Viguiliouk, E., C.W.C. Kendall, S.B. Mejia, A.I. Cozma, V. Ha, A. Mirrahimi, V.H. Jayalath, L.S.A. Augustin, L. Chiavaroli, L.A. Leiter, R.J. de Souza, D. J.A. Jenkins, J.L. Sievenpiper, 2014. Effect of tree nuts on glycemic control in diabetes: A systematic review and meta-analysis of randomized controlled dietary trials. PLOS ONE. DOI: 10.1371/journal.pone.0103376
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0103376
Background: Tree nut consumption has been associated with reduced diabetes risk, however, results from randomized trials on glycemic control have been inconsistent. Objective: To provide better evidence for diabetes guidelines development, we conducted a systematic review and meta-analysis of randomized controlled trials to assess the effects of tree nuts on markers of glycemic control in individuals with diabetes. Data Sources: MEDLINE, EMBASE, CINAHL, and Cochrane databases through 6 April 2014. Study Selection: Randomized controlled trials ≥3 weeks conducted in individuals with diabetes that compare the effect of diets emphasizing tree nuts to isocaloric diets without tree nuts on HbA1c, fasting glucose, fasting insulin, and HOMA-IR. Data Extraction and Synthesis: Two independent reviewer’s extracted relevant data and assessed study quality and risk of bias. Data were pooled by the generic inverse variance method and expressed as mean differences (MD) with 95% CI’s. Heterogeneity was assessed (Cochran Q-statistic) and quantified (I2). Results: Twelve trials (n = 450) were included. Diets emphasizing tree nuts at a median dose of 56 g/d significantly lowered HbA1c (MD = −0.07% [95% CI:−0.10, −0.03%]; P = 0.0003) and fasting glucose (MD = −0.15 mmol/L [95% CI: −0.27, −0.02 mmol/L]; P = 0.03) compared with control diets. No significant treatment effects were observed for fasting insulin and HOMA-IR, however the direction of effect favoured tree nuts. Limitations: Majority of trials were of short duration and poor quality. Conclusions: Pooled analyses show that tree nuts improve glycemic control in individuals with type 2 diabetes, supporting their inclusion in a healthy diet. Owing to the uncertainties in our analyses there is a need for longer, higher quality trials with a focus on using nuts to displace high-glycemic index carbohydrates.
Mejia, S.B. C.W.C. Kendall, E. Viguiliouk, L.S. Augustin, V. Ha, A.I. Cozma, A. Mirrahimi, A. Maroleanu, L. Chiavaroli, L.A. Leiter, R. J. de Souza, D.J. A. Jenkins, J.L. Sievenpiper, 2014. Effect of tree nuts on metabolic syndrome criteria: a systematic review and meta-analysis of randomised controlled trials. BMJ Open. DOI:10.1136/bmjopen-2013-004660
http://bmjopen.bmj.com/content/4/7/e004660.full?keytype=ref%5B1%5D&ijkey=wszZ1mCN44mw0KO
Objective: To provide a broader evidence summary to inform dietary guidelines of the effect of tree nuts on criteria of the metabolic syndrome (MetS). Design: We conducted a systematic review and meta-analysis of the effect of tree nuts on criteria of the MetS. Data sources: We searched MEDLINE, EMBASE, CINAHL and the Cochrane Library (through 4 April 2014). Eligibility criteria for selecting studies: We included relevant randomised controlled trials (RCTs) of ≥3 weeks reporting at least one criterion of the MetS. Data extraction: Two or more independent reviewers extracted all relevant data. Data were pooled using the generic inverse variance method using random effects models and expressed as mean differences (MD) with 95% CIs. Heterogeneity was assessed by the Cochran Q statistic and quantified by the I2 statistic. Study quality and risk of bias were assessed. Results: Eligibility criteria were met by 49 RCTs including 2226 participants who were otherwise healthy or had dyslipidaemia, MetS or type 2 diabetes mellitus. Tree nut interventions lowered triglycerides (MD=−0.06 mmol/L (95% CI −0.09 to −0.03 mmol/L)) and fasting blood glucose (MD=−0.08 mmol/L (95% CI −0.16 to −0.01 mmol/L)) compared with control diet interventions. There was no effect on waist circumference, high-density lipoprotein cholesterol or blood pressure with the direction of effect favouring tree nuts for waist circumference. There was evidence of significant unexplained heterogeneity in all analyses (p<0.05). Conclusions: Pooled analyses show a MetS benefit of tree nuts through modest decreases in triglycerides and fasting blood glucose with no adverse effects on other criteria across nut types. As our conclusions are limited by the short duration and poor quality of the majority of trials, as well as significant unexplained between-study heterogeneity, there remains a need for larger, longer, high-quality trials.
