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Research Nut: Walnuts

Tocopherols and total phenolics in 10 different nut types

Kornsteiner, M., K.H. Wagner, I. Elmadfa, 2006. Tocopherols and total phenolics in 10 different nut types. Food Chemistry. 98:381-87.

The study was conducted to assess the content of tocopherols (α-, β-, γ- and δ-) and carotenoids (α- and β-carotene, zeaxanthin, lutein, cryptoxanthin and lycopene) in the unsaponifiable matter as well as the amount of total phenols of 10 different types of nuts. Tocopherols and carotenoids were analyzed with HPLC, total phenols photometrically. The mean value of α-tocopherol equivalents ranged from non-detectable (macadamias) to 33.1 mg/100 g extracted oil (hazelnuts). Among all nuts, almonds and hazelnuts had the highest mean α-tocopherol content (24.2 and 31.4 mg/100 g extracted oil, respectively). β- and γ-tocopherols were prevalent in Brazil nuts, cashews, peanuts, pecans, pines, pistachios and walnuts. Mean values oscillated between 5.1 (cashews) and 29.3 (pistachios). Traces of δ-tocopherol (<4 mg/100 g extracted oil) were analyzed in cashews, hazelnuts, peanuts, pecans, pines, pistachios and walnuts. There were no carotenoids detected in the tested nuts with the exception of pistachios. The mean content of total phenolics varied between 32 mg gallic acid equivalents/100 g (pines) and 1625 mg (walnuts). The results show the eterogenic amounts of antioxidants in nuts, which emphasizes the recommendation of a mixed nuts intake.

Consumption and portion sizes of tree nuts, peanuts and seeds in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts from 10 European countries

Jenab, M., J. Sabate’, N. Slimani, P. Ferrari, M. Mazuir, C. Casagrande, G. Deharveng, A. Tjønneland, A. Olsen, K. Overvad, M.-C. Boutron-Ruault, F. Clavel-Chapelon, H. Boeing, C. Weikert, J. Linseisen, S. Rohrmann, A. Trichopoulou, A. Naska, D. Palli, C. Sacerdote, R. Tumino, A. Mattiello, V. Pala, H.B. Bueno-de-Mesquita, M.C. Ocke’, P.H. Peeters, D. Engeset, G. Skeie, P. Jakszyn, E. Ardanaz, J.R. Quiro’s, M.D. Chirlaque, C. Martinez, P. Amiano, G. Berglund, R. Palmqvist, B. van Guelpen, S. Bingham, T. Key, E. Riboli, 2006. Consumption and portion sizes of tree nuts, peanuts and seeds in the European Prospective Investigation into Cancer and Nutrition (EPIC) cohorts from 10 European countries. British Journal of Nutrition. 96, Suppl. 2, S12-S23

Tree nuts, peanuts and seeds are nutrient dense foods whose intake has been shown to be associated with reduced risk of some chronic diseases. They are regularly consumed in European diets either as whole, in spreads or from hidden sources (e.g. commercial products). However, little is known about their intake profiles or differences in consumption between European countries or geographic regions. The objective of this study was to analyze the population mean intake and average portion sizes in subjects reporting intake of nuts and seeds consumed as  whole, derived from hidden sources or from spreads. Data was obtained from standardized 24-hour dietary recalls collected from 36,994 subjects in 10 different countries that are part of the European Prospective Investigation into Cancer and Nutrition (EPIC). Overall, for nuts and seeds consumed as whole, the percentage of subjects reporting intake on the day of the recall was: tree nuts = 4.4%, peanuts = 2.3% and seeds = 1.3%. The data show a clear northern (Sweden: mean intake = 0.15 g/d, average portion size = 15.1 g/d) to southern (Spain: mean intake = 2.99 g/d, average portion size = 34.7 g/d) European gradient of whole tree nut intake. The three most popular tree nuts were walnuts, almonds and hazelnuts, respectively. In general, tree nuts were more widely consumed than peanuts or seeds. In subjects reporting intake, men consumed a significantly higher average portion size of tree nuts (28.5 v. 23.1 g/d, P<0.01) and peanuts (46.1 v. 35.1 g/d, P<0.01) per day than women. These data may be useful in devising research initiatives and health policy strategies based on the intake of this food group.

