Serum lipid profiles in Japanese women and men during consumption of walnuts

Effect of nut consumption on blood lipids: An updated systematic review and meta-analysis of randomized controlled trials

AIMS

Nuts are nutrient-dense foods touted for their health-promoting effects, especially regarding cardiovascular health, yet inconsistencies in the literature remain in relation to their effect on blood lipids. Hence, a systematic review and meta-analysis of randomized controlled trials (RCTs) was conducted to determine the effect of nut intake on blood lipids.

DATA SYNTHESIS

MEDLINE-PubMed and Cochrane databases were searched. 113 unique trials met eligibility criteria (n = 8060 adults with various health status) assessing the effect of a median daily dose of 45.5 g/d of nuts compared to a non-nut control on blood lipid outcomes met inclusion criteria. Overall, nut consumption resulted in moderate reductions in total cholesterol (mean difference, -0.14 mmol/L [95 % confidence interval, -0.18 to -0.10 mmol/L]) and LDL-C (-0.12 mmol/L [-0.14 to -0.09 mmol/L]), with small reductions in triglycerides (-0.05 mmol/L [-0.07 to -0.03 mmol/L]), TC:HDL-C (-0.11 [-0.16 to -0.06]), LDL-C:HDL-C (-0.19 [-0.24 to -0.12]), and apolipoprotein B (-0.04 g/L [-0.06 to -0.02 g/L]). There was no significant impact on HDL-cholesterol or other assessed measures. Certainty of evidence was high for apolipoprotein A, and generally moderate/low for all other outcomes. Sensitivity analysis did not change the evidence on the main outcomes. Significant effect modifications in subgroup analysis were shown for most of the lipid parameters assessed. None of these subgroup effects altered the evidence of heterogeneity for any primary outcome.

CONCLUSIONS

Current evidence provides a good indication that consuming nuts may advantageously affect blood lipids in adults with a mix of health status.

PROSPERO REGISTRATION

PROSPERO identifier, CRD42022358688.

Does Medication Status Impact the Effectiveness of Nuts in Altering Blood Pressure and Lipids? A Systematic Review and Meta-Analysis

CONTEXT

Nut consumption is attributed to improvements in risk factors for cardiovascular disease (CVD), including high blood pressure (BP) and dyslipidemia. However, it is unclear whether these effects are altered with concurrent treatment with BP and lipid-lowering medication.

OBJECTIVE

We sought to investigate the effects of the consumption of whole tree nuts and peanuts (collectively termed nuts) on BP and lipids, and whether BP and lipid-lowering medication use alters these effects.

DATA SOURCES

The MEDLINE, EMBASE, Scopus, and Web of Science databases were systematically searched through June 21, 2023, for randomized controlled trials (RCTs) assessing the effects of nut consumption on BP and/or lipids.

DATA EXTRACTION

Random effects meta-analyses (mean difference, 95% confidence interval [CI]) were conducted, with subgroup analyses based on reported participant use of BP or lipid-lowering medication, including medicated, unmedicated, unreported (ie, use not specified), and mixed (ie, included combined data from medicated and unmedicated participants). A total of 115 studies were included in the review, of which 109 were meta-analysed.

DATA ANALYSIS

Nut consumption significantly reduced triglycerides (TG), total cholesterol, low-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B, with no effect on high-density lipoprotein cholesterol or blood pressure. Few studies were conducted in medicated participants only (n = 1 for lipid outcomes only), and for the studies including both medicated and unmedicated participants (ie, mixed), outcomes by medication use were not reported. Significant differences in TG and apolipoprotein B were observed between medication use groups, with nut consumption resulting in the largest reductions in unmedicated participants. Strong heterogeneity was observed with no evidence of publication bias.

CONCLUSIONS

Lipid-lowering, but not BP-lowering benefits of nut consumption were observed; however, few studies reported the effect based on participants' medication status. Future studies are required to determine if there are additional benefits of including nuts in the diet of medicated patients with cardiovascular disease.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration code CRD42022296849.

Tree Nut and Peanut Consumption and Risk of Cardiovascular Disease: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Cardiovascular disease (CVD) is the leading cause of death globally. Habitual consumption of tree nuts and peanuts is associated with cardioprotective benefits. Food-based dietary guidelines globally recommend nuts as a key component of a healthy diet. This systematic review and meta-analysis were conducted to examine the relationship between tree nut and peanut consumption and risk factors for CVD in randomized controlled trials (RCTs) (PROSPERO: CRD42022309156). MEDLINE, PubMed, CINAHL, and Cochrane Central databases were searched up to 26 September, 2021. All RCT studies that assessed the effects of tree nut or peanut consumption of any dose on CVD risk factors were included. Review Manager software was used to conduct a random effect meta-analysis for CVD outcomes from RCTs. Forest plots were generated for each outcome, between-study heterogeneity was estimated using the I2 test statistic and funnel plots and Egger's test for outcomes with ≥10 strata. The quality assessment used the Health Canada Quality Appraisal Tool, and the certainty of the evidence was assessed using grading of recommendations assessment, development, and evaluation (GRADE). A total of 153 articles describing 139 studies (81 parallel design and 58 cross-over design) were included in the systematic review, with 129 studies in the meta-analysis. The meta-analysis showed a significant decrease for low-density lipoprotein (LDL) cholesterol, total cholesterol (TC), triglycerides (TG), TC:high-density lipoprotein (HDL) cholesterol, LDL cholesterol:HDL cholesterol, and apolipoprotein B (apoB) following nut consumption. However, the quality of evidence was "low" for only 18 intervention studies. The certainty of the body of evidence for TC:HDL cholesterol, LDL cholesterol:HDL cholesterol, and apoB were "moderate" because of inconsistency, for TG were "low," and for LDL cholesterol and TC were "very low" because of inconsistency and the likelihood of publication bias. The findings of this review provide evidence of a combined effect of tree nuts and peanuts on a range of biomarkers to create an overall CVD risk reduction.

Association of nut consumption with CVD risk factors in young to middle-aged adults: The Coronary Artery Risk Development in Young Adults (CARDIA) study

BACKGROUND AND AIMS

Few studies have examined long-term associations of walnut, other nut, and no nut consumption with cardiovascular disease (CVD) risk factors. Results from prospective studies with long-term follow-up can provide further evidence for dietary guideline messaging to consume nuts. Therefore, we examined the associations of walnut, other nut, and no nut consumption with diet quality and CVD risk factors over 30 years of follow-up.

METHODS AND RESULTS

Data were analyzed from 3092 young adults enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. Dietary intake, including walnuts and other nuts, was assessed 3 times over 20 years. CVD risk factors were measured at multiple exams. General linear regression evaluated the associations of walnut, other nut, and no nut consumption with CVD risk factors over 30 years (Y30) of follow-up. The 20-year cumulative mean intake of walnuts (0.74 oz/d), other nuts (1.6 oz/d), or no nut consumption was differentially associated with HEI-2015 and CVD risk factors by Y30. Generally, walnut consumers had significantly higher HEI-2015, lower body mass index, waist circumference, blood pressure, and triglyceride concentration, and gained less weight since baseline than other nut consumers (p ≤ 0.05 for all). Further, walnut consumers had lower fasting blood glucose than no nut consumers (p ≤ 0.05).

CONCLUSION

Study findings that walnut and other nut consumption was associated with better CVD risk factors and diet quality aligns with the 2020-2025 US. Dietary Guidelines for Americans recommendation to consume nuts, such as walnuts, within the context of a healthy diet.

The comparison of omega-3 and flaxseed oil on serum lipids and lipoproteins in hyperlipidemic male rats

Hyperlipidemia affects a significant number of patients despite treatment with cholesterol-lowering drugs. Due to the low efficacy of synthetic drugs, there is a need for new agents with low side effects. Therefore, the effects of flaxseeds oil and animal omega-3 on the hyperlipidemic rats were investigated. Forty male Wistar rats were assigned to four groups (n = 10): 1) control group that was fed with a standard diet (pallets). 2) high-fat diet (HFD) control group that was fed with high-fat food for 42 days, 3) Omega-3 group that received HFD for 21 days, followed by HFD + omega-3 capsule (600 mg/kg; 21 days/gavage), and 4) flaxseed oil group that received HFD for 21 days, followed by HFD + flaxseed oil (10 ml/kg; 21 days/gavage). Blood samples were collected three times and at the stages one to third of the experiment from the rats' tail. The results showed that high levels of fat significantly increased cholesterol, triglyceride (TG), and low-density lipoprotein (LDL) in the flaxseed, HFD control, and omega-3 groups in the second stages of the experiment. Inverse, omega-3 or flaxseed oil supplementation decreased cholesterol, TG, and LDL levels and increased high-density lipoprotein (HDL) level in comparison with the HFD control group in the third stages of the experiment. There was no significant difference in the studied parameters between the flaxseed- and omega-3-treated groups. It can be concluded that flaxseed oil similar to omega-3 is effective in the treatment of hyperlipidemia.

