Since the taste is a little milder than that of sugar, most people end up consuming more than they require. For example, if a person usually mixed a tablespoon of sugar in a cup of tea or coffee, someone not used to the taste of jaggery would end up adding more than they need to.
Again, it’s not free food. Jaggery contains roughly the same number of calories as sugar. So by adding more, you also increase your calorie intake. Jaggery also contains sucrose, which raises blood sugar levels and can be harmful to diabetic patients.
If you don’t take pure, well-aged jaggery, you might be eating food with preservatives, which, again, isn’t very helpful.