Nuts, body weight and insulin resistance

Rajaram, S., J. Sabate’, 2006. Nuts, body weight and insulin resistance. British Journal of Nutrition. 96, Suppl. 2, S79-S86.

Traditionally, nuts have been considered a staple food, but because of their high energy and fat content are not considered good for body weight control or insulin sensitivity. Frequent consumption of nuts reduces the risk of coronary artery disease and type-2 diabetes and nut-enriched diets favorably alter blood lipids in normal and hypercholesterolemic individuals under controlled and free-living dietary conditions. However, whether or not frequent consumption of nuts can cause weight gain and impair insulin sensitivity is not fully understood. Review of the available data to date suggests that adding nuts to habitual diets of free-living individuals does not cause weight gain. In fact, nuts have a tendency to lower body weight and fat mass. In the context of calorie-restricted diets, adding nuts produces a more lasting and greater magnitude of weight loss among obese subjects while improving insulin sensitivity. Further studies are needed to clarify the effect of long-term ($ year) consumption of nuts on body weight and their role in altering insulin sensitivity both in normal and type-2 diabetics. In the meantime, there is sufficient evidence to promote the inclusion of nuts as part of healthy diets.

Food allergy: nuts and tree nuts

Crespo, J.F., J.M. James, C. Fernandez-Rodriguez, J. Rodriguez, 2006. Food allergy: nuts and tree nuts. British Journal of Nutrition. 96, Suppl. 2, S95-S102.

Nuts are a well-defined cause of food allergy, which affect approximately 1% of the general population in the UK and the USA. There do appear to be differences in the frequency of nut allergy between different countries because of different dietary habits and cooking procedures. For example, in the USA and France, peanuts are one of the most frequent causes of food allergy, but in other countries, it seems to be less common. Genetic factors, in particular, appear to play a role in the development of peanut allergy. While the majority of nut allergens are seed storage proteins, other nut allergens are profilins and pathogenesis-related protein homologues, considered as panallergens because of their widespread distribution in plants. The presence of specific IgE antibodies to several nuts is a common clinical finding, but the clinical relevance of this cross-reactivity is usually limited. Allergic reactions to nuts appear to be particularly severe, sometimes even life-threatening, and fatal reactions following their ingestion have been documented. Food allergy is diagnosed by identifying an underlying immunological mechanism (i.e. allergic testing), and establishing a causal relationship between food ingestion and symptoms (i.e. oral challenges). In natural history investigations carried out in peanut-allergic children, approximately 20% of the cases outgrew their allergy or developed oral tolerance. The treatment of nut allergies should include patient and family education about avoiding all presentations of the food and the potential for a severe reaction caused by accidental ingestion. Patients and families should be instructed how to recognize early symptoms of an allergic reaction and how to treat severe anaphylaxis promptl

Qualified health claim for nuts and heart disease prevention, development of consumer-friendly language

Ternus, M., K. Lapsley, K. McMahon, G. Johnson, 2006. Qualified health claim for nuts and heart disease prevention, development of consumer-friendly language. Nutrition Today. 41(2):62-66.

In 2003, the US Food and Drug Administration (FDA) began authorizing qualified health claims for conventional foods. Although the FDA had developed generic qualifying language for these claims, the language had not yet been tested with consumers. A shopping mall intercept was conducted among a random sample of 408 adults. The research tested consumer preference, understanding and believability, and impact on nut consumption of 4 variations of the ‘‘B’’ level qualified health claim for nuts and heart disease. The FDA generic language was used as the control. The results show that one of the alternatives was ranked significantly higher than the FDA generic claim for clarity and understandability but was similar in all other categories, including the scientific uncertainty associated with the claim. This research demonstrates that it is possible to meet FDA’s standards for truthful and not misleading health claims using consumer-friendly language.

