Rice bran – czy gamma-oryzanol jest dopingiem?

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Rice bran – czy gamma-oryzanol jest dopingiem?

Rice bran is famous for stimulating muscle building and muscle repair, which is why it is used more and more often for sport horses. It owes this mainly to one substance – gamma-oryzanol – which often raises doubts, especially among owners of horses competing actively at high-level shows. Why?

Rice bran comes from the processing of brown rice in order to produce white rice, and it is high in fat, because it contains as much as 20-25% rice oil. Gamma-oryzanol is a fat-soluble compound, and the richest natural source of this substance is the rice bran oil just mentioned.

Gamma-oryzanol supplementation attracts a great deal of interest in the feeding of horses in intense physical work. In vitro studies have shown a beneficial effect of this substance on skeletal muscle damage in horses in active training. Gamma-oryzanol does, however, raise controversy around doping, because it stimulates muscle development and speeds up the burning of fat tissue, which some people believe may have a direct effect on improving the performance of horses competing at events.

Substances regarded as doping are strictly defined by the latest list of substances prohibited and controlled by the FEI (you will find the link beneath the article 🧐). Gamma-oryzanol has been removed from it. Does that mean it can be used in sport horses during competitions?

To clear up any doubt, let us also look at how gamma-oryzanol affects a rise in the blood testosterone level, which appears on the list of substances controlled by the FEI. Studies carried out on endurance horses fed gamma-oryzanol showed that at no point did the testosterone level in their urine or serum rise above the critical value (the doping threshold set by the FEI). Interestingly, other studies in animals suggest that gamma-oryzanol may even reduce testosterone production.

Podsumowując…

There is no justification for horses having to stop eating feeds that contain rice bran, especially when it makes up only part of the recipe. Intake of such small amounts of this compound in a horse’s everyday diet is entirely safe, and no withdrawal of the feed is required before a competition. By law, gamma-oryzanol derived from the lipid fraction of rice bran may be used in sport horses, because it has been removed from the FEI list of prohibited doping substances. According to the latest knowledge, gamma-oryzanol also has no direct effect on improving the performance of horses competing at events, or on raising the testosterone level in urine and blood.

>List of substances prohibited for horses (Equine Prohibited Substances List)<

robert-gryzonie

Notes:

Lista niedozwolonych dla koni substancji (ang. Equine Prohibited Substances List): https://inside.fei.org/sites/default/files/2024%20Prohibited%20Substances%20List.pdf

Eslami, Saghar, et al. “Effects of gamma oryzanol supplementation on anthropometric measurements & muscular strength in healthy males following chronic resistance training.” The Indian journal of medical research 139.6 (2014): 857.
Kobayashi, Eri, et al. “Evaluation of γ-oryzanol accumulation and lipid metabolism in the body of mice following long-term administration of γ-oryzanol.” Nutrients 11.1 (2019): 104. Mirowski A., “Gamma-oryzanol jako składnik odżywczy o właściwościach prozdrowotnych” Życie Weterynaryjne 96(11)(2021): 767-768.
Mösseler, A., et al. “Can oral intake of gamma-oryzanol (experimentally given orally as pure substance) result in doping relevant testosterone levels in the urine of mares and geldings?. The Impact of Nutrition on the Health and Welfare of Horses.” Wageningen Academic Publishers 128 (2010): 293-296.
Ostaszewski, Piotr, et al. “Effects of β-hydroxy-β-methylbutyrate and γ-oryzanol on blood biochemical markers in exercising thoroughbred race horses.” Journal of Equine Veterinary Science 32.9 (2012): 542-551.