My grandmother told me that if I ate fish it would give me brains and if I did not eat the crusts from my bread the curl would go from my hair. By age 11 I had straight hair but I was a little swot.
One thing from my grandmother that really does work. If you have a bruise, coldsore, pimple or boil and you wet it with your spit (especially your fasting spit) it will heal quickly. Apparently human spit contains elements from their immune system.
My mother also had the thing about shoes on the table and opening an umbrella in the house was unlucky.
If you gave someone a purse or a bag for a gift you always had to place a small coin in it so they would never go short. I stll do that if I sell a vintage purse online.