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Almond Bioaccessibility in a Randomized Crossover Trial: Is a Calorie a Calorie?

  • Stephanie K. Nishi
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada

    Toronto 3D (Diet, Digestive Tract and Disease) Knowledge Synthesis and Clinical Trials Unit, Ontario, Canada

    Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Ontario, Canada
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  • Cyril W.C. Kendall
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada

    Toronto 3D (Diet, Digestive Tract and Disease) Knowledge Synthesis and Clinical Trials Unit, Ontario, Canada

    Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Ontario, Canada

    College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Canada
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  • Richard P. Bazinet
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada
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  • Anthony J. Hanley
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada

    Dalla Lana School of Public Health, University of Toronto, Ontario, Canada

    Department of Medicine, University of Toronto, Ontario, Canada
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  • Elena M. Comelli
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada

    Joannah and Brian Lawson Centre for Child Nutrition, University of Toronto, Ontario, Canada
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  • David J.A. Jenkins
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada

    Department of Medicine, University of Toronto, Ontario, Canada

    Toronto 3D (Diet, Digestive Tract and Disease) Knowledge Synthesis and Clinical Trials Unit, Ontario, Canada

    Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Ontario, Canada

    Division of Endocrinology & Metabolism, St. Michael’s Hospital, Toronto, Ontario, Canada

    Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
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  • John L. Sievenpiper
    Correspondence
    Correspondence: Address to John L. Sievenpiper, MD, PhD, FRCPC, St. Michael’s Hospital, 6137-61 Queen St E, Toronto, ON M5C 2T2, Canada
    Affiliations
    Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Ontario, Canada

    Department of Medicine, University of Toronto, Ontario, Canada

    Toronto 3D (Diet, Digestive Tract and Disease) Knowledge Synthesis and Clinical Trials Unit, Ontario, Canada

    Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Ontario, Canada

    Division of Endocrinology & Metabolism, St. Michael’s Hospital, Toronto, Ontario, Canada

    Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
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Open AccessPublished:April 11, 2021DOI:https://doi.org/10.1016/j.mayocp.2021.01.026

      Abstract

      Objective

      To investigate the energy and macronutrient bioaccessibility of almonds in individuals with hyperlipidemia.

      Methods

      In a previously reported randomized crossover trial, men and postmenopausal women with hyperlipidemia incorporated 3 isoenergetic supplements into a National Cholesterol Education Program Step 2 diet for 1 month each between September 20, 2000, and June 27, 2001. Supplements provided consisted of full-dose almonds (73±5 g/d), half-dose almonds (38±3 g/d) plus half-dose muffins, and full-dose muffins (control). Energy and macronutrients, including individual fatty acids, were measured in the dietary supplements and fecal samples using gas chromatography and Association of Official Analytical Chemists methods. Serum was measured for lipids and fatty acids. Bioaccessibility of energy and macronutrients from almond consumption was assessed from dietary intake (7-day food records) and fecal output.

      Results

      Almond-related energy bioaccessibility was 78.5%±3.1%, with an average energy loss of 21.2%±3.1% (40.6 kcal/d in the full-dose almond phase). Bioaccessibility of energy and fat from the diet as a whole was significantly less with almond consumption (in both half- and full-dose phases) compared with the control. Bioaccessibility of fat was significantly different between treatment phases (P<.001) and on average lower by 5.1% and 6.3% in the half- and full-dose almond phases, respectively, compared with the control phase. Energy bioaccessibility was significantly different between the treatment phases (P=.02), decreasing by approximately 2% with the inclusion of the full dose of almonds compared with the control.

      Conclusion

      Energy content of almonds may not be as bioaccessible in individuals with hyperlipidemia as predicted by Atwater factors, as suggested by the increased fat excretion with almond intake compared with the control.

      Trial Registration

      ClinicalTrials.gov identifier: NCT00507520.

      Abbreviations and Acronyms:

