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.
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Effects of Mixed Nut Consumption on LDL Cholesterol, Lipoprotein(a), and Other Cardiometabolic Risk Factors in Overweight and Obese Adults
Background and Aims: Elevated LDL-C, lipoprotein(a) [Lp(a)], and inflammation are associated with greater risk for atherosclerotic cardiovascular events. Consumption of individual nut types decreases these risk factors but knowledge about the effect of mixed nuts on Lp(a) is limited. The objective of this study was to determine the effects of consuming 42.5 g/day of mixed nuts on LDL-C, Lp(a), and inflammatory markers in individuals with overweight or obesity. Methods and Results: In a 16-week randomized control trial, 29 participants with overweight or obesity (BMI 25-40 kg/m2) consumed either 42.5 g/day of mixed nuts (cashews, almonds, macadamia nuts, Brazil nuts, pecans, pistachios, walnuts, and peanuts) or 69 g/day isocaloric pretzels. Blood samples were collected at baseline, week 8, and week 16 for analysis on total cholesterol (TC), LDL-C, Lp(a), inflammation markers, glucose, insulin, adiponectin and liver function enzymes. No significant differences were seen in TC, LDL-C, HDL-C, Lp(a), or liver function enzymes between the two groups. Participants consuming mixed nuts had significantly lower body fat percentage and diastolic blood pressure, and higher adiponectin (all P≤0.05). C-reactive protein (CRP) and 8-oxo-deoxyguanosis (8-oxodG) showed non-significant decreasing trends and total antioxidant capacity (TAC) had a non-significant increasing trend in the mixed nut group. Conclusion: Consumption of mixed nuts had no evidence of an effect on LDL-C or Lp(a) throughout the intervention. Notably, mixed nut consumption lowered body fat percentage without significant changes in body weight or BMI. Future studies with larger sample sizes investigating the changing trends of CRP, 8-oxodG, and TAC are warranted. https://doi.org/10.1016/j.numecd.2023.05.013
Association between nut consumption and prostate cancer risk in adults: a systematic review and dose-response meta-analysis of observational studies
Background and aims: Data on the association between nut consumption and prostate cancer risk are conflicting. Therefore, this systematic review and dose-response meta-analysis aimed to summarize available findings from observational studies on the associations of nut intake with risk of total, advanced, non-advanced, and fatal prostate cancers. Methods and results: We searched the online databases of PubMed, Scopus, and Web of Science as well as Google Scholar using appropriate keywords to identify eligible articles up to September 2022. In total, 11 articles with a total sample size of 287,786 participants and 32,213 cases of prostate cancer were included in the current systematic review and meta-analysis. By comparing the highest and lowest intake of total nuts, pooled relative risks (RRs) and 95% confidence intervals (95% CIs) for total, advanced, non-advanced, and fatal prostate cancers were 0.94 (95% CI: 0.85-1.04, P=0.22), 1.10 (95% CI: 0.98-1.24, P=0.12), 0.97 (95% CI: 0.85-1.11, P= 0.69), 0.97 (95% CI: 0.79-1.18, P=0.73), respectively, which indicated non-significant inverse associations for total, non-advanced, and fatal prostate cancers and a non-significant positive association for advanced prostate cancer. In the dose-response analyses, we found no evidence of a linear or non-linear association between total nut intake and prostate cancer risk. Data on other types of nuts including walnut, tree nuts, peanut, and peanut butter were not sufficient for performing a meta-analysis. Conclusion: We found no significant association between nut intake and risk of total, advanced, non-advanced, and fatal prostate cancer. Further studies are required to confirm our findings. https://doi.org/10.1016/j.numecd.2023.04.004
Expression of concern on Gunathilake et al., "Effects of nut consumption on blood lipid profile: A meta-analysis of randomized controlled trials".
Declaration of competing interest SKN reports no potential conflicts of interest. ER reports research grants through his institution, personal fees, non-financial support and other from the California Walnut Commission and non-financial support from the International Nut and Dried Fruit Council. JS reports research grants through his institution from California Walnut Commission, Almond Board of California, Peanut Institute and International Nut and Dry Fruit Council. JSS reports receiving within the last 5 years, personal fees, and research grants through his institution from the International Nut and Dried Fruit Foundation. JSS has also received nut products in-kind for the PREDIMED-plus pilot study form the Almond board of California and Pistachio Growers. https://doi.org/10.1016/j.numecd.2022.11.011
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. https://doi.org/10.1016/j.numecd.2022.07.013
The association between left ventricular hypertrophy and consumption of nuts, including peanuts, pine nuts, and almonds
Background and aims: Studies have reported that nut consumption is potentially beneficial in preventing cardiovascular disease. However, data are insufficient regarding the association between nut consumption and left ventricular hypertrophy (LVH).
