From Beans to Nuts

Nuts and legumes, which are sources of protein, fiber, vitamins, and minerals, are nutritional powerhouses in little packages. With today’s movement toward less-processed and all-natural foods, they are positioned to perfectly fit this demand. Because of their nutritional profiles, nuts and legumes have been linked to reducing risk of coronary heart disease (CHD), aiding with weight management, and affecting risk factors associated with diabetes. Here is a closer look at some of these specific foods.

Nutty Nutrition
Much of the recent research related to nuts has focused on their benefits for weight management and diabetes prevention or control. For example, research presented last year at the American Dietetic Assn. Food and Nutrition Conference and Exposition in Denver, Colo., showed that tree nuts (almonds, Brazil nuts, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios, and walnuts) were associated with better diet, lower body weight measures, and lower prevalence of health risks (International Tree Nut Council, 2009a). The study looked at 13,292 men and women (ages 19+) participating in the 1999–2004 National Health and Nutrition Examination Surveys. Nut consumers were defined as those who consumed ≥ ¼ oz/day.

Another study presented last year at the Experimental Biology Conference in New Orleans showed that tree nuts may play an important role in the management of diabetes (International Tree Nut Council, 2009b). Researchers from the University of Toronto and St. Michael’s Hospital in Toronto, Canada, revealed that the full dose nut group (½ cup mixed nuts) had significantly reduced low density lipoprotein (LDL) and total cholesterol levels compared with the control group. In addition, there was a significant reduction from baseline in HbA1c, a marker of blood sugar control, in the full dose nut group.

While the previous studies focused on a mixture of tree nuts, specific nuts have also shown potential in addressing today’s health concerns.

• Almonds. Rajaram et al. (2009) looked at the effect of an almond-enriched high-monounsaturated fat diet on CHD risk factors such as inflammation and hemostasis. The study included 25 healthy adults (11 men; 14 women), ages 22–53. Subjects were assigned in random order to three diets for 4 weeks each: a heart-healthy control diet with no nuts, a low-almond diet, and a high-almond diet. Serum E-selectin, a cell adhesion molecule, was significantly lower on the high-almond diet compared with the control diet. C-reactive protein, which increases in response to inflammation, was lower in both of the almond diets compared with the control diet. Researchers concluded that consumption of almonds influenced a few but not all of the markers of inflammation and hemostasis.

Jenkins et al. (2008) showed that almonds reduced biomarkers of lipid peroxidation in hyperlipidemic adults. Researchers compared the dose-response effects of whole almonds, taken as snacks, to low–saturated fat whole wheat muffins (control) in the therapeutic diets of 27 hyperlipidemic subjects. For one month, adults consumed full-dose almonds (73 ± 3 g/d), half-dose almonds plus half-dose muffins (half-dose almonds), or full-dose muffins (control). At 4 weeks, the full-dose almond group reduced serum concentrations of malondialdehyde (MDA) and creatinine-adjusted urinary isoprostane output compared with the control. Almond antioxidant activity was demonstrated by their effect on these two biomarkers of lipid peroxidation. The researchers noted that antioxidant activity provides an additional possible mechanism (in addition to lowering cholesterol) that may account for the reduction in CHD risk with nut consumption.

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• Hazelnuts. Mercanlıgil et al. (2006) looked at the effects of a hazelnut-enriched diet on plasma cholesterol and lipoprotein profiles in 15 hypercholesterolemic adult men age 48 ± 8 years. Results showed that a single serving a day of hazelnuts favorably altered multiple plasma lipid variables and reduced risk of CHD. Compared with baseline, the hazelnut-enriched diet decreased the concentrations of very low density lipoprotein (VLDL) cholesterol, triacylglycerol, and apolipoprotein B by 29.5, 31.8, and 9.2%, respectively, while increasing high density lipoprotein (HDL) cholesterol concentrations by 12.6%.

• Macadamia nuts. Griel et al. (2008) showed that macadamia nuts can be included in a heart-healthy dietary pattern that reduces lipid/lipoprotein cardiovascular disease (CVD) risk factors. Researchers compared a diet rich in macadamia nuts (1.5 oz) vs an average American diet on the lipid/lipoprotein profile of 15 mildly hypercholesterolemic subjects. Serum concentrations of total cholesterol (TC) and LDL cholesterol (LDL-C) following the macadamia diet were lower than with the average American diet. The serum non-HDL cholesterol (HDL-C) concentration and the ratios of TC:HDL-C and LDLC: HDL-C were reduced following consumption of the macadamia diet.

• Pistachios. Last year, the University of Toronto unveiled study findings at the Experimental Biology Conference in New Orleans that showed incorporating pistachios into a meal resulted in delayed emptying of the stomach and blunting of the blood sugar curve (Western Pistachio Assn., 2009). Fifteen subjects ate three nutritionally equivalent test meals on three separate occasions: 1) white bread alone; 2) white bread plus 2 oz pistachios; or 3) white bread with butter and cheese. The researchers measured blood sugar and gut hormone responses to each of the test meals over a three-hour period. Results showed that, compared to the white bread alone, pistachios blunted the blood sugar response, delayed gastric emptying, and increased levels of the satiety hormone ghrelin. Researchers concluded that pistachios consumed with carbohydrate-rich meals may blunt/moderate the blood sugar response after a meal and thus may be of benefit in improving long-term glycemic control.

