Most studies examining the effects of pistachios nuts on cholesterol involved people consuming pistachios -- about 15 to 20 percent of their daily caloric intake. Additionally, participants with and without high cholesterol were studied. Most studies indicate that eating three ounces of pistachio nuts a day for one month can raise high-density lipoprotein (HDL), or "good" cholesterol, up to an average of 15 percent. This roughly equals to about two handfuls of pistachio nuts a day.