The Effects of Peanuts and Tree Nuts on Lipid Profile in Type 2 Diabetic Patients: A Systematic Review and Meta-Analysis of Randomized, Controlled-Feeding Clinical Studies

Background: Type 2 diabetes mellitus was found to be associated with metabolic disorders, particularly abnormal glucose and lipid metabolism. Dietary food choices may have profound effects on blood lipids. The primary objective of this study was to examine the effects of peanuts and tree nuts intake on lipid profile in patients with type 2 diabetes.

Methods: According to preferred reporting items for systematic reviews and meta-analysis guidelines, we performed a systematic search of randomized controlled clinical trials and systematic reviews published in PubMed, Web of Science, Embase, Scopus, and Cochrane library, from inception through June 2021. Studies in populations with type 2 diabetes, which compare nuts or peanuts to a controlled-diet group were included. We used the mean difference with 95% CIs to present estimates for continuous outcomes from individual studies. In addition, we used the GRADEpro tool to evaluate the overall quality of evidence.

Results: Sixteen studies involving 1,041 participants were eligible for this review. The results showed that peanuts and tree nuts supplementation did not induce significant changes in low-density lipoprotein-cholesterol (LDL-C) (mean difference = −0.11; 95%CI: −0.25 – 0.03, p = 0.117) and high-density lipoprotein-cholesterol (HDL-C) (mean difference = 0.01; 95%CI: −0.01 – 0.04, p = 0.400) in patients with type 2 diabetics. In addition, we found that peanuts and tree nuts intake may cause a significantly reduction in total cholesterol (TC) (mean difference = −0.14; 95%CI: −0.26 – −0.02, p = 0.024) and triglyceride (TG) (mean difference = −0.10; 95%CI: −0.17 – −0.02, p = 0.010). In the subgroup analysis, a significantly greater reduction in TC was observed in studies which duration was <12 weeks (mean difference = −0.22; 95%CI: −0.37 – −0.08, p = 0.002). The quality of the body of evidence was “moderate” for TC and TG, the quality of evidence for LDL-C and HDL-C were “low.”

Conclusion: Our findings suggest that consuming peanuts and tree nuts might be beneficial to lower TC concentration and TG concentration in type 2 diabetics subjects. Furthermore, peanuts and tree nuts supplementation could be considered as a part of a healthy lifestyle in the management of blood lipids in patients with type 2 diabetes. Given some limits observed in the current studies, more well-designed trials are still needed.

Pecan-enriched diets decrease postprandial lipid peroxidation and increase total antioxidant capacity in adults at-risk for cardiovascular disease

Pecans are a rich source of antioxidants, but the effect of regular consumption on post-meal responses is unknown. The objective of this study was to examine the impact of daily pecan consumption for 8 weeks on fasting and postprandial lipid peroxidation, total antioxidant capacity (TAC), and tocopherols in adults at higher risk for cardiovascular disease (CVD) (hypercholesterolemia or elevated adiposity). We hypothesized that daily pecan consumption would result in increased fasting γ-tocopherol, increased fasting and postprandial TAC, and decreased fasting and postprandial lipid peroxidation. This was a randomized, parallel, controlled trial with 3 treatments: two pecan groups and a nut free control (n = 16). The ADD group (n = 15) consumed pecans as part of a free-living diet, and the SUB group (n = 16) substituted the pecans for isocaloric foods from their habitual diet. At the pre- and post-intervention, a high saturated fat breakfast shake was consumed with postprandial blood draws over 2h. In the ADD and SUB groups, postprandial lipid peroxidation was suppressed (iAUC: 0.9 ± 1.3 to -2.9 ± 2.0 and 4.5 ± 1.7 to 0.7 ± 1.1 µM/2h, respectively; P <0.05) and TAC was elevated (iAUC: -240.8 ± 110.2 to 130.9 ± 131.7 and -227.6 ± 131.2 to 208.7 ± 145.7 µM Trolox Equivalents/2h, respectively; P <0.01) from pre- to post-intervention. Furthermore, there was an increase in γ-tocopherol from pre- to post-intervention within the ADD (1.4 ± 0.1 to 1.8 ± 0.1 µg/mL; P <0.001) and SUB groups (1.8 ± 0.2 to 2.1 ± 0.2 µg/mL; P <0.05). There were no changes in any variable within the control group. These findings suggest that daily pecan consumption protects against oxidative stress that occurs following a high-fat meal in adults at risk for CVD.

Impact of Brazil Nut (Bertholletia excelsa, H.B.K.) Supplementation on Body Composition, Blood Pressure, and the Vascular Reactivity of Wistar Rats When Submitted to a Hypersodium Diet

Introdution: Endothelium integrity is a key that maintains vascular homeostasis but it can suffer irreversible damage by blood pressure changes, reflecting an imbalance in the maintenance of vascular homeostasis.Objective: The aim of this study was to investigate the impact of Brazil nut (Bertholletia excelsa, H.B.K.) (BN) supplementation (10% in chow, wt/wt) on the vascular reactivity of Wistar rats during chronic exposure to a sodium overload (1% in water).Methods: First, male Wistar rats were allocated into two groups: Control Group (CG) and the Hypersodic Group (HG) for 4 weeks. Afterward, the CG was divided into the Brazil Nut Group (BNG) and the HG Group into the Hypersodic Brazil Nut Group (HBNG) for a further 8 weeks, totaling 4 groups. Blood pressure was measured during the protocol. At the end of the protocol, the vascular reactivity procedure was performed. Glucose, lipid profile, lipid peroxidation, and platelet aggregation were analyzed in the serum. Body composition was determined by the carcass technique.Results: The groups that were supplemented with the BN chow presented less body mass gain and body fat mass, together with lower serum glucose levels. The HG Group presented an increase in blood pressure and a higher platelet aggregation, while the BN supplementation was able to blunt this effect. The HG Group also showed an increase in contractile response that was phenylephrine-induced and a decrease in maximum relaxation that was acetylcholine-induced when compared to the other groups.Conclusion: The BN supplementation was able to prevent an impaired vascular function in the early stages of arterial hypertension, while also improving body composition, serum glucose, and platelet aggregation.

Regulation of Apolipoprotein B by Natural Products and Nutraceuticals: A Comprehensive Review

Cardiovascular Disease (CVD) is the most important and the number one cause of mortality in both developing and industrialized nations. The co-morbidities associated with CVD are observed from infancy to old age. Apolipoprotein B100 (Apo B) is the primary apolipoprotein and structural protein of all major atherogenic particles derived from the liver including Very-Low- Density Lipoproteins (VLDL), Intermediate-density Lipoprotein (IDL), and Low-density Lipoprotein (LDL) particles. It has been suggested that measurement of the Apo B concentration is a superior and more reliable index for the prediction of CVD risk than is the measurement of LDL-C. Nutraceuticals and medicinal plants have attracted significant attention as it pertains to the treatment of non-communicable diseases, particularly CVD, diabetes mellitus, hypertension, and Nonalcoholic Fatty Liver Disease (NAFLD). The effect of nutraceuticals and herbal products on CVD, as well as some of its risk factors such as dyslipidemia, have been investigated previously. However, to the best of our knowledge, the effect of these natural products, including herbal supplements and functional foods (e.g. fruits and vegetables as either dry materials, or their extracts) on Apo B has not yet been investigated. Therefore, the primary objective of this paper was to review the effect of bioactive natural compounds on plasma Apo B concentrations. It is concluded that, in general, medicinal plants and nutraceuticals can be used as complementary medicine to reduce plasma Apo B levels in a safe, accessible, and inexpensive manner in an attempt to prevent and treat CVD.