Nuts: source of energy and macronutrients

Brufau, G., J. Boatella, M. Rafecas, 2006. Nuts: source of energy and macronutrients. British Journal of Nutrition. 96, Suppl. 2, S24-S28.

On the basis of the high fat content of nuts, they are traditionally considered as foods that provide a high amount of energy. However, epidemiologic and clinical observations do not indicate an association between nut intake and increased BMI. There is a notorious variability in macronutrient composition among nuts, although they have some consistent patterns. Nuts contain all major macronutrients: protein, carbohydrate, and fat. The total protein content is relatively high, which makes them a good source of plant protein (especially for vegetarians). Although nuts contain low amounts of some essential amino acids, this is not a nutritional concern due to the complement of protein. In addition, nuts have a low lysine:arginine ratio, which is inversely associated with the risk of developing hypercholesterolemia and atherosclerosis. Carbohydrates are the second highest macronutrient in nuts in terms of total calories provided. The fat fraction is characterized by a high amount of unsaturated fatty acids and a low content of saturated fatty acids. In conclusion, the high content in unsaturated fatty acids, the low lysine:arginine ratio, and the presence of other bioactive molecules (such as fiber, phytosterols, vitamin and other antioxidants, and minerals) make the addition of nuts to healthy diets a useful tool for the prevention of cardiovascular heart diseases.

Fatty acid composition of nuts – implications for cardiovascular health

Ros, E., J. Mataix, 2006. Fatty acid composition of nuts – implications for cardiovascular health. British Journal of Nutrition. 96, Suppl. 2, S29-S35.

It is well established that, due to their high content of saturated fatty acids (SFA), the intake of meat and meat products is strongly associated with elevated blood cholesterol concentrations and an increased risk of hypertension, diabetes and cardiovascular diseases. Conversely, the intake of foods rich in unsaturated fatty acids, such as those contained in most vegetable fats and oils and oily fish, is associated with improved lipid profiles, a lower potency of intermediate biomarkers of atherosclerosis and lesser incidence of cardiovascular diseases. There are persuasive evidences that dietary substitution of monounsaturated fatty acids (MUFA) or n-6 polyunsaturated fatty acids (PUFA) for SFA lowers blood cholesterol and may have beneficial effects on inflammation, thrombosis, and vascular reactivity. MUFA may have an advantage over PUFA because enrichment of lipoprotein lipids with MUFA increases their resistance to oxidation. Marine n-3 PUFA have a number of anti-atherosclerotic effects, including anti-arrhythmic properties and, at relatively high doses, reduce serum triglycerides. These effects appear to be shared in part by vegetable n-3 PUFA. Nuts are natural foods rich in unsaturated fatty acids; most nuts contain substantial amounts of MUFA, while walnuts are especially rich in both n-6 and n-3 PUFA. Healthy fats in nuts contribute to the beneficial effects of frequent nut intake observed in epidemiological studies (prevention of coronary heart disease, diabetes, and sudden death) and in short-term feeding trials (cholesterol lowering, LDL resistance to oxidation, and improved endothelial function).

Nuts and coronary heart disease: an epidemiological perspective

Kelly Jr., J.H., J. Sabaté’, 2006. Nuts and coronary heart disease: an epidemiological perspective. British Journal of Nutrition. 96, Suppl. 2, S61-S67

The epidemiological evidence for the cardio-protective effect of nut consumption is presented and reviewed. Four large prospective epidemiological studies of primary prevention of coronary heart disease are reviewed and discussed (Adventist Health Study, Iowa Women’s Health Study, Nurses’ Health Study and the Physicians’ Health Study). Other studies of nuts and coronary heart disease risk are addressed. The combined evidence for a cardio-protective effect from nut consumption is summarized and presented graphically. The risk of coronary heart disease is 37% lower for those consuming nuts more than four times per week compared to those who never or seldom consume nuts, with an average reduction of 8·3% for each weekly serving of nuts. The evidence for a causal relationship between nut consumption and reduced risk of coronary heart disease is outlined using Hill’s criteria for causality and is found to support a causal cardio-protective relationship.

