Nutrient displacement associated with walnut supplementation in men


  • S. Kranz,

    Corresponding author
    1. Department of Nutrition Science, Purdue University, West Lafayette, IN, USA
    • Correspondence

      S. Kranz, Department of Nutrition Science, Purdue University, 204 Stone Hall, 700 W. State Street, West Lafayette, IN 47907, USA.

      Tel.: +1 765 494 6758

      Fax: +1 765 494 0674


    Search for more papers by this author
  • A. M. Hill,

    1. Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA
    2. Nutritional Physiology Research Centre, University of South Australia, Adelaide, SA, Australia
    Search for more papers by this author
  • J. A. Fleming,

    1. Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA
    Search for more papers by this author
  • T. J. Hartman,

    1. Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA
    2. Department of Epidemiology, Emory University, Atlanta, GA, USA
    Search for more papers by this author
  • S. G. West,

    1. Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA
    2. Department of Biobehavioral Health, Pennsylvania State University, University Park, PA, USA
    Search for more papers by this author
  • P. M. Kris-Etherton

    1. Department of Nutritional Sciences, The Pennsylvania State University, University Park, PA, USA
    Search for more papers by this author



Dietary guidance issued by various global government agencies recommends nut consumption within the context of a healthy-eating pattern. Nuts are nutrient dense and may promote nutrient adequacy. As an energy-dense food, nuts must replace other foods in the diet to prevent an excess of calories.


We evaluated how recommending the inclusion of walnuts (75 g day−1) in the diet affected energy and nutrient intake in men (45–75 years; mean body mass index = 27.6 kg m–2; n = 19) at risk for developing prostate cancer. Guidance was provided about incorporating walnuts isocalorically in a healthy diet. Three-day food records and body weight were collected at baseline and after two 8-week diet periods (usual versus walnut supplement diets).


Energy intake on the walnut supplement diet exceeded the usual diet, although body weight was maintained. Energy intake was lower on the actual walnut supplement diet than the calculated walnut diet [10 865 kJ (2595 kcal) versus 11 325 kJ (2705 kcal) per day, respectively] and contributed 23% less energy than 75 g of walnuts. Approximately, 86% and 85% of the total fat and saturated fatty acids from walnuts were not displaced, whereas the increase in fibre from the usual diet to the actual walnut supplement diet represented less than one-half (39%) of the fibre provided by 75 g of walnuts. Walnuts were substituted, in part, for other foods, and the nutrient profile of the diet was improved, however, the beneficial effect of walnuts on the diet quality was not optimized.


Individuals do not optimally implement food-based guidance. Consequently, nutrition professionals play a key role in teaching the implementation of food-based recommendations.


The recently released Global and Disease Burden Study (Lim et al., 2012) provides strong evidence to support recommendations to include nuts in a healthy dietary pattern. In a ranking of dietary risk factors that affect ischaemic heart disease, a diet low in nuts and seeds ranked first. Ischaemic heart disease was ranked as the number one health problem in the world by the World Health Organization (WHO). Numerous government health organisations have developed dietary guidelines for the prevention and treatment of cardiovascular disease (CVD) and these include regular consumption of nuts. Current dietary recommendations issued by the American Heart Association are to consume fruits and vegetables (4.5 cups per day), fatty fish (two 3.5 oz servings per week) and fibre-rich whole grains (three servings per day), and to decrease sodium (<1500 mg day−1) and added sugars (Lloyd-Jones et al., ). Secondary goals are to consume nuts and seeds (unsalted) and legumes ≥4 (1 oz) servings per week, to consume none or ≤2 servings per week of processed meats, and to decrease saturated fatty acids (SFA) to <7% of calories.

The 2010 Dietary Guidelines for Americans also recommend the consumption of 0.5 oz (~14 g) nuts and seeds per day or 2–8 oz per week (57–227 g week−1) as a source of plant protein (U.S. Department of Agriculture & U.S. Department of Health and Human Services, 2010). The Australian Dietary Guidelines recommend enjoying a wide variety of nutritious foods daily, including one to three servings (30–90 g) per day of lean meats and poultry, fish, eggs, tofu, nuts and seeds, and legumes/beans depending on age and sex (Department of Health and Ageing, 2013), whereas the UK advises the consumption of moderate amounts of protein-rich foods, such as meat, fish, eggs and alternatives such as nuts and pulses (Public Health England in association with the Welsh Government, the Scottish Government and the Food Standards Agency in Northern Ireland, 2013).

