Munoz, S., M. Merlos, D. Zambon, C. Rodriguez, J. Sabaté, E. Ros, J.C. Laguna, 2001. Walnut-enriched diet increases the association of LDL from hypercholesterolemic men with human HepG2 cells. J Lipid Res. 42(12):2069-76.
In a randomized, cross-over feeding trial involving 10 men with polygenic hypercholesterolemia, a control, Mediterranean-type cholesterol-lowering diet, and a diet of similar composition in which walnuts replaced approximately 35% of energy from unsaturated fat, were given for 6 weeks each. Compared with the control diet, the walnut diet reduced serum total and LDL cholesterol by 4.2% (P = 0.176), and 6.0% (P = 0.087), respectively. No changes were observed in HDL cholesterol, triglycerides, and apolipoprotein A-I levels or in the relative proportion of protein, triglycerides, phospholipids, and cholesteryl esters in LDL particles. The apolipoprotein B level declined in parallel with LDL cholesterol (6.0% reduction). Whole LDL, particularly the triglyceride fraction, was enriched in polyunsaturated fatty acids from walnuts (linoleic and alpha-linolenic acids). In comparison with LDL obtained during the control diet, LDL obtained during the walnut diet showed a 50% increase in association rates to the LDL receptor in human hepatoma HepG2 cells. LDL uptake by HepG2 cells was correlated with alpha-linolenic acid content of the triglyceride plus cholesteryl ester fractions of LDL particles (r(2) = 0.42, P < 0.05). Changes in the quantity and quality of LDL lipid fatty acids after a walnut-enriched diet facilitate receptor-mediated LDL clearance and may contribute to the cholesterol-lowering effect of walnut consumption.
Anderson et al, 2001. Walnut polyphenolics inhibit in vitro human plasma and LDL oxidation. J Nutr. 0022-3166
Recent epidemiologic studies have associated nut consumption with a reduced incidence of cardiovascular mortality. However, little is known about the contribution of nut polyphenols to antioxidant and cardiovascular protection. In this investigation, polyphenol-rich extracts from English walnuts (Juglans regia) were studied and compared with ellagic acid for their ability to inhibit in vitro plasma and LDL oxidation, as well as their effects on LDL ý-tocopherol during oxidative stress. In addition, the Trolox equivalent antioxidant activity (TEAC) was determined and liquid chromatography electrospray detection mass spectrometry (LC-ELSD/MS) analyses of the walnut extracts were performed. 2,2′-Azobis'(2-amidino propane) hydrochloride (AAPH)-induced LDL oxidation was significantly inhibited by 87 and 38% with the highest concentration (1.0 ýmol/L) of ellagic acid and walnut extract, respectively. In addition, copper-mediated LDL oxidation was inhibited by 14 and 84% in the presence of ellagic acid and walnut extract, respectively, with a modest, significant LDL ý-tocopherol sparing effect observed. Plasma thiobarbituric acid reacting substance (TBARS) formation was significantly inhibited by walnut extracts and ellagic acid in a dose-dependent manner, and the extracts exhibited a TEAC value greater than that of ý-tocopherol. LC-ELSD/MS analysis of the walnut extracts identified ellagic acid monomers, polymeric ellagitannins and other phenolics, principally nonflavonoid compounds. These results demonstrate that walnut polyphenolics are effective inhibitors of in vitro plasma and LDL oxidation. The polyphenolic content of walnuts should be considered when evaluating their antiatherogenic potential.
