Archive

Research Area: Cardiovascular Health

Effects of diet composition and insulin resistance status on plasma lipid levels in a weight loss intervention in women.

Le, T., S.W. Flatt, L. Natarajan, B. Pakiz, E.L. Quintana, D.D. Heath, B.K. Rana, C.L. Rock, 2016. Effects of diet composition and insulin resistance status on plasma lipid levels in a weight loss intervention in women. J Am Heart Assoc. 5(1). doi: 10.1161/JAHA.115.002771.

Background: Optimal macronutrient distribution of weight loss diets has not been established. The distribution of energy from carbohydrate and fat has been observed to promote differential plasma lipid responses in previous weight loss studies, and insulin resistance status may interact with diet composition and affect weight loss and lipid responses. Methods and Results: Overweight and obese women (n=245) were enrolled in a 1‐year behavioral weight loss intervention and randomly assigned to 1 of 3 study groups: a lower fat (20% energy), higher carbohydrate (65% energy) diet; a lower carbohydrate (45% energy), higher fat (35% energy) diet; or a walnut‐rich, higher fat (35% energy), lower carbohydrate (45% energy) diet. Blood samples and data available from 213 women at baseline and at 6 months were the focus of this analysis. Triglycerides, total cholesterol, and high‐ and low‐density lipoprotein cholesterol were quantified and compared between and within groups. Triglycerides decreased in all study arms at 6 months (P<0.05). The walnut‐rich diet increased high‐density lipoprotein cholesterol more than either the lower fat or lower carbohydrate diet (P<0.05). The walnut‐rich diet also reduced low‐density lipoprotein cholesterol in insulin‐sensitive women, whereas the lower fat diet reduced both total cholesterol and high‐density lipoprotein cholesterol in insulin‐sensitive women (P<0.05). Insulin sensitivity and C‐reactive protein levels also improved. Conclusions: Weight loss was similar across the diet groups, although insulin‐sensitive women lost more weight with a lower fat, higher carbohydrate diet versus a higher fat, lower carbohydrate diet. The walnut‐rich, higher fat diet resulted in the most favorable changes in lipid levels.

Key area: insulin resistance, lipids, walnuts/ weight management/weight, satiety,

Pairing nuts and dried fruit for cardiometabolic health.

Carughi, A., M.J. Feeney, P. Kris-Etherton, V. Fulgoni III, C.W.C. Kendall, M. Bulló, D. Webb, 2016. Pairing nuts and dried fruit for cardiometabolic health. Nutrition Journal. 15:23. doi.org/10.1186/s12937-016-0142-4.

Certain dietary patterns, in which fruits and nuts are featured prominently, reduce risk of diabetes and cardiovascular disease. However, estimated fruit consumption historically in the U.S. has been lower than recommendations. Dried fruit intake is even lower with only about 6.9 % of the adult population reporting any consumption. The 2015 Dietary Guidelines Advisory Committee identified a gap between recommended fruit and vegetable intakes and the amount the population consumes. Even fewer Americans consume tree nuts, which are a nutrient-dense food, rich in bioactive compounds and healthy fatty acids. Consumption of fruits and nuts has been associated with reduced risk of cardiometabolic disease. An estimated 5.5 to 8.4 % of U.S. adults consume tree nuts and/or tree nut butter. This review examines the potential of pairing nuts and dried fruit to reduce cardiometabolic risk factors and focuses on emerging data on raisins and pistachios as representative of each food category. Evidence suggests that increasing consumption of both could help improve Americans’ nutritional status and reduce the risk of chronic diseases.

More pistachio nuts for improving the blood lipid profile. Systematic review of epidemiological evidence.

Lippi, G., G. Cervellin, C. Mattiuzzi, 2016. More pistachio nuts for improving the blood lipid profile. Systematic review of epidemiological evidence. Acta Biomed. 87(1): 5-12.