      BMI (body mass index), FAME (fatty acid methyl ester), LDL-C (low-density lipoprotein cholesterol), NCEP (National Cholesterol Education Program)
      Almonds, a nutrient-dense tree nut, gained the public’s attention because of their serum lipid–lowering effects
      • Spiller G.A.
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      Nuts and plasma lipids: an almond-based diet lowers LDL-C while preserving HDL-C.
      ,
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      • Marchie A.
      • et al.
      Dose response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-density lipoproteins, lipoprotein(a), homocysteine, and pulmonary nitric oxide: a randomized, controlled, crossover trial.
      and additionally for their cardiometabolic health benefits.
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      Nut consumption and incidence of cardiovascular diseases and cardiovascular disease mortality: a meta-analysis of prospective cohort studies.
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      Effect of tree nuts on metabolic syndrome criteria: a systematic review and meta-analysis of randomised controlled trials.
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      • et al.
      Effect of tree nuts on glycemic control in diabetes: a systematic review and meta-analysis of randomized controlled dietary trials [erratum appears in PLoS One. 2014;9(9):e109224].
      Despite that almonds are a plant-based protein source providing vitamins, minerals, fiber, and phytonutrients, they are also viewed as an energy-dense food choice owing to their high-fat content. Diabetes and cardiovascular guidelines often include a disclaimer with nut consumption advice to be cautious of their calorie concentration.
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      • et al.
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      Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes.
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      • Petersen K.S.
      Nutrition and cardiovascular disease—an update.
      With overweight and obesity being major public health concerns, knowledge of the energy value of foods in relation to what is actually digested and absorbed by the body is important for informing recommendations. The Atwater system, which denotes an energy value for each macronutrient based on general heats of combustion regardless of the food source, is currently widely applied to estimate the energy content of foods.
      • Atwater W.O.
      • Woods C.D.
      The chemical composition of American food materials. U.S. Department of Agriculture Office of Experiment Stations Bulletin No. 28.
      FAO Food and Nutrition Paper 77
      Food energy—methods of analysis and conversion factors. Report of a Technical Workshop, December 3-6, 2002.
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      A digest of metabolism experiments in which the balance of income and outgo was determined. U.S. Department of Agribulture Office of Experiment Stations Bulletin No. 45.
      Despite the high calculated calorie amount of almonds, nuts have not been shown to increase adiposity measures.
      • Flores-Mateo G.
      • Rojas-Rueda D.
      • Basora J.
      • Ros E.
      • Salas-Salvadó J.
      Nut intake and adiposity: meta-analysis of clinical trials.
      A potential explanation for this is that the bioaccessibility of macronutrients from almonds during mastication and digestion may be less than expected on the basis of the Atwater factor determinations. This has previously been demonstrated in vitro and in healthy individuals but not in participants with relevant health conditions.
      • Gebauer S.K.
      • Novotny J.A.
      • Bornhorst G.M.
      • Baer D.J.
      Food processing and structure impact the metabolizable energy of almonds.
      • Novotny J.A.
      • Gebauer S.K.
      • Baer D.J.
      Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets.
      • Grundy M.M.
      • Grassby T.
      • Mandalari G.
      • et al.
      Effect of mastication on lipid bioaccessibility of almonds in a randomized human study and its implications for digestion kinetics, metabolizable energy, and postprandial lipemia.
      • Grundy M.M.
      • Wilde P.J.
      • Butterworth P.J.
      • Gray R.
      • Ellis P.R.
      Impact of cell wall encapsulation of almonds on in vitro duodenal lipolysis.
      This may have implications for chronic disease and weight management recommendations.
      It is hypothesized that the bioaccessibility of macronutrients, particularly fat, from an almond-enriched diet will be less compared with a control diet. Our aim was to investigate the effect of adding almonds to daily dietary intake on energy and macronutrient bioaccessibility in the diet in individuals with hyperlipidemia. This exploratory analysis was undertaken in a randomized crossover trial, which showed beneficial health effects of almond intake on lipid parameters.
      • Jenkins D.J.
      • Kendall C.W.
      • Marchie A.
      • et al.
      Dose response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-density lipoproteins, lipoprotein(a), homocysteine, and pulmonary nitric oxide: a randomized, controlled, crossover trial.

      Methods

      The methods of this randomized crossover trial have been previously published.
      • Jenkins D.J.
      • Kendall C.W.
      • Marchie A.
      • et al.
      Dose response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-density lipoproteins, lipoprotein(a), homocysteine, and pulmonary nitric oxide: a randomized, controlled, crossover trial.

      Ethics, Consent, and Permissions

      This study was approved by the Ethics Committees of the University of Toronto and St. Michael’s Hospital. All participants gave informed consent.

      Study Design

      The investigation is an exploratory analysis of a randomized crossover trial of participants with hyperlipidemia consuming 3 isoenergetic supplements (ie, 3 phases), each for 1 month, with at least a 2-week washout period between each phase conducted from September 20, 2000, through June 27, 2001. The Figure shows the design of the study. After an overnight fast (12-14 hours), anthropometric measurements, blood pressure, and blood samples were obtained at randomization and at the end of each phase. At week 4 of each phase, 7-day weighed diet records, questionnaires on satiety and bowel movements, and fecal samples were collected. Fecal samples consisted of 3-day fecal collections made on an outpatient basis. Participants were provided with under-seat lavatory frames lined with plastic bags to be removed after use. Feces were weighed and stored at −20°C before mixing, homogenizing, and freeze-drying. Given the nature of the foods provided, participants and dietitians providing dietary counseling could not be blinded. However, investigators involved in the preparation of databases and laboratory determinations were blinded with respect to treatment sequence.
      Figure thumbnail gr1
      FigureSchematic of the randomized, controlled, crossover study design. I, information session; S, screening visit; –2, training visit; R, randomization. The asterisk represents the timings of the collection of the 7-day diet records, serum samples, and fecal samples used in the analyses. The study design consisted of 3 phases and 3 treatments; each participant consumed all 3 treatments in different phases, with the treatment order depending on the randomization. Treatments consisted of isoenergetic intake of a control, half-dose almonds, or full-dose almonds per day, which were consumed as part of a National Cholesterol Education Program (NCEP) Step 2 background diet.

