While it’s perfectly safe to drink distilled water – and, if you’re immunocompromised, it may be the safest option – it’s best to stick with tap or purified spring water. , especially for cooking.
The National Center for Complementary and Integrative Health states that minerals like magnesium, calcium, potassium, etc. are necessary for optimal health. These essential minerals, also called electrolytes, are found in our drinking water. Because distilled water removes all minerals, your body may lack the ones it needs, especially if your diet isn’t rich in them.
Cook’s Illustrated claims that distilled water, devoid of its own, strips essential minerals from vegetables, reducing their nutritional value. This is backed up by research, in particular a 2014 study published in the Medical Journal Armed Forces India, which found a decrease of up to 60% in calcium and magnesium (and even more for other minerals) in the food cooked in soft food (i.e. not mineralized water). In comparison, nutrient loss was significantly lower for foods cooked in hard water.
According to The Spruce Eats, for a number of reasons, you should avoid distilled water when cooking unless you have no alternative. As Food Network explains, most of the recommended uses for distilled water have nothing to do with drinking it.
That said, if you decide to cook a recipe with distilled water, don’t do it with aluminum pots or pans (via Cook’s Illustrated). Distilled water, according to The Spruce Eats, will draw metal ions away from aluminum and cast iron cookware, which will not only corrode cookware, but give your cooked food a metallic taste.