For meat: at long last some scientists have come forward to debunk claims that meat eating is “evil”:
  https://www.breitbart.com/environment/2019/11/28/scientists-counter-claims-meat-evil/

“A team of UK scholars have fired back at unscientific claims by PETA and other groups that veganism is a “greener” option that eating meat, insisting that meat has “massive social benefits.” Speaking at a panel in central London, scientists from the University of Edinburgh and Scotland’s Rural College argued that eating meat is crucial for the physical and mental health of children, especially in developing countries, adding that that alternatives to livestock farming would not improve land use. “We feel that while livestock production has a range of economic, social and environmental costs and benefits, the costs have perhaps been receiving far more attention recently than some of the benefits,” said Professor Geoff Simm, Director of Global Academy Agriculture and Food Security at the University of Edinburgh. “Meat has massive social benefits,” Simm said. “It’s an important source of dietary protein, energy, highly bioavailable micronutrients, even small amounts of animal-sourced food have a really important effect on the development of children, in the developing world on their cognitive and physical development and they are really important.” Simm also said that claims that veganism would benefit land use are not based on serious research, the Telegraph reported. “Often the argument is made that going vegan would minimise land use, and the modelling studies that have been done demonstrate that that’s not the case,” he said. Prof Mike Coffey, from Scotland’s Rural College expressed his agreement, while adding that livestock breeding actually contributes positively to the environment. “It’s completely unnecessary to go vegan,” Coffey said. “If everybody went vegan it would be devastating for the UK environment. Animals bred for food help boost biodiversity.” Concerns over bovine methane emissions are also being effectively addressed, the panel declared, since researchers are attempting to breed cattle that grow faster and eat less, which could further reduce the amount of methane released by cows. Already the difference in methane emissions from best and worst cattle was about 30 percent, Prof. Coffey said, which means that if all UK farmers used the most digestively efficient animals carbon emissions could be reduced by nearly a third. Experiments in breeding is leading to dairy cows that consume less feed for the amount of milk they produce, Coffey said, and soon livestock farmers will be able to measure methane emissions from groups of animals. “My expectation is that at some point in the near future there will be product labels that relates to the efficiency or carbon impact of the food,” he said. Caution is to be recommended before recommending veganism as a cure-all, said Edinburgh University Professor Andrea Wilson.”

     But, now the vegans have struck back, this time with a focus upon the bedroom:
  https://www.dailymail.co.uk/news/article-7721429/Vegan-men-best-lovers-just-one-meat-free-meal-improve-skills-bed.html

“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.”

     This is hardly strongly scientific, having an extremely small sample, but who knows there could be further research done, with expensive tax payer funded research grants, to explore this hypothesis further. And what would it matter anyway, since sex should not be the equivalent of some Olympic style sports event!