Nuts are a rich source of nutrients including fibre, monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), vitamin E, folate, magnesium potassium, and calcium (Segura et al., 2006), and also are low in SFA. Walnuts, in particular, are an excellent source of α-linolenic acid, which is an important omega-3 fatty acid that has been linked to reductions in cardiovascular disease and cancer risk (Sabate et al., 1993; Hu & Manson, 2012). Epidemiological studies suggest that the antioxidant vitamin E, specifically the γ-tocopherol (γ-T) form found in walnuts, may decrease the risk of cardiovascular disease (Rimm et al., 1993) and prostate cancer (Helzlsouer et al., 2000). Specifically, 75 g day−1 of walnuts contain 15.6 mg γ-T, as well as ellagic acid (590 μg g−1), which also has been shown to effectively inhibit certain steps involved in carcinogenesis (Narayanan et al., 1999; Labrecque et al., 2005). In addition, several clinical trials have reported total and low-density lipoprotein-cholesterol lowering effects following the consumption of approximately 70–80 g day−1 of walnuts (Sabate et al., 1993; Abbey et al., 1994; Chisholm et al., 1998).

Because nuts are energy dense, they must replace other foods in the diet to control calories, and prevent an excess energy intake and weight gain. Given the high prevalence of overweight/obesity and nutrient inadequacies in developed countries, it is imperative that messages about increasing energy and nutrient dense foods be communicated effectively.

In both epidemiological (Fraser et al., 1992; Hu et al., 1998; Bes-Rastrollo et al., 2007) and clinical studies (Alper & Mattes, 2002; Fraser et al., 2002; Sabate et al., 2005), the inclusion of nuts in the diet does not result in an increased body weight (Martínez-González & Bes-Rastrollo, 2011) and, indeed, observational studies demonstrate that nut consumers have a lower body mass index (BMI) than nonconsumers (Mattes et al., 2008). One possible mechanism to explain the favourable association between nuts and body weight is energy displacement. That is, the higher fibre, protein and total fat content, as well as the low glycaemic index of nuts, may increase satiety and reduce energy intake. The concept of energy displacement when nuts are included in the diet was reported by Fraser et al. (2002) and Jaceldo-Siegl et al. (2004); free-living subjects consuming a daily supplement of almonds (54 g day−1) displaced 54% of the additional energy by reducing the consumption of other foods. This ‘compensation’ occurred without formal dietary advice. During the first 6 months of the study, subjects consumed their habitual diets and, in the second 6 months, they included almonds in their diet. At the end of the 1-year study, there was a nonsignificant weight gain (<0.5 kg). In addition, an improved nutrient profile of the almond-supplemented diet was reported.

Certain beneficial nutrients, however, such as fibre, did not increase as much as would be expected by adding 54 g day−1 of almonds to the diet, suggesting that individuals compensated for a portion of the calories in the nuts by reducing their intake of other fibre-containing foods. This raises two questions. (i) How can the dietary recommendation for nuts be implemented in a way that optimises diet quality? (ii) Is specific dietary advice about food substitutions needed to achieve the greatest improvements in the nutrient quality of the diet without exceeding energy needs?

The 2010 Dietary Guidelines Advisory Committee Report noted that ‘because nuts and seeds are high in calories, they should be eaten in small portions and used to replace other protein foods, like some meat or poultry, rather than being added to the diet’ (Dietary Guidelines Advisory Committee, 2010). In the present study, we evaluated how individuals interpret and implement the recommendations to incorporate nuts in their diet. Specifically, we examined the nutrient and calorie ‘displacement effect’ associated with supplementing the usual diet of men aged 45–75 years with 75 g (~2.6 oz) of walnuts per day in a free-living setting. Unlike the study conducted by Fraser et al. (2002), general strategies were provided for isocalorically substituting walnuts for other energy sources in the diet. Thus, the present study aimed to assess an individual's ability to isocalorically incorporate nuts in the diet by displacement of low nutrient, high energy-dense foods.

Materials and methods

The study design and recruitment details have been reported previously (Spaccarotella et al., 2008). Briefly, this was an intervention study designed to examine the effect of walnut supplementation (75 g day−1) on risk factors related to prostate cancer and CVD in men who presented with high prostate-specific antigen (PSA) levels. This amount of walnuts was selected based on the content of γ-T, which has been shown to be protective against prostate cancer (Helzlsouer et al., 2000). In addition, the high energy content of walnuts allowed for a more accurate assessment of dietary displacement. That is, the measurement error surrounding dietary assessment methods may have masked the energy displacement if a smaller portion of walnuts was provided.