Salas-Salvado´, J., M. Guasch-Ferre´, M. Bullo´, J. Sabate´, 2014. Nuts in the prevention and treatment of metabolic syndrome. Am J Clin Nutr. 100(suppl):399S–407S,
Nuts are rich in many bioactive compounds that can exert beneficial effects on cardiovascular health. We reviewed the evidence relating nut consumption and the metabolic syndrome (MetS) and its components. Nuts reduce the postprandial glycemic response; however, long-term trials of nuts on insulin resistance and glycemic control in diabetic individuals are inconsistent. Epidemiologic studies have shown that nuts may lower the risk of diabetes incidence in women. Few studies have assessed the association between nuts and abdominal obesity, although an inverse association with body mass index and general obesity has been observed. Limited evidence suggests that nuts have a protective effect on blood pressure and endothelial function. Nuts have a cholesterol-lowering effect, but the relation between nuts and hypertriglyceridemia and high-density lipoprotein cholesterol is not well established. A recent pooled analysis of clinical trials showed that nuts are inversely related to triglyceride concentrations only in subjects with hypertriglyceridemia. An inverse association was found between the frequency of nut consumption and the prevalence and the incidence of MetS. Several trials evaluated the effect of nuts on subjects with MetS and found that they may have benefits in some components. Compared with a low-fat diet, a Mediterranean diet enriched with nuts could be beneficial for MetS management. The protective effects on metabolism could be explained by themodulation of inflammation and oxidation. Further trials are needed to clarify the role of nuts in MetS prevention and treatment.
Nishi, S.K., C.W.C. Kendall, R.P. Bazinet, B. Bashyam, C.A. Ireland, L.S.A. Augustin, S. Blanco Mejia, J.L. Sievenpiper, D.J.A. Jenkins, 2014. Nut consumption, serum fatty acid profile and estimated coronary heart disease risk in type 2 diabetes. Nutrition, Metabolism & Cardiovascular Diseases. 24(8):845-852.
Background and aims: Nut consumption has been associated with decreased risk of coronary heart disease (CHD) and type 2 diabetes which has been largely attributed to their healthy fatty acid profile, yet this has not been ascertained. Therefore, we investigated the effect of nut consumption on serum fatty acid concentrations and how these relate to changes in markers of glycemic control and calculated CHD risk score in type 2 diabetes. Methods and results: 117 subjects with type 2 diabetes consumed one of three iso-energetic (mean 475 kcal/d) supplements for 12 weeks: 1. full-dose nuts (50e100 g/d); 2. half-dose nuts with half-dose muffins; and 3. full-dose muffins. In this secondary analysis, fatty acid concentrations in the phospholipid, triacylglycerol, free fatty acid, and cholesteryl ester fractions from fasting blood samples obtained at baseline and week 12 were analyzed using thin layer and gas chromatography. Full-dose nut supplementation significantly increased serum oleic acid (OA) and MUFAs compared to the control in the phospholipid fraction (OA: P = 0.036; MUFAs: P = 0.024). Inverse associations were found with changes in CHD risk versus changes in OA and MUFAs in the triacylglycerol (r = -0.256, P = 0.011; r = -0.228, P = 0.024, respectively) and phospholipid (r = -0.278, P = 0.006; r = -0.260, P = 0.010, respectively) fractions. In the cholesteryl ester fraction, change in MUFAs was inversely associated with markers of glycemic control (HbA1c: r = -0.250, P = 0.013; fasting blood glucose: r = -0.395, P < 0.0001). Conclusion: Nut consumption increased OA and MUFA content of the serum phospholipid fraction, which was inversely associated with CHD risk factors and 10-year CHD risk
Jackson, C.L., F. Hu, 2014. Long-term associations of nut consumption with body weight and obesity. Am J Clin Nutr. 100(suppl):408S-llS.
