How hemerroid start & how to stop or prevent it?

Fiber. Constipation forces straining to deliver stool. This increases the intraabdominal venous pressure and hemorrhoidal venous plexus pressure thus causing the veins in the anus to engorge and dilate.Blood inside clots and causes a thrombosed hemorrhoid. High fiber diet increases water in stools and volume in the ampulla, this triggers defecation.High fiber helps prevent colonic diverticulae as well.
Diet,fluids. Hemorrhoids are present from birth but only when abused by constipation or diarrhea or excessive straining do thwey become symptomatic. Drink plenty of non alcoholic, non caffeinated fluids, eat a high fiber diet, don't read on the toilet and the hemorrhoids and you should live to a ripe old age without any significant issues.