Twenty-one men aged 45–75 years, with body weight data available for all time points, were included in the analysis. Eligible participants included healthy, nonsmoking men at risk for prostate cancer (based on PSA levels) but not clinically diagnosed at study entry. Exclusion criteria included: (i) the presence of nut-allergies; (ii) the use of prescription and/or nonprescription medications known to alter PSA concentrations, hormone levels, blood pressure or lipids; and (iii) the regular use of a vitamin E supplement and an unwillingness to discontinue supplementation during the research study. The Institutional Review Board at the Pennsylvania State University approved the protocol and all individuals provided their written informed consent.

Research design

We conducted a two-period, two-treatment, cross-over dietary intervention study. Participants received two treatments in a random order (walnut supplement diet versus usual diet; 8 weeks per treatment). There was a 2-week washout period between treatments. Body weight was measured when participants were wearing indoor clothing but without shoes on digital scales at weeks 1, 2, 3, 4, 6 and 8 at the General Clinical Research Centers at University Park and Hershey (Milton S. Hershey Medical Center), PA, USA.


Participants received 75 g (~2.6 oz) per day of English walnuts during the walnut supplement diet period. The supplement contributed approximately 2056 kJ (491 kcal), 48.9 g of fat, 4.6 g of SFA, 6.7 g of MUFA, 35.4 g of PUFA and 5.0 g of dietary fibre. Although the amount of walnuts provided daily was higher than current 2010 Dietary Guideline recommendations (0.5 oz or 14 g day−1), it provided a good opportunity to test the displacement hypothesis. The walnuts were shelled, unroasted, unsalted, purchased from a single lot, preweighed, packaged and stored frozen at −17 °C.

To ensure that weight remained stable, participants were encouraged to maintain physical activity levels and were instructed to replace another fat or protein source in their usual diet with the walnuts and to consume the walnuts throughout the day with snacks and meals. For example, general tips were provided about consuming walnuts (i.e. substituting walnuts for croutons on salads, or eating walnuts out of hand as a stand-alone mid or afternoon snack, instead of baked goods, savory snacks or other snacks). No further instructions were given so as to mimic the guidance provided by current dietary recommendations. In addition, participants were not required to report what specific substitution strategies they implemented for weight maintenance.

Participants provided five, 3-day food records, at baseline and weeks 4 and 8 of each diet period to monitor compliance. Participants were provided with instructions for completing the food records (i.e. preparation techniques, time of day, inclusion of brand names, etc.) and a portion size poster for estimating serving sizes. During weeks 4 and 8 of both diet periods, participants met with a registered dietitian, who reviewed the food records with the participants to identify any signs of misreporting and to obtain additional information or clarification as needed. In addition, weight maintenance strategies, similar to those provided as part of the 2005 Dietary Guidelines for Americans, were provided if needed. For example, participants were encouraged to replace high-saturated fat protein foods (i.e. cheese, processed meats) with walnuts or to replace high-fat desserts or snacks (i.e. ice cream, chips and baked goods) with walnuts.

Dietary outcome and compliance measures

Food record data were analysed using nutrition data system for research, version 5.0_35 (Nutrition Coordinating Center, University of Minnesota, Minneapolis, MN, USA). At each time point, intakes were averaged across 3 days to estimate usual intakes of total energy, carbohydrate, protein, fat (total, SFA, MUFA, PUFA and omega-3 fatty acids) cholesterol, dietary fibre (total, soluble and insoluble fibre), selected micronutrients important for general and cardiovascular health (folate, calcium, iron and zinc) and vitamin E (α-, β-, γ- and δ-tocopherol). No outliers or individuals who reported extreme intakes [< 5024 kJ (1200 kcal) or > 20 934 kJ (5000 kcal)] were identified. Quantification of serum γ-T, a biomarker of walnut consumption, provided an assessment of compliance during the walnut supplement period (Spaccarotella et al., 2008).

Statistical analysis

Statistical analysis was performed using sas, version 9.1.3 (SAS Institute Inc., Cary, NC, USA). Dietary variables were tested for the effects of sequence, period, treatment and baseline BMI using linear mixed model regression analyses.

