It's the stuff you learn watching QI with Sandi Toksvig late on a Friday night, right?!

A devil's advocate was a person appointed by the Roman Catholic Church to challenge a proposed beatification or canonization, or the verification of a miracle.

They "argued against the canonization of a candidate in order to uncover any character flaws or misrepresentation of the evidence favouring canonization".

It was hard to be a saint in the old days.

However, In recent history - with devil's advocates being made redundant and all - pretty much anyone can get a start.

There's not a lot of fact-checking going on now in the departments of canonization, miracles and Facebook alike.

In fact, you have to be your own devil's advocate.

Bingeing food documentaries greedily, like I do, you have to take them all with a grain of salt.

If you have a girlfriend who has recently gone vegan seemingly out of the blue, there's a good chance they've watched What the Health.

If it's a male colleague or partner, it might have something to do with The Game Changers.

Advertised as "The Health Film That Health Organisations Don't Want You To See", What The Health advocates a solely plant-based diet for peak health.

What the Health draws links between eating animal proteins and getting cancer, type 2 diabetes, and generally poisoning you with toxins.

Despite the backlash to the film from doctors, nutritionists and investigative journalists over allegedly cherry-picking its research, the film unnerved me about how much meat we eat.

Critics argue that the film's claims (i.e. eating eggs is as bad for you as smoking cigarettes) are nuts and overblown, while supporters say that there's nothing untoward about discussing the benefits of a plant-based diet.

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Now, The Game Changers has grabbed predominantly the men's attention.

Voiced by former bodybuilder and actor Arnold Schwarzenegger, The Game Changers explores the meat industry and how eating meat is marketed as "manly" to men so that they can build muscle to become stronger.

Throughout history and even today, the documentary says some professional fighters are fueled by plants, so its aim is to understand how plant energy makes them so powerful.

It profiles the strongest man in the world, German-based Patrik Baboumian, who holds several world records in power lifting. He became a vegetarian in 2005 and vegan in 2011.

Then the film went on to appeal to the everyday hero.

A fascinating experiment on male athletes in The Game Changers showed the profound impact of a plant-based diet on sexual vitality in men.

This scene alone gave veganism new-found, cult status.

But the problem with following any one-size-fits-all diet - medical conditions aside - is that the theories behind them get blown out of the water every few years in line with new research.

Firstly, protein was pitched as the big evil in the western world, then came fat, followed by sugar, then carbohydrates, gluten and, most recently, meat.

A strict, lifelong gluten-free diet is the appropriate medical treatment for coeliac disease but researchers have become increasingly vocal about the implications of this diet on people who are not gluten-intolerant.

Several studies have shown gluten-free diets (without proper supplementation) may not provide adequate trace elements and vitamins.

At the end of the day, however, eating a little less meat and a few more vegetables can't be bad for any of us.

Of course, someone out there will argue against it.

Devil's advocates are like that!