Recent evidence suggests that regular intake of nuts may be associated with reduction of all-cause mortality, especially cardiovascular deaths. Among all types of nuts, pistachio displays the most favorable dietary composition. Therefore, we searched Medline and ISI Web of Science to identify interventional studies which evaluated changes of conventional blood lipids after replacing part of normal caloric intake with pistachio nuts in humans. Overall, 9 studies were finally included in our systematical literature review (4 randomized crossover, 3 randomized controlled and 2 prospective). In 67% interventional studies total cholesterol and low-density lipoprotein cholesterol (LDL-C) decreased, whereas high-density lipoprotein cholesterol (HDL-C) increased. In all studies total cholesterol/HDL-C ratio and LDL-C/HDL-C ratio decreased after replacing caloric intake with pistachio nuts for not less than 3 weeks. A significant reduction of triglycerides could only be observed in 25% studies. Even more importantly, in no interventional study the intake of pistachio nuts was associated with unfavorable changes of the lipid profile. The results of our literature search provide solid evidence that intake of pistachio nuts may exerts favorable effects on the traditional blood profile, provided that their consumption does not increase the habitual or recommended daily caloric intake. It seems also reasonable to suggest that further studies aimed to investigate the favorable effects of nuts on human diseases should distinguish between one type and the others, since the different nuts exhibit unique dietary composition and may hence produce distinctive biological effects in humans.

Associations between nut consumption and inflammatory biomarkers

Yu, Z., V.S. Malik, N. Keum, F.B. Hu, E.L. Giovannucci, M.J. Stampfer, W.C. Willett, C.S. Fuchs, Y. Bao, 2016. Associations between nut consumption and inflammatory biomarkers. AJCN. First published ahead of print July 27, 2016 as doi: 10.3945/ajcn.116.134205.

Background: Increased nut consumption has been associated with reduced risk of cardiovascular disease and type 2 diabetes, as well as a healthy lipid profile. However, the associations between nut consumption and inflammatory biomarkers are unclear. Objective: We investigated habitual nut consumption in relation to inflammatory biomarkers in 2 large cohorts of US men and women. Design: We analyzed cross-sectional data from 5013 participants in the Nurses’ Health Study (NHS) and Health Professionals Follow-Up Study (HPFS) who were free of diabetes. Nut intake, defined as intake of peanuts and other nuts, was estimated from food frequency questionnaires, and cumulative averages from 1986 and 1990 in the NHS and from 1990 and 1994 in the HPFS were used. Plasma biomarkers were collected in 1989–1990 in the NHS and 1993–1995 in the HPFS. Multivariate linear regression was used to assess the associations of nut consumption with fasting plasma C-reactive protein (CRP, n = 4941), interleukin 6 (IL-6, n = 2859), and tumor necrosis factor receptor 2 (TNFR2, n = 2905). Results: A greater intake of nuts was associated with lower amounts of a subset of inflammatory biomarkers, after adjusting for demographic, medical, dietary, and lifestyle variables. The relative concentrations (ratios) and 95% CIs comparing subjects with nut intake of $5 times/wk and those in the categories of never or almost never were as follows: CRP: 0.80 (0.69, 0.90), P-trend = 0.0003; and IL-6: 0.86 (0.77, 0.97), P-trend = 0.006. These associations remained significant after further adjustment for body mass index. No significant association was observed with TNFR2. Substituting 3 servings of nuts/wk for 3 servings of red meat, processed meat, eggs, or refined grains/wk was associated with significantly lower CRP (all P , 0.0001) and IL-6 (P ranges from 0.001 to 0.017). Conclusion: Frequent nut consumption was associated with a healthy profile of inflammatory biomarkers.

Effects of hazelnut consumption on blood lipids and body weight: A systematic review and Bayesian meta-analysis.

S. Perna, A. Giacosa, G. Bonitta, C. Bologna, A. Isu, D. Guido, M. Rondanelli, 2016. Effects of hazelnut consumption on blood lipids and body weight: A systematic review and Bayesian meta-analysis. Nutrients. 8,747; doi:10.3390/nu8120747.