Intakes of total energy, macro- and micronutrients were compared and nutrient displacement was calculated using the method of Jaceldo-Siegl et al. (2004). According to this method, energy and nutrient intake levels as a result of the addition of walnuts to the diet, referred to here as the calculated walnut diet (C), are equal to the energy and nutrient intake during the usual diet (U) plus the energy, macro- and micronutrients provided by the walnuts (C = U + walnuts). Displacement (D) of energy and nutrients in absolute terms was determined by subtracting the intake of energy and nutrients when on the actual walnut supplement diet (A) from the calculated amount (C) (D = C − A). To indicate the percentage change in energy and nutrient intake when on the actual walnut supplement diet, the ratio of the observed displacement over the energy and nutrients from the walnuts was calculated (D% = (D/walnuts) × 100).

Distributions for total energy, macro- and micronutrient intake during the two diet periods were skewed. Therefore, median intakes were used for all analyses. The nonparametric Wilcoxon signed rank test for paired observations was employed to determine whether D was significant at P ≤ 0.05.


Of the 21 participants who began the study, two participants were excluded from the data analysis: one participant did not complete the study and the other did not have a complete set of body weight records. The final sample size was 19. Table 1 presents the baseline characteristics of the 19 participants in the present analysis. The mean (SD) age of the participants was 65.6 (6.4) years with a body weight of 83.5 (12) kg and a BMI of 27.6 (3.2) kg m–2. Participants randomised to the walnut supplemented diet during their first diet period had lower baseline body weights and BMIs than those randomised to their usual diet during their first diet period.

Table 1. Baseline characteristics of study participants by treatment sequence and the full sample (n = 19)
 Treatment sequence
Group 1a (n = 10)Group 2b (n = 9)Total (n = 19)
Mean (SD)95% CIMean (SD)95% CIMean (SD)95% CI
  1. a

    Participants in group 1 consumed their usual diet for the first 8-week period followed by the walnut supplement diet.

  2. b

    Participants in group 2 consumed the walnut supplement diet for the first 8-week period followed by their usual diet.

  3. BMI, body mass index; CI, confidence interval.

Age (years)65.7 (6.1)62.9–68.565.6 (6.8)62.2–69.065.6 (6.4)63.5–67.7
Weight (kg)87.0 (10.5)82.1–91.979.7 (13.4)73.1–86.483.5 (12.4)79.5–87.6
Height (cm)175.6 (6.5)172.6–178.7171.9 (4.7)169.6–174.2173.9 (6.0)171.9–175.8
BMI (kg m–2)28.2 (2.9)26.8–29.626.8 (3.5)25.1–28.627.6 (3.2)26.5–28.6

The 75 g of walnuts consumed each day during the walnut supplement diet contained 2051 kJ (490 kcal) of energy and 48.9 g of fat; a nutrient analysis of a sample of the walnuts used in the present study showed that they contained approximately 23 mg of γ-T, which is the amount expected. As reported previously (Spaccarotella et al., 2008), analysis of the participants' diet records during the walnut supplement diet period showed significant increases [mean (SD)] in energy {2001 kJ [478 (616) kcal] day−1; = 0.003}, total fat [44.4 (30.9) g day−1; < 0.0001], MUFA [6.9 (13.3) g day−1; = 0.02] and PUFA [29.1 (18.3); <0.0001], suggesting that participants were compliant with the walnut treatment. In addition, serum γ-T [13.7 (7.99) mg day−1; < 0.0001] levels were elevated (Spaccarotella et al., 2008), which is a biomarker for walnut intake. Details of body weight change have been reported previously for the complete cohort (n = 21) (Spaccarotella et al., 2008). Mean (SD) weight was 84.8 (2.9) kg at the screening visit, 83.4 (2.8) kg at the end of the usual diet and 84.3 (2.9) kg at the end of the walnut supplement diet. Participants on the usual diet lost 1.36 (0.39) kg (= 0.001), whereas participants on the walnut supplement diet maintained their weight. The between group difference was not significant.

Dietary displacement

Table 2 shows total energy, macro- and micronutrients on the usual diet (U), the calculated walnut diet (C), the actual walnut supplement diet (A) diet, as well as the contribution from the walnuts alone, and the absolute and relative displacement (D).

Table 2. Dietary intakes (median) and displacement of selected nutrients after an 8-week period of walnut supplementation (n = 19)
 Intake on usual diet (U)Amount from 75 g of walnutsCalculated intake on walnut diet (C)Actual intake on walnut diet (A)Absolute displace-ment (D)P-valueDisplace-ment
  1. a

    Statistical significance at P-value <0.05.

  2. b

    The estimated mean total daily expenditure for the sample population is 10 467 kJ (2500 kcal).

