In the new research, the researchers looked at the association of nut consumption with total and cause-specific mortality among 76,464 women between 1980 and 2010 in the Nurses' Health Study and 42,498 men from 1986 to 2010 in the Health Professionals Follow-up Study.

Participants in the studies filled out detailed food questionnaires every two to four years. With each food questionnaire, participants were asked to estimate how often they consumed nuts in a serving size of one ounce. A typical small packet of peanuts from a vending machine contains one ounce (about 28 grams).

"In all these analyses, the more nuts people ate, the less likely they were to die over the 30-year follow-up period," said Ying Bao, of Brigham and Women's Hospital, the first author of the report.

Those who ate nuts less than once a week had a seven percent reduction in mortality; once a week, 11 percent reduction; two to four times per week, 13 percent reduction; five to six times per week, 15 percent reduction, and seven or more times a week, a 20 percent reduction in death rate.

The researchers noted that this large study cannot definitively prove the cause and effect but the findings are strongly consistent with "a wealth of existing observational and clinical trial data to support health benefits of nut consumption on many chronic diseases."

Nuts contain important nutrients such as unsaturated fats, high quality protein, vitamins, minerals and phytochemicals, all of which may offer cardioprotective, anticarcinogenic, anti- inflammatory and antioxidant properties.

The U.S. Food and Drug Administration concluded in 2003 that eating 1.5 ounces (about 42.5 grams) per day of most nuts "may reduce the risk of heart disease."