The DASH diet limits sodium to less than than the RDA. Sodium is an essential mineral. Limiting sodium can cause a variety of negative health effects, even though it does typically lower blood pressure. These negative health effects can be magnified by other components of the DASH diet, particularly the ones that emphasize consuming large amounts other minerals that need to be in balance with sodium. Of course most Americans have the opposite problem, with sodium consumption that is several times higher than RDA, due to high sodium in many processed foods.
In my opinion, many general aspects of the DASH diet are good to incorporate in to a typical healthy diet such as eating fruits and vegetables, whole grains, lean meats; and avoiding processed foods. However, I’d be wary of limiting any essential mineral with no recommended minimum, particularly if you do not have the medical condition for which the diet was intended (DASH is an acronym for Dietary Approaches to Stop Hypertension).