  3. A, actual intake on walnut diet; C, calculated intake on walnut diet; D, absolute displacement of calories; DFE, dietary folate equivalent; MUFA, monounsaturated fatty acids; NS, not significant; PUFA, polyunsaturated fatty acids; SFA, saturated fatty acids; U, intake on usual diet.

Total energy (kcal day−1)b9274 kJ (2215 kcal)2056 kJ (491 kcal)11 325 kJ (2705 kcal)10 865 kJ (2595 kcal)636 kJ (152 kcal)0.003aNegative
Carbohydrate (g day−1)245.510.3255.8258.9−12.70.445NS
Protein (g day−1)72.811.484.
Total fat (g day−1)85.748.9134.6127.83.0<0.001aNegative
SFA (g day−1)28.14.632.732.0−0.10.053NS
MUFA (g day−1)29.66.736.338.2−0.20.01aPositive
PUFA (g day−1)15.935.451.347.921.340.006aNegative
Omega-3 fatty acids(g)<0.001aNegative
Total fibre (g day−1)
Vitamin C (mg day−1)−10.00.421NS
Vitamin E (mg day−1)
Folate (DFE μg day−1)450.274.3523.7442.316.00.059NS
Calcium (mg day−1)839.924.2913.4893.1107.20.778NS
Iron (mg day−1)
Zinc (mg day−1)11.12.313.413.10.90.134NS

Mean total energy intake and intake for most nutrients was higher when individuals reported intakes on the actual walnut supplement diet (A) than on their usual diet (U), with the exception of folate, which was similar. In comparison with the calculated walnut diet (C), the intakes of all nutrients, except carbohydrate, MUFA and vitamin C, were lower on the actual walnut supplement diet (A). Significant differences in the intake of nutrients on the actual walnut supplement diet, compared to the calculated walnut diet, reflect nutrient displacement. Significant effects were observed for total energy, total fat, PUFA, omega-3 fatty acids and total fibre. As shown in Table 2, the median total energy intake was 460 kJ (110 kcal) day−1lower on the actual walnut supplement diet than the calculated walnut diet (2595 kcal day−1 and 2705 kcal day−1, respectively) and contributed 23% less than the amount of energy provided by adding 75 g of walnuts to the usual diet. That is, approximately 25% of the calories from the walnuts were displaced. The increase in total fat and SFA represented 86% and 85% of the amounts contributed by the walnuts, respectively, demonstrating 15% displacements for both nutrients. Conversely, the increase in fibre from the usual diet to the actual walnut supplement diet represented less than half (39%) of the fibre provided by 75 g of walnuts.


The results of the present study demonstrate that participants complied with the dietary protocol, and modified their diet to include 75 g day−1 of walnuts. However, the energy displacement was not complete. As reported previously, participants maintained their weight (Spaccarotella et al., 2008). The latter results might be explained by new findings showing that energy derived from nut consumption is less than the energy values calculated from Atwater factors (Novotny et al., 2012). That is, the energy content of nuts in the diet may be an overestimation of the actual metabolisable energy content. In a study of almonds, Novotny et al. (2012) measured the urine and faeces of healthy volunteers following a 9-day treatment period and reported that the energy content of almonds was approximately 540 kJ (129 kcal) 28 g−1 serving. This is significantly less than the energy content measured by the Atwater factors [703–712 kJ (168–170 kcal) 28 g−1 serving]. Moreover, although the study participants actively displaced some calories when incorporating walnuts in their diet, they did not fully understand how to obtain the maximum benefit of substituting walnuts for other less nutrient dense foods. Additional nutrition education is needed that focuses on teaching individualised strategies about how to include nuts in the diet to achieve recommended food, energy and nutrient intakes. Specific strategies to optimise diet quality may include: replacing high-fat, low nutrient dense snacks (i.e. cookies, chips) with walnuts or a nutrient dense food that contains walnuts such as trail mix; replacing high-fat ice cream with low-fat regular or frozen yogurt topped with walnuts; replacing croutons, high-fat cheeses and creamy dressings on salad with walnuts; and substituting walnuts and a variety of herbs for butter in vegetable dishes. Providing detailed strategies such as these may prove to be more successful for optimising diet quality compared to general recommendations that promote the substitution of nuts for other protein sources (as well as nutrient poor foods) in the diet.