Protocol for a randomized controlled trial to test the acceptability and adherence to 6-months of walnut supplementation in Chinese adults at high risk of cardiovascular disease

Background

Consumption of nuts improves cardio-metabolic risk factors in clinical trials and relates to lower risk of cardiovascular disease (CVD) in prospective observational studies. However, there has not been an adequately powered randomized controlled trial to test if nuts supplementation actually reduces incident CVD. In order to establish the feasibility of such a trial, the current study aimed to assess the acceptability and adherence to long-term nut supplementation amongst individuals at high CVD risk in China.

Methods

This protocol described a 6-month trial performed in Ningxia Province in China among participants with a history of CVD or older age (female ≥65 years, male ≥60 years) with multiple CVD risk factors. Participants were randomized to control (received non-edible gift), low dose walnut (30 g/d), or high dose walnut (60 g/d) groups in a 1:1:1 ratio. Walnuts were provided at no cost to participants and could be consumed according to personal preferences. Follow-up visits were scheduled at 2 weeks, 3 months and 6 months. The primary outcome was fasting plasma alpha linolenic acid (ALA) levels used as an indicator of walnut consumption. Secondary outcomes included self-reported walnut intake from the 24 h dietary recalls. The target sample size of 210 provided 90% statistical power with two-sided alpha of 0.05 to detect a mean difference of 0.12% (as percent of total fatty acid) in plasma ALA between randomized groups.

Results

Two hundred and ten participants were recruited and randomized during October 2019. Mean age of participants was 65 years (SD = 7.3), 47% were females, and 94% had a history of CVD at baseline. Across the three study groups, participants had similar baseline demographic and clinical characteristics.

Discussion

This trial will quantify acceptability and adherence to long-term walnut supplementation in a Chinese population at high risk of CVD. The findings will support the design of a future large trial to test the effect of walnut supplementation for CVD prevention.

Trial registration

NCT04037943

Protocol version: v3.0 August 14 2019

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-020-00660-7.

Tree Nuts and Peanuts as a Source of Natural Antioxidants in our Daily Diet

Tree nuts and peanuts are healthy foods with a proven track record of helping to reduce the incidence of chronic diseases, most notably cardiovascular disease. At the point of consumption, all nuts contain low moisture and ≥ 50% lipid contents, but this is where similarities end. The levels of key nutrients and bioactives including vitamin C, vitamin E, L-arginine, minerals (such as selenium and zinc), and phenolics can differ markedly. Distinctions in the types and quantities of phenolic constituents for tree nut species, as well as the impact of digestion, will affect the nuts' antioxidant potential in vivo. This work provides some insight into the different types of phenolics found in tree nuts and peanuts, the antioxidant potential of their phenolic extracts using in vitro chemical assays, the effect of thermal processing on the stability of the nuts' endogenous phenolics, and the impact on biomarkers of human health arising from randomized clinical trials. Key biomarkers include measures in the reduction of LDL oxidation as well as increases in the levels of vitamin E and selected phenolic compounds in blood plasma postprandially from those of baseline.

Moderate walnut consumption improved lipid profile, steroid hormones and inflammation in trained elderly men: a pilot study with a randomized controlled trial

The present study aimed to investigate the effect of walnut consumption on lipid profile, steroid hormones and inflammation in trained elderly men performing concurrent (resistance and endurance) training. Twenty healthy elderly males were divided into two matched groups, in a randomized controlled trial, that trained three sessions per week: concurrent training + dietary walnut consumption (15 g/day for six weeks, CTW: n = 10); concurrent training + control diet (CT: n = 10). Fasting blood samples were taken 48 hours before and after intervention for biochemical assessments. levels of high-density lipoprotein (HDL) increased only in CTW compared to baseline (19.8%, p < 0.01). Total cholesterol (TC), low-density lipoprotein (LDL) and triglyceride (TG) levels significantly decreased only for CTW (i.e., 13%, 18%, and 18.5% at p < 0.01 for all). Testosterone (T) increased after the training compared to pre-training for CTW and CT (10.3%, p < 0.01, 4.27% p < 0.05, respectively), but the increase was significantly higher in CTW (p < 0.05). Serum cortisol (C) was lower for CTW compared to CT (p < 0.01). C-reactive protein (CRP) decreased in CTW in comparison with CT. The present study revealed that 6-week moderate walnut supplementation (15 g/day) improved lipid profile, steroid hormones and systematic inflammation in aged men performing concurrent training. These findings could be attributable to the potential effect of polyunsaturated fatty acids (PUFA) contained in walnut (linoleic acid, n-6; linolenic acid, n-3).

Effects of α-linolenic acid intake on blood lipid profiles：a systematic review and meta-analysis of randomized controlled trials

To investigate the effect of ALA intake on blood lipid profiles, including triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very-low-density lipoprotein (VLDL-C) and ratio of TC to HDL-C. We systematically searched randomized controlled trials of ALA intervention on PubMed, Embase, Cochrane library and related references up to March 2018. The final values were calculated as weighted mean difference (WMD) by using a random effects model. Subgroup analysis and meta-regression were used to explore the source of heterogeneity. Generalized least square was performed for dose-response analysis. Forty-seven studies with 1305 individuals in the ALA arm and 1325 individuals in the control arm were identified. Compared with control group, dietary intake of ALA significantly reduced the concentrations of TG (WMD -0.101 mmol/L; 95% CI: -0.158 to -0.044 mmol/L; P = 0.001), TC (WMD -0.140 mmol/L; 95% CI: -0.224 to -0.056 mmol/L; P = 0.001), LDL-C (WMD -0.131 mmol/L; 95% CI: -0.191 to -0.071 mmol/L; P < 0.001), VLDL-C (WMD -0.121 mmol/L; 95% CI: -0.170 to -0.073 mmol/L; P < 0.001), TC/HDL-C ratio (WMD -0.165 mmol/L; 95% CI: -0.317 to -0.013 mmol/L; P = 0.033) and LDL-C/HDL-C ratio (WMD -0.158 mmol/L; 95% CI: -0.291 to -0.025 mmol/L; P = 0.02). There is no effect of ALA intake on HDL-C (WMD 0.008 mmol/L; 95% CI: -0.018 to 0.034 mmol/L; P = 0.541). Dose-response analysis indicated that 1 g per day increment of ALA was associated with a 0.0016 mmol/L, 0.0071 mmol/L, 0.0015 and 0.0061 mmol/L reduction in TG (95% CI: -0.0029 to -0.0002 mmol/L), TC (95% CI: -0.0085 to -0.0058 mmol/L), HDL-C (95% CI: -0.0020 to -0.0011 mmol/L) and LDL-C (95% CI: -0.0073 to -0.0049 mmol/L) levels, respectively. The effects of ALA intake on TG, TC and LDL-C concentrations were more obvious among Asian participants, and also more obvious on patients with hyperlipidemia or hyperglycemia compared to healthy individuals. Dietary ALA intervention improves blood lipid profiles by decreasing levels of TG, TC, LDL and VLDL-C. Our findings add to the evidence that increasing ALA intake could potentially prevent risk of cardiovascular diseases.

Effects of Supplementing the Usual Diet with a Daily Dose of Walnuts for Two Years on Metabolic Syndrome and Its Components in an Elderly Cohort

Accumulating evidence links nut consumption with an improved risk of metabolic syndrome (MetS); however, long-term trials are lacking. We examined the effects of a daily dose of walnuts for two years on MetS in a large elderly cohort. A total of 698 healthy elderly participants were randomly assigned to either a walnut supplemented or a control diet. The participants in the walnut group were provided with packaged walnuts (1, 1.5, or 2 oz. or ~15% of energy) and asked to incorporate them into their daily habitual diet. The participants in the control group were asked to continue with their habitual diet and abstain from eating walnuts and other tree nuts. Intake of n-3 fatty acid supplements was not permitted in either group. Fasting blood chemistries, blood pressure, and anthropometric measurements were obtained at baseline and at the end of intervention. A total of 625 participants (67% women, mean age 69.1 y) completed this two-year study (90% retention rate). Triglycerides decreased in both walnut (-0.94 mg/dl) and control (-0.96 mg/dl) groups, with no significant between-group differences. There was a non-significant decrease in systolic and diastolic blood pressure in the walnut group (-1.30 and -0.71 mm Hg, respectively) and no change in the control group. Fasting blood glucose decreased by ~1 point in both the walnut and control groups. There were no significant between-group differences in the development or reversion of MetS. In conclusion, supplementing the diet of older adults with a daily dose of walnuts had no effect on MetS status or any of its components, although the walnut group tended to have lower blood pressure.

