If you know where to look in academic journals, it turns out there is indeed lots of good evidence to suggest that some organically grown crops can be higher in certain vitamins and minerals. The tricky thing is, there are also lots of studies that suggest the exact opposite is the case. The more you delve into the literature, the more confused and conflicted the answer to what seems like a simple question appears to be. There is very good reason for this.
Imagine you are a scientist trying to solve this conundrum. You might, for example, buy a range of fruit and vegetables, grown both organically and conventionally, then test these crops for nutrient content and compare the results. After all, this kind of like-for-like comparison most realistically reflects the choices available to consumers, right? But here is the problem: this isn’t a like-for-like comparison at all. The crop varieties grown by organic farmers are often not the same as those grown by conventional ones. As genetics tends to be the principal factor that determines the chemical make-up of a crop, the unique DNA of one variety can result in a very different nutrient profile to another, even if they are grown under the exact same conditions. One head of lettuce might look and taste nearly identical to another variety grown next to it, but their level of nutrients , like vitamin A can vary 20-fold.
The organic and conventional crops on your supermarket shelves will probably differ in other important ways, too. They are often grown in very different climates, even continents, with distinct soil chemistry, irrigation levels, ambient temperatures and sunlight exposure, all of which have been shown to dramatically affect the nutrient composition of crops. Studies have demonstrated that this can vary in the same plant – with two apples from the same tree having different levels of nutrient – even on two sides of the same fruit.
All this is before we get on to how the storage, transport and display of crops can affect their nutrient levels. For instance, we know that simply being exposed to the fluorescent lights of supermarkets can result in a crop of spinach being similar to a crop stored in darkness. This is because even once harvested, the fresh fruit and vegetables are still alive and so constantly react to their environment, like plants in a field. This creates a hugely complex set of variables that it is almost impossible to control for.
There are many reasons why you might wish to go organic. But given the complicated and often contradictory nature of the evidence so far, it is impossible to claim that organically grown fruit and vegetables are automatically a nutritionally superior choice without cherry-picking studies (or parts of studies) that support this narrative, while ignoring evidence to the contrary. (by James Wong, botanist and science writer, in the New Scientist, 6 July 2019)