While this is true, it is far safer to satisfy that urge with willow baskets, untreated wood, and hay or straw. These are grain products which may be supplemented with dehydrated vegetables, and shaped into a form which mimics a vegetable product. The high carbohydrate content of these snacks means they are robbing your rabbit of important fiber and overloading him with sugars. These products also tout the vitamins that are added back - which are merely replacing those originally lost during the processing of the treat. The high sugar is the culprit here.
Many rabbits have a sweet tooth, but sweetness means high sugar content.
As we discussed above, excessive sugar is converted to fat, or will pass into the cecum where the bacteria will use it for energy and then rapidly overgrow, possibly leading to bacterial imbalance and gastrointestinal stasis. The same can occur after feeding too much fruit. In a word, don't. For nearly all rabbits, a diet containing a variety of fresh vegetables, restricted high quality pellets, and unlimited hay provides all the vitamins your rabbit requires. While special health situations may require nutrient supplements, these are best handled after consultation with your veterinarian.