Walnuts change lipoprotein composition suppressing TNFα-stimulated cytokine production by diabetic adipocyte

Walnut consumption can provide both vascular and metabolic health benefits, and walnut-induced changes in lipoprotein particle chemical payloads may be responsible for these health benefits. To explore this possibility with a focus on metabolic health, this study investigated the impact of walnut consumption on lipoprotein lipid composition and changes in LDL anti-inflammatory properties, as reported by inflamed adipocyte. Hypercholesterolemic, postmenopausal females were treated with 40 g/day (i.e., 1.6 servings/day; n=15) of walnuts for 4 weeks. Fatty acids and their oxygenated metabolites, i.e., oxylipins, were quantified in isolated lipoproteins. Human primary adipocytes were exposed to LDL and TNFα-stimulated adipokine production was measured. Walnut treatment elevated α-linolenic acid and its epoxides in all lipoproteins and depleted mid-chain alcohols in VLDL and LDL, but not HDL. Walnuts also reduced TNFα-induced diabetic adipocyte production of IL-6 (-48%, P=.0006) and IL-8 (-30%, P=.01), changes inversely correlated with levels of α-linolenic acid-derived epoxides but not α-linolenic acid itself. In conclusion, modest walnut consumption can alter lipoprotein lipid profiles and enhance their ability to inhibit TNFα-dependent pro-inflammatory responses in human diabetic primary adipocytes. Moreover, this study suggests the oxylipins, rather than the parent fatty acids, mediate LDL action of adipocytes.

Biomarkers of food intake for nuts and vegetable oils: an extensive literature search

Nuts and vegetable oils are important sources of fat and of a wide variety of micronutrients and phytochemicals. Following their intake, several of their constituents, as well as their derived metabolites, are found in blood circulation and in urine. As a consequence, these could be used to assess the compliance to a dietary intervention or to determine habitual intake of nuts and vegetable oils. However, before these metabolites can be widely used as biomarkers of food intake (BFIs), several characteristics have to be considered, including specificity, dose response, time response, stability, and analytical performance. We have, therefore, conducted an extensive literature search to evaluate current knowledge about potential BFIs of nuts and vegetable oils. Once identified, the strengths and weaknesses of the most promising candidate BFIs have been summarized. Results from selected studies have provided a variety of compounds mainly derived from the fatty fraction of these foods, but also other components and derived metabolites related to their nutritional composition. In particular, α-linolenic acid, urolithins, and 5-hydroxyindole-3-acetic acid seem to be the most plausible candidate BFIs for walnuts, whereas for almonds they could be α-tocopherol and some catechin-derived metabolites. Similarly, several studies have reported a strong association between selenium levels and consumption of Brazil nuts. Intake of vegetable oils has been mainly assessed through the measurement of specific fatty acids in different blood fractions, such as oleic acid for olive oil, α-linolenic acid for flaxseed (linseed) and rapeseed (canola) oils, and linoleic acid for sunflower oil. Additionally, hydroxytyrosol and its metabolites were the most promising distinctive BFIs for (extra) virgin olive oil. However, most of these components lack sufficient specificity to serve as BFIs. Therefore, additional studies are necessary to discover new candidate BFIs, as well as to further evaluate the specificity, sensitivity, dose-response relationships, and reproducibility of these candidate biomarkers and to eventually validate them in other populations. For the discovery of new candidate BFIs, an untargeted metabolomics approach may be the most effective strategy, whereas for increasing the specificity of the evaluation of food consumption, this could be a combination of different metabolites.

Nitrite-induced testicular toxicity in rats: therapeutic potential of walnut oil

Objective:

To determine the impact of walnut oil on nitrite-induced testicular toxicity in Sprague-Dawley (SD) rats. Available evidence suggests that walnut oil contains high levels of important unsaturated fatty acids including alpha-linolenic acid (ALA) and omega-3; nitrite is a reproductive toxicant that causes the loss of germ cells in the seminiferous tubules and generates oxidative stress in the testes, thus reducing sperm counts and affecting sperm morphology.

Methods:

This study included 24 male and 24 female adult SD rats. The male rats randomly assigned to Group A (controls) were given normal saline 2 ml/kg. The rats in Groups B, C, and D were given 50mg/kg body weight (bwt) of walnut oil, 0.08 mg/kg bwt of nitrite, and 0.08 mg/kg bwt of nitrite + 50 mg/kg of walnut oil respectively for 28 days via gastric gavage. Tested parameters included: testicular histology, sperm parameters, reproductive hormones, fertility, malondialdehyde (MDA), superoxide dismutase (SOD), reduced glutathione, and catalase (CAT).

Results:

A severe decrease in spermatogenic cell series, hypocellularity, tubular atrophy, decreased sperm quality, and increased MDA levels were observed in the rats given nitrite only when compared to controls. Rats given 50 mg/kg of walnut oil had significant growth of seminiferous epithelium compared to controls. The rats given walnut oil and nitrite had significant growth of seminiferous epithelium, improved sperm quality, and had decreased MDA levels.

Conclusion:

Walnut oil attenuated the deleterious effects of nitrite to the testes, reduced oxidative stress, and promoted spermatogenesis.

Nuts and Cardio-Metabolic Disease: A Review of Meta-Analyses

OBJECTIVES

Accumulating epidemiological and intervention evidence suggest that nut consumption is associated with reduced incidence of some cardiometabolic diseases. However, to date no review of meta-analyses of epidemiological and intervention studies has evaluated the effects of nut consumption on cardiometabolic disease. Design/Results: Electronic searches for meta-analyses of epidemiological and intervention studies were undertaken in PubMed®/MEDLINE®. Meta-analyses of prospective studies show that nut consumption appears to be associated with reduced all-cause mortality by 19⁻20% (n = 6), cardiovascular disease (CVD) incidence (19%; n = 3) and mortality (25%; n = 3), coronary heart disease (CHD) incidence (20⁻34%; n = 2) and mortality (27⁻30%; n = 2) and stroke incidence (10⁻11%; n = 7) and mortality (18%; n = 2). No association between nut consumption and the risk of type 2 diabetes mellitus (T2DM) was observed in meta-analyses of prospective studies, whereas a decrease in fasting blood glucose ranging from 0.08 to 0.15 mmol/L was observed in 3 meta-analyses of intervention studies. In the interventions, nut consumption also had favorable effects on total cholesterol (0.021 to 0.28 mmol/L reduction from 8 meta-analyses of interventions) and low-density lipoprotein cholesterol (0.017 to 0.26 mmol/L reduction from 8 meta-analyses of interventions) and endothelial function (0.79 to 1.03% increase in flow-mediated dilation from 4 meta-analyses of interventions). Nut consumption did not significantly affect body weight. Nut consumption had no effect on inflammatory markers in intervention studies. The effect on blood pressure was inconsistent. A higher nut consumption was associated with a lower incidence of hypertension in prospective studies, while nut consumption did not improve blood pressure in intervention studies.

CONCLUSIONS

Nut consumption appeared to be associated with lower all-cause mortality and CVD and CHD mortality. There was no association between nut consumption and the incidence of T2DM although fasting blood glucose is decreased in intervention studies. In intervention studies nuts lower total cholesterol and low-density lipoprotein cholesterol (LDL-C).

Quantities of Phospholipid Molecular Classes in Japanese Meals and Prediction of Their Sources by Multiple Regression Analysis

Dietary intake of total phospholipids (PLs) accounts for approximately 10% of total dietary lipids. Each PL molecular class has various beneficial effects on health. However, limited information is available regarding the intake of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylserine (PS), lysophosphatidylcholine (LPC) and sphingomyelin (SM) among Japanese people, and the relevant food sources. In this study, we quantified the contents of PC, PE, PI, PS, LPC, and SM in 120 meal samples served in a Japanese company's dormitory and cafeteria. Additionally, we measured the weight of each food group and estimated the contents of nutrients in these meals. Furthermore, we conducted a stepwise multiple regression analysis to identify predictors (food groups) of each PL class intake. The contents of total PL, PC, PE, PI+PS, LPC, and SM (mean value) were 4.44, 2.17, 0.632, 0.123, 0.313, and 0.127 g/d, respectively. These values were considered as daily PL intake in accordance with data (three macronutrients, vitamins, and minerals) from our study and the National Health and Nutrition Survey (NHNS) Japan, 2015. The content of eggs, meat, fish and shellfish, milk, pulses, fruits, mushrooms, cereals, and fats and oils in the meals predicted the PL and PC contents. The content of eggs, pulses, and mushrooms in the meals predicted the PE contents. Our results determined the daily intake of PL molecular classes among Japanese people and the food sources of PC and PE, and suggested that multiple regression analysis is useful for the prediction of food sources of bioactive components.

