A number of studies have established a body of evidence linking nut consumption to potential beneficial effects for heart disease, diabetes, Alzheimer's Disease, and cancer:
Heart Disease: Researchers from Loma Linda University (California, USA) studied results of 25 nut consumption trials involving 583 men and women with normal and high cholesterol levels. Results showed that daily consumption of a small bag (67g) of nuts reduced total cholesterol by 5.1% and LDL cholesterol by 7.4%. Eating nuts was also found to reduce triglyceride levels by 10.2% in participants with blood triglyceride levels of at least 150 mg/dL, but not in those with lower levels. The benefits of nut consumption were greatest in those with high baseline LDL cholesterol levels and a low body mass index (BMI).
A team from Pennsylvania State University (Pennsylvania, USA) followed a group of 25 men and women with mildly elevated cholesterol levels, for a five-week period. One subgroup consumed an “average” American diet [33% total fat, including 11% monunsaturated fatty acids (MUFA) and 5% polyunsaturated fatty acids (PUFA)] and the other subgroup ate a Macadamia nut-rich diet [33% total fat, including 18% MUFA and 5% PUFA]. In the group consuming the macadamia nut-rich diet, the ratio of total cholesterol to HDL cholesterol decreased (4.60, versus 4.90 in the group following the American diet). In addition, the macadamia nut-diet group experienced a decrease in LDL (low-density, or “bad”) cholesterol (3.14 mmol/L, versus 3.44 mmol/L in the group following the American diet).
Diabetes: Yale University School of Medicine (Connecticut, USA) researchers studied 14 women and 10 men, median age 58 years, with type 2 diabetes, assigning some of them to consume 56 grams of walnuts daily, for 8 weeks. At the conclusion of the study period, the researchers found significant improvements in the function of the blood vessel lining (endothelium), with blood flow improved by 2.2% in the group that consumed walnuts (as compared to 1.2% in the non- supplemented group). The walnut-enriched diet also increased lowered serum total cholesterol and low-density lipoprotein.
Researchers from University of Montreal (Canada) studied whether cashew extracts could improve the body's response to its own insulin. Examining the impact of leaves, bark, seeds and apples from cashew trees, native to northeastern Brazil and other countries of the southern hemisphere, the team found that only cashew seed extract significantly stimulated blood sugar absorption by muscle cells, with extracts of other plant parts having no such effect.
Alzheimer’s Diseas e: A team New York State Institute for Basic Research in Developmental Disabilities (New York, USA) studied the effect of dietary supplementation of walnuts on the memory, anxiety and learning skills in a mouse model of Alzheimer’s Disease. The team fed walnuts to the mice, and observed that mental skills were preserved. In contrast, the Alzheimer-model mice that were not fed the nuts suffered a dramatic loss in learning, memory and physical and emotional control.
Texas Woman’s University (Texas, USA) researchers studied 36 healthy subjects, each of whom either were assigned to an intervention group consisting of a pistachio diet or a control group. After a two-week baseline period, an intervention period of four weeks followed in which the intervention group was provided with 68 grams (about 2 ounces or 117 kernels) of pistachios per day (the control group ate a normal diet). The researchers observed a significant increase in energy-adjusted dietary intake of gamma-tocopherol at weeks three and four in those on the pistachio diet, as compared with those on the control diet. The similar effect was seen at weeks five and six among those on the pistachio diet compared with those on the control diet. For those on the pistachio diet, cholesterol-adjusted serum gamma-tocopherol was significantly higher at the end of the intervention period compared to baseline.
Prostate Cancer: Researchers from the University of California/Davis (California, USA) fed a diet with whole walnuts to mice that had been genetically programmed to get prostate cancer. After 18 weeks, the researchers found that consuming the human equivalent of 2.4 ounces of walnuts per day resulted in significantly smaller, slower-growing prostate tumors, as compared to mice consuming the same diet with an equal amount of fat, but not from walnuts. The team also found that not only was prostate cancer growth reduced by 30 to 40%, but the mice had lower blood levels of a particular protein, insulin-like growth factor (IGF-1), which has been strongly associated with prostate cancer.
Nuts can be part of a heart-healthy diet pattern that may prove to be key dietary interventions in some of today’s leading diseases. Because they are calorically dense, enjoy no more than 3 ounces of nuts per day as part of a balanced diet.