Hazelnuts are rich in monounsaturated fatty acids and antioxidant bioactive substances: their consumption has been associated with a decreased risk of cardiovascular disease events. A systematic review and a meta-analysis was performed to combine the results from several trials and to estimate the pooled (overall) effect of hazelnuts on blood lipids and body weight outcomes. Specifically, a Bayesian random effect meta-analysis of mean differences of ∆-changes from baseline across treatment (MD∆) (i.e., hazelnut-enriched diet vs. control diet) has been conducted. Nine studies representing 425 participants were included in the analysis. The intervention diet lasted 28–84 days with a dosage of hazelnuts ranging from 29 to 69 g/day. Out of nine studies, three randomized studies have been meta-analyzed showing a significant reduction in low-density lipoprotein (LDL) cholesterol (pooled MD∆ = −0.150 mmol/L; 95% highest posterior density interval (95% HPD) = −0.308; −0.003) in favor of a hazelnut-enriched diet. Total cholesterol showed a marked trend toward a decrease (pooled MD∆ = −0.127 mmol/L; 95% HPD = −0.284; 0.014) and high-density lipoprotein (HDL) cholesterol remained substantially stable (pooled MD∆ = 0.002 mmol/L; 95% HPD = −0.140; 0.147). No effects on triglycerides (pooled MD∆ = 0.045 mmol/L; 95% HPD = −0.195; 0.269) and body mass index (BMI) (pooled MD∆ = 0.062 kg/m2 ; 95% HPD = −0.293; 0.469) were found. Hazelnut-enriched diet is associated with a decrease of LDL and total cholesterol, while HDL cholesterol, triglycerides and BMI remain substantially unchanged.

The effects of almond consumption on fasting blood lipid levels: a systematic review and meta-analysis of randomised controlled trials.

Musa-Veloso, K; L. Paulionis, T. Poon, H-Y. Lee, 2016. The effects of almond consumption on fasting blood lipid levels: a systematic review and meta-analysis of randomised controlled trials. J. Nutr. Sci. 5(e34):1-15.

A systematic review and meta-analysis of randomised controlled trials was undertaken to determine the effects of almond consumption on blood lipid levels, namely total cholesterol (TC), LDL-cholesterol (LDL-C), HDL-cholesterol (HDL-C), TAG and the ratios of TC:HDL-C and LDL-C:HDL-C. Following a comprehensive search of the scientific literature, a total of eighteen relevant publications and twenty-seven almond-control datasets were identified. Across the studies, the mean differences in the effect for each blood lipid parameter (i.e. the control-adjusted values) were pooled in a meta-analysis using a random-effects model. It was determined that TC, LDL-C and TAG were significantly reduced by -0·153 mmol/l (P < 0·001), -0·124 mmol/l (P = 0·001) and -0·067 mmol/l (P = 0·042), respectively, and that HDL-C was not affected (-0·017 mmol/l; P = 0·207). These results are aligned with data from prospective observational studies and a recent large-scale intervention study in which it was demonstrated that the consumption of nuts reduces the risk of heart disease. The consumption of nuts as part of a healthy diet should be encouraged to help in the maintenance of healthy blood lipid levels and to reduce the risk of heart disease.

Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials.

Del Gobbo, L.C., M.C. Falk, R. Feldman, K. Lewis, D. Mozaffarian, 2015. Effects of tree nuts on blood lipids, apolipoproteins, and blood pressure: systematic review, meta-analysis, and dose-response of 61 controlled intervention trials. AJCN. First published ahead of print November 11, 2015 as doi: 10.3945/ajcn.115.110965.

