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Baru nuts reduce abdominal adiposity in type 2 diabetic adults: a randomized, placebo-controlled, crossover trial

Amêndoa de baru reduz a adiposidade abdominal de adultos com diabetes Mellitus tipo 2: um estudo randomizado, placebo-controlado, crossover

ABSTRACT

Objective:

This study aimed to evaluate the effect of baru nuts supplementation on body composition and metabolic profile in adults with type 2 diabetes.

Methods:

This is a randomized, placebo-controlled, crossover trial with 30 adults with type 2 diabetes. The assay had two periods of 12 weeks each, with a washout period of 12 weeks between treatments. The subjects were randomized and received the two treatments in alternate periods: supplementation of 30g baru nuts or placebo. Anthropometry, body composition, blood pressure, blood sampling, food intake, and physical activity data were analyzed.

Results:

Baru nut intake reduced waist circumference (p=0.032), compared to placebo group. In the intra-group analysis, baru nut intake reduced total cholesterol (p=0.012) and LDL-c (p=0.017).

Conclusion:

The daily intake of baru nuts improved abdominal adiposity. Therefore, these nuts should be included in the diet to improve the health status of adults with type 2 diabetes.

Keywords:
Body composition. Diabetes Mellitus; Type 2. Dietary modification. Nuts. Obesity managements

RESUMO:

Objetivo:

Avaliar o efeito da suplementação com amêndoa de baru sobre a composição corporal e perfil metabólico de adultos com diabetes Mellitus tipo 2.

Métodos:

Este é um estudo randomizado, placebo-controlado, crossover com 30 adultos com diabetes Mellitus tipo 2. O ensaio clínico foi dividido em dois períodos de 12 semanas cada, com um washout de 12 semanas entre os tratamentos. Os sujeitos foram randomizados e receberam dois tratamentos em períodos alternativos: suplementação com 30 g de amêndoa de baru ou placebo. Foram coletados dados referentes à antropometria, composição corporal, pressão arterial, amostras de sangue, ingestão de alimentos e práticas de atividade física.

Resultados:

A ingestão de amêndoa de baru reduziu a circunferência da cintura (p=0,032), em comparação com o grupo placebo. Na análise intragrupo, a ingestão de amêndoa de baru também reduziu o colesterol total (p=0,012) e LDL-c (p=0,017).

Conclusão:

A ingestão diária de amêndoa de baru melhorou a adiposidade abdominal, portanto, deve ser incluída na dieta para a melhora do estado de saúde de adultos com diabetes Mellitus tipo 2.

Palavras-chave:
Composição corporal; Diabetes Mellitus Tipo 2; Intervenção dietética; Nozes; Manejo da obesidade

INTRODUCTION

According to the International Diabetes Federation, in 2021, 536.6 million (10.5%) people aged 20-79 were diabetic. This number is estimated to grow to 783.2 million diabetics worldwide by 2045. In 2021, the health care of diabetics generated a cost of 966 billion dollars, 316% more than in 2007. In addition, 6.7 million people in this age group died due to type 2 diabetes Mellitus (T2D), which represents 12.2% of all causes of mortality [11. International Diabetes Federation. IDF Diabetes Atlas 2021. 10th ed. Brussels: International; 2021 [cited 2023 Feb 2]. Available from: Available from: https://diabetesatlas.org/atlas/tenth-edition/?dlmodal=active&dlsrc=https%3A%2F%2Fdiabetesatlas.org%2Fidfawp%2Fresource-files%2F2021%2F07%2FIDF_Atlas_10th_Edition_2021.pdf
https://diabetesatlas.org/atlas/tenth-ed...
]. In this sense, seeking prevention and treatment strategies for this public health problem is necessary.

The T2D is a multifactorial disease. Initially, it was characterized by hyperglycemia caused by insulin resistance in muscle and liver cells, associated with a failure in β-cell insulin production [22. DeFronzo AR. From the triumvirate to the ominous octet: a new paradigm for the treatment of Type 2 Diabetes Mellitus. Diabetes. 2009;58(4):773-95. https://doi:10.2337/db09-9028
https://doi.org/https://doi:10.2337/db09...
]. However, more recent studies have shown that diabetes does not include only dysfunctions in the muscle, liver, and β cells of the pancreas but also in fat cells, the gastrointestinal tract, pancreatic, kidney, and brain cells [22. DeFronzo AR. From the triumvirate to the ominous octet: a new paradigm for the treatment of Type 2 Diabetes Mellitus. Diabetes. 2009;58(4):773-95. https://doi:10.2337/db09-9028
https://doi.org/https://doi:10.2337/db09...
].

The T2D, in general, is caused by unhealthy dietary patterns, sedentary lifestyles, and genetic predisposition [33. Oliveira Sousa AG, Fernandes DC, Alves AM, Almeida JB, Naves MMV. Nutritional quality and protein value of exotic almonds and nut from the Brazilian Savanna compared to peanut. Food Res Int. 2011;44(7):2319-25. https://doi:10.1016/j.foodres.2011.02.013
https://doi.org/https://doi:10.1016/j.fo...
]. To provide better control of the glycemic profile of diabetic individuals and to reduce the risk of complications in T2D, it is important to control the Body