There is some concern that the high-fat, energy-dense content of nuts may promote weight gain. Nuts, however, are rich in protein and dietary fiber, which are associated with increased satiety. They also contain high amounts of vitamins, minerals, antioxidants, and phytoesterols that may confer health benefits for cardiovascular disease and type 2 diabetes delay and prevention. Therefore, it is important to determine the association between nut consumption and long-term weight change and disease risk to reach scientific consensus and to make evidence-based public health recommendations. Several cross-sectional analyses have shown an inverse association between higher nut consumption and lower body weight. In addition, several independent prospective studies found that increasing nut consumption was associated with lower weight gain over relatively long periods of time. Moreover, high consumption of nuts (especially walnuts) has been associated with lower diabetes risk. Therefore, regular consumption (approximately one handful daily) of nuts over the long term, as a replacement to less healthful foods, can be incorporated as a component of a healthy diet for the prevention of obesity and type 2 diabetes.
Jaceldo-Siegl, K., E. Haddad, K. Oda, G.E. Fraser, J. Sabate´, 2014. Tree nuts are inversely associated with metabolic syndrome and obesity: The Adventist Health Study-2. PLoS ONE 9(1): e85133. doi:10.1371/journal.pone.0085133.
Objective: To examine the relationships of nut consumption, metabolic syndrome (MetS), and obesity in the Adventist Health Study-2, a relatively healthy population with a wide range of nut intake. Research Design and Methods: Cross-sectional analysis was conducted on clinical, dietary, anthropometric, and demographic data of 803 adults. MetS was defined according to the American Heart Association and the National Heart, Lung, and Blood Institute diagnostic criteria. We assessed intake of total nuts, tree nuts and peanuts, and also classified subjects into low tree nut/low peanut (LT/LP), low tree/high peanut (LT/HP), high tree nut/high peanut (HT/HP), and high tree/low peanut (HT/LP) consumers. Odds ratios were estimated using multivariable logistic regression. Results: 32% of subjects had MetS. Compared to LT/LP consumers, obesity was lower in LT/HP (OR = 0.89; 95% CI = 0.53, 1.48), HT/HP (OR = 0.63; 95% CI = 0.40, 0.99) and HT/LP (OR = 0.54; 95% CI = 0.34, 0.88) consumers, p for trend = 0.006. For MetS, odds ratios (95% CI) were 0.77 (0.47, 1.28), 0.65 (0.42, 1.00) and 0.68 (0.43, 1.07), respectively (p for trend = 0.056). Frequency of nut intake (once/week) had significant inverse associations with MetS (3% less for tree nuts and 2% less for total nuts) and obesity (7% less for tree nuts and 3% less for total nuts). Conclusions: Tree nuts appear to have strong inverse association with obesity, and favorable though weaker association with MetS independent of demographic, lifestyle and dietary factors.
Bao, Y., J. Han, F.B. Hu, E.L. Giovannucci, M.J. Stampfer, W.C. Willett, C.S. Fuchs, 2013. Association of nut consumption with total and cause-specific mortality. N Engl J Med. 369:2001-2011.
Background: Increased nut consumption has been associated with a reduced risk of major chronic diseases, including cardiovascular disease and type 2 diabetes mellitus. However, the association between nut consumption and mortality remains unclear. Methods: We examined the association between nut consumption and subsequent total and cause-specific mortality among 76,464 women in the Nurses’ Health Study (1980–2010) and 42,498 men in the Health Professionals Follow-up Study (1986–2010). Participants with a history of cancer, heart disease, or stroke were excluded. Nut consumption was assessed at baseline and updated every 2 to 4 years. Results: During 3,038,853 person-years of follow-up, 16,200 women and 11,229 men died. Nut consumption was inversely associated with total mortality among both women and men, after adjustment for other known or suspected risk factors. The pooled multivariate hazard ratios for death among participants who ate nuts, as compared with those who did not, were 0.93 (95% confidence interval [CI], 0.90 to 0.96) for the consumption of nuts less than once per week, 0.89 (95% CI, 0.86 to 0.93) for once per week, 0.87 (95% CI, 0.83 to 0.90) for two to four times per week, 0.85 (95% CI, 0.79 to 0.91) for five or six times per week, and 0.80 (95% CI, 0.73 to 0.86) for seven or more times per week (P<0.001 for trend). Significant inverse associations were also observed between nut consumption and deaths due to cancer, heart disease, and respiratory disease. Conclusions: In two large, independent cohorts of nurses and other health professionals, the frequency of nut consumption was inversely associated with total and cause-specific mortality, independently of other predictors of death.