Background: The effects of nuts on major cardiovascular disease (CVD) risk factors, including dose-responses and potential heterogeneity by nut type or phytosterol content, are not well established. Objectives: We examined the effects of tree nuts (walnuts, pistachios, macadamia nuts, pecans, cashews, almonds, hazelnuts, and Brazil nuts) on blood lipids [total cholesterol, low-density lipoprotein (LDL) cholesterol, high-density lipoprotein, and triglycerides], lipoproteins [apolipoprotein A1, apolipoprotein B (ApoB), and apolipoprotein B100], blood pressure, and inflammation (C-reactive protein) in adults aged $18 y without prevalent CVD. Design: We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Two investigators screened 1301 potentially eligible PubMed articles in duplicate. We calculated mean differences between nut intervention and control arms, dose-standardized to one 1-oz (28.4 g) serving/d, by using inverse-variance fixed-effects meta-analysis. Dose-response for nut intake was examined by using linear regression and fractional polynomial modeling. Heterogeneity by age, sex, background diet, baseline risk factors, nut type, disease condition, duration, and quality score was assessed with meta-regression. Publication bias was evaluated by using funnel plots and Egger’s and Begg’s tests. Results: Sixty-one trials met eligibility criteria (n = 2582). Interventions ranged from 3 to 26 wk. Nut intake (per serving/d) lowered total cholesterol (24.7 mg/dL; 95% CI: 25.3, 24.0 mg/dL), LDL cholesterol (24.8 mg/dL; 95% CI: 25.5, 24.2 mg/dL), ApoB (23.7 mg/dL; 95% CI: 25.2, 22.3 mg/dL), and triglycerides (22.2 mg/dL; 95% CI: 23.8, 20.5 mg/dL) with no statistically significant effects on other outcomes. The dose-response between nut intake and total cholesterol and LDL cholesterol was nonlinear (P-nonlinearity , 0.001 each); stronger effects were observed for $60 g nuts/d. Significant heterogeneity was not observed by nut type or other factors. For ApoB, stronger effects were observed in populations with type 2 diabetes (211.5 mg/dL; 95% CI: 216.2, 26.8 mg/dL) than in healthy populations (22.5 mg/dL; 95% CI: 24.7, 20.3 mg/dL) (P-heterogeneity = 0.015). Little evidence of publication bias was found. Conclusions: Tree nut intake lowers total cholesterol, LDL cholesterol, ApoB, and triglycerides. The major determinant of cholesterol lowering appears to be nut dose rather than nut type. Our findings also highlight the need for investigation of possible stronger effects at high nut doses and among diabetic populations.

Nuts and CVD.

Ros, E., 2015. Nuts and CVD. Br J Nutr. 113, S111–S120.

Nuts are nutrient-dense foods with complex matrices rich in unsaturated fatty acids and other bioactive compounds, such as l-arginine, fibre, healthful minerals, vitamin E, phytosterols and polyphenols. By virtue of their unique composition, nuts are likely to beneficially affect cardiovascular health. Epidemiological studies have associated nut consumption with a reduced incidence of CHD in both sexes and of diabetes in women, but not in men. Feeding trials have clearly demonstrated that consumption of all kinds of nuts has a cholesterol-lowering effect, even in the context of healthy diets. There is increasing evidence that nut consumption has a beneficial effect on oxidative stress, inflammation and vascular reactivity. Blood pressure, visceral adiposity and the metabolic syndrome also appear to be positively influenced by nut consumption. Contrary to expectations, epidemiological studies and clinical trials suggest that regular nut consumption is not associated with undue weight gain. Recently, the PREvención con DIeta MEDiterránea randomised clinical trial of long-term nutrition intervention in subjects at high cardiovascular risk provided first-class evidence that regular nut consumption is associated with a 50% reduction in incident diabetes and, more importantly, a 30% reduction in CVD. Of note, incident stroke was reduced by nearly 50% in participants allocated to a Mediterranean diet enriched with a daily serving of mixed nuts (15 g walnuts, 7·5 g almonds and 7·5 g hazelnuts). Thus, it is clear that frequent nut consumption has a beneficial effect on CVD risk that is likely to be mediated by salutary effects on intermediate risk factors.

