The drug-testing bodies in sports always say the cheaters are ahead of them. It's a constant struggle to catch up to the new science and develop a test to detect it.
Now the World Anti-Doping Agency, the IOC, MLB, NFL and all the rest may have to chase athletes who are behind them too. According to this Reuters article, ancient Olympians used to chew on raw animal testicles to boost performance.
WADA has hundreds of substances on its prohibited list, but testicles are not listed. I also searched for "gonads," "bull testicles," "sheep testicles" and even "human testicles." (Don’t pretend an athlete wouldn't resort to cannibalism to win gold.) None of them are banned. Yet I will probably be banned from the coffee shop where I did this research if they check the search history on the computer. It's unfair, but journalism requires sacrifice.
Athletes, have at it. It's not cheating if it's not against the rules. Eat testicles to your heart's content. Luckily, you're in the right country for it. The Scottish eat haggis, so it's not as if anyone will look at you weird for eating testicles. This British cooking website even has a recipe for breaded testicles with stewed peppers and onions. Mmm. The taste of victory.
You can thank me for all this information later. But not now. It's rude to speak with your mouth full.