Nuts are already known to be good for your heart when eaten in moderation as part of a low-fat diet. Since 2003, the FDA has allowed almonds, hazelnuts, pecans, pistachios, walnuts, and peanuts to make a qualified health claim to that effect.
The new study, published in The American Journal of Clinical Nutrition, is only about pistachios. Almonds and walnuts have been featured in most of the previous nut studies, so the researchers, who included Pennsylvania State University graduate student Sarah Gebauer and Distinguished Professor Penny Kris-Etherton, PhD, put pistachios in the spotlight.
The key question: Would one or two daily servings of pistachios pack a punch against LDL cholesterol?
The pistachio study included 28 adults whose LDL cholesterol level was higher than the optimal range. Their average LDL level was in "borderline high" range when the study started.
First, participants spent two weeks on a standard American diet rich in full-fat cheese, oil, and butter and lacking pistachios.
Next came a month on a low-fat diet without pistachios, another month on a healthy diet that included one daily serving of pistachios, and a third month eating a similar diet with two daily servings of pistachios, with two-week breaks between each type of diet.
Participants got all their food, packaged into appropriate serving sizes, from the researchers. And they stuck to their assigned diets pretty well, the study shows.
Average LDL levels fell when participants ate pistachios -- not enough to get their LDL levels into the optimal range, but enough to get it out of the "borderline high" category.
LDL cholesterol level dropped by 9% during the month that participants ate a daily serving of pistachios and by 12% when they had two daily servings of pistachios.
As for the low-fat diet, it didn't trim LDL cholesterol. That surprised the researchers. What happened? The researchers aren't sure, but they note that the low-fat diet was lower in polyunsaturated fats (which include heart-healthy omega-3 fatty acids) and higher in carbohydrates than the pistachio diets.
The study was funded in part by the California Pistachio Commission.