I assume that you're referring to magnesium deficiency problems, e.g.: "Magnesium deficiency in tap water in Israel: The desalination era" https://www.science

I assume that you're referring to magnesium deficiency problems, e.g.: "Magnesium deficiency in tap water in Israel: The desalination era" https://www.sciencedirect.com/science/article/pii/S0011916417313401 https://www.sciencedirect.com/science/article/pii/S001191641... So, yes, make sure that you're supplementing magnesium or getting plenty from foods if you switch from plain tap water to RO or distilled water.