hi there,
There is no
essential nutrient in fruit that isn't also found in vegetables. Except sugar, and it's not essential
There are certain phytonutrients that may be more abundant in certain fruits, such as proanthocyanins in blueberries or grape skins. But although those nutrients may have specific therapeutic benefits, they are not essential to health .. if they were, then people living in parts of the world where those things aren't native would be suffering deficiency diseases, which they are not. As Lisa pointed out, vegetables provide protein, vitamins, antioxidants and minerals in abundance; and also much fiber, both soluble and insoluble.
I'm not aware of a study comparing the nutrition in fruits and vegetables, since they are usually considered the same food group. Botanically speaking, the difference between a fruit and a vegetable is the part of the plant it comes from. Vegetables are the leaves, stems and roots, while fruits contain the seeds. The following "vegetables" are in fact fruits: tomato, zucchini/courgette, squash/pumpkin, olives, avocado, eggplant/aubergine, chayote, tomatillo, cucumber, pepper/capsicum.
IMO, if you choose a wide variety of vegetables, especially dark green and leafy varieties (not just iceberg lettuce which has very little nutrition to offer) ... and supplement with a little low-glycemic fruit as allowed on your chosen low-carb program -- some berries or a slice of melon -- you will be getting plenty of good nutrition.
Fact: a spear of broccoli has more potassium than a banana, and more fiber than an apple. It also has way more calcium than either of those fruits. It also has only 4g net carbs
hth,
Doreen