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reference
Kay CD, Gebauer SK, West SG, Kris-Etherton PM. Pistachios increase serum antioxidants and decrease serum oxidized LDL in adults with hypercholesterolemia.J Nutr. 2010;140(6):1093-1098
design
A Randomized, Controlled-Feeding Crossover Study to Evaluate 2 Doses of Pistachios on Serum Antioxidants and Biomarkers of Oxidative Status
Participant
28 hypercholesterolemic adults (LDL cholesterol ≥2.86 mmol/L)
Study medications and dosage
After two weeks of a basic Western diet, participants ate one of three diets, all of which provided similar calorie intake, for four weeks. The control diet did not contain pistachios and was lower in fat (25% total fat). The other two diets contained either 1 or 2 servings of pistachios per day. One serving consisted of 32 to 63 grams of nuts.
Main target parameters
Plasma lutein, alpha-carotene, beta-carotene, gamma-tocopherol, lipid profiles and oxidized LDL
Key findings
Both the 1 serving/day and 2 servings/day pistachio-fortified diets significantly reduced oxidized LDL levels compared to the control diet
Effects on practice
The amount of LDL found in the blood is a long-known indicator of the risk of cardiovascular disease. More recently, the amount of oxidized LDL (Ox-LDL) has been recognized as a factor contributing to the development and progression of cardiovascular disease.1High Ox-LDL levels are associated with a higher risk of metabolic syndrome, coronary artery disease, and acute coronary syndrome.2Reducing Ox-LDL levels, as this study shows, is an important goal for disease prevention. Previous studies have already shown that eating pistachios improves standard lipid profiles.
This recent paper by Kay et al. is in fact a further analysis of data from a pistachio clinical trial first reported in 2008 by Gebaur et al. was published.3The first analysis of the data looked specifically at the impact of a diet rich in pistachios on more common cardiovascular risk factors. For both studies, blood samples and data from the same controlled feeding study were analyzed. Gebauer et al. reported that participants who ate 2 cans of pistachios per day reduced total cholesterol by 8% and LDL cholesterol by 11.6% (P< 0.05) compared to the control diet. The total cholesterol/HDL cholesterol ratio and the LDL cholesterol/HDL cholesterol ratio decreased by 8% and 11%, respectively, for this group of participants (P<0.05).
This work does not alone indicate that pistachios and other nuts reduce the risk of cardiovascular disease.
This work does not alone indicate that pistachios and other nuts reduce the risk of cardiovascular disease. In April 2010, Sari et al. from Gaziantep University School of Medicine in Turkey about their own pistachio feeding trial. They had fed 32 healthy young men a Mediterranean diet for a month and then added pistachios for another month. Compared to the Mediterranean diet, the pistachio diet reduced blood sugar levels by 8.8% (±8.5%).P< 0.001), decreased LDL by 23.2% (±11.9%), decreased total cholesterol by 21.2% (±9.9%,P< 0.001) and triglycerides by 13.8% (±33.8%,P= 0.008). The pistachio diet significantly improved endothelium-dependent vasodilation by 30% (P= 0.002), decreased serum interleukin-6, total oxidation status, lipid hydroperoxide and malondialdehyde, and increased superoxide dismutase (P< 0.001 for all).4
In 2007, Sheridan et al. reported on a randomized, controlled, crossover study in which 15 volunteers were fed pistachios in quantities that represented 15% of their total calories for four weeks. Statistically significant reductions were observed in the total cholesterol/HDL ratio (-0.38; 95% CI, -0.57 to -0.19;P= 0.001), LDL/HDL (-0.40; 95% CI, -0.66 to -0.15;P= 0.004) and a statistically significant increase in HDL (+2.3; 95% CI, 0.48 to 4.0;P= 0.02).5
Other nuts have also been proven to improve lipid levels. In May 2010, Sabaté and colleagues at California's Loma Linda University reported a pooled analysis of intervention studies on nuts and blood lipids.6They pooled individual primary data from 25 studies of nut consumption conducted in 7 countries in 583 men and women with normolipidemia and hypercholesterolemia who were not taking lipid-lowering medications. In the pooled data, average nut consumption was 67 grams per day. Total cholesterol concentration decreased by 10.9 mg/dl (-5.1% change). LDL cholesterol decreased by 10.2 mg/dl (-7.4% change). The LDL/HDL ratio decreased by 0.22 (-8.3% change) and the total cholesterol/HDL ratio decreased by 0.24 (-5.6% change) (P< .001 for all). Triglyceride levels decreased by 20.6 mg/dl (-10.2%) in subjects whose levels were above 150 mg/dl (P< .05).
Not all nut studies have been equally positive. Phung et al. wrote a meta-analysis of 5 studies on almonds with a total of 142 participants and found a neutral effect on lipid profiles.7A year earlier, Jenkins reported that almonds reduced lipid oxidation.8Even though almonds have a neutral effect on lipid levels, they may still provide cardiovascular protection.
In addition to the results of these feeding trials, there is also increasing evidence in epidemiological studies of the cardiovascular benefits of nut consumption. In a review of five large epidemiological studies published in May, Sabaté and Vienna reported “an 8.3% reduction in the risk of death from coronary heart disease for each weekly serving of nuts.”9
Given the number and strength of studies on nuts and the number of years since these benefits were first noticed (Sabaté's first paper on walnuts was published in 1993), it is surprising that many doctors are unaware that nuts are now considered beneficial.10Patients still tell me that their doctors advised them to reduce their consumption of nuts to lower their cholesterol levels. This is a medical myth that we should loudly refute. Getting patients to increase nut consumption, choose nuts as a snack, or add them as an ingredient to other foods is a simple intervention that has been shown to provide benefits.