Higher Walnut Consumption Linked to Improved Total Cholesterol and Triglyceride Levels

by | Dec 15, 2022 | 2022, Blood Lipids, Cardiovascular Health, Nuts and Seeds

Written by Taylor Woosley, Staff Writer. Results of the systemic review and meta-analysis of 13 randomized controlled trials shows that intake of walnuts was significantly associated with improved total cholesterol, LDL-C, and triglyceride levels. 

walnutsCardiovascular disease (CVD) is the leading cause of premature mortality across the world, and it is estimated that by the year 2030, 23.6 million people will die of CVD per year1. The pathophysiology of CVD is characterized by endothelial dysfunction, vascular inflammation, atherosclerosis, fibrosis, and thrombosis, with multiple pathways simultaneously perturbed2. Traditional risk factors for CVD include hypertension, diabetes mellitus, nutrition, physical inactivity, and dyslipidemia3. In particular, high levels of low-density lipoprotein (LDL-C), along with low levels of triglycerides (TG), correlate with CVD risk4.

The role of a healthy dietary pattern in the prevention of CVD has well been recognized5. Lifestyle improvements, such as the intake of specific nutrients or food groups, can positively influence dyslipidemia6. The consumption of walnuts has been associated with a lower risk of CVD and has been researched for its ability to decrease the production of pro-inflammatory cytokines interleukin-6 (IL-6) and TNF-α by peripheral blood mononuclear cells7. Furthermore, walnuts are a rich source of polyunsaturated fatty acids (PUFA) and contain a large quantity of polyphenolic compounds that have been shown to consistently lower LDL cholesterol8.

Alshahrani et al. conducted a systemic review and meta-analysis to analyze the effects of walnut intake (intervention) in comparison with a control diet on the lipid profile, including total cholesterol (TC), LDL-C, high-density lipoprotein cholesterol (HDL-C), and TG. Study selection included having assessed the effect of walnut consumption compared with a control diet on lipids, with lipids being the primary outcome of interest in the trial. Additionally, studies had to report baseline and follow-up values for the outcomes of interest, with a clearly stated amount and frequency of walnut consumption over the course of the trial.

Cochrane’s risk of bias tool was used for interventional studies. Cochrane RevMan 5.4 software was utilized using the generic inverse variance weighting method with a random-effects model to account for potential variabilities between studies. Majority of studies demonstrated a low risk of bias in random sequence generation, incomplete outcomes results, and selective reporting. The final analysis included 13 randomized controlled trials. Ten of the trials were cross-over designs and three were parallel designs. Trial duration ranged from 6 to 16 weeks, with one trial lasting for 52 weeks. Walnut usage ranged from 15-99 g/d in the trials, with one trial using 100 mg Juglans regia leaves extract powder capsule twice a day. Ten trials were conducted on both men and women, with one trial being conducted only on men. Five trials were conducted on healthy subjects, three on diabetic individuals, two on obese subjects, one on hypercholesterolemic patients, and one on participants with metabolic syndrome.

Average age of participants ranged from 23-62 years, with an average BMI of 24-33 kg/m2. Sample sizes of trials ranged from 30-212 participants. The effect of walnut intake on lipid outcomes (TC, LDL-C, HDL-C, and TG) were evaluated in all studies (515 in the intervention group and 522 in the control group). Significant finding of the systemic review and meta-analysis are as follows:

  • Overall effect of the weighted mean difference (WMD) showed significant reductions in TC (WMD: -58 mg/dL; 95% CI: -12.94, -5.21; p < 0.0001), LDL-C (WMD: -5.68 mg/dL; 95% CI: -8.13, -3.24; p < 0.0001), and TG (WMD: -10.94 mg/dL; 95% CI: -15.65, -6.23; p < 0.0001).
  • However, walnut consumption was not associated with HDL-C (WMD: -57 mg/dL; 95% CI: -1.24, 0.09; p = 0.09).

Results of the review show that walnut consumption significantly improved all lipid outcomes except for HDL-C levels. Subgroup analysis indicated that further lipid improvements were observed in those who had BMI > 25 kg/m2, comorbidities, and normal levels of TC and LDL-C compared to those with BMI ≤ 25 kg/m2, no comorbidities, and abnormal TC and LDL-C levels. Further research should continue to explore the lipid-lowering effects of walnuts and their potential role in reducing the risk of CVD.

Source: Alshahrani, Saeed Mastour, Reham M. Mashat, Diaa Almutairi, Alaa Mathkour, Sahar Saad Alqahtani, Amirah Alasmari, Abdullah Hassan Alzahrani et al. “The Effect of Walnut Intake on Lipids: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.” Nutrients 14, no. 21 (2022): 4460.

© 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Click here to read the full text study.

Posted December 15, 2022.

Taylor Woosley studied biology at Purdue University before becoming a 2016 graduate of Columbia College Chicago with a major in Writing. She currently resides in Glen Ellyn, IL.

References:

  1. Francula-Zaninovic S, Nola IA. Management of Measurable Variable Cardiovascular Disease’ Risk Factors. Curr Cardiol Rev. 2018;14(3):153-163. doi:10.2174/1573403×14666180222102312
  2. Kalea AZ, Drosatos K, Buxton JL. Nutriepigenetics and cardiovascular disease. Curr Opin Clin Nutr Metab Care. Jul 2018;21(4):252-259. doi:10.1097/mco.0000000000000477
  3. Leopold JA, Loscalzo J. Emerging Role of Precision Medicine in Cardiovascular Disease. Circulation research. Apr 27 2018;122(9):1302-1315. doi:10.1161/circresaha.117.310782
  4. Berberich AJ, Hegele RA. A Modern Approach to Dyslipidemia. Endocr Rev. Jul 13 2022;43(4):611-653. doi:10.1210/endrev/bnab037
  5. Trautwein EA, McKay S. The Role of Specific Components of a Plant-Based Diet in Management of Dyslipidemia and the Impact on Cardiovascular Risk. Nutrients. Sep 1 2020;12(9)doi:10.3390/nu12092671
  6. Cicero AFG, Fogacci F, Stoian AP, et al. Nutraceuticals in the Management of Dyslipidemia: Which, When, and for Whom? Could Nutraceuticals Help Low-Risk Individuals with Non-optimal Lipid Levels? Curr Atheroscler Rep. Aug 4 2021;23(10):57. doi:10.1007/s11883-021-00955-y
  7. Borkowski K, Yim SJ, Holt RR, et al. Walnuts change lipoprotein composition suppressing TNFα-stimulated cytokine production by diabetic adipocyte. J Nutr Biochem. Jun 2019;68:51-58. doi:10.1016/j.jnutbio.2019.03.004
  8. Tindall AM, Petersen KS, Skulas-Ray AC, Richter CK, Proctor DN, Kris-Etherton PM. Replacing Saturated Fat With Walnuts or Vegetable Oils Improves Central Blood Pressure and Serum Lipids in Adults at Risk for Cardiovascular Disease: A Randomized Controlled-Feeding Trial. J Am Heart Assoc. May 7 2019;8(9):e011512. doi:10.1161/jaha.118.011512