Almario, R.U., V. Vonghavaravat, R. Wong, S.E. Kasim-Karakas, 2001. Effects of walnut consumption on plasma fatty acids and lipoproteins in combined hyperlipidemia. Am J Clin Nutr. 74:72-9
BACKGROUND: Epidemiologic studies show an inverse relation between nut consumption and coronary heart disease. OBJECTIVE: We determined the effects of walnut intake on plasma fatty acids, lipoproteins, and lipoprotein subclasses in patients with combined hyperlipidemia. DESIGN: Participants sequentially adhered to the following diets: 1) a habitual diet (HD), 2) a habitual diet plus walnuts (HD+W), 3) a low-fat diet (LFD), and 4) a low-fat diet plus walnuts (LFD+W). RESULTS: In 13 postmenopausal women and 5 men (x ± SD age 60 ± 8 y), walnut supplementation did not increase body weight despite increased energy intake and the LFD caused weight loss (1.3 ± 0.5 kg; P < 0.01). When comparing the HD with the HD+W, linoleic acid concentrations increased from 29.94 ± 1.14% to 36.85 ±1.13% and ?-linolenic acid concentrations increased from 0.78 ± 0.04% to 1.56 ± 0.11%. During the LFD+W, plasma total cholesterol concentrations decreased by 0.58± 0.16 mmol/L when compared with the HD and by 0.46 ± 0.14 mmol/L when compared with the LFD. LDL-cholesterol concentrations decreased by 0.46 ± 0.15 mmol/L when compared with the LFD. Measurements of lipoprotein subclasses and particle size suggested that walnut supplementation lowered cholesterol preferentially in small LDL (46.1 ± 1.9% compared with 33.4 ± 4.3%, HD compared with HD+W, respectively; P < 0.01). HDL-cholesterol concentrations decreased from 1.27 ± 0.07 mmol/L during the HD to 1.14 ± 0.07 mmol/L during the HD+W and to 1.11 ± 0.08 mmol/L during the LFD. The decrease was seen primarily in the large HDL particles. Conclusions: Walnut supplementation may beneficially alter lipid distribution among various lipoprotein subclasses even when total plasma lipids do not change. This may be an additional mechanism underlying the anti-atherogenic properties of nut intake.
Zambón, D., J. Sabate´, S. Muñoz, B. Campero, E. Casals, M. Merlos, J.C. Laguna, E. Ros, MD, 2000. Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women a randomized crossover trial. Ann Intern Med. 132:538-546.
Background: It has been reported that walnuts reduce serum cholesterol levels in normal young men. Objective: To assess the acceptability of walnuts and their effects on serum lipid levels and low-density lipoprotein (LDL) oxidizability in free-living hypercholesterolemic persons. Design: Randomized, crossover feeding trial. Setting: Lipid clinic at a university hospital. Patients: 55 men and women (mean age, 56 years) with polygenic hypercholesterolemia. Intervention: A cholesterol-lowering Mediterranean diet and a diet of similar energy and fat content in which walnuts replaced approximately 35% of the energy obtained from monounsaturated fat. Patients followed each diet for 6 weeks. Measurements: Low-density lipoprotein fatty acids (to assess compliance), serum lipid levels, lipoprotein (a) levels, and LDL resistance to in vitro oxidative stress. Results: 49 persons completed the trial. The walnut diet was well tolerated. Planned and observed diets were closely matched. Compared with the Mediterranean diet, the walnut diet produced mean changes of -4.1% in total cholesterol level, -5.9% in LDL cholesterol level, and -6.2% in lipoprotein(a) level. The mean differences in the changes in serum lipid levels were 20.28 mmol/L (95% CI, 20.43 to 20.12 mmol/L) (-10.8 mg/dL [0-16.8 to -4.8 mg/dL]) (P< 0.001) for total cholesterol level, -0.29 mmol/L (CI, -0.41 to -0.15 mmol/L) (-11.2 mg/dL [-16.3 to -6.1 mg/dL]) (P< 0.001) for LDL cholesterol level, and -0.021 g/L (CI, -0.042 to -0.001 g/L) (P = 0.042) for lipoprotein ( a) level. Lipid changes were similar in men and women except for lipoprotein (a) levels, which decreased only in men. Low-density lipoprotein particles were enriched with polyunsaturated fatty acids from walnuts, but their resistance to oxidation was preserved. Conclusion: Substituting walnuts for part of the monounsaturated fat in a cholesterol-lowering Mediterranean diet further reduced total and LDL cholesterol levels in men and women with hypercholesterolemia.
Lino, M., K. Marcoe, J.M. Dinkins, H. Hiza, R. Anand, 2000. USDA Center for Nutrition Policy and Promotion. The role of nuts in a healthy diet. Insight 23, December.
While not a staple in the American diet, nuts are consumed by many Americans. This Nutrition Insight examines the contribution nuts can make to a diet, consumption of nuts, characteristics of people who eat nuts, and the association of nut consumption with diet quality.
Zambón, D., J. Sabaté, S. Munoz, B. Campero, E. Casals, M. Merlos, J.C. Laguna, E. Ros, 2000. Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women. A randomized crossover trial. Ann Intern Med. 132:538-546.