Effects of walnut consumption on blood lipids and other cardiovascular risk factors: an updated meta-analysis and systematic review of controlled trials

BACKGROUND

Intervention studies suggest that incorporating walnuts into the diet may improve blood lipids without promoting weight gain.

OBJECTIVE

We conducted a systematic review and meta-analysis of controlled trials evaluating the effects of walnut consumption on blood lipids and other cardiovascular risk factors.

DESIGN

We conducted a comprehensive search of PubMed and EMBASE databases (from database inception to January 2018) of clinical trials comparing walnut-enriched diets with control diets. We performed random-effects meta-analyses comparing walnut-enriched and control diets for changes in pre-post intervention in blood lipids (mmol/L), apolipoproteins (mg/dL), body weight (kg), and blood pressure (mm Hg).

RESULTS

Twenty-six clinical trials with a total of 1059 participants were included. The following weighted mean differences (WMDs) in reductions were obtained for walnut-enriched diets compared with control groups: -6.99 mg/dL (95% CI: -9.39, -4.58 mg/dL; P < 0.001) (3.25% greater reduction) for total blood cholesterol (TC) and -5.51 mg/dL (95% CI: -7.72, -3.29 mg/dL; P < 0.001) (3.73% greater reduction) for low-density lipoprotein (LDL) cholesterol. Triglyceride concentrations were also reduced in walnut-enriched diets compared with control [WMD = -4.69 (95% CI: -8.93, -0.45); P = 0.03; 5.52% greater reduction]. More pronounced reductions in blood lipids were observed when walnut interventions were compared with American and Western diets [WMD for TC = -12.30 (95% CI: -23.17, -1.43) and for LDL = -8.28 (95% CI: -13.04, -3.51); P < 0.001]. Apolipoprotein B (mg/dL) was also reduced significantly more on walnut-enriched diets compared with control groups [WMD = -3.74 (95% CI: -6.51, -0.97); P = 0.008] and a trend towards a reduction was observed for apolipoprotein A [WMD = -2.91 (95% CI: -5.98, 0.08); P = 0.057]. Walnut-enriched diets did not lead to significant differences in weight change (kg) compared with control diets [WMD = -0.12 (95% CI: -2.12, 1.88); P = 0.90], systolic blood pressure (mm Hg) [WMD = -0.72 (95% CI: -2.75, 1.30); P = 0.48], or diastolic blood pressure (mm Hg) [WMD = -0.10 (95% CI: -1.49, 1.30); P = 0.88].

CONCLUSIONS

Incorporating walnuts into the diet improved blood lipid profile without adversely affecting body weight or blood pressure.

The Effect of Daily Walnut Consumption on Dyslipidemia

The aim of this study was to investigate the effect of daily walnut consumption on dyslipidemia in dietary. Within a year, the patients who have been suggested taking walnut or not in their individual dietary were scanned retrospectively and randomized into 2 groups. The first group consists of 72 cases (only those taken on the diet program) and the second group consists of 73 cases (walnut consumption in regulated diet). Baseline blood lipid parameters and anthropometric measurements were assessed in both groups and compared with values at 3rd month. p values < 0.05 were considered statistically significant. In addition, Maras 18 walnut cultivar was analyzed to determine the fatty acid profiles by chromatographic technique. When comparing lipid parameters at baseline and at the 3rd month, total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, and triglyceride levels significantly decreased and high-density lipoprotein cholesterol levels significantly increased. As compared with the end of 3rd month values of the groups, the reduction in total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, triglyceride levels of the subjects group (walnut consumption in regulated diet) were significantly higher than the control group (only regulated diet). Also, there was no significant difference in increase on high-density lipoprotein cholesterol levels between the groups. The results showed that daily consumption of walnut improved blood lipid levels. However, more extensive studies are needed on therapeutic usage in dyslipidemia.

Phytochemical profile and biological activity of Juglans regia

Juglans regia Linn. (Juglandaceae), popularly known as English or Persian walnut, is a valuable medicinal plant with a potency to cure various diseases in traditional medicine. Since ancient time, different local ethnic groups have used various part of J. regia for a wide array of ailments including helminthiasis, diarrhea, sinusitis, stomach ache, arthritis, asthma, eczema, scrofula, skin disorders, diabetes mellitus, anorexia, thyroid dysfunction, cancer and infectious diseases. Biological activities of J. regia have been reported in several peer review journals and scientific attention is increasing. The present review attempts to provide comprehensive information on plant description, ethnobotanical use, toxicity, phytochemical profile, pharmacology, clinical studies and current research prospective of the J. regia. Currently, there is an immense interest on isolation/identification of active constituents from walnut and screening those active compounds for pharmacological activities. In addition, researchers are performing clinical trials as well as screening various solvent extracts or fractions of J. regia in several animal diseases models to identify promising therapeutic benefits. In the present work, we review the latest information based on published scientific investigations of J. regia.

Benefits of Nut Consumption on Insulin Resistance and Cardiovascular Risk Factors: Multiple Potential Mechanisms of Actions

Epidemiological and clinical studies have indicated that nut consumption could be a healthy dietary strategy to prevent and treat type 2 diabetes (T2DM) and related cardiovascular disease (CVD). The objective of this review is to examine the potential mechanisms of action of nuts addressing effects on glycemic control, weight management, energy balance, appetite, gut microbiota modification, lipid metabolism, oxidative stress, inflammation, endothelial function and blood pressure with a focus on data from both animal and human studies. The favourable effects of nuts could be explained by the unique nutrient composition and bioactive compounds in nuts. Unsaturated fatty acids (monounsaturated fatty acids and polyunsaturated fatty acids) present in nuts may play a role in glucose control and appetite suppression. Fiber and polyphenols in nuts may also have an anti-diabetic effect by altering gut microbiota. Nuts lower serum cholesterol by reduced cholesterol absorption, inhibition of HMG-CoA reductase and increased bile acid production by stimulation of 7-α hydroxylase. Arginine and magnesium improve inflammation, oxidative stress, endothelial function and blood pressure. In conclusion, nuts contain compounds that favourably influence glucose homeostasis, weight control and vascular health. Further investigations are required to identify the most important mechanisms by which nuts decrease the risk of T2DM and CVD.

Low-density lipoprotein oxidation biomarkers in human health and disease and effects of bioactive compounds

Based on the significance of oxidized low-density lipoprotein (LDL) in health and disease, this review focuses on human studies addressing oxidation of LDL, including three lines of biomarkers, (i) ex vivo LDL resistance to oxidation, a "challenge test" model, (ii) circulating oxidized LDL, indicating the "current in vivo status", and (iii) autoantibodies against oxidized LDL as fingerprints of an immune response to oxidized LDL, along with circulating oxysterols and 4-hydroxynonenal as biomarkers of lipid peroxidation. Lipid peroxidation and oxidized LDL are hallmarks in the development of various metabolic, cardiovascular and other diseases. Changes further occur across life stages from infancy to older age as well as in athletes and smokers. Given their responsiveness to targeted nutritional interventions, markers of LDL oxidation have been employed in a rapidly growing number of human studies for more than 2 decades. There is growing interest in foods, which, besides providing energy and nutrients, exert beneficial effects on human health, such as protection of DNA, proteins and lipids from oxidative damage. Any health claim, however, needs to be substantiated by supportive evidence derived from human studies, using reliable biomarkers to demonstrate such beneficial effects. A large body of evidence has accumulated, demonstrating protection of LDL from oxidation by bioactive food compounds, including vitamins, other micronutrients and secondary plant ingredients, which will facilitate the selection of oxidation biomarkers for future human intervention studies and health claim support.

