Unfortunately, water can be contaminated by all sorts of substances: materials from ageing municipal pipes, agricultural chemicals, pharmaceuticals, metals such as lead. Recently, perfluoroalkyl substances (PFASs, also known as “forever chemicals”) have been much in the news as they are present in both city water and in the aquifers that supply wells.

Some filters, such as activated charcoal, do not remove these toxic chemicals very well, as described in an article on the website for the Nicholas School of the Environment at Duke.

I have always recommended a good quality water filter for patients on this nutritional program. An article on Forbes.com reviewed all the different methods available for water filtration. Their highest marks went to reverse osmosis and distillation.

With any method, proper maintenance of the system is extremely important, as dirty filters can become counterproductive.