Although intakes of PUFA, omega-3 fatty acids and dietary fibre increased on the walnut supplement diet, they were less than what would be expected if walnuts were added to the diet with no displacement. This suggests that participants substituted walnuts, in part, for food sources of PUFA, omega-3 fatty acids and dietary fibre. The consumption of MUFA increased to levels higher than the amount of MUFA contributed from the walnuts added to the diet. These results suggest that other MUFA-rich foods were not displaced. The increase in total dietary fibre represented less than half of the calculated amount during the walnut supplement diet period. This increase was significantly lower than that achievable if specific food substitutions were made, especially for insoluble fibre. The lack of a decrease in SFA indicates that walnuts were not completely substituted for food sources of SFA.

To date, the concept of nutrient displacement has not been studied extensively, especially for nuts, perhaps because of the difficulty in evaluating changes in dietary patterns of free-living individuals. Our understanding of how specific food intake modifications affect the consumption of other foods is in the early stages of research. As indicated by the present study, participants who incorporated walnuts in their usual diet had increases in nutrient and energy intakes that were less than the amount expected when walnuts are added to the diet, providing evidence of some (but not optimal) dietary displacement. These findings reaffirm the importance of providing more specific strategies for implementing food-based dietary recommendations.

The main limitation of the present study is the small sample size. In addition, we did not specifically identify food changes that were made in response to walnut supplementation. This was a result of the markedly different strategies that our participants used to incorporate walnuts in their diets, the difficulty in assessing such data, especially in a small group of subjects, and the marked variation in their usual diets. Dietary reporting by participants in free-living studies also is problematic, with particular trends toward under-reporting energy intake. Although this limitation cannot be resolved completely, the assessment of dietary intake using a validated method in the present study may partially alleviate these methodological issues. Moreover, as reported previously (Jaceldo-Siegl et al., 2004), the change in serum γ-tocopherol levels, a biomarker of walnut intake, indicated that participants consumed the walnuts.


Food-based dietary recommendations are intended to achieve an optimal nutrient profile and energy intake that promotes health and well-being. In the present study, the recommendation to incorporate 75 g (~2.6 oz) of walnuts in the daily diet resulted in an energy intake that not only exceeded the usual diet, but also fell short of achieving the intended nutrient benefits. It is clear that walnuts were substituted, in part, for other foods, and the nutrient profile of the diet was improved, however, the beneficial effect of walnuts on the diet quality was not optimized. Although beneficial nutrients (PUFA, omega-3 fatty acids and dietary fibre) increased less than expected on the walnut supplement diet, they nonetheless increased, indicating that participants modified their diet by consuming fewer foods with these nutrients. Conversely, SFA increased as calculated when walnuts were incorporated in the diet, indicating that subjects did not substitute them for food sources of saturated fat.

Current dietary guidelines recommend the consumption of nuts, including walnuts. Evaluating how the nutrient profile of the diet changes in response to walnut supplementation provides some insight about candidate food substitutions that might have been made. Clearly, more information is needed about the specific food substitutions that are made when nuts are incorporated in the diet. This information will be useful to dietitians for educating consumers on strategies to create healthy dietary patterns that contain nuts. Dietitians and other health professionals play a key role in teaching individuals how to implement food-based recommendations to achieve healthier dietary patterns consistent with overall health. Thus, further research is required to better understand how to optimise nutrition messages for incorporating nuts in the diet to attain a nutrient profile that maximally optimises plasma lipids and reduces the risk of chronic diseases.


We are grateful to the individuals who elected to participate in the present study, as well as Kim Spaccarotella who conducted the Walnut Consumption on Prostate Specific Antigen in Men Study as part of her doctorial work at Penn State University. Research was conducted at the Pennsylvania State University.

Conflict of interests, source of funding and authorship

The authors declare that there are no conflicts of interest.

Funding was provided by the California Walnut Commission.

SK was responsible for the analysis and interpretation of data, drafting of the manuscript, critical revision of the manuscript and obtaining funding. AMH was responsible for the analysis and interpretation of data, drafting of the manuscript and critical revision of the manuscript. JAF was responsible for the analysis and interpretation of data, critical revision of the manuscript and administrative, technical or material support. TJH contributed to the conception and design of the study, acquisition of data, critical revision of the manuscript and obtaining funding. SGW was responsible for the statistical analysis, drafting of the manuscript and critical revision of the manuscript. PMK-E was responsible for the acquisition of data, analysis and interpretation of data, drafting of the manuscript, critical revision of the manuscript, obtaining funding and supervision. All authors critically reviewed the manuscript and approved the final version submitted for publication.