Metabolic and Blood Pressure Effects of Walnut Supplementation in a Mouse Model of the Metabolic Syndrome

There is extensive evidence that walnut consumption is protective against cardiovascular disease and diabetes in the healthy population, but the beneficial effects of walnut consumption in individuals with the metabolic syndrome (MetS) remain uncertain. We compared a range of cardio-metabolic traits and related tissue gene expression associated with 21 weeks of dietary walnut supplementation in a mouse model of MetS (MetS-Tg) and wild-type (WT) mice (n = 10 per genotype per diet, equal males and females). Compared to standard diet, walnuts did not significantly alter food consumption or body weight trajectory of either MetS-Tg or WT mice. In MetS-Tg mice, walnuts were associated with reductions in oral glucose area under the curve (gAUC, standard diet 1455 ± 54, walnut 1146 ± 91, p = 0.006) and mean arterial blood pressure (MAP, standard diet 100.6 ± 1.9, walnut 73.2 ± 1.8 mmHg, p < 0.001), with neutral effects on gAUC and MAP in WT mice. However, in MetS-Tg mice, walnuts were also associated with trends for higher plasma cholesterol (standard diet 4.73 ± 0.18, walnut 7.03 ± 1.99 mmol/L, p = 0.140) and triglyceride levels (standard diet 2.4 ± 0.5, walnut 5.4 ± 1.6 mmol/L, p = 0.061), despite lowering cholesterol and having no effect on triglycerides in WT mice. Moreover, in both MetS-Tg and WT mice, walnuts were associated with significantly increased liver expression of genes associated with metabolism (Fabp1, Insr), cell stress (Atf6, Ddit3, Eif2ak3), fibrosis (Hgf, Sp1, Timp1) and inflammation (Tnf, Ptpn22, Pparg). In conclusion, dietary walnuts were associated with modest favourable effects in WT mice, but a combination of beneficial and adverse effects in MetS-Tg mice, and up-regulation of hepatic pro-fibrotic and pro-inflammatory genes in both mouse strains.

Serum metabolites from walnut-fed aged rats attenuate stress-induced neurotoxicity in BV-2 microglial cells

The shift in equilibrium towards excess reactive oxygen or nitrogen species production from innate antioxidant defenses in brain is a critical factor in the declining neural function and cognitive deficit accompanying age. Previous studies from our laboratory have reported that walnuts, rich in polyphenols, antioxidants, and omega fatty acids such as alpha-linolenic acid and linoleic acid, improve the age-associated declines in cognition and neural function in rats. Possible mechanisms of action of these effects include enhancing protective signaling, altering membrane microstructures, decreasing inflammation, and preventing accumulation of polyubiquitinated protein aggregates in critical regions of the brain. In the current study, we investigated whether the serum collected from aged animals fed with walnut diets (0, 6, and 9%, w/w) would enhance protection on stressed BV-2 microglia in vitro. In the growth medium, fetal bovine serum was substituted with the serum collected from 22-month-old rats fed per protocol for 12 weeks. Walnut diet serum (6 and 9%) significantly attenuated lipopolysaccharide-induced nitrite release compared to untreated control cells and those treated with serum from rats fed 0% walnut diets. The results also indicated a significant reduction in pro-inflammatory tumor necrosis factor-alpha, cyclooxygenase-2, and inducible nitric oxide synthase. These results suggest antioxidant and anti-inflammatory protection or enhancement of membrane-associated functions in brain cells by walnut serum metabolites.

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

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 (-4.7 mg/dL; 95% CI: -5.3, -4.0 mg/dL), LDL cholesterol (-4.8 mg/dL; 95% CI: -5.5, -4.2 mg/dL), ApoB (-3.7 mg/dL; 95% CI: -5.2, -2.3 mg/dL), and triglycerides (-2.2 mg/dL; 95% CI: -3.8, -0.5 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 (-11.5 mg/dL; 95% CI: -16.2, -6.8 mg/dL) than in healthy populations (-2.5 mg/dL; 95% CI: -4.7, -0.3 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.

Nut consumption for the primary prevention of cardiovascular disease

BACKGROUND

Nuts contain a number of nutritional attributes which may be cardioprotective. A number of epidemiological studies have shown that nut consumption may have a beneficial effect on people who have cardiovascular disease (CVD) risk factors. However, results from randomised controlled trials (RCTs) are less consistent.

OBJECTIVES

To determine the effectiveness of nut consumption for the primary prevention of CVD.

SEARCH METHODS

We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, EMBASE, Web of Science Core Collection, CINAHL, Database of Abstracts of Reviews of Effects (DARE), Health Technology Assessment Database (HTA) and Health Economics Evaluations Database (HEED) up to 30 July 2015. We searched trial registers and reference lists of reviews for further studies. We did not apply any language restrictions.

SELECTION CRITERIA

We included RCTs of dietary advice to increase nut consumption or provision of nuts to increase consumption lasting at least three months and including healthy adults or adults at moderate and high risk of CVD. The comparison group was no intervention or minimal intervention. The outcomes of interest were CVD clinical events and CVD risk factors.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, abstracted the data and assessed the risk of bias in included trials.

MAIN RESULTS

We included five trials (435 participants randomised) and one ongoing trial. One study is awaiting classification. All trials examined the provision of nuts to increase consumption rather than dietary advice. None of the included trials reported on the primary outcomes, CVD clinical events, but trials were small and short term. All five trials reported on CVD risk factors. Four of these trials provided data in a useable format for meta-analyses, but heterogeneity precluded meta-analysis for most of the analyses. Overall trials were judged to be at unclear risk of bias.There were variable and inconsistent effects of nut consumption on CVD risk factors (lipid levels and blood pressure). Three trials monitored adverse events. One trial reported an allergic reaction to nuts and three trials reported no significant weight gain with increased nut consumption. None of the included trials reported on other secondary outcomes, occurrence of type 2 diabetes as a major risk factor for CVD, health-related quality of life and costs.

AUTHORS' CONCLUSIONS

Currently there is a lack of evidence for the effects of nut consumption on CVD clinical events in primary prevention and very limited evidence for the effects on CVD risk factors. No conclusions can be drawn and further high quality longer term and adequately powered trials are needed to answer the review question.

The effect of tree nut, peanut, and soy nut consumption on blood pressure: a systematic review and meta-analysis of randomized controlled clinical trials

BACKGROUND

Although several studies have assessed the effects of nut consumption (tree nuts, peanuts, and soy nuts) on blood pressure (BP), the results are conflicting.

OBJECTIVE

The aim was to conduct a systematic review and meta-analysis of published randomized controlled trials (RCTs) to estimate the effect of nut consumption on BP.

DESIGN

The databases MEDLINE, SCOPUS, ISI Web of Science, and Google Scholar were searched for RCTs carried out between 1958 and October 2013 that reported the effect of consuming single or mixed nuts (including walnuts, almonds, pistachios, cashews, hazelnuts, macadamia nuts, pecans, peanuts, and soy nuts) on systolic BP (SBP) or diastolic BP (DBP) as primary or secondary outcomes in adult populations aged ≥18 y. Relevant articles were identified by screening the abstracts and titles and the full text. Studies that evaluated the effects for <2 wk or in which the control group ingested different healthy oils were excluded. Mean ± SD changes in SBP and DBP in each treatment group were recorded for meta-analysis.

RESULTS

Twenty-one RCTs met the inclusion criteria. Our findings suggest that nut consumption leads to a significant reduction in SBP in participants without type 2 diabetes [mean difference (MD): -1.29; 95% CI: -2.35, -0.22; P = 0.02] but not in the total population. Subgroup analyses of different nut types suggest that pistachios, but not other nuts, significantly reduce SBP (MD: -1.82; 95% CI: -2.97, -0.67; P = 0.002). Our study suggests that pistachios (MD: -0.80; 95% CI: -1.43, -0.17; P = 0.01) and mixed nuts (MD: -1.19; 95% CI: -2.35, -0.03; P = 0.04) have a significant reducing effect on DBP. We found no significant changes in DBP after the consumption of other nuts.

CONCLUSIONS

Total nut consumption lowered SBP in participants without type 2 diabetes. Pistachios seemed to have the strongest effect on reducing SBP and DBP. Mixed nuts also reduced DBP.

Weight loss with a modified Mediterranean-type diet using fat modification: a randomized controlled trial

BACKGROUND/OBJECTIVES

There is evidence that Mediterranean diets with a high proportion of olive oil and nuts can be effective for weight management and prevention of cardiovascular disease. It might be difficult for populations with other eating habits to follow such diets. Therefore, a modified Mediterranean-type diet using fat modification through neutral and butter-flavored canola oil, walnuts and walnut oil with two portion-controlled sweet daily snacks was tested in Germany.