BACKGROUND: It has been reported that walnuts reduce serum cholesterol levels in normal young men. OBJECTIVE: To assess the acceptability of walnuts and their effects on serum lipid levels and low-density lipoprotein (LDL) oxidizability in free-living hypercholesterolemic persons. DESIGN: Randomized, crossover feeding trial. SETTING: Lipid clinic at a university hospital. PATIENTS: 55 men and women (mean age, 56 years) with polygenic hypercholesterolemia. INTERVENTION: A cholesterol-lowering Mediterranean diet and a diet of similar energy and fat content in which walnuts replaced approximately 35% of the energy obtained from monounsaturated fat. Patients followed each diet for 6 weeks. MEASUREMENTS: Low-density lipoprotein fatty acids (to assess compliance), serum lipid levels, lipoprotein (a) levels, and LDL resistance to in vitro oxidative stress. RESULTS: 49 persons completed the trial. The walnut diet was well tolerated. Planned and observed diets were closely matched. Compared with the Mediterranean diet, the walnut diet produced mean changes of -4.1% in total cholesterol level, -5.9% in LDL cholesterol level, and -6.2% in lipoprotein (a) level. The mean differences in the changes in serum lipid levels were -0.28 mmol/L (95% CI, -0.43 to -0.12 mmol/L) (-10.8 mg/dL [-16.8 to -4.8 mg/dL]) (P<0.001) for total cholesterol level, -0.29 mmol/L (CI, -0.41 to -0.15 mmol/L) (-11.2 mg/dL [-16.3 to -6.1 mg/dL]) (P<0.001) for LDL cholesterol level, and -0.021 g/L (CI, -0.042 to -0.001 g/L) (P = 0.042) for lipoprotein(a) level. Lipid changes were similar in men and women except for lipoprotein (a) levels, which decreased only in men. Low-density lipoprotein particles were enriched with polyunsaturated fatty acids from walnuts, but their resistance to oxidation was preserved. CONCLUSION: Substituting walnuts for part of the mono-unsaturated fat in a cholesterol-lowering Mediterranean diet further reduced total and LDL cholesterol levels in men and women with hypercholesterolemia.
Lavedrine, F., D. Zmirou, A. Ravel, F. Balducci, J. Alary, 1999. Blood cholesterol and walnut consumption: a cross-sectional survey in France. Prev Med. 28(4):333-9.
BACKGROUND: The preventive role of polyunsaturated fatty acids in cardiovascular disease has been recognized. We conducted a cross-sectional study to assess the association between walnut consumption (oil and kernel) as a source of polyunsaturated fatty acids and blood lipid levels. METHODS: Seven hundred ninety-three persons, males and females, ages 18-65 years, living in a walnut production area (Dauphiný, France) attended health screening visits organized by the Agriculture Social Security. Past diet (1-year recall, including walnut and animal fat consumption) and cardiovascular risk factors were ascertained using food frequency questionnaires. For each participant a blood sample was taken to measure HDL, LDL, and total cholesterol; apo A1; and apo B. RESULTS: A high level of HDL cholesterol and apo A1 was associated with a high amount of walnut consumption (oil and kernel) in the regular diet, with a positive trend with increasing degree of walnut consumption. This association did not appear to be confounded by dietary animal fat and alcohol as measured in this study. Other blood lipids did not show significant associations with walnut consumption. CONCLUSION: The positive effect of walnut consumption on blood HDL cholesterol and apo A1 is of special interest since these lipid parameters have been shown to be negatively correlated with cardiovascular morbidity.
Kris-Etherton, P.M., S. Yu-Poth, J. Sabaté, H.E. Ratcliffe, G. Zhao, T.D. Etherton, 1999. Nuts and their bioactive constituents: effects on serum lipids and other factors that affect disease risk. Am J Clin Nutr.70 (suppl.):504S-11S.