      Study Participants

      Men and postmenopausal women with hyperlipidemia but otherwise healthy were recruited by newspaper advertisement and from patients visiting the Risk Factor Modification Centre of St. Michael’s Hospital, Toronto, Ontario, Canada. Inclusion criteria included low-density lipoprotein cholesterol (LDL-C) concentration of more than 4.1 mmol/L at recruitment. People were excluded if they were taking lipid-lowering medications, exhibited clinical or biochemical evidence of diabetes or renal or hepatic disease, had a body mass index (BMI) above 32 kg/m2, used antibiotics within 3 months of the study start date, used hormone replacement therapy, smoked or consumed significant amounts of alcohol (>1 drink/d), or had a triglyceride level above 4.0 mmol/L. Participants were randomized by use of a computer number generator and received treatment allocation by sealed opaque envelopes.

      Study Diets

      During all phases, participants were counseled on strategies to facilitate weight maintenance and followed their self-selected, low-fat therapeutic diets (based on National Cholesterol Education Program [NCEP] Step 2 dietary guideline recommendations) into which they incorporated the provided study supplements. Nuts, soy, and dietary supplements (vitamins, minerals, or herbal remedies) were excluded in the background diet during all phases of the study. Raw almonds and the control muffins were supplied, with the control supplement being matched to the calculated energy content of the almond supplement interventions. The 3 isoenergetic dietary supplements provided 22.2% of daily energy. Daily energy requirements were assessed by Lipid Research Clinics tables
      Lipid Research Clinics Program
      Population Studies Data Book, vol 2. The Prevalence Study—Nutrient Intake.
      and consisted of full-dose almonds, half-dose almonds plus half-dose muffins, and full-dose muffins (control; Supplemental Table 1, available online at http://www.mayoclinicproceedings.org). The muffins were made from whole-wheat flour with corn oil sufficient to provide the same amount of fiber, saturated fats, and polyunsaturated fats as the almonds, and skim milk powder and egg white to provide a similar level of protein, although the muffin protein was 46% of animal origin. This balance allowed comparison of the effects of monounsaturated fat from almonds with starch from muffins. No directions were provided with respect to mastication of the dietary supplements.

      Analyses

      Body weight was measured with a calibrated digital scale, and height was measured with a calibrated stadiometer; BMI was calculated as weight divided by height in meters squared. Body fat was determined using bioelectrical impedance analysis.
      The 7-day diet records were analyzed using the computer program ESHA, the Food Processor SQL (version 10.9.0), based on data from the Canadian Nutrient File
      Health Canada
      Nutrient Values of Some Common Foods.
      and the US Department of Agriculture
      US Department of Agriculture
      Composition of Foods, Agriculture Handbook No. 23: The Agriculture Research Service.
      with additional measurements made for local foods. Adherence to study supplements was assessed from the 7-day diet records, a supplement checklist, and the return of empty supplement packaging along with uneaten supplements that were weighed and recorded. Satiety was measured using a 9-point Likert scale (from starved/feeling weak to painfully full).
      Macronutrients and dietary fiber were measured in freeze-dried fecal samples by standard Association of Official Analytical Chemists methods for macronutrients
      Association of Official Analytical Chemists
      AOAC Official Methods of Analysis.
      and fiber.
      • Prosky L.
      • Asp N.G.
      • Furda I.
      • DeVries J.W.
      • Schweizer T.F.
      • Harland B.F.
      Determination of total dietary fiber in foods and food products: collaborative study.
      The methods of Folch and gas chromatography were used to determine the fatty acid profiles of the fecal and serum samples
      • Folch J.
      • Lees M.
      • Sloane Stanley G.H.
      A simple method for the isolation and purification of total lipides from animal tissues.
      using reported methods.
      • Nishi S.
      • Kendall C.W.
      • Gascoyne A.M.
      • et al.
      Effect of almond consumption on the serum fatty acid profile: a dose-response study.
      ,
      • Nishi S.K.
      • Kendall C.W.
      • Bazinet R.P.
      • et al.
      Nut consumption, serum fatty acid profile and estimated coronary heart disease risk in type 2 diabetes.
      The fatty acid composition of the fecal samples was determined by converting the fatty acids of the fecal lipids to fatty acid methyl esters (FAMEs) with 14% boron trifluoride/methanol at 100°C for 1 hour. The FAMEs were quantified on a Varian 430-GC gas chromatograph equipped with a Varian FactorFour capillary column (VF-23 ms; 30 m × 0.25 mm internal diameter × 0.25 μm film thickness) and a flame ionization detector. Samples were injected in splitless mode. The injector and detector ports were set at 250°C. The FAMEs were eluted using a temperature program set initially at 50°C for 2 minutes, increased at 20°C per minute and held at 170°C for 1 minute, then at 3°C per minute and held at 212°C for 5 minutes to complete the run at 28 minutes. The carrier gas was helium, set to a constant flow rate of 0.7 mL/min. Peaks were identified by retention times of FAME standards (Nu-Chek-Prep). Fatty acid concentrations were calculated by proportional comparison of gas chromatography peak areas with that of the heptadecanoic acid internal standard.
      A 6-point Likert scale was used to measure ease of bowel movements (from easy to pass to difficult to pass), stool consistency (watery to very hard), flatus (none to severe), abdominal pain (none to severe), and bloating (none to severe). The Lipid Research Clinics protocol was followed to assess serum total cholesterol, triglyceride, and high-density lipoprotein cholesterol levels after dextran sulfate–magnesium chloride precipitation, and LDL-C concentrations were calculated.
      Lipid Research Clinics Program
      Population Studies Data Book, vol 2. The Prevalence Study—Nutrient Intake.
      ,
      Lipid Research Clinics Program
      Manual of Laboratory Operations. Lipid and Lipoprotein Analysis (revised 1982).
      With use of the fecal and dietary data, energy and macronutrient bioaccessibility was calculated by an equation equivalent to that for digestibility
      • Merrill A.L.
      • Watt B.K.
      Energy Value of Foods: Basis and Derivation.
      :
      Bioaccessibility (%) = [(Intake − Excreted)/Intake]∗100
      where intake is based on the average daily value for the dietary variable being assessed obtained from the 7-day diet records, and excreted is based on the average daily fecal output for the corresponding variable of interest. For fat content, as a result of almond enrichment of the diet, the amount excreted was determined by subtracting the fecal fat loss in the control arm from each almond arm. Likewise, the percentage of energy loss from fat content from almond enrichment was determined by dividing the amount of fat excreted related directly or indirectly to almonds by the almond fat intake.

