Four of the largest cohort studies in nutritional epidemiology have reported that eating nuts frequently is associated with a 30-50% decreased risk of coronary heart disease. Possible mechanisms include reduction in LDL cholesterol, the antioxidant actions of vitamin E, and the effects on the endothelium and platelet function of higher levels of nitric oxide.
According to a report in the Journal of Agricultural and Food Chemistry pistachio nuts have a very high phytosterol content (about 270-290 mg in 100 g). Phytosterols are plant components that have a chemical structure similar to cholesterol except for the addition of an extra methyl or ethyl group. Phytosterols reduce cholesterol absorption, which assists in the reduction of circulating levels of cholesterol.
An animal study has shown that consumption of pistachio nuts as 20% of daily caloric intake leads to significant improvement in high-density lipoprotein (HDL) and total cholesterol/HDL cholesterol ratio and inhibits LDL cholesterol oxidation. HDL helps remove cholesterol from the body by transporting it to the liver. The total cholesterol to HDL cholesterol ratio helps to predict the risk of developing atherosclerosis. Pistachio nut consumption increased serum paraoxonase activity by 35% and arylesterase activity by 60%, which are known to inhibit LDL cholesterol oxidation. Oxidized cholesterol boosts total cholesterol levels and promotes atherosclerosis more than non-oxidized cholesterol.
The results of a small study conducted in 24 healthy men and 20 healthy women indicated that consumption of pistachio nuts decreased oxidative stress, and improved total cholesterol and HDL levels in healthy volunteers. Half of the subjects were randomized to a regular diet group and the other half were randomized to a pistachio group which involved substituting pistachio nuts for 20% of their daily caloric intake for 3 weeks.
In another study it was found that a diet consisting of 15% of calories as pistachio nuts (about 2-3 ounces per day) over a four week period favorably improved some lipid profiles in subjects with moderate hypercholesterolemia (high blood cholesterol) and could reduce risk of coronary disease.
In a randomized crossover trial 15 subjects with moderate hypercholesterolemia (serum cholesterol greater than 210 mg/dL) underwent 4 weeks of dietary modification with 15% caloric intake from pistachio nuts. Statistically significant reductions were seen in total cholesterol/HDL cholesterol ratio, LDL cholesterol/HDL cholesterol ratio and a statistically significant increase was seen in HDL cholesterol. The LDL/HDL ratio is a more accurate ratio to help predict the risk of developing atherosclerosis.
Unroasted pistachio nuts were used in all of the studies, roasting affects antioxidant activity adversely.
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2. Kocyigit A, Koylu AA, Keles H. Effects of pistachio nuts consumption on plasma lipid profile and oxidative status in healthy volunteers. Nutr Metab Cardiovasc Dis. 2006 Apr;16(3):202-9. Epub 2006 Feb 9. PMID: 16580587.
3. Sheridan MJ, Cooper JN, Erario M, Cheifetz CE. Pistachio nut consumption and serum lipid levels. J Am Coll Nutr. 2007 Apr;26(2):141-8. PMID: 17536125.
4. Fraser GE. Nut consumption, lipids, and risk of a coronary event. Clin Cardiol. 1999 Jul;22(7 Suppl):III11-5. PMID: 10410300.
5. Katherine M. Phillips, et al. Phytosterol Composition of Nuts and Seeds Commonly Consumed in the United States. J. Agric. Food Chem., 2005, 53 (24), pp 9436-9445. DOI: 10.1021/jf051505h.