Tree nuts and the lipid profile: a review of clinical studies

Griel, A.E., P.M. Kris-Etherton, 2006. Tree nuts and the lipid profile: a review of clinical studies. British Journal of Nutrition. 96, Suppl. 2, S68-S78

Tree nuts have a fatty acid profile that favorably affects blood lipids and lipoproteins. They are low in saturated fat and high in unsaturated fatty acids and are rich sources of other nutrients. An extensive database consistently shows total and LDL cholesterol-lowering effects of diets low in saturated fat and cholesterol and high in unsaturated fat provided by a variety of tree nuts. Collectively, a summary of studies conducted to date shows that tree nuts reduce LDL cholesterol by 3-19% compared with Western and lower-fat diets. Nuts also contain many nutrients and bioactive compounds that appear to contribute to the favorable effects on lipids and lipoproteins – these include plant sterols, dietary fiber and antioxidants. Because of their unique nutrient profile, nuts can be part of a diet that features multiple heart-healthy foods resulting in a cholesterol lowering response that surpasses that of cholesterol-lowering diets typically used to reduce CVD risk.

Effects of a Mediterranean-style diet in cardiovascular risk factors: A randomized trial

Estruch, R., M.A. Martínez-González, D. Corella, J. Salas-Salvadó, V. Ruiz-Gutiérrez, M.I. Covas, M. Fiol, E. Gómez-Gracia, M.C. López-Sabater, E. Vinyoles, F. Arós, M. Conde, C. Lahoz, J. Lapetra. G. Sáez, E. Ros for the PREDIMED Study, 2006. Effects of a Mediterranean-style diet in cardiovascular risk factors: A randomized trial. Annals of Inter Med. 145:1-11.

Background: The Mediterranean diet has been shown to have beneficial effects on cardiovascular risk factors. Objective: To compare the short-term effects of 2 Mediterranean diets versus those of a low-fat diet on intermediate markers of cardiovascular risk. Design: Substudy of a multicenter, randomized, primary prevention trial of cardiovascular disease (Prevencio’ n con Dieta Mediterra’nea [PREDIMED] Study). Setting: Primary care centers affiliated with 10 teaching hospitals. Participants: 772 asymptomatic persons 55 to 80 years of age at high cardiovascular risk who were recruited from October 2003 to March 2004. Interventions: Participants were assigned to a low-fat diet (n=257) or to 1 of 2 Mediterranean diets. Those allocated to Mediterranean diets received nutritional education and either free virgin olive oil, 1 liter per week (n = 257), or free nuts, 30 g/d (n= 258). The authors evaluated outcome changes at 3 months. Measurements: Body weight, blood pressure, lipid profile, glucose levels, and inflammatory molecules. Results: The completion rate was 99.6%. Compared with the low-fat diet, the 2 Mediterranean diets produced beneficial changes in most outcomes. Compared with the low-fat diet, the mean changes in the Mediterranean diet with olive oil group and the Mediterranean diet with nuts group were -0.39 mmol/L (95% CI, -0.70 to -0.07 mmol/L) and -0.30 mmol/L (CI, -0.58 to -0.01 mmol/L), respectively, for plasma glucose levels; -5.9 mm Hg (CI, -8.7 to -3.1 mm Hg) and -7.1 mm Hg (CI, -10.0 to -4.1 mm Hg), respectively, for systolic blood pressure; and -0.38 (CI, -0.55 to -0.22) and -0.26 (CI, -0.42 to -0.10), respectively, for the cholesterol-high-density lipoprotein cholesterol ratio. The Mediterranean diet with olive oil reduced C-reactive protein levels by 0.54 mg/L (CI, 1.04 to 0.03 mg/L) compared with the low-fat diet. Limitations: This short-term study did not focus on clinical outcomes. Nutritional education about low-fat diet was less intense than education about Mediterranean diets. Conclusion: Compared with a low-fat diet, Mediterranean diets supplemented with olive oil or nuts have beneficial effects on cardiovascular risk factors.