Methods and results: In the Kangbuk Samsung Health Study, the participants were 34,617 men and 12,257 women who completed a food-frequency questionnaire for nut consumption and received echocardiography. Nut consumption was evaluated only for peanuts, pine nuts, and almonds defining 15 g as one serving/servings dose. Multivariable adjusted odds ratio (OR) and 95% confidence interval (CI) for LVH were evaluated according to the consumption frequency of one serving dose of nut. The frequency of nut consumption was categorized into five groups (<1/month, 1/month-1/week, 1-2/week, 2-4/week, and ≥4/week). The subgroup analysis was conducted by dividing the participants into the following two groups: the nonhypertensive/nondiabetic group and hypertensive or diabetic group. In women, nut consumption ≥2/week had the lower multivariable adjusted OR and 95% CI for LVH (2-4/week: 0.46 [0.26-0.81] and ≥4/week: 0.48 [0.25-0.92]) when compared with nut consumption <1/month. This association was identically observed in the subgroup analysis for women without hypertension and diabetes mellitus (DM) and women with hypertension or DM. However, men did not show the significant association.
Conclusion: In women, nut consumption ≥2/week was associated with the decreased probability of LVH. Further research studies should investigate whether the beneficial effect of nut consumption on LV structure results in better cardiovascular prognosis.
The effects of foods on LDL cholesterol levels: A systematic review of the accumulated evidence from systematic reviews and meta-analyses of randomized controlled trials
Aims: To systematically evaluate the evidence regarding the effects of foods on LDL cholesterol levels and to compare the findings with current guidelines.
Data Synthesis: From inception through June 2019, we searched PubMed, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials for guidelines, systematic reviews, and RCTs (for coffee intake only) of at least 13 days duration. Additionally, we searched Trip database for guidelines from 2009 through Oct 2019. Language was restricted to English. The strength of evidence was evaluated using The Grading of Recommendations Assessment, Development, and Evaluation (GRADE). A total of 37 guidelines, 108 systematic reviews, and 20 RCTs were included. With high evidence, foods high in unsaturated and low in saturated and trans fatty acids (e.g. rapeseed/canola oil), with added plant sterols/stanols, and high in soluble fiber (e.g. oats, barley, and psyllium) caused at least moderate (i.e. 0.20–0.40 mmol/L) reductions in LDL cholesterol. Unfiltered coffee caused a moderate to large increase. Soy protein, tomatoes, flaxseeds, and almonds caused small reductions. With moderate evidence, avocados and turmeric caused moderate to large reductions. Pulses, hazelnuts, walnuts, high-fiber/wholegrain foods, and green tea caused small to moderate reductions, whereas sugar caused a small increase. Other identified foods were either neutral or had low or very low evidence regarding their effects.
Conclusions: Several foods distinctly modify LDL cholesterol levels. The results may aid future guidelines and dietary advice for hypercholesterolemia.
Walnut Consumption and Cardiac Phenotypes: the Coronary Artery Risk Development in Young Adults (CARDIA) Study.
Background and aims: Observational studies and clinical trials have shown cardiovascular benefits of nut consumption, including walnuts. However, the relations of walnut consumption with systolic and diastolic function, risk factors for heart failure, are unknown. We examined the associations of walnut consumption with cardiac structure and function parameters in black and white adults enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) study. Methods and results: After exclusions, the study population included 3341 participants. Dietary intake was assessed using the CARDIA Diet History questionnaire at baseline, year 7 and year 20 exams. Cardiac structure and function were measured by echocardiography at year 25. Multivariable linear regression evaluated the associations of walnut consumption with blood pressure (BP), heart rate, and cardiac phenotypes, adjusting for age, sex, race, lifestyle habits, and clinical characteristics. We found the majority of walnut consumers compared to non-consumers were females, whites, and more highly educated, and had lower waist circumference, diastolic BP, and heart rate, and higher diet quality score. Even though cardiac structure and function measures were generally within normal ranges among participants, walnut consumers had significantly better values for diastolic function parameters A wave, E/A ratio, septal and lateral e' than non-consumers. Further adjustment for body mass index and diabetes status did not materially change the significance between walnut consumer groups. Systolic function parameters did not differ by walnut group. Conclusion: Compared to non-consumers, walnut consumption is associated with better diastolic dysfunction in young to middle-aged adults.
Long term association of nut consumption and cardiometabolic risk factors.
Consumption of nuts and risk of total and cause-specific mortality over 15 years.
BACKGROUND AND AIMS: The published literature shows that nut consumption has a favorable impact on health. We aimed to assess the association between nut consumption and risk of 15-year total mortality, and mortality from cardiovascular disease (CVD) (including ischemic heart disease, IHD, and stroke), and cancer. METHODS AND RESULTS: Prospective analyses involved 2893 participants aged ≥49 years at baseline. Dietary data were collected by using a semi-quantitative food-frequency questionnaire, and nut intakes were calculated. Deaths and cause of death were confirmed by data linkage with the Australian National Death Index. Over 15 years, 1044 participants had died, of these 430 had died from stroke and another 430 had died from IHD. Participants in the second tertile of nut consumption versus those in the first tertile of intake had reduced risk of total mortality: multivariable-adjusted HR 0.76 (95% CI 0.65-0.89). Participants in the second tertile compared to those in the first tertile had 24% and 23% reduced risk of 15-year CVD and IHD mortality, respectively. Associations were more marked in women compared to men. Women in the second versus first tertile of nut consumption had 27%, 39%, 34% and 49% reduced risk of death from all causes (n = 489), CVD (n = 258), IHD (n = 188) and stroke mortality (n = 101), respectively. CONCLUSIONS: Nut consumption was independently associated with a decreased risk of overall and vascular-disease mortality, particularly in women.