Spinach is rich in many nutrients, including Vitamin A, Vitamin C, Vitamin K, iron, folate, and potassium. Spinach is chock full of fiber. Eating too much fiber can cause gas, cramping, and abdominal pain. Spinach is rich in oxalate, a naturally occurring substance found in almost all plants.Spinach has vitamins and minerals like vitamin E and magnesium that support your immune system. This system keeps you safe from viruses and bacteria that cause disease.