      Statistical Analyses

      All statistical analyses were performed with SAS (University Edition). The power calculation to determine sample size was based on the primary outcome of LDL-C concentration, described previously.
      • Jenkins D.J.
      • Kendall C.W.
      • Marchie A.
      • et al.
      Dose response of almonds on coronary heart disease risk factors: blood lipids, oxidized low-density lipoproteins, lipoprotein(a), homocysteine, and pulmonary nitric oxide: a randomized, controlled, crossover trial.
      Absolute differences between treatments were assessed by the method of least squares means within the mixed model procedure (PROC MIXED) with a Tukey adjustment for multiple means comparisons. The statistical model includes the interaction term of diet by sex and by sequence, in addition to accounting for the crossover design by including a random term that represents the individual participant. Associations between dietary intakes and fecal outputs, fecal fatty acids, and serum fatty acids were assessed using the PROC CORR procedure for Pearson correlations. Results are expressed as mean ± standard error of the mean, and a P value of less than .05 was considered significant for all analyses.

      Results

      In the analyses, 22 participants completing 7-day diet records and fecal samples at the end of each phase were included. Supplemental Figure 1 (available online at http://www.mayoclinicproceedings.org) shows the flow of participants. Supplemental Table 2 (available online at http://www.mayoclinicproceedings.org) shows that there were no significant differences in the baseline characteristics between completers and noncompleters. Supplemental Table 3 (available online at http://www.mayoclinicproceedings.org) shows the baseline characteristics of the 22 participants (12 men and 10 women) who completed the study, which comprised individuals aged 64.5±9.0 years with body weight of 72.0±13.2 kg, BMI of 25.7±3.2 kg/m2, and LDL-C concentration of 4.5±0.8 mmol/L. There were no significant differences in body weight or other measured indicators of adiposity between the phases.
      Table 1 presents the dietary intake, showing that the incorporation of the study supplements into an NCEP Step 2 dietary pattern resulted in higher fat (specifically monounsaturated fatty acids, notably oleic acid) and lower carbohydrate intakes during the almond phases compared with the control phase. Energy, protein, fiber, polyunsaturated fatty acid, and saturated fatty acid intakes remained comparable between the 3 phases. Aside from oleic acid intake, which was significantly increased with almond consumption (P<.001), there were no differences in the other dietary fatty acids analyzed. Adherence to study supplement intake was more than 90% across all treatments.
      Table 1Dietary Intake and Satiety Evaluation (n=22)
      ControlHalf-dose almondsFull-dose almondsP value
      Energy (kJ/d)8711.1 (460.2)8470.5 (415.9)8886.8 (485.3).20
      Energy (kcal/d)2082.0 (110.0)2024.5 (99.4)2124.0 (116.0).20
      Carbohydrate (%)58.4 (1.2)a53.6 (1.1)b50.2 (1.5)c<.001
      Total fiber (g/d)32.3 (2.1)32.9 (2.0)34.4 (2.0).11
      Protein (%)17.1 (0.5)17.9 (0.5)17.5 (0.5).07
      Fat (%)26.0 (0.9)a30.1 (1.0)b33.6 (1.1)c<.001
      Total fat (g/d)60.3 (3.8)a67.4 (3.6)b79.3 (5.2)b<.001
      SFA (g/d)15.9 (1.4)15.0 (1.16)15.3 (1.4).50
       Lauric acid (g/d)0.31 (0.08)0.23 (0.03)0.26 (0.04).67
       Myristic acid (g/d)1.05 (0.15)0.99 (0.11)0.98 (0.12).74
       Palmitic acid (g/d)9.18 (0.79)8.66 (0.59)9.03 (0.80).39
       Stearic acid (g/d)3.43 (0.37)3.14 (0.27)3.46 (0.36).23
