Pistachios May Reduce Lung Cancer Risk
A diet that incorporates a daily dose of pistachios may help reduce the risk of lung and other cancers, according to data presented at the American Association for Cancer Research Frontiers in Cancer Prevention Research Conference, held Dec. 6-9, 2009.
“It is known that vitamin E provides a degree of protection against certain forms of cancer. Higher intakes of gamma-tocopherol, which is a form of vitamin E, may reduce the risk of lung cancer,” said Ladia M. Hernandez, M.S., R.D., L.D., senior research dietitian in the Department of Epidemiology at the University of Texas M. D. Anderson Cancer Center, and doctoral candidate at Texas Woman’s University - Houston Center.
“Pistachios are a good source of gamma-tocopherol. Eating them increases intake of gamma-tocopherol so pistachios may help to decrease lung cancer risk,” she said.
Pistachios are known to provide a heart-healthy benefit by producing a cholesterol-lowering effect and providing the antioxidants that are typically found in food products of plant origin. Hernandez and colleagues conducted a six-week, controlled clinical trial to evaluate if the consumption of pistachios would increase dietary intake and serum levels of gamma-tocopherol. A pistachio-rich diet could potentially help reduce the risk of other cancers from developing as well, according to Hernandez.
“Because epidemiologic studies suggest gamma-tocopherol is protective against prostate cancer, pistachio intake may help,” she said. “Other food sources that are a rich source of gamma-tocopherol include nuts such as peanuts, pecans, walnuts, soybean and corn oils.”
The study, conducted at Texas Woman’s University - Houston Center, included 36 healthy participants who were randomized into either a control group or the intervention group consisting of a pistachio diet. There were 18 participants in the control group and 18 in the intervention group._There was a two-week baseline period, followed by a four-week intervention period in which the intervention group was provided with 68 grams (about 2 ounces or 117 kernels) of pistachios per day; the control group continued with their normal diet.
The effect on the intake and serum cholesterol-adjusted gamma-tocopherol was investigated. Intake was calculated using the Nutrition Data System for Research Version 2007, and consumption was monitored using diet diaries and by measuring the weights of the returned pistachios.
Hernandez and colleagues found a significant increase in energy-adjusted dietary intake of gamma-tocopherol at weeks three and four in those on the pistachio diet 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.
“Pistachios are one of those ‘good-for-you’ nuts, and 2 ounces per day could be incorporated into dietary strategies designed to reduce the risk of lung cancer without significant changes in body mass index,” said Hernandez.
Pistachios offer potential heart health benefits
Adding to a growing body of evidence, new research shows that a daily dose of pistachios may offer protective benefits against cardiovascular disease, according to a study published in the Volume 26, Number 2 issue of the Journal of the American College of Nutrition, June 2007.
The study, conducted by James N. Cooper M.D., of George Mason University and Michael J. Sheridan, Sc.D., of Inova Fairfax Hospital, found that in people with moderately high cholesterol levels, a daily diet consisting of 15% of calories from pistachios (about two to three ounces or one to two handfuls of kernels) over a four-week period favorably improved some blood lipid levels.
"These results are exciting because the research indicates that adding pistachios to the daily diet can help protect the heart without a dramatic dietary lifestyle change," said Dr. James Cooper. "This research challenges the previously-held belief that a low-fat diet is best for heart health. Studies now show that a diet with a moderate amount of healthful monounsaturated fat, like the kind found in pistachios, is a more effective way to prevent heart disease than reducing overall fat intake. What's more, we noted very good compliance and a positive response from participants during the four-week period."
About Blood Lipids and Heart Disease
High levels of most blood lipids increase the risk of developing both heart disease and stroke while lowering blood lipid levels has been shown to reduce the risk. Lipids join with protein in the blood to form lipoproteins, known as cholesterol. There are three kinds of lipoproteins in the blood including high-density cholesterol (HDL); low-density cholesterol (LDL); and very low-density (VLDL) cholesterol. A normal total cholesterol level is 200 mg/dL or less; a normal LDL level is 130 mg/dL or less.
About the Study
In a randomized crossover trial, 15 free-living humans with moderately high blood cholesterol (greater than 210 mg/Hg) were given a diet where 15% of daily calories came from pistachios to see if it would have a significant impact on their blood lipid levels. All subjects consumed their normal diets during a five-day baseline period. Then, half the subjects were randomized to the pistachio diet for four weeks followed by four weeks on the regular diet; the other half followed the diets in reverse order. Subjects were instructed to substitute the pistachio nuts for normally consumed high-fat snacks. Subjects who did not normally consume high-fat snacks were asked to substitute pistachio nuts as fat calories. Otherwise, subjects consumed their normal diets.