SUBJECTS/METHODS

Randomized waiting-list control study with overweight/grade 1 obese subjects: 12-week self-help modified Mediterranean-type diet, 6 weeks of diet plans and 6 weeks of weight loss maintenance training. Trial duration was 12 months. Intervention group (IG) included 100 participants (average age of 52.4 years, weight 85.1 kg and body mass index (BMI) 30.1 kg/m(2)), waiting-list control group (CG) included 112 participants (52.6 years, 84.1 kg and 30.1 kg/m(2)).

RESULTS

Per-protocol weight loss after 12 weeks was 5.2 kg in IG vs 0.4 kg in CG (P ⩽ 0.0001), BMI -1.8 vs -0.1 kg/m(2) (P ⩽ 0.0001), waist circumference -4.7 vs -0.9 cm (P ⩽ 0.0001). Triglycerides, total cholesterol and LDL cholesterol improved significantly in IG but not in CG. One-year dropouts: 44% in IG and 53% in CG. Weight loss after 12 months: 4.2 kg (pooled data).

CONCLUSION

A five-meal modified Mediterranean-type diet with two daily portion-controlled sweet snacks was effective for weight management in a self-help setting for overweight and grade 1 obese subjects. Fat modification through canola oil, walnuts and walnut oil improved blood lipids even at 12 months.

Effect of tree nuts on metabolic syndrome criteria: a systematic review and meta-analysis of randomised controlled trials

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 I(2) 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.

TRIAL REGISTRATION NUMBER

NCT01630980.

A review of the effects of nuts on appetite, food intake, metabolism, and body weight

Tree nuts and peanuts are good sources of many nutrients and antioxidants, but they are also energy dense. The latter often limits intake because of concerns about their possible contribution to positive energy balance. However, evidence to date suggests that nuts are not associated with predicted weight gain. This is largely due to their high satiety value, leading to strong compensatory dietary responses, inefficiency in absorption of the energy they contain, a possible increment in resting energy expenditure, and an augmentation of fat oxidation. Preliminary evidence suggests that these properties are especially evident when they are consumed as snacks.

Nuts in the prevention and treatment of metabolic syndrome

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 the modulation of inflammation and oxidation. Further trials are needed to clarify the role of nuts in MetS prevention and treatment.

Nut consumption for vascular health and cognitive function

Nuts are rich in many nutrients that can benefit multiple cardiometabolic functions, including arterial compliance, blood pressure, inflammation, glucoregulation and endothelial vasodilatation. Impaired vasodilatation may contribute to impaired cognitive performance due to poor cerebral perfusion. The present narrative review examines associations between nut consumption, vascular health and cognitive function. It includes a systematic search which identified seventy-one epidemiological or intervention studies in which effects of chronic nut consumption on blood pressure, glucoregulation, endothelial vasodilator function, arterial compliance, inflammatory biomarkers and cognitive performance were evaluated. Weighted mean changes were estimated where data were available; they indicate that nut consumption reduces blood pressure and improves glucoregulation, endothelial vasodilator function and inflammation, whilst a limited number of studies suggest that nut consumption may also improve cognitive performance. Further clinical trials are warranted to explore relationships between nut consumption, endothelial function and cognitive function.

Effects of supplementing n-3 fatty acid enriched eggs and walnuts on cardiovascular disease risk markers in healthy free-living lacto-ovo-vegetarians: a randomized, crossover, free-living intervention study

Background

Plant and marine n-3 fatty acids (FA) may favorably modify select markers of cardiovascular disease risk. Whether supplementing the habitual diet of lacto-ovo-vegetarians (LOV) with walnuts (containing α-linolenic acid, ALA) and n-3 FA enriched eggs (containing primarily docosahexaenoic acid, DHA and ALA) would have equivalent effects on CVD risk factors is explored in this study.

Methods

In this study, 20 healthy free-living LOVs following their habitual diet were randomly assigned in a crossover design to receive one of three supplements: n-3 FA enriched egg (6/week), walnuts (28.4 g, 6/week) or a standard egg, 6/week (control) for 8 weeks each with 4-wk washout between treatments. Erythrocyte membrane fatty acids, serum lipids and inflammatory markers were measured at the end of each treatment.

Results

Dietary compliance was observed by an expected increase in erythrocyte membrane ALA following the walnut treatment and in DHA following the n-3 FA enriched egg treatment. Walnut treatment lowered serum triacylglycerol, total cholesterol and Apo B (p < 0.05) compared to the standard egg but not the n-3 FA enriched egg treatment. However, walnut treatment significantly reduced total: HDL cholesterol ratio compared to both egg treatments. There were no differences between treatments for any of the inflammatory markers.

Conclusions

For LOV, a direct source of DHA such as n-3 FA enriched eggs seems necessary to increase membrane levels of DHA. However for producing an overall favorable blood lipid profile, daily consumption of a handful of walnuts rich in ALA may be a preferred option for lacto-ovo vegetarian.

Walnut-enriched diet reduces fasting non-HDL-cholesterol and apolipoprotein B in healthy Caucasian subjects: a randomized controlled cross-over clinical trial

BACKGROUND

Walnut consumption is associated with reduced risk of coronary heart disease (CHD).

OBJECTIVE

We assessed the effect of walnuts on lipid and glucose metabolism, adipokines, inflammation and endothelial function in healthy Caucasian men and postmenopausal women ≥50years old.

DESIGN

Forty subjects (mean±SEM: age 60±1years, BMI 24.9±0.6kg/m(2); 30 females) were included in a controlled, cross-over study and randomized to receive first a walnut-enriched (43g/d) and then a Western-type (control) diet or vice-versa, with each lasting 8weeks and separated by a 2-week wash-out. At the beginning and end of each diet phase, measurements of fasting values, a mixed meal test and an assessment of postprandial endothelial function (determination of microcirculation by peripheral artery tonometry) were conducted. Area under the curve (AUC), incremental AUC (iAUC) and treatment×time interaction (shape of the curve) were evaluated for postprandial triglycerides, VLDL-triglycerides, chylomicron-triglycerides, glucose and insulin.

RESULTS

Compared with the control diet, the walnut diet significantly reduced non-HDL-cholesterol (walnut vs. control: -10±3 vs. -3±2mg/dL; p=0.025) and apolipoprotein-B (-5.0±1.3 vs. -0.2±1.1mg/dL; p=0.009) after adjusting for age, gender, BMI and diet sequence. Total cholesterol showed a trend toward reduction (p=0.073). Fasting VLDL-cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides and glucose, insulin, HOMA-IR, and HbA1c did not change significantly. Similarly, fasting adipokines, C-reactive protein, biomarkers of endothelial dysfunction, postprandial lipid and glucose metabolism and endothelial function were unaffected.

CONCLUSION

Daily consumption of 43g of walnuts for 8weeks significantly reduced non-HDL-cholesterol and apolipoprotein-B, which may explain in part the epidemiological observation that regular walnut consumption decreases CHD risk.

Walnut extract exhibits anti-fatigue action via improvement of exercise tolerance in mice

This study was conducted to investigate the anti-fatigue effect of walnut extract (WE) on forced swimming capacity in mice. Twenty-eight male ICR mice were randomly divided into four groups, a vehicle control (VC) or one of three WE administered groups (300, 600 and 900 mg/kg/day). WE was orally administered to mice once a day for 4 weeks, during which time a forced swimming test was conducted once a week. The vehicle control group was given a corresponding volume of sterile distilled water. After 4 weeks, the forced swimming capacity and levels of blood lactate, glucose, glutamine, ammonia and triacylglycerol, and liver glycogen were measured. In the WE administration group (600 and 900 mg/kg) the maximum swimming time increased significantly when compared with the vehicle control group. WE (600 and 900 mg/kg) significantly decreased the levels of lactate andammonia and increased the blood glutamine levels and liver glycogen content after forced swimming relative to the vehicle control group. The results of this study demonstrated the anti-fatigue effects of WE in a dose-dependent manner. The effects of WE at 600 and 900 mg/kg were similar. Overall, these results suggest that walnut has anti-fatigue activity and could elevate exercise tolerance.