      MUFA (g/d)20.1 (1.5)a29.2 (1.6)b39.2 (2.6)c<.001
       Palmitoleic acid (g/d)0.75 (0.08)0.82 (0.08)0.83 (0.07).06
       Oleic acid (g/d)17.9 (1.4)a26.8 (1.5)b36.7 (2.5)c<.001
      PUFA (g/d)18.8 (0.9)17.7 (0.8)18.7 (1.2).18
       Omega-3 (g/d)1.64 (0.15)1.52 (0.22)1.70 (0.27).49
      α-Linolenic acid (g/d)1.17 (0.14)0.93 (0.11)1.20 (0.25).26
      Omega-6 (g/d)16.7 (0.8)15.7 (0.6)16.5 (1.0).28
      Linoleic acid (g/d)15.8 (0.82)14.8 (0.6)15.4 (0.9).29
      Ash (mg/d)21.0 (1.2)a18.9 (1.0)b18.4 (1.1)b.002
      Almonds (g/d)0.0 (0.0)38.3 (2.5)72.7 (4.6)<.001
      Satiety1 (0-2)1 (0-2)1 (0-2).86
      MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; SFA, saturated fatty acid.
      Data are presented as mean (standard error of the mean), except for satiety, for which data are presented as median (range).
      Values in the same row with different superscript letters are significantly different.
      Table 2 shows that the number of bowel movements per day did not significantly differ between the phases; however, fecal composition did differ with almond consumption. Fecal wet weight and dry weight increased nonsignificantly with almond consumption. Fecal samples after almond consumption contained significantly greater amounts of fat (P<.001), carbohydrate (P=.04), and energy (P=.01). The amount of fecal protein content did not differ between treatments. There were no reported differences between treatments in abdominal pain, consistency, ease of bowel movement, or flatus.
      Table 2Bowel Movements and Fecal Composition (n=22)
      ControlHalf-dose almondsFull-dose almondsP value
      Bowel movements (No./d)1.4 (0.1)1.4 (0.1)1.5 (0.2).19
      Wet weight (g/d)182.4 (18.1)187.8 (10.9)188.3 (14.6).85
      Dry weight (g/d)45.6 (4.7)47.5 (2.5)50.9 (3.6).32
      Energy (kcal/d)155.4 (16.1)a177.7 (9.6)a,b207.5 (14.5)b.01
      Total carbohydrate (g/d)18.9 (2.3)15.2 (0.7)16.0 (1.4).17
      Available carbohydrate (g/d)4.8 (0.7)a3.0 (0.2)b3.4 (0.5)a.04
      Total fiber (g/d)14.6 (1.7)12.3 (0.6)12.6 (1.1).20
      Protein (g/d)13.6 (1.5)12.3 (0.8)13.1 (1.1).48
      Fat (g/d)5.9 (0.9)a10.2 (0.7)b12.9 (1.0)c<.001
      SFA (mg/d)938.0 (98.5)a1420.1 (130.9)b1547.7 (142.4)b<.001
       12:013.2 (6.1)8.7 (4.2)11.9 (3.9).71
       14:029.0 (7.1)20.0 (5.3)23.9 (5.8).26
       16:0463.1 (44.2)a764.9 (51.4)b785.8 (62.9)b<.001
       18:0418.1 (53.2)a615.8 (97.0)b708.5 (108.2)b.004
      MUFA (mg/d)636.4 (88.7)a3308.3 (306.1)b4369.2 (501.0)c<.001
       16:1n-76.9 (1.8)a22.4 (4.9)b35.9 (8.6)b<.001
       18:1n-9558.9 (82.7)a3020.8 (282.5)b3959.9 (425.3)c<.001
      PUFA (mg/d)525.1 (82.5)a1099.1 (133.0)b1399.3 (197.7)b<.001
       Omega-369.3 (27.5)101.8 (38.3)101.2 (39.9).44
      18:3n-3 (ALA)67.3 (27.1)100.3 (38.1)99.8 (39.9).43
      Omega-6455.8 (67.7)a997.4 (112.2)b1298.1 (174.8)b<.001
      18 :2n-6 (LA)450.7 (67.5)a991.4 (111.6)b1291.8 (174.2)b<.001
      Ash, g/d6.9 (0.7)6.5 (0.4)6.6 (0.5).67
      ALA, α-linolenic acid; LA, linoleic acid; MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; SFA, saturated fatty acid.
      Data are presented as mean (standard error of the mean).
      Values in the same row with different superscript letters are significantly different.