Because nuts have favorable fatty acid and nutrient profiles, there is growing interest in evaluating their role in a heart-healthy diet. Nuts are low in saturated fatty acids and high in monounsaturated and polyunsaturated fatty acids. In addition, emerging evidence indicates that there are other bioactive molecules in nuts that elicit cardioprotective effects. These include plant protein, dietary fiber, micronutrients such as copper and magnesium, plant sterols, and phytochemicals. Few feeding studies have been conducted that have incorporated different nuts into the test diets to determine the effects on plasma lipids and lipoproteins. The total- and lipoprotein-cholesterol responses to these diets are summarized in this article. In addition, the actual cholesterol response was compared with the predicted response derived from the most current predictive equations for blood cholesterol. Results from this comparison showed that when subjects consumed test diets including nuts, there was a ~25% greater cholesterol-lowering response than that predicted by the equations. These results suggest that there are non-fatty acid constituents in nuts that have additional cholesterol-lowering effects. Further studies are needed to identify these constituents and establish their relative cholesterol lowering potency.
Hu, F.B., M.J. Stampfer, 1999. Nut consumption and risk of coronary heart disease: a review of epidemiologic evidence. Current Atherosclerosis Reports. (1):205-10.
Traditionally nuts have been perceived as an unhealthy food because of their high fat content. However, recent accumulative evidence suggests that frequent consumption of nuts may be protective against coronary heart disease (CHD). So far, five large prospective cohort studies (the Adventist Health Study, the Iowa Women Health Study, the Nurses’ Health Study, the Physicians’ Health Study, and the CARE Study) have examined the relation between nut consumption and the risk of CHD and all have found an inverse association. In addition, several clinical studies have observed beneficial effects of diets high in nuts (including walnuts, peanuts, almonds, and other nuts) on blood lipids. The beneficial effects of nut consumption observed in clinical and epidemiologic studies underscore the importance of distinguishing different types of fat. Most fats in nuts are mono- and polyunsaturated fats that lower low-density lipoprotein cholesterol level. Based on the data from the Nurses’ Health Study, we estimated that substitution of the fat from 1 ounce of nuts for equivalent energy from carbohydrate in an average diet was associated with a 30% reduction in CHD risk and the substitution of nut fat for saturated fat was associated with 45% reduction in risk. Given the strong scientific evidence for the beneficial effects of nuts, it seems justifiable to move nuts to a more prominent place in the United States Department of Agriculture Food Guide Pyramid. Regular nut consumption can be recommended in the context of a healthy and balanced diet.
Chisolm, A., J. Mann, M. Skeaff, C. Franpton, W. Sutherland, A. Duncan, S. Tiszavari, 1998. A diet rich in walnuts favorably influences plasma fatty acid profile in moderately hyperlipidemic subjects. Eur J Clin Nutr. 52:12-6.
Objective: To compare two low fat diets one rich in walnuts on parameters of lipid metabolism in a group of hyperlipidemic subjects. Design: A randomized cross over study. Setting: Department of Human Nutrition, University of Otago, Dunedin, New Zealand Subjects: Twenty one men with mean (s.d) levels of total and LDL cholesterol of 6.58 (0.60) and 4.63 (0.58) respectively. Interventions: For two periods of four weeks subjects were asked to consume two low fat diets (fat 30% total energy), one containing, on average, 78 g=d walnuts. Walnuts obtained through Lincoln University and the Walnut Growers Group (South Canterbury). Results: Participants reported a higher total fat intake on the walnut diet (38% compared with 30% on the low fat diet P<0.01) The most consistent change in fatty acid profile of triacylglycerol, phospholipid and cholesterol ester on the walnut diet was a significant (P<0.01) increase in linoleic acid. Triacylglycerol linolenate also increased significantly (P<0.01). Total and LDL cholesterol were lower on both experimental diets than at baseline, 0.25 mmol/l and 0.36 mmol/l respectively on the walnut diet and 0.13 mmol/l and 0.20 mmol/l respectively on the low fat diet. High density lipoprotein cholesterol was higher on both the walnut and low fat diets when compared to baseline (0.15 mmol/l and 0.12 mmol/l, respectively). When comparing the walnut and low fat diets only apo B was significantly lower (P<0.05) on the walnut diet. Conclusions: Despite an unintended increase in the total fat intake on the walnut diet, fatty acid profile of the major lipid fractions showed changes which might be expected to reduce risk of cardiovascular disease. The reduction of apolipoprotein B suggests a reduction in lipoprotein mediated risk, the relatively low myristic acid content of both diets perhaps explaining the absence of more extensive differences in lipoprotein levels on the two diet
