On a very very technical level kinda yes, a weird quirk of gravity is that it has infinite range even though it follows the inverse square law. This means that the moons gravity imparts some amount of force on you. Not just the moon either, all objects in the observable universe impart some force on you, as do you impart some force on them. The problem Is that this force is so absolutely infinitesimally small It may as well be zero. So in the world of theoretical physics yes kind of but your friend probably isn't a physicist. Sounds like they're more woo woo astrological magic type people that believe the moon imparts some metaphysical healing magic on their insides.

Edit: The moons gravity affects everything on the planet. That doesn't mean it is harmful. It's going to be very insignificant.

That might explain werewolves. Since the full moon is heavier it attracts wolf enzymes that are usually stored in the pancreas to be released into the blood stream.

It's a very small force. If you consider such small forces to have an effect, you must also consider gravitational pull of objects that have the same or a larger effect: passing trucks, entering buildings, passing a mountain, going upstairs, going underground.

Also, all movement will cause same type of force on you (acceleration) plus change your body's alignment to Earth gravity has a large effect on gravity's pull on organs: shifting position, leaning, walking, driving, taking an elevator, lying down, figeting, trying to stand on a wooden floor, all have several orders of magnitude more effect on you than the moon.

In short: You can't hear someone whispering ten rows behind you at a Metallica concert.

Take an inflatable swimming pool, let it sit outside. Notice any tide? No? Well, why would your kidneys have tides then?

https://oceanservice.noaa.gov/facts/gltides.html

If the great lakes only see a fluctuation of 5cm max, I don't think it is affecting the human body in any meaningful way.

Gravity affects all things with a mass>0, and nothing can be done against it.

Haven't you read your Einstein? ;-)

Maybe your friend is thinking about menstrual cycles? Of course they aren't really influenced by the moon but they (often) have a period of 1 month, like the moon phases.

I do think that in fact if you embrace your friend, he has a higher gravitational pull on you than you moon. Or so I believe, the math should work itself out.

In theory it has some kind of affect but not anything anyone would notice. Like I'm not even sure it would show up on a scale and anyone trying to measure it with something sensitive enough to do so would have a hell of a time separating the change from normal things like eating, going to the bathroom, sweating, or just breathing.

If we say for a moment that it does have an affect on people the next question would be what effect might there be. Again I think a major issue would be measuring results when there would be so many other things at play. Also what are we measuring? What might the proposed effect be?

This idea mostly sounds like pseudo science or a half assed attempt at supporting some new age idea.

Ask them how the moon effects weightless astronauts. I imagine you'll get a confused response before they find some way to integrate it into their narrative.

The moon actually pulls on the land a little bit but it’s such a small amount it’s only measurable with very specific instruments and in large timetables. Not enough to really affect any individual on the planet.

I would ask your friend what the “so what” of that is. I have heard a lot of anecdotal evidence from teachers experiencing more crazy behavior from their kids around the full moon or people sleeping or feeling worse around that time. Might just be something we don’t understand yet, but again, what’s your friends answer to the “so what”? We can’t do anything about it, as far as I know.

Well it does affect the gravitational pull, and were like 70% water. So yes it does fuck with us on a biological level. So full moons causing people to go crazy is a real thing, but it's exaggerated of course and very subtle.

Idk why I'm getting downvotes, this is a very real thing https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7322537/

No. If gravity on such a small scale affected us, we'd have evolved to incorporate it as many animals do for navigate, or evolve to ignore it. We did the latter, if it was ever necessary. The gravity of the earth is many magnitudes greater. And you can prove that the shifting gravity from the moon is moot by the sheer fact that you can sleep on your back, either side, or stomach and not feel inverse affects. You can even move around through the night, like the moon does.

Also the tides thing is half right. About half as strong in tidal energy is the sun. Solar tides exist. So the question would also need to be "does the sun's gravity affect us?" And the answer is the same as before.