      Table 3 shows that the bioaccessibility of macronutrients and energy from the diet as a whole was slightly affected by the addition of almonds to the dietary pattern. The bioaccessibility of fat was significantly different between treatment phases (P<.001) and on average lower by 5.1% and 6.3% in the half- and full-dose almond phases, respectively, compared with the control phase. The bioaccessibility of saturated, monounsaturated, and polyunsaturated fatty acids was also significantly lower in the half- and full-dose almond phases compared with the control phase (P<.05). Of the saturated fatty acids, there were greater amounts of stearic acid (18:0) in the fecal matter during the almond phases compared with the control, despite that the quantity consumed was comparable across all 3 phases, resulting in less bioaccessibility of this saturated fatty acid with almond consumption. Oleic acid (18:1n-9) was consumed in higher quantities during the almond phases; still, bioaccessibility for this monounsaturated fatty acid was less during the almond phases compared with the control phase. Whereas intake of the polyunsaturated linoleic acid (18:2n-6) was equivalent across all 3 phases, the fecal composition during the almond phases was higher in linoleic acid, leading to less bioaccessibility. In assessing fat specifically consumed from almonds, bioaccessibility was 78.5%±3.1%, and the average energy loss from almond fat was 21.2%±3.1% (40.6 kcal/d).
      Table 3Bioaccessibility of Energy and Macronutrients for the Diet as a Whole (n=22)
      ControlHalf-dose almondsFull-dose almondsP value
      Energy (%)92.3 (0.8)a91.0 (0.5)b90.1 (0.6)b.02
      Total carbohydrate (%)92.9 (0.8)94.2 (0.3)93.6 (0.6).19
      Protein (%)84.1 (1.8)86.0 (0.9)85.8 (1.0).41
      Fat (%)89.5 (2.0)a84.0 (1.3)b83.2 (1.2)b.001
      Fatty acids (%)
       SFA93.5 (0.7)a89.0 (1.5)b88.5 (1.4)b.007
      Lauric acid94.3 (1.7)95.5 (2.0)89.6 (5.7).48
      Myristic acid98.8 (0.4)98.9 (0.5)97.9 (1.1).58
      Palmitic acid99.7 (0.1)99.8 (0.1)99.7 (0.1).61
      Stearic acid99.8 (0.1)a99.2 (0.2)b98.8 (0.4)b.003
       MUFA96.6 (0.5)a88.2 (1.2)b88.2 (1.6)b.001
      Palmitoleic acid91.6 (2.0)a68.0 (8.3)b54.8 (12.6)b.003
       Oleic acid96.5 (0.6)a88.1 (1.3)a,b88.5 (1.6)b<.001
       PUFA97.2 (0.4)a93.7 (0.8)b92.0 (1.2)b.006
      Omega-396.2 (1.4)94.5 (2.3)94.5 (2.2).57
      α-Linolenic acid (ALA)94.3 (2.3)89.5 (4.5)93.3 (2.5).36
      Omega-698.2 (0.4)a96.4 (0.9)a,b94.4 (1.5)b.003
      Linoleic acid97.1 (0.5)a93.2 (0.8)b91.1 (1.3)b<.001
       Ash (%)63.3 (3.9)65.3 (2.0)64.4 (2.3).89
      MUFA, monounsaturated fatty acid; PUFA, polyunsaturated fatty acid; SFA, saturated fatty acid.
      Data are presented as mean (standard error of the mean).
      Values in the same row with different superscript letters are significantly different.
      Energy bioaccessibility was significantly different between the treatment phases (P=.019), decreasing by approximately 2% with the inclusion of the full dose of almonds compared with the control. Energy bioaccessibility was positively associated with body fat percentage (r=0.288; P=.02), although almond consumption was not correlated with body weight or other measures of adiposity assessed. Almond consumption was positively associated with dietary intake of oleic acid (r=0.839; P<.001) and fecal output of oleic acid (r=0.651; P<.001) but was inversely associated with oleic acid bioaccessibility (r=−0.349; P=.004). Yet, the percentage of fecal oleic acid was not associated with the serum percentage (r=−0.233; P=.06). There was no relationship between almond consumption and dietary intake of linoleic acid (r=0.172; P=.17), but almond consumption was positively associated with fecal output of linoleic acid (R=0.558; P<.001) and inversely associated with linoleic acid bioaccessibility (r=−0.420; P<.001). The percentage of fecal linoleic acid output was not associated with the serum percentage (r=−0.003; P=.98).