Walnut ingestion in adults at risk for diabetes: effects on body composition, diet quality, and cardiac risk measures.

Njike, V.Y., R. Ayettey, P. Petraro, J.A. Treu, D.L. Katz, 2015. Walnut ingestion in adults at risk for diabetes: effects on body composition, diet quality, and cardiac risk measures. BMJ Open Diabetes Research and Care. doi:10.1136/bmjdrc-2015-000115.

Background: Despite their energy density, walnuts can be included in the diet without adverse effects on weight or body composition. The effect of habitual walnut intake on total calorie intake is not well studied. Effects on overall diet quality have not been reported. Methods: Randomized, controlled, modified Latin square parallel design study with 2 treatment arms. The 112 participants were randomly assigned to a diet with or without dietary counseling to adjust calorie intake. Within each treatment arm, participants were further randomized to 1 of the 2 possible sequence permutations to receive a walnut-included diet with 56 g (providing 366 kcal) of walnuts per day and a walnut-excluded diet. Participants were assessed for diet quality, body composition, and cardiac risk measures. Results: When compared with a walnut-excluded diet, a walnut-included diet for 6 months, with or without dietary counseling to adjust caloric intake, significantly improved diet quality as measured by the Healthy Eating Index 2010 (9.14±17.71 vs 0.40±15.13; p=0.02 and 7.02±15.89 vs -5.92±21.84; p=0.001, respectively). Endothelial function, total and low-density lipoprotein (LDL) cholesterol improved significantly from baseline in the walnut-included diet. Body mass index, percent body fat, visceral fat, fasting glucose, glycated hemoglobin, and blood pressure did not change significantly. CONCLUSION: The inclusion of walnuts in an ad libitum diet for 6 months, with or without dietary counseling to adjust calorie intake, significantly improved diet quality, endothelial function, total and LDL cholesterol, but had no effects on anthropometric measures, blood glucose level, and blood pressure.

Effects of short-term walnut consumption on human microvascular function and its relationship to plasma epoxide content.

Holt, R.R., S.J. Yim, G.C. Shearer, R.M. Hackman, D. Djurica, J.W. Newman, A.W. Shindel, C.L. Keen, 2015. Effects of short-term walnut consumption on human microvascular function and its relationship to plasma epoxide content. J Nutr Biochem. 26(12):1458-66.

Improved vascular function after the incorporation of walnuts into controlled or high fat diets has been reported, however the mechanism(s) underlying this effect of walnuts are poorly defined. The objective of the current study was to evaluate the acute and short-term effects of walnut intake on changes in microvascular function and the relationship of these effects to plasma epoxides, the cytochrome P450 derived metabolites of fatty acids. Thirty-eight hypercholesterolemic postmenopausal women were randomized to 4 weeks of 5 g or 40 g of daily walnut intake. All outcomes were measured after an overnight fast and 4 hours after walnut intake. Microvascular function, assessed as the reactive hyperemia index (RHI) was the primary outcome measure, with serum lipids and plasma epoxides as secondary measures. Compared to 5 g of daily walnut intake, consuming 40 g/d of walnuts for 4 weeks increased the RHI and Framingham RHI. Total cholesterol and low and high density-cholesterol did not significantly change after walnut intake. The change in RHI after 4 weeks of walnut intake was associated with the change in the sum of plasma epoxides (r=0.65, p = 0.002), but not with the change in the sum of plasma hydroxyeicosatetraenoic acids (HETE). Of the individual plasma epoxides, arachidonic acid derived 14(15)-epoxyeicosatrienoic acid (EpETrE) was most strongly associated with the change in microvascular function (r=0.72, p < 0.001).  These data support the concept that the intake of walnut-derived fatty acids can favorably affect plasma epoxide production, resulting in improved microvascular function.