Vitamin c, while also well known for its ability to boost/strengthen the immune system, it also helps reduce levels of stress hormones. One study found vitamin c could lower high blood pressure and levels of cortisol(stress hormone) when people took the vitamin before a stressful task.
Pistachios, are a good source for healthy fats. A handful may help lower stress, cholesterol, and inflammation.
Avocados are another great source of healthy fats but its on this list for its potassium. Avocados are rich in potassium. One avocado actually has three times as much potassium as one banana. Potassium is a great way to reduce stress and blood pressure.