      Discussion

      The analyses investigated the effect of almond consumption on dietary energy and macronutrient bioaccessibility in individuals with hyperlipidemia. Findings indicate that substitution of a carbohydrate-based food with almonds (ie, approximately 75 g or 150 g of a carbohydrate-based food for 38 g or 75 g of almonds, respectively) into an NCEP Step 2 background dietary pattern leads to lower fat and energy bioaccessibility without negatively affecting serum levels of beneficial (18:1n-9) or essential (18:2n-6) fatty acids. The 2% decrease in energy availability observed between the full-dose almond and control phases suggests that by incorporating almonds into a typical 2000- to 3000-kcal daily intake level may result in 40 to 60 kcal/d less than expected being digested and absorbed by the body. During the course of a year, assuming no compensation, this could result in mitigating weight gain or possibly leading to a weight loss by 1.9 to 2.9 kg (4.2 to 6.3 lb). In this trial, body weight was maintained with no difference between phases, yet comparison of the energy intakes showed on average an increase of 42 kcal/d in energy intake during the full-dose almond phase compared with the control phase.
      Previous studies have examined the effect of nut intake on energy and macronutrient bioaccessibility, showing a marked increase in fecal fat excretion in healthy individuals. Novotny et al
      • Novotny J.A.
      • Gebauer S.K.
      • Baer D.J.
      Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets.
      found that compared with no almond consumption, 84 g/d of almonds caused a 5% reduction in overall diet energy bioaccessibility in healthy individuals. The lower dietary fiber content in the control diet compared with the almond arms possibly contributed to the greater differences in fat and energy digestibility seen in their study, whereas dietary fiber was comparable across treatments in these analyses. This is noteworthy as dietary fiber, both soluble and insoluble, has been shown to increase fat excretion and to reduce fat digestibility.
      • Chen H.L.
      • Haack V.S.
      • Janecky C.W.
      • Vollendorf N.W.
      • Marlett J.A.
      Mechanisms by which wheat bran and oat bran increase stool weight in humans.
      The analyses indicate that even when accounting for dietary fiber, there remained a difference in fat and energy bioaccessibility between diets incorporating almonds compared with a control supplement.
      Possible interactions with other food components, such as dietary fiber, is one factor that may affect fat bioaccessibility. Several other factors may also influence the proportion of an ingested nutrient that is absorbed by the body, including the food matrix and the level of processing or mastication. Fecal fat excretion has been shown to be significantly higher with less processing (ie, whole nuts vs nut butters vs nut oils) and mastication.
      • Grundy M.M.
      • Grassby T.
      • Mandalari G.
      • et al.
      Effect of mastication on lipid bioaccessibility of almonds in a randomized human study and its implications for digestion kinetics, metabolizable energy, and postprandial lipemia.
      ,
      • Ellis P.R.
      • Kendall C.W.
      • Ren Y.
      • et al.
      Role of cell walls in the bioaccessibility of lipids in almond seeds.
      • Cassady B.A.
      • Hollis J.H.
      • Fulford A.D.
      • Considine R.V.
      • Mattes R.D.
      Mastication of almonds: effects of lipid bioaccessibility, appetite, and hormone response.
      • Mandalari G.
      • Grundy M.M.
      • Grassby T.
      • et al.
      The effects of processing and mastication on almond lipid bioaccessibility using novel methods of in vitro digestion modelling and micro-structural analysis.
      • Levine A.S.
      • Silvis S.E.
      Absorption of whole peanuts, peanut oil, and peanut butter.
      Ellis et al
      • Ellis P.R.
      • Kendall C.W.
      • Ren Y.
      • et al.
      Role of cell walls in the bioaccessibility of lipids in almond seeds.
      examined fecal samples after whole almond intake and identified almond tissue in the fecal material, confirming that cotyledonary cells remained intact with cell walls encapsulating intracellular lipid. This intracellular lipid was thus not susceptible to colonic fermentation by microbial degradation and hence impeded the release of fat available for digestion. Gebauer et al
      • Gebauer S.K.
      • Novotny J.A.
      • Bornhorst G.M.
      • Baer D.J.
      Food processing and structure impact the metabolizable energy of almonds.
      further demonstrated that the amount of energy absorbed from almonds is dependent on the form in which they are consumed, whereby whole (natural and roasted) and chopped almonds, but not almond butter, had significantly lower measured metabolizable energy values compared with Atwater factors. As this study assessed whole, natural almonds, it is likely that chewing, processing, and transit along the gastrointestinal tract did not disrupt all cell walls, leading to the observed fecal fat excretion and, as the lipid fraction represents the largest amount of available energy in almonds, reduced energy bioaccessibility.
      This study supports previous research suggesting that Atwater factors may overestimate the energy value of almonds.
      • Gebauer S.K.
      • Novotny J.A.
      • Bornhorst G.M.
      • Baer D.J.
      Food processing and structure impact the metabolizable energy of almonds.
      ,
      • Novotny J.A.
      • Gebauer S.K.
      • Baer D.J.
      Discrepancy between the Atwater factor predicted and empirically measured energy values of almonds in human diets.
      Similar discrepancies between the predicted Atwater factor and empirically measured energy values have also been observed in cashews,
      • Baer D.J.
      • Novotny J.A.
      Metabolizable energy from cashew nuts is less than that predicted by Atwater factors.
      pistachios,
      • Baer D.J.
      • Gebauer S.K.
      • Novotny J.A.
      Measured energy value of pistachios in the human diet.
      and walnuts.
      • Baer D.J.
      • Gebauer S.K.
      • Novotny J.A.
      Walnuts consumed by healthy adults provide less available energy than predicted by the Atwater factors.
      This is of importance as Health Canada and the US Food & Drug Administration require that nutrition information be present on all prepackaged food products sold, with only a few exemptions.
      Government of Canada
      Health Canada. Regulations and compliance—nutrition labelling.
      Government of Canada
      Health Canada. Nutrition labelling. Directory of nutrition facts table formats.
      U.S. Food & Drug Administration
      CFR-Code of Federal Regulations Title 21.
      U.S. Food & Drug Administration
      Guidance for Industry: Food Labeling Guide.
      Similar legislative regulations are found worldwide.
      European Commission
      Regulation (EU) No 1169/2011 of the European Parliament and of the Council on the Provision of Food Information to Consumers.

