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IN OUR information-saturated digital age, where we can pick and choose our own narrative about how the world works, I have often wondered if this has an impact on the rate of cultural change. As an ethnobotanist trained to study our cultural attitude towards plants and their uses, I have been witnessing with total fascination what seems to be a rapid shift in how plants are viewed in received nutritional wisdom. I wonder if this may be a sign of things to come.

I first noticed the trend about 15 years ago with the emergence of the “paleo” diet movement. This largely repackaged ideas from the ultra-low carbohydrate diets that came before it, but underpinned them with a “return to nature” narrative. According to the paleo school of thought, in order to be truly healthy, we need to eat as our hunter-gatherer ancestors did, ditching as many carbohydrates as possible. This meant a diet based predominantly on meat, with a few low-carbohydrate vegetables like leaves, stems and flowers. Pretty much all fruit, however, was off limits due to its sugar content.

Many questionable justifications have been used to support this. For instance, in our deep Palaeolithic past, fruit was available, but highly seasonal. So, the argument went that, while consuming restricted amounts in a short window in the summer was fine, today’s hyperabundance and year-round availability was the root cause of chronic diseases.

It might be easy to dismiss these ideas as only belonging to a particularly devoted set of niche dieters. However, such thinking quickly started popping up in different guises in the mainstream and even, albeit in a diluted form, as government health advice in some places.

What is interesting about the paleo diet idea to a botanist is that it assumes all early humans lived in the world’s temperate zones where fruit is seasonal, as (perhaps unsurprisingly) do the creators of these diets. It is almost like humans aren’t a species that evolved in the tropics at all. This Western-centric focus is often extended to the idea that you should specifically avoid “tropical” fruits as they are higher in sugar.

That is another curious claim, as there doesn’t appear to be any data that supports the generalisation. In fact, the highest sugar fruits I can think of, like dates and grapes, aren’t tropical, but temperate in origin. That is before we consider that animals in temperate climates are subject to seasonal availability too. Think of bird eggs and spawning salmon. Does that mean we should avoid these too?

“If we are only meant to eat things that “want” to be eaten, I have really bad news for meat lovers”

So it was an enormous surprise that, over the past few months, leading lights in the paleo and carnivore diets community have seemingly reversed some of their most central beliefs about plant foods. Several are now saying that adding fruit to their diets over the pandemic has transformed their health, including many who claimed cutting out fruit had the same effect just a year or two ago.

To justify this change of heart, they are pointing to (actually often very sound) evolutionary reasoning, such as our excellent red-green colour vision compared with that of many animals, which is thought to allow us to detect ripe fruit faster. Voices that once described fruit as “bags of sugar” are now pointing to our instinctive preference for sweet flavours as justification for eating it.

From a scientific point of view, this cultural shift all seems like a positive step. That is because the research consensus is that consuming fruit is beneficial for our health, but the vast majority of us aren’t eating enough of it.

However, cultures are funny things. The fruit U-turn seems to have coincided with some paleo diet devotees calling for the exclusion of vegetables. It is now argued that these are full of potentially toxic compounds designed to deter herbivores, and so can be harmful to our health. Appealing to imagined ideas of human evolution, proponents are now arguing that fruit is safe as plants “want” these parts to be eaten in order for the seeds they contain to be spread around in faeces, hence they don’t contain these toxic compounds.

Leaving aside the fact that the distinction between “fruit” and “vegetable” isn’t based in any kind of botanical reality, but is just a cultural quirk, it is true to say that many common edible plants do contain toxic compounds. Yet these are at very low doses for us and toxicity is dose dependent. More fundamentally, if we are only meant to eat things that “want” to be eaten, I have really bad news for anyone who consumes meat.

In the past, profound dietary shifts like this could take decades, even centuries to take hold. However, in the internet age, they seem to be unfolding in a matter of months. Given how quickly radical ideas can diffuse into more mainstream culture, I wonder if we’ll see them become widely accepted in years to come, despite the lack of evidence.