmed accepted abbreviation): Br. J. Sports Med.
doi (if applicable): 10.1136/bjsports-2011-090102
Iron Iron deficiency is one of the most prevalent vitamin deficiencies in athletes. Peak performance relies on adequate iron status for efficient delivery of oxygen to the muscles; it is necessary for the function of hemoglobin and myoglobin. In addition, iron is present in the electron transport chain, and is therefore imperative for effective utilization of oxygen to generate ATP energy. Female athletes (in child-bearing years) have a greater risk for deficiency than male athletes due to menstrual blood losses and typically lower intake. The recommendation for adult male athletes is 8 mg/day and for female athletes is 18 mg/day. Iron from meat, heme iron, is more efficiently absorbed and iron from plants (examples include spinach and beans) is less easily absorbed but more often comprises a large part of total iron intake. Ascorbic acid (vitamin C) tends to increase iron absorption and caffeinated beverages tend to decrease absorption. It is well established that iron supplementation can increase performance in iron deficiency-anemic athletes, but it is debated if athletes with low iron status who are not anemic experience benefits from iron supplementation. Anemia may take 6-8 wks to improve with the use of oral supplementation. A faster alternative to oral supplementation is intramuscular injections. A more rapid method, though banned by the World Anti-Doping Agency, is intravenous infusions of iron. There have not been benefits of iron supplementation in athletes with healthy iron stores.
α -Ketoglutarate (AKG) AKG is a compound in the tricarboxylic acid (TCA) cycle, and is therefore a key player in energy generation. AKG also provides a source of glutamine to stimulate protein synthesis. Supplementation with AKG may increase anabolic hormones such as insulin, growth factor, and insulin-like growth factor I, however there has been very little research to date on humans and AKG.
α-Ketoisocaproate (KIC) KIC is a product of leucine metabolism, a precursor to β-hydroxy β-methylbutryic acid (HMB; a compound thought to encourage muscle synthesis) and is thought to have biological activity of its own. KIC may attenuate exercise-associated soreness and/or be converted to ketone bodies and be used as an energy source during intense exercise. At this point, there is not sufficient evidence to recommend KIC as an ergogenic aid.
It is important for athletes to maintain healthy iron status in order to prevent ailments in sports performance but also fatigue and other symptoms related to iron deficiency anemia. There is not sufficient evidence to recommend use of AKG or KIC for enhanced muscle growth.