By David Kiefer, MD
Synopsis: Improvements in some, but not all, lipid parameters were seen by substituting some carbohydrates with two servings of pistachios daily in people with elevated serum LDL cholesterol.
Source: Holligan SD, et al. A moderate-fat diet containing pistachios improves emerging markers of cardiometabolic syndrome in healthy adults with elevated LDL levels. Br J Nutr 2014;112:744-752.
In this issue of Integrative Medicine Alert, we’ve already learned that 2 ounces of pistachios, as a source of mono- and poly-unsaturated fats and plant sterols, can decrease fasting blood glucose and insulin resistance in people with impaired fasting glucose (previously called “prediabetes”). These results were a refinement of some of the recent recommendations about nut intake for cardiometabolic risk reduction. In the current trial, 28 adults with elevated low-density lipoprotein (LDL) levels participated in a crossover, controlled feeding study. The controlled “feeds” involved a control diet (a “typical Western diet,” 25% total fat), one serving of pistachios daily (30% total fat), and two servings of pistachios daily (34% total fat). A serving of pistachios was considered to be 1.5 ounces, 50% of which were salted, and these calories replaced carbohydrates. People stayed on the diets for 4 weeks, then had a 2-week break, and then proceeded with another of the diets, and so forth. Other variables, such as amount and intensity of physical activity, were controlled for.
Small and dense LDL levels decreased with the two-serving pistachio diet vs one-serving and control diets (P = 0.03 and P = 0.001, respectively), but changes in high-density lipoprotein (HDL) and lipoprotein A levels were insignificant. An indirect measurement of insulin resistance, the triglyceride to HDL ratio, decreased when the two-serving pistachio diet was compared to the control diet (P = 0.036). Fasting glucose and insulin levels, however, did not differ between the diets. The authors add these promising results to their prior work demonstrating a lowering of another cardiometabolic risk, LDL cholesterol.
Of note, one of the coauthors, Kris-Etherton, listed as the corresponding author, has published in the arena of omega-3 fatty acids and other fats and their connection to cardiovascular disease risk.1,2 As we malign fat intake less and switch our thinking more to the quality of the fats that we consume, perhaps Kris-Etherton, a well-known researcher, is adding to our current state of knowledge by examining which foods contain fats that may have a healthy physiological effect. It appears that pistachios, at least in the amounts studied here, fit this bill with respect to lipid parameters.
An important consideration is the presence of potential conflicts of interest. The California Pistachio Commission of Fresno provided primary funding for this research, and two of the authors received research and travel grants from the Western Pistachio Association. It would have been good to see a statement assuring the research community that these organizations had no oversight nor involvement in the data analysis, but that was not provided. It will be important to conduct future research in this area that is not potentially biased due to such circumstances.
- Kris-Etherton PM, et al. Polyunsaturated fatty acids in the food chain in the United States. Am J Clin Nutr 2000;71:179S-188S.
Kris-Etherton PM, et al; American Heart Association Nutrition Committee. Fish consumption, fish oil,
omega-3 fatty acids, and cardiovascular disease
Circulation 2002;106:2747-2757. [published correction appears in Circulation 2003;107:512].