The Food and Drug Administration allows a qualified health claim for nuts. Eating 1.5 ounces a day of most nuts, including pistachios, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.
The word "qualified" matters. It means the evidence supports the link but does not meet the agency's strictest standard of significant scientific agreement.
A Pennsylvania State University trial published in Hypertension, an American Heart Association journal, gives that language substance. Daily pistachios lowered systolic blood pressure and dampened the vascular response to stress in adults with elevated cholesterol.
What the AHA journal trial found
The Penn State team studied 28 adults with dyslipidemia in a randomized, crossover, controlled-feeding trial. Participants moved through three diets in sequence. First a low-fat control, then one serving of pistachios a day (about 1.5 ounces), then two servings (about 3 ounces).
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After the one-serving diet, average systolic blood pressure fell 4.8 mmHg compared with control. Peripheral vascular resistance also dropped during a mental arithmetic test and a cold-water challenge, meaning blood vessels stayed more relaxed under acute stress.
Cholesterol effects across multiple trials
A systematic review and meta-analysis of 12 randomized controlled trials, published in Critical Reviews in Food Science and Nutrition, reported that pistachio consumption reduced LDL cholesterol by 3.82 mg/dL, total cholesterol by 7.48 mg/dL and triglycerides by 11.19 mg/dL on average. HDL cholesterol did not change.
Earlier work from the same Penn State group also found that both a 1.5-ounce and a 3-ounce daily dose lowered oxidized LDL, a more damaging form of LDL that contributes to artery-wall plaque, while raising blood levels of the antioxidant lutein.
A second trial in type 2 diabetes
In a 2014 randomized trial in the Journal of the American Heart Association, 30 adults with well-controlled type 2 diabetes ate a pistachio-rich diet for four weeks. Twenty-four-hour ambulatory systolic blood pressure fell 3.5 mmHg, with the largest reduction, 5.7 mmHg, occurring during sleep.
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"After the pistachio diet, blood vessels remained more relaxed and open during the stress tests," said Sheila G. West, professor of biobehavioral health and nutritional sciences at Penn State, in a university statement.
No weight gain at the studied serving
At the tested doses, up to 3 ounces a day, participants did not gain weight, though the trials were short and tightly controlled. Cleveland Clinic dietitian Julia Zumpano recommends 1 to 1.5 ounces a day and suggests buying pistachios in the shell to slow eating.
A 1-ounce serving is about 49 kernels and 159 calories, so the FDA's 1.5-ounce target works out to roughly 70 to 75 pistachios. Salted varieties add sodium, which can push blood pressure up, so unsalted or lightly salted is the safer pick. Anyone taking blood pressure or cholesterol medication should discuss large dietary changes with their doctor first.
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This article is made and published by Jesper Bengtson, who may have used AI in the preparation.