      Ministry of Health, Peoples Republic of China. General rules for nutrition labeling of prepackaged foods. Accessed April 25, 2020.

      Food Standard Australia New Zealand
      Nutrition information user guide to standard 1.2.8—nutrition information requirements.
      This mandatory nutrition information includes energy and fat content per serving and is used to inform and to guide consumers’ choices. The present findings are relevant for general consumers as well as clinically for health care practitioners and patients as diabetes, cardiovascular, and general healthy eating guidelines tend to warn consumers against energy-dense foods because of their obesogenic potential; nuts, including almonds, have been stigmatized as a result of their perceived high energy density. Whereas this view has been shifting and nuts have been acknowledged for their health benefits, remnants of this concern remain, with caveats noting the energy density of nuts following statements recommending their consumption for health benefits. Globally, this is reflected by the relatively low estimated average total tree nut and peanut intake levels (15-17 g/d), which are less than half of the amounts generally recommended by dietary and health guidelines and the Food & Drug Administration–qualified health claim.
      International Nut & Dried Fruit Council
      Nuts & dried fruits statistical yearbook 2019/2020.
      International Nut & Dried Fruit Council
      Nuts & dried fruits statistical yearbook 2017/2018.
      U.S. Food & Drug Administration
      Guidance for industry: a food labeling guide (12. Appendix D: Qualified Health Claims). Qualified health claims: letter of enforcement discretion—nuts and coronary heart disease (Docket No 02P-0505).
      Strengths of these analyses consist of the robust design of a randomized crossover trial and high adherence to the study treatments by completers. Moreover, the study population is relevant to those who are at high risk for diabetes and cardiovascular disease, for whom many guidelines recommending nuts, including almonds, are geared to their lipid- and blood glucose–lowering health benefits. These analyses, however, do possess a number of limitations. On the basis of the current investigation, it is difficult to discern whether the increased fecal fat content observed during the almond phase is due to fat excreted from the almonds directly or whether almond consumption induced fat malabsorption from other foods. As well, gastrointestinal secretions and mucosal cell loss may affect the composition of the fecal samples,
      • Keller J.
      • Layer P.
      The pathophysiology of malabsorption.
      yet this analysis was unable to measure this potential contribution and had to assume that all of the nitrogen and fat found in the fecal samples was derived directly from the dietary protein and fat, respectively. Nevertheless, this may be controlled for by the crossover design. The findings are also limited in that urine samples were not available for analyses; thus, the absolute protein and energy bioaccessibility values should be interpreted with caution. Whereas the digestibility values for protein and energy may be lower than currently reported, it is not expected that this would greatly affect the comparison between treatments as urinary excretion of nitrogen was not found to be significantly different between tree nut and control in another investigation.
      • Baer D.J.
      • Novotny J.A.
      Metabolizable energy from cashew nuts is less than that predicted by Atwater factors.
      In addition, short-chain fatty acids (eg, acetate, propionate, and butyrate) were not able to be assessed. As short-chain fatty acids may provide an extra energy source for de novo lipogenesis, this may have implications in the metabolic responses of the host individual.

      Conclusion

      Incorporating almonds into an NCEP dietary pattern resulted in less fat and energy bioaccessibility at both almond doses of 38 g/d and 73 g/d, without an observed dose response, compared with a carbohydrate-based control in hyperlipidemia. These findings in conjunction with previous investigations suggest it is possible that the energy content of almonds may not be as bioaccessible as predicted by Atwater factors. With less fat being bioaccessible, the concern of the “high energy density” of almonds and risk of weight gain may be overstated.
      Given that the Atwater system is often used to determine the energy values for mandatory nutrient labeling of food products, food labeling of items with whole almonds may require adjustment to better reflect the metabolizable energy. Future research may investigate other food sources with similar complex food matrices to almonds, such as seeds and pulses, to determine whether there are more appropriate ways to establish and to present energy content of these foods.

      Acknowledgments

      We wish to thank the volunteer participants, Dr Balachandran Bashyam (laboratory technician), and Dr Dorothea Faulkner (registered dietitian) as well as Chole Kavcic, Diana Ghidanac, and Sarah Muncaster (hospital volunteers) at St. Michael’s Hospital and the University of Toronto for their assistance and expertise.
      None of the sponsors had a role in any aspect of this study, including design and conduct of the study; collection, management, analysis, and interpretation of the data; and preparation, review, and approval of the manuscript or decision to publish.

      Supplemental Online Material

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