Choosing a healthy and environmentally aware diet is a modern problem. Well-intentioned people are puzzled. Should we pick up “plant chicken pieces” that come from a factory in Holland, or a leg of grass-fed British lamb? Which is the better choice for both personal and planetary health?

If the Veganuary entreaty has struck a chord with you, your choice should be a no-brainer: fake, factory meat is clearly preferable to the real thing. No animals were killed for it, and even if no one other than a food technologist really understands the processes and ingredients that created it, it must surely be a boon for the planet. If it’s vegan, it must be green and healthy, right?

Supermarkets, global food manufacturers and biotech and chemical companies have enthusiastically embraced Veganuary. Fast-food enterprises, formerly seen as the nemesis of public health and the environment, have recast themselves as their saviours. McDonald’s was feted when it launched its first vegan Veggie Dippers meal: nuggets that contain around 40 ingredients, many of which can’t be found in any domestic larder, served with chips and a soft drink. And although Greggs hasn’t made public the ingredient composition of its new vegan “steak” bake, this hasn’t stopped it earning extensive kudos for the product. The composition of KFC’s recently launched “zero chicken vegan burger” is a similar enigma, but that needn’t concern its marketing department. Just when ultra-processed food manufacturers were being skewered for the health damage their products cause, the plant-based push has given them a get-out-of-jail-free card.

It’s a pity that the public food discourse has become so binary: animal foods bad, plant foods good. Perhaps it’s time to reacquaint ourselves with the defining characteristics of food that keeps us, and the planet, healthy. Whether it comes from the plant or animal kingdom is irrelevant. What really matters is how that food is produced. Though some animal foods are factory farmed in a way that harms animals and the environment, not all animal products are equally damaging.

The sausage that sits on your full English platter at a motorway service station is, excuse the pun, quite a different animal to that which arrives in your box from a company such as Riverford, which sells food to consumers direct from its producers. Its milk and meat come from animals that are reared on organic farms, where they are free to range (weather permitting). Free-range farming produces food using the sun’s energy, on land that could often serve no other agricultural purpose.

In turn, free-range livestock fertilise the soil, and the pastures they graze on soak up surplus water and prevent soil erosion. This is quite different from livestock reared indoors, using methods that contribute to deforestation and water pollution. Where livestock manure builds soil fertility, fossil fuel-derived pesticides and fertilisers sprayed on intensively grown plant crops have depleted it. Without fertile soil, vegans and omnivores alike go hungry. As livestock producers put it: it’s not the cow, but the how.

But, in a process fuelled by Netflix and the BBC, our consciousness has been flooded with visceral documentaries based on worst-case environmental and animal welfare scenarios. Thoughtful viewers who want to eat ethically but are unfamiliar with the mechanics of food production can’t be blamed for thinking these depictions represent all livestock production. Yet not all meat, eggs and dairy products come from factory farming; 52% of the eggs we buy in the UK, for example, are free range.

These days it’s fashionable to eulogise plant foods as the secret for personal health and sound stewardship of our planet. But in the process of squaring up to the challenge of climate breakdown, we seem to have forgotten that plant foods too can be either badly or well produced. Wholemeal bread seems like a wholesome, peaceful, uncontentious food choice until you learn that two-thirds of bread sampled by Defra contained residues of the pesticide glyphosate. Classed as a “probable carcinogen”, glyphosate has no safe level in food, yet it has contaminated our web of life.

Perhaps you agonise over whether you should ditch cow’s milk for almond milk. If so, did you realise that your pint of plant milk was almost certainly manufactured from almonds grown in California, where farmers deploy a chemical cocktail of insecticide and fungicides that kills off millions of honeybees every year? Might organic British cow’s milk be a more responsible choice?

And think of all those avocados we mash on toast. Although they seem the pure embodiment of healthy plant food – so much better than the omnivore’s eggs or black pudding – they take on a sicklier hue if you know that the lucrative Mexican avocado trade is controlled by drug cartels, which are driving the clearing of Mexico’s native forests.

As long as we demonise animal foods and eulogise plant foods, any prospect of a natural food supply is shattered. We are left to depend for sustenance on the tender mercies of the techno-food corporations that see a little green V and the word “plant” as a formula for spinning gold from straw through ultra-processing. I for one don’t relish that.

• Joanna Blythman is an investigative journalist