Organic produce can contain more phytochemicals than non-organic produce. Many studies (but not all) have found organic produce contains significantly higher concentrations of antioxidants and other healthy compounds, such as anthocyanins, flavonoids, carotenoids and phenolic compounds. It turns out that we may have pests to thank for this difference.
When a leaf is injured, whether the cause is a rabbit, an aphid or a harvest knife, the plant’s immune system is triggered. The chemicals that are released trigger a complex set of chemical reactions that end up producing healthier produce.
Scientists examined this phenomenon by creating 50 or 100 holes in strawberry leaves using a paper hole punch; this was considered to be enough damage to trigger a response but not reduce photosynthetic potential significantly. Fruit harvested from the injured plants two weeks later had higher rates of healthy phytochemicals than fruit from unharmed plants. The researchers hypothesize that the effect of leaf damage on phytochemicals may be greater in fruit than leafy produce (keep in mind, “fruit” includes tomatoes, peppers, squash, etc.).
Source: Ibanez, Facundo, WooYoung Bang, Leonardo Lombardini and Luis Cisneros-Zevallos. 2019. Solving the controversy of healthier organic fruit: Leaf wounding triggers distant gene expression response of polyphenol biosynthesis in strawberry fruit (Fragaria x ananassa). Nature Scientific Reports. Issue 9. 19239. www.nature.com/articles/s41598-019-55033-w.pdf
— Janet Wallace