It has all the makings of a delicious smoothie – a dollop of almond butter, an avocado, a few slices of mango, a handful of blueberries, a sprinkle of cocoa powder and perhaps a glug of soya milk.

As a tasty, vegan-friendly drink to start your day, it is packed with nutrients and will do wonders for your health. But it may be doing far less good for the planet.

There is no doubt that meat – beef in particular – makes an unsurpassable contribution to the planet’s greenhouse gas emissions. It also devours more land and water and causes more environmental damage than any other single food product. The recent rigorous report by the EAT-Lancet Commission recommends reducing our consumption of animal products to not only benefit human health, but the health of our planet. Even the “greenest” sources of meat still produce more greenhouse gases than plant-based proteins.

But anyone looking to adopt a vegan or vegetarian diet for environmental reasons may also want to consider whether there are some plant-based foods that also come with a heavy price.

“Nothing really compares to beef, lamb, pork, and dairy – these products are in a league of their own in the level of damage they typically do to the environment, on almost every environmental issue we track,” says Joseph Poore, a researcher at the University of Oxford who studies the environmental impacts of food. “But it’s essential to be mindful about everything we consume: air-transported fruit and veg can create more greenhouse gas emissions per kilogram than poultry meat, for example."

Delicate fruits like blueberries and strawberries, for example, are often imported to Europe and the US by air to fill gaps left when local fruit are out of season. Research by Angelina Frankowska, who studies sustainability at the University of Manchester, recently found that asparagus eaten in the UK has the highest carbon footprint compared to any other vegetable eaten in the country, with 5.3kg of carbon dioxide being produced for every kilogram of asparagus, mainly because much of it is imported by air from Peru. She and her colleagues found, in fact, that the succulent green stalks have the largest environmental footprint of any of the 56 vegetables they looked at, including its land use and water use (which was three times greater than the next highest).

More from The Vegan Season on BBC Good Food

Without carefully considering where our food comes from and how it is grown, our diets can have unintended consequences. Take the strange case of two vegans in an Italian study who were found to have an environmental impact considerably higher than many meat-eaters. When the researchers dug a little further, they discovered the pair exclusively ate fruit.

“They ate a huge quantity of fruits,” explains Francesca Scazzina, an expert on human nutrition at the University of Parma, Italy. “In fact, I remember [it was] 7-8kg (15.4 to17.6lb) per day of fruit. We collected their data in the summer so they especially ate watermelons and cantaloupes.”

The water, land and carbon footprint of growing and transporting such large, perishable fruit meant the environmental impact was far larger than they had expected. Once the data from all 153 vegans, vegetarians and omnivores in the study was taken into account, however, it showed that eating meat was on average worse for the environment.