A-Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance- Part 16

Journal Title (Medline/Pubmed accepted abbreviation): Br. J. Sports Med.
Year: 2011
Volume: 45
Page numbers: 73-74
doi (if applicable): 10.1136/bjsm.2010.081505

Summary of the review:

This review covers the use of folate, γ-aminobutyric acid (GABA), γ-oryzanol, ferulic acid, γ-hydroxybutyrate (GHB), and γ-butyrolactone in sports performance.
                Folate is a vitamin that is important in cell division. It is imperative for an athlete to be in good folate status in order to develop adequate, healthy, red blood cells since these have a fast rate of turnover. Folate is present in many foods including green, leafy vegetables and fortified cereals. It has been shown that male athletes tend to have adequate folate intake as long as their energy intake is adequate although active females tend to exhibit higher incidences of inadequate intake. Supplementation above the recommended levels has not been shown to increase performance, either among those in good or poor folate status.
                GABA is a major inhibitory neurotransmitter in the brain and is responsible for relaxation and sedation. A synthetic form of GABA has been shown to increase time to fatigue. It has also been shown that GABA ingestion may increase the effects of resistance training in skeletal muscle. More research is required to confirm these effects and to elucidate the mechanism by which GABA can improve performance.
GHB is a short fatty acid found in the brain that is a precursor for GABA but also may have its own functions in the brain. γ-Butyrolactone is a precursor to GHB and therefore may have similar effects. It has been shown that GHB can increase mood and sex-drive and can help establish sleep patterns. A recent study showed that GHB may increase levels of growth hormone during sleep causing deeper levels of sleep and potentially enhancing muscle growth. GHB is not typically found in the diet but is found in some natural and/or artificial flavors. GHB or any of its precursors have not yet been studied in an athletic setting. Concerns associated with GHB are side effects such as drowsiness, alcohol-like inebriation, and dizziness. Further the potential for accidental overdose exists and this could lead to coma, respiratory depression, and death. The article notes that there have been case reports of GHB dependence and prolonged usage. Given that there is no evidence of benefit to athletes and some potential risks, GHB is not recommended for athletes.
                γ-Oryzanol is found in the fat-soluble portion of many plants, including rice, and is composed of plant sterols and ferulic acid. Due to the sterols’ structural similarity to cholesterol, γ-oryzanol has been purported to lower blood cholesterol and augment testosterone activity. Therefore, it is hypothesized (and promoted) that γ-oryzanol could increase the effects of strength training in ways similar to testosterone. γ-Oryzanol is not taken up readily by the small intestine due to its hydrophobic character, but ferulic acid is. There are only a few studies to date that investigate either γ-oryzanol or ferulic acid and performance and none that strongly corroborate the claims.

Interpretation of findings/Key practice applications:

 It is healthful to maintain good folate status. Supplementation for females with low folate status does improve several markers of folate status, but, in the studies so far available, did not improve performance. There is insufficient evidence to recommend GABA, γ-oryzanol, ferulic acid, γ-hydroxybutyrate (GHB), or γ-butyrolactone for sports performance at this time.
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