Are pistachios your favorite nut? If so, you're in luck! Research has shown that pistachios help to lower cholesterol and provide antioxidants as well. 

Scientists at Penn State University fed study participants either 1.5 ounces or three ounces of pistachios nuts each day for a month. Those who ate three ounces of pistachios a day lowered their total cholesterol by 8.4 percent and their low-density lipoprotein (LDL or bad cholesterol) by 11.6 percent.

It should be noted, however, that these study participants also followed a lower-cholesterol and lower-fat diet during the study — meaning that you can't go on eating burgers, pizza, and fries and then expect to keep your cholesterol under control by adding some pistachio nuts. 
  
Pistachios help lower cholesterol because they contain high amounts of monounsaturated fats, which, compared with saturated fats, decrease total cholesterol and LDL cholesterol while increasing high-density lipoprotein (HDL or good cholesterol). Pistachios also contain the antioxidants lutein, beta-carotene, and vitamin E, which can help to lower cholesterol levels too. 

The researchers found that, when it comes to pistachios, serving size is crucial. One ounce of pistachios makes up about 50 kernels and contains 160 calories.

So if you suddenly start eating three ounces of pistachios each day, you'll be consuming an extra 480 calories — enough to add an extra pound to your weight a week. And gaining weight will send your cholesterol levels up.

So the moral of this story is, if you do decide to eat pistachios, eat them in place of something else so you're not simply consuming more calories and putting on extra weight.