Cardioprotective Shift in Some Important Blood Lipids
On the pistachio diet, statistically significant reductions were seen in TC/HDL-C (mean difference,-0.38; 95% CI, -0.57 to -0.19; p=0.001), LDL-C/HDL-C (mean difference, -0.40; 95% CI, -0.66 to -0.15; p=0.004), B-100/A-1 (mean difference, -0.11; 95% CI, -0.19 to -0.03, p=0.0009) and a statistically significant increase in HDL-C (mean difference, 2.3; 95% CI, 0.48 to 4.0; p= 0.02). Subjects consumed less saturated fat and more polyunsaturated fat and fiber. Statistically significant differences favoring the pistachio diet were observed for some blood lipid values, predictors of heart disease.
No Weight Gain on the Pistachio Diet
Subjects on the pistachio diet showed no changes in blood pressure, body mass index, or weight gain; further supporting previous studies which have also demonstrated no weight gain from the addition of pistachios to a daily diet. Nut consumption, in general, is associated with a lower body mass index and has not been shown to cause weight gainƒ¡.
Source of Heart Healthy Fats; Nutrient Dense Snack Choice
Most of the fat in pistachios -- almost 90% - is "good" or monounsaturated fat, which can lower blood cholesterol along with heart disease2. Monounsaturated fat comprises 55% of the fat in pistachios; 32% is polyunsaturated. Both monounsaturated and polyunsaturated fat reduce blood cholesterol levels and lower the risk of heart disease when they replace saturated fats in the diet3. Of all snack nuts, pistachios offer the highest level of phytosterols, and are a powerful source of fiber, both of which reduce the absorption of cholesterol from the diet4,5. Pistachios make a wise snack choice as they are contain dense levels of eight nutrients including thiamin, vitamin B6, copper, manganese, potassium, fiber, phosphorus and magnesium.
Pistachios Carry FDA's First-Ever Qualified Heart Health Claim
The study further affirms the FDA's first-ever qualified claim for heart health, issued in July 2003, which states: "Scientific evidence suggests, but does not prove, that eating 1.5 ounces per day of most nuts, such as pistachios, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."
Eating Pistachios May Reduce the Impact of Carbohydrates on Blood Sugar Levels
“Heart disease remains the leading cause of death among both men and women and another 20 million people are living with diabetes each year – so these findings are very exciting and relevant,” said Dr. Cyril Kendall, lead researcher of the study and a professor in the University of Toronto's Department of Nutritional Sciences. “We know that controlling blood glucose levels is important for preventing and controlling diabetes and recent data indicate that it is also important in preventing heart disease. Controlling postmeal fluctuations in glucose appears to be particularly important. Pistachios have been shown to decrease risk factors for heart disease, however little has been known about the specific effects of pistachios on blood glucose until now. Our preliminary findings demonstrate that suppressing the glycemic (blood sugar) response of high carbohydrate foods may be part of the mechanism by which pistachios contribute to cardiovascular health and to the prevention and control of diabetes. More research is definitely warranted.”
“Glycemic Response of Pistachios – A Dose Response Study and Effect of Pistachios Consumed with Different Common Carbohydrate Foods on Postprandial Glycemia was presented May 2007 to more than 10,000 scientists at the Experimental Biology Conference in Washington, DC. The study is the first of its kind to examine the effects of pistachios and glucose levels in combination with carbohydrates. The research was led by University of Toronto’s Dr. Cyril Kendall and Dr. David Jenkins - researchers well known for their studies of the glycemic index which measures how rapidly sugars from foods are absorbed into the blood stream. Certain carbohydrates elevate blood sugar levels more quickly than other foods – like pistachios – that contain higher levels of protein, fiber and monounsaturated fat. In general, foods that do not quickly raise blood sugar are often considered healthier than their more processed counterparts.
Drs. Jenkins and Kendall and their research colleagues studied 10 healthy individuals who participated in a number of acute dietary studies over the course of two months. After an overnight fast, participants were given a one-, two- or three-ounce serving of pistachios alone or served with a slice of white bread and blood sugar levels were measured over a two-hour period. The findings suggest that consumption of pistachios with a carbohydrate-rich meal significantly lowered the d blood glucose response. As consumption of pistachios increased, the blood sugar lowering response was enhanced. In addition, when pistachios were consumed alone, the rise in blood glucose was minimal.
