Hemorrhoids do not cause constipation according to WebMD. Instead, constipation contributes to hemorrhoids because the straining during a bowel movement aggravates the hemorrhoids, and the hard stools irritate the already swollen veins.
Diet plays a big role in preventing hemorrhoids and constipation from occurring. People who eat a high-fiber diet suffer less from constipation and, therefore, have fewer hemorrhoid problems. Those who eat a diet high in processed foods or low in fiber suffer more bouts with constipation and hemorrhoid flare-ups. According to WebMD, approximately 40 percent of people aged 20 to 50 in the United States suffer from hemorrhoids at some point.