London - Champions of a meat-free diet tend to be passionate about the cause. And passion, it seems, is the operative word.
For a medical experiment suggests that men who have a vegan diet may be better lovers.
If a Netflix documentary is to be believed, just one meat-free meal could improve their performance in the bedroom.
The 'Game Changers' casts doubt on the idea that "real men eat meat". It includes an experiment led by US urologist Dr Aaron Spitz, which measured the virility of three male athletes after different meals.
The men were given burritos containing grass-fed beef, organic chicken or organic pork on one night, then a plant-based replacement burrito containing soy and pea protein the following night.
The programme stopped short of seeing how well men performed with their partners, but instead looked at their activity as they slept.
After a meat-free meal, the men’s night-time sexual arousal lasted three to four times longer through the night. The athletes concluded that they might want a vegetarian dinner on their next date, with Dr Spitz stating: "This is not a scientifically validated study, but the results that we are seeing are very exciting. I think this is going to wake a lot of people up."
The programme, presented by British mixed martial artist James Wilks, states that a single meal can affect blood flow throughout the "entire body".
It asked three college athletes to record its more intimate effects.
The athletes – who were a basketball player, a baseball player and a hurdler – wore a monitoring device which measured their arousal during the night and how many minutes they spent in an excited state.
After switching from meat to a plant-based dinner, the athletes’ night-time sexual arousal lasted between three and 4.77 times longer.
Dr Spitz said: "When I think of a manly man, I think of somebody who has strength, endurance, sexual prowess and fertility. In fact, what the scientific studies are showing is that the more meat men eat, the more quickly they lose their manly manhood."
But Dr Raj Mathur, a consultant gynaecologist at Manchester University NHS Foundation Trust, said: "We can’t really draw any clinical lessons from this, unfortunately. I certainly don’t think we can advise men to stop eating meat on this basis.
"Men who experience erectile dysfunction should of course look at their lifestyle – weight, smoking, exercise, illnesses and stress are all important."
Some experts believe too much meat in the diet may be bad for men’s staying power in the bedroom, because it slows blood flow to their genitals and restricts the dilation of their arteries.
Plants may be good for sexual prowess because they tend to boost nitric oxide levels in the body, which increases blood flow.