The researchers also monitored the effect of pistachios consumed with different common carbohydrate foods on postprandial glycemia, or blood sugar levels after eating. The addition of pistachios to a number of other commonly consumed carbohydrate-rich foods – such as mashed potatoes, pasta and rice – also resulted in significant reductions in the blood sugar response, compared to when these foods were eaten alone.
In July 2003, the U.S. Food and Drug Administration (FDA) approved a much-awaited qualified health claim for nuts and heart disease prevention. The claim states, "Scientific evidence suggests but does not prove that eating 1.5 ounces per day of most nuts, such as pistachios, as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease." According to the California Pistachio Commission, the University of Toronto’s research findings are important for individuals who are living a heart-healthy lifestyle and those that monitor their blood sugar levels.
“Most people with diabetes have other risk factors – such as high blood pressure and cholesterol that increase one's risk for heart disease and stroke. When combined with diabetes, these risk factors can add up to serious health problems,” explains Constance Geiger, PhD, RD, and consultant to the California Pistachio Commission. “Recent research has suggested that pistachios are a heart-healthy, high-protein snack. Now people have yet another reason to grab a handful – they may blunt the blood sugar response of meals and may be beneficial for assisting with long-term blood glucose control.”
Pistachios may lower vascular response to stress in type 2 diabetes
Among people with type 2 diabetes, eating pistachios may reduce the body's response to the stresses of everyday life, according to Penn State researchers.
"In adults with diabetes, two servings of pistachios per day lowered vascular constriction during stress and improved neural control of the heart," said Sheila G. West, professor of biobehavioral health and nutritional sciences. "Although nuts are high in fat, they contain good fats, fiber, potassium and antioxidants. Given the high risk of heart disease in people with diabetes, nuts are an important component of a heart healthy diet in this population."
West and her colleagues investigated the effects of pistachios on responses to standardized stress tasks in patients with well-controlled Type 2 diabetes who were otherwise healthy. They used a randomized, crossover study design in which all meals were provided. Each of the diets contained the same number of calories.
After two weeks on the typical American diet -- containing 36 percent fat and 12 percent saturated fats -- participants were randomized to one of two test diets. During the four-week test diets, participants ate only food supplied by the study. The researchers reported the results of this study in a recent issue of the Journal of the American Heart Association.
Test diets included a standard heart-healthy diet -- 27 percent fat and 7 percent saturated fat -- and a diet containing two servings per day of pistachios -- about 3 ounces or 20 percent of calories from pistachio nuts. The typical research participant consumed about 150 pistachio nuts per day. The pistachio diet contained 33 percent fat and 7 percent saturated fat. Half of the nuts consumed each day were salted and half were unsalted. At the end of each four-week diet period, the researchers measured blood pressure and total peripheral vascular resistance at rest and during two stress tests -- a cold water challenge and a confusing mental arithmetic test.
"After the pistachio diet, blood vessels remained more relaxed and open during the stress tests," West said.
Although laboratory measurements of blood pressure were not affected by pistachios, real-world measures of blood pressure (measured by an automated monitor) were significantly lower after the pistachio diet. Katherine A. Sauder, former graduate student in biobehavioral health, conducted these measurements.
"We found that systolic blood pressure during sleep was particularly affected by pistachios," she said. "Average sleep blood pressure was reduced by about 4 points and this would be expected to lower workload on the heart."
The researchers found that the pistachio diet lowered vascular constriction during stress. When arteries are dilated, the load on the heart is reduced. The physical challenge involved immersing one hand into icy water for two minutes.
"This cold stressor produces a large vascular constriction response in most people," said West. "In comparison with a low fat diet, the pistachio diet blunted that vascular response to stress."
The same pattern was seen when participants engaged in a challenging and confusing mental arithmetic task.
"Our participants still felt frustrated and angry during the math test," West noted. "The pistachio diet reduced their bodies' responses to stress, but nuts are not a cure for the emotional distress that we feel in our daily lives."
Sauder added: "As in our last study of pistachios, we did not see lower blood pressure in the laboratory setting with this dose of nuts. However, we were surprised and pleased to see that 24-hour ambulatory blood pressure was lower after the pistachio diet."
The researchers also recorded improvements in heart rate variability, a measure of how well the nervous system controls heart function. These data indicate that pistachios increased the activity of the vagus nerve, an important part of the parasympathetic nervous system that can be damaged with diabetes.
"If sustained with longer term treatment, these improvements in sleep blood pressure, vascular response to stress and vagal control of the heart could reduce risk of heart disease in this high risk group," West said.