Health benefits of nut consumption with special reference to body weight control

Nuts are an integral part of the Mediterranean food patterns, and their incorporation into the regular diets of human beings is believed to provide many health benefits. The recent recognition of nuts as "heart-healthy" foods by the U.S. Food and Drug Administration has given a major boost to the positive image of nuts. Nut consumption has been associated with several health benefits, such as antioxidant, hypocholesterolemic, cardioprotective, anticancer, anti-inflammatory, and antidiabetic benefits, among other functional properties. However, although nuts possess these many health benefits, their consumption has been hampered by a lack of adequate information regarding those benefits. In addition, because nuts are energy-dense foods with high-fat content, there is a misconception among consumers that increased consumption may lead to unwanted gain in body weight with the risk of developing overweight/obesity. Nonetheless, available epidemiologic studies and short-term controlled feeding trials have supported the theory that the inclusion of nuts in the typical diet does not induce weight gain, despite an expected increase in total caloric intake. To address the misperception about nuts and body weight gain, the present review focuses mainly on the relation between nut consumption and body weight gain, in the context of the many health benefits of nuts.

Gender differences in the long-chain polyunsaturated fatty acid status: systematic review of 51 publications

BACKGROUND/AIMS

Sex hormones may influence the activity of enzymes which are involved in the synthesis of long-chain polyunsaturated fatty acids. The objective of this review was to assess the role of gender in determining the fatty acid composition of human samples, like plasma and erythrocyte membrane lipids, and adipose tissue.

METHODS

The method included a structured search strategy on MEDLINE, Scopus and the Cochrane databases, with formal inclusion/exclusion criteria, data extraction procedure and meta-analysis.

RESULTS

We evaluated 51 publications, dated from 1975 to 2011. Meta-analysis showed significantly lower values of both arachidonic acid (AA) and docosahexaenoic acid (DHA) in total plasma lipids (32 and 33 studies) and in plasma phospholipids (PL; 21 and 23 studies) in men than in women. Primary analysis of the phospholipid fraction showed the mean difference in AA to be 0.42% weight/weight (95% CI: 0.18-0.65, n = 7,769) and in DHA 0.37% weight/weight (95% CI: 0.24-0.51, n = 8,541), while there was no gender difference in the values of linoleic acid and α-linolenic acid.

CONCLUSIONS

This systematic review based on 51 publications showed significantly lower contribution of AA and DHA to plasma total lipids and plasma PL in men than in women. Gender distribution should be regarded as a significant potential confounding factor in every study assessing data on fatty acid composition.

Tree nut phytochemicals: composition, antioxidant capacity, bioactivity, impact factors. A systematic review of almonds, Brazils, cashews, hazelnuts, macadamias, pecans, pine nuts, pistachios and walnuts

Tree nuts contain an array of phytochemicals including carotenoids, phenolic acids, phytosterols and polyphenolic compounds such as flavonoids, proanthocyanidins (PAC) and stilbenes, all of which are included in nutrient databases, as well as phytates, sphingolipids, alkylphenols and lignans, which are not. The phytochemical content of tree nuts can vary considerably by nut type, genotype, pre- and post-harvest conditions, as well as storage conditions. Genotype affects phenolic acids, flavonoids, stilbenes and phytosterols, but data are lacking for many other phytochemical classes. During the roasting process, tree nut isoflavones, flavanols and flavonols were found to be more resistant to heat than the anthocyanins, PAC and trans-resveratrol. The choice of solvents used for extracting polyphenols and phytosterols significantly affects their quantification, and studies validating these methods for tree nut phytochemicals are lacking. The phytochemicals found in tree nuts have been associated with antioxidant, anti-inflammatory, anti-proliferative, antiviral, chemopreventive and hypocholesterolaemic actions, all of which are known to affect the initiation and progression of several pathogenic processes. While tree nut phytochemicals are bioaccessible and bioavailable in humans, the number of intervention trials conducted to date is limited. The objectives of the present review are to summarise tree nut: (1) phytochemicals; (2) phytochemical content included in nutrient databases and current publications; (3) phytochemicals affected by pre- and post-harvest conditions and analytical methodology; and (4) bioactivity and health benefits in humans.

Nuts, hypertension and endothelial function

BACKGROUND AND AIMS

High blood pressure (BP) is considered a major risk factor for cardiovascular disease. Among lifestyle factors, diet plays a key role in the prevention and control of high BP. Therefore, it is important to elucidate which dietary components can exert beneficial effects on BP through modulation of endothelial function (EF) or by other mechanisms. In this paper we review the role of nutrients, foods, particularly nuts, and dietary patterns on BP control.

DATA SYNTHESIS

Because nuts are low in sodium and contain significant amounts of mono- and polyunsaturated fatty acids, fiber, minerals such as magnesium, potassium and calcium, and antioxidants, they have been suggested as potentially protective foods against hypertension. Limited evidence from prospective studies and clinical trials suggests that nut consumption has a beneficial effect on both BP and EF. However, BP changes were a secondary outcome in nut feeding trials and no study used ambulatory BP monitoring as the standard for BP measurements.

CONCLUSIONS

Further clinical trials, ideally using ambulatory BP monitoring, are needed to establish the potential protective effect of nut consumption on hypertension and vascular reactivity.

Nuts: anti-atherogenic food?

The prevalence of cardiovascular disease as the leading cause of morbidity and mortality is increasing worldwide. This fact is mainly attributed to the modern lifestyle with predominant characteristics the change of dietary habits and the reduced physical activity which lead to metabolic disorders such as obesity and diabetes. Therefore, drastic dietary interventions are considered necessary in order to reduce cardiovascular risk. Nuts, as a nutritional component have drawn particular attention, due to their beneficial cardiovascular properties derived from their nutrient composition. This is a comprehensive review concerning the potential general effects of nuts. It includes data from older large epidemiologic studies as well as recent significant information from clinical trials regarding this topic. All studies conclude that nuts can play an important role as part of a healthy diet in order to minimize cardiovascular risk and obtain multiple health benefits.

Effect of moderate walnut consumption on lipid profile, arterial stiffness and platelet activation in humans

BACKGROUND/OBJECTIVES

A large intake of walnuts may improve lipid profile and endothelial function. The effect of moderate walnut consumption is not known. We investigated whether a moderate intake of walnuts would affect lipid profile, arterial stiffness and platelet activation in healthy volunteers.

SUBJECTS/METHODS

A total of 30 healthy males were recruited into a single-blind randomized controlled crossover trial of 4 weeks of dietary walnut supplementation (15 g/day) and 4 weeks of control (no walnuts). Arterial stiffness was assessed using pulse waveform analysis to determine the augmentation index and augmented pressure. Platelet activation was determined using flow cytometry to measure circulating platelet-monocyte aggregates.

RESULTS

There were no differences in lipid profile after 4 weeks of walnut supplementation compared with control. Dietary intake of α-linolenic acid was increased during the walnut diet (2.1±0.4 g/day versus 0.7±0.4 g/day, P<0.0001). There were no differences in augmentation index or augmented pressure during walnut supplementation. Walnut supplementation did not affect platelet-monocyte aggregation.

CONCLUSIONS

Dietary intervention with a moderate intake of walnuts does not affect lipid profile, arterial stiffness or platelet activation in man. Our results suggest that the potentially beneficial cardiac effects of walnuts may not be apparent at lower and more practical levels of consumption.

Ellagitannins, ellagic acid and vascular health

Hydrolysable tannins are phenolic phytochemicals that show high antioxidant and free-radical scavenging activities. For this reason their potential effects preventing oxidative related diseases, such as cardiovascular diseases, have been largely studied. In vitro studies show that ellagitannins, at concentrations in the range 10-100 μM, show some relevant anti-atherogenic, anti-thrombotic, anti-inflammatory and anti-angiogenic effects, supporting the molecular mechanisms for the vascular health benefits. While there is good evidence supporting the vascular effects in vitro, the evidence on animal models or humans is much scarcer. The in vitro results often do not match the findings in the in vivo studies. This could be explained by the low bioavailability of the antioxidant ellagitannins and ellagic acid. The main ellagitannin metabolites circulating in plasma are ellagic acid microbiota metabolites known as urolithins, and they have lost their free-radical scavenging activity. They are present in plasma as glucuronide or sulphate conjugates, at concentrations in the nM range. Future studies should focus in the bioavailable metabolites, urolithins, and in the form (conjugated with glucuronic acid or sulphate) and concentrations (nM range) in which they are found in plasma. In this review we critically discuss the role of ellagitannins and ellagic acid on vascular health.