Data unveiled at the 2008 Experimental Biology Conference in San Diego showed that snacking on pistachios had a positive impact on improving cardiovascular health by significantly reducing inflammation in the body (Western Pistachio Assn., 2008). The study, led by researcher Penny Kris-Etherton from Penn State University’s Dept. of Nutritional Sciences, included 28 healthy men and women (ages 30–70) with slightly elevated cholesterol levels. It tested three cholesterol-lowering diets, one without pistachio consumption and two with varied levels of pistachios intake (1.5 oz and 3.0 oz). Compared to baseline, both the 1.5 oz and 3.0 oz pistachio diets resulted in reduction of total cholesterol and LDL cholesterol. In addition, including pistachios as part of a heart-healthy diet also significantly reduced inflammation at the cellular level.

• Walnuts. Ma et al. (2010) looked at the effect of daily walnut consumption on CVD risk factors in type 2 diabetics. A total of 24 adults with type 2 diabetes participated in the study and were instructed to eat 2 oz of walnuts each day along with their normal diets during one 8-week period and to follow their normal diets during another 8-week period. Endothelial function significantly improved after consumption of a walnut-enriched ad libitum diet compared with function after consumption of a diet without walnuts. Researchers concluded that a walnut-enriched ad libitum diet  improved endothelium-dependent vasodilatation in type 2 diabetic individuals, suggesting a potential reduction in overall cardiac risk.

Tapsell et al. (2009) looked at the effect of walnut consumption on metabolic outcomes in type 2 diabetes. Fifty overweight adults with noninsulin-treated diabetes (mean age 54 ± 8.7 years) were randomized to receive lowfat dietary advice ± 30 g/ day walnuts targeting weight maintenance for 1 year. The walnut group consumed significantly more polyunsaturated fatty acids than the control, an outcome attributed to walnut consumption. The walnut group produced significantly greater reductions in fasting insulin levels, an effect seen largely in the first 3 mo. Researchers concluded that dietary fat can be manipulated with whole foods such as walnuts, producing reductions in fasting insulin levels.

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Beany Nutrition
Legumes are plant species that have seed pods that split along both sides when ripe. Some of the more common legumes used for human consumption are peanuts, pulses, and soybeans.

• Peanuts. In addition to providing an excellent source of niacin, peanuts are also good sources of folate, vitamin E, and fiber. Sanders et al. (2000) also showed that peanuts contain resveratrol, a naturally occurring phytochemical that has been associated with reduced risk of CVD.

• Pulses. The edible seeds of legumes, pulses include lentils, beans, peas, and chickpeas. Because of pulses’ high protein and fiber content, they have been shown to benefit cholesterol levels and aid in weight management.

Pulses have a low glycemic index (GI), which is particularly beneficial for people with diabetes. Sievenpiper et al. (2009) reported that pulses improved markers of longer-term glycemic control in humans. Researchers conducted a systematic review and meta-analysis of 41 randomized controlled experimental trials investigating the effect of pulses alone or as part of low-GI or high-fiber diets, on markers of glycemic control in people with and without diabetes. When eaten on their own or as part of a high-fiber diet, pulses lowered fasting blood glucose levels. Pulses were also found to improve glycosylated hemoglobin (HbA1c), an indicator of long-term blood sugar control. In fact, when pulses were eaten as part of a high-fiber or low-glycemic diet, the significant reduction in HbA1c seen in people with type 2 diabetes was comparable to that achieved by oral medications.

• Soybeans. Shu et al. (2009) showed that soyfood consumption was significantly linked to a decreased risk of death and cancer recurrence among breast cancer patients. Researchers evaluated the association of soy food intake after diagnosis of breast cancer with total mortality and cancer recurrence in a large, population-based cohort study of 5,042 female breast cancer survivors in China. Soy food intake, as measured by either soy protein or soy isoflavone intake, was inversely associated with mortality and recurrence. The findings showed that the women in the study who consumed higher amounts of soy protein had a 7.4% mortality rate and an 8.0% cancer recurrence rate. In contrast, the women who consumed the least amount of soy had a 10.3% mortality rate and 11.2% recurrence rate.

Nanri et al. (2010) conducted a study with Japanese adults that investigated the relationship between soy product and isoflavone intake and the risk of developing type 2 diabetes. A total of 25,872 men and 33,919 women ages 45–75 with no history of diabetes participated in the study. Over the five years, a total of 1,114 new cases of type 2 diabetes were self-reported. While intakes of soy products and isoflavones were not significantly associated with type 2 diabetes in either men or women, researchers found that among overweight women, a higher intake of soy products was associated with a lower risk of type 2 diabetes.

Pipe et al. (2009) looked at the effect of soy protein isolate (SPI) consumption on serum lipids in 29 adults with diet-controlled type 2 diabetes. Subjects consumed SPI (80 mg/day aglycone isoflavones) or milk protein isolate (MPI) for 57 days separated by a 28-day washout period. SPI consumption reduced serum LDL cholesterol, LDL cholesterol:HDL cholesterol, and apolipoprotein B:apolipoprotein A-I compared with MPI. The data demonstrated that consumption of soy protein can modulate some serum lipids in a direction beneficial for CVD risk in adults with type 2 diabetes.

by Linda Milo Ohr,
Contributing Editor,
Denver, Colo.
[email protected]

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