What's a common health myth people fall for?

Things being low fat. Sometimes it's just watered down or packed with sugar, so it may not be healthy at all

Counter point - fat is actually healthy
- No one food is "healthy" or "unhealthy", it always depends on how much of it and what else you eat.
- Trans fats are bad.
  Excess saturated fat could be bad depending on the health condition of the person.
Fat-phobia has been way overblown ever since the 1960s, when the sugar industry diverted public attention to it and away from their own products.

There's a myth that MSG is bad for you and is found in Chinese restaurants. MSG has been studied extensively and never found to cause the symptoms people claim, furthermore MSG is used widely in a huge range of food production (lots of sauces, fast foods etc etc)

MSG is very common in mushrooms, Parmesan cheese, and tomatoes. It's why people love Italian food ao much
I can literally buy it by the bucket.
Same with aspartame. Its been studied until the cows come home and it is safe.

That individual health can be discussed separately from societal conditions such as what the market offers, salary levels, pollution, transport system, working hours, labour market, insurance system et cetera. "If you want to be healthy it is just your own individual responsibility to purchase healthy commercial products and services".

Where I grew up, the well water was poisoned by a chemical dump in the 70's. The public water system that was to replace the wells, draws their water just down stream of said dumpsite and downstream of a nuclear processing plant that dumps heavy radioactive metals into the river.
Guess its my fault for contributing to global pollution by buying bottled water shipped dozens of miles away.

Detoxing.
If you have working kidneys, you shouldn't need to detox.
Also: weight-loss teas. they give you diharrea so you lose weight in water, which you will immediately gain again.

I have a co-worker who says she was using some pads that you put on the bottom of your feet and then go to sleep. You wake up in the morning and remove the pad to see it covered in black stuff. Claiming to have all those toxins leave her body.
I highly doubt that was the case.

That there are a lot of "Chemicals" in something, and that it's bad for you.

Everything is Chemicals.
dihydrogen monoxide = water

You need to shower/bathe often. Actually the skin, the biggest organ of our bodies, is great at taking care of itself and washing it (especially with soap et.al) is bad if done too much.

"But(t) smell!"

Well yeah, I agree, but that doesn't change the way our skin has evolved :P

I have seborrheic dermatitis so not washing my skin causes a rash.
- But that's a fungus allergy so aren't you mostly treating it with anti-fungus medication?
  (One of the proposed mechanisms for why skin becomes allergic to the malassezia yeast in the first place is that we disturb it through our washing routines but there's no consensus on that afaik)
  I'm candida overgrowth myself and too much washing with soap worsens it in my case. The human body is a wonderful thing :P

Anti-vaxxers sadly

I remember fondly when my family were in this cute little phase. Now they have moved onto harder drugs like 5G, chemtrails, fluoride, vaccines, white nationalism, pizzagate, and idolising American right wing insanity. Good luck!

Normal blood tests means you are healthy

That said, more people should do blood tests regularly and observe the trends. I wish I had my blood tested much earlier. By the time the symptoms surface, a lot of damage is already done.
- Yes. It goes both ways but since it was about myths, I posted only one side.
Ugh. Love, Long Covid.

Detoxing

But it removes the toxins !!!?!?
- Let me introduce you to two of my best friends. Noodle, this is Liver and these are the twins, Kidneys (their parents had no imagination)
  😝

RFK Jr.

Most of common sense advice about nutrition (everything since the 1950s) is basically 180 degrees backwards

[Update to clarify, HERE IS THE CORRECT ADVICE]

carbohydrates are not essential
fat is healthy and shouldn't be avoided
cico isn't helpful
industrial food oils are not good for you
cholesterol is healthy
meat is healthy, avoiding meat is bad for health
grains should be avoided and not be the base of people's diets

To be clear: the above points are FALSE and the true is the opposite. (Just to avoid people misread and keep pushing wrong ideas)
Given how internet people usually apply brain, a "/s" would have been not a bad idea :)
- Some of these aren't true even when flipped, though.
  A lot of food advice about what's good/bad for you should really just be "eating this is helpful/safe in reasonable amounts" rather than a simple it is good/bad.
  There are things you have to eat a minimum of because they are essential to the composition or processes of the body. Almost everything else you can eat, and even turn into useful energy, but then it is about not poisoning/overfeeding yourself.
- Many of the points OP made are indeed true. You would be the one stuck with the myths ;)
- Considering their responses to my comment, no.
  They did NOT flip their arguments.
- I stand behind everything I said. I'm happy to provide references if any specific thing is interesting to you
Cico is incredibly helpful, what are you on about? Our bodies do, in fact, follow the laws of thermodynamics. Sure, nutrients are also important, but if we're just talking about weight, cico is key