After watching a video titled "How Bacteria Rule Over Your Body – The Microbiome"[1] from "kurzgesagt", I'm very curious to know if unfiltered water can have also a positive effect on our microbiome. Maybe we're creating a world that's too hygienic? (edit: the video doesn't answer, or even mention, what I'm asking. I'm asking because the idea sounded plausible to me)

[1]: https://www.youtube.com/watch?v=VzPD009qTN4

Giardia and Cryptosporidium aren’t going to give you a positive effect. They are going to make you sick. And those are the biggest risks from untreated stream water.

Any many other microorganisms including Leptospira. The latter can be acquired through the skin by swimming in the wrong areas in Hawaii [1]. Giardia can be difficult to treat and give you horrible problems for years as happened to one friend. Another friend acquired boils with visible nematodes under the skin from wading near Belem in Brazil. As a field biologist one is constantly reminded that nature is not benign. However local knowledge can usually keep one out of trouble, with the disclaimer that sadly in almost all of the world even its wildest most remote corners, the organism that poses the greatest danger is Homo sapiens.

1 http://health.hawaii.gov/about/files/2013/06/leptobrochure.p...

There is always the appeal to nature argument. Slightly off topic. On one of my hikes with my dog. I wouldn't let him drink from a stream. Some people near by waved to me and said "It is fine! Dogs know good water". I thought how absurd. Another time we came across some small animals. He has a high prey drive. He made some aggressive advancements towards the creatures. I called him off. A person sharing our hike made the comment that it was okay. If he ate the small animal it would be good for him. It is natural. I said no the possibility of my dog contracting a parasite like tape worm would be a very bad thing. Nature can kill or hurt you in very natural ways.

In Switzerland we asked while mountain biking if it was safe to fill up from one of these spring water things we saw everywhere: they would dump into a large log cut out into a sort of sink. They looked at us, puzzled "what do you mean, it's spring water," and they filled their bottles.

Backpacking everywhere in Switzerland people drank directly from these, and from streams And waterfalls, without filtration. And the Swiss are looking for any excuse to have something to spend their money on.

It’s unfiltered fresh spring water yes, but these are still human-built fountains with a known source where the water quality is measured in regular intervals. It’s not a random stream in the woods.

Switzerand is much smaller, so we have people checking on these regularly.

I always drink from these fountains, they’re all safe except the very few that have a “not potable” sign.

I wouldn’t drink from a random stream of water in the woods.

I see. Well, anyways we also filled up from streams and waterfalls, as did other locals among us. I also filled up from streams and waterfalls in many other parts of the world--I'm am avid backpacker and I have done thois hundreds of times. I've never been sick. However, I this was always water coming down from mountain summits. I wouldn't fill up from a stream running through the middle of a cattle ranch.

I suspect that there is a difference in risk between various specific spots in Switzerland and American at large.

I’d never drink untreated water in Michigan. Michigan was a giant swamp. Near the top of a summit in Switzerland with no livestock nearby? Sure.