Bao, Y., F.B. Hu, E.L. Giovannucci, B.M. Wolpin, M.J. Stampfer, W.C. Willett, C.S. Fuchs, 2013. Nut consumption and risk of pancreatic cancer in women. Br J Cancer. 109(11):2911-2916.
Background: Increasing nut intake has been associated with reduced risk of diabetes mellitus, which is a risk factor for pancreatic cancer. Methods: We prospectively followed 75 680 women in the Nurses’ Health Study, and examined the association between nut consumption and pancreatic cancer risk. Participants with a previous history of cancer were excluded. Nut consumption was assessed at baseline and updated every 2 to 4 years. Relative risks (RRs) and 95% confidence intervals (95% CIs) were estimated using Cox proportional hazards models. Results: We documented 466 incident cases of pancreatic cancer. After adjusting for age, height, smoking, physical activity, and total energy intake, women who consumed a 28-g (1 oz) serving size of nuts ≥2 times per week experienced a significantly lower risk of pancreatic cancer (RR, 0.65; 95% CI, 0.47–0.92; P for trend=0.007) when compared with those who largely abstained from nuts. The results did not appreciably change after further adjustment for body mass index (BMI) and history of diabetes mellitus (RR, 0.68; 95% CI, 0.48–0.95; P for trend=0.01). The inverse association persisted within strata defined by BMI, physical activity, smoking, and intakes of red meat, fruits, and vegetables. Conclusion: Frequent nut consumption is inversely associated with risk of pancreatic cancer in this large prospective cohort of women, independent of other potential risk factors for pancreatic cancer.
Sabaté, J., M. Wien, 2013. Consumption of nuts in the prevention of cardiovascular disease. Curr Nutr Rep. 2:258–266.
The leading cause of morbidity and mortality in highly developed and low- and middle-income nations is cardiovascular disease (CVD). The establishment of healthy dietary patterns is one of the cornerstones of CVD prevention, and nuts have emerged as favorable components of dietary patterns associated with reducing the CVD epidemic. The etiological connection between nuts for the prevention of CVD is based upon several lines of evidence. First, nuts are nutrient-dense whole foods that contain a distinctive mix of macronutrients, specific micronutrients and non-nutrients that have been associated with cardioprotection. Second, numerous human feeding trials have demonstrated that nut intake improves the serum lipid profile, reduces oxidation and inflammation, and improves vascular reactivity. Third, nut consumption is consistently associated with a reduced risk of CVD in many epidemiological studies. Lastly, a recent large randomized clinical trial conducted in Spain demonstrated that consuming mixed nuts daily lowers CVD risk by 30%.
Flores-Mateo G., D. Rojas-Rueda, J. Basora, E. Ros, J. Salas-Salvadó, 2013. Nut intake and adiposity: meta-analysis of clinical trials. Am J Clin Nutr. 97(6):1346-1355.
BACKGROUND: Epidemiologic studies have shown an inverse association between the frequency of nut consumption and body mass index (BMI) and risk of obesity. However, clinical trials that evaluated nut consumption on adiposity have been scarce and inconclusive. OBJECTIVE: We performed a systematic review and meta-analysis of published, randomized nut-feeding trials to estimate the effect of nut consumption on adiposity measures. DESIGN: MEDLINE and the Cochrane Central Register of Controlled Trials databases were searched for relevant clinical trials of nut intake that provided outcomes of body weight, BMI (in kg/m2), or waist-circumference measures and were published before December 2012. There were no language restrictions. Two investigators independently selected and reviewed eligible studies. The weighted mean difference (WMD) between nut or control diets was estimated by using a random-effects meta-analysis with 95% CIs. RESULTS: Thirty-three clinical trials met our inclusion criteria. Pooled results indicated a nonsignificant effect on body weight (WMD: -0.47 kg; 95% CI: -1.17, 0.22 kg; I2 = 7%), BMI (WMD: -0.40 kg/m(2); 95% CI: -0.97, 0.17 kg/m(2); I2 = 49%), or waist circumference (WMD: -1.25 cm; 95% CI: -2.82, 0.31 cm; I2 = 28%) of diets including nuts compared with control diets. These findings were remarkably robust in the sensitivity analysis. No publication bias was shown. CONCLUSION: Compared with control diets, diets enriched with nuts did not increase body weight, body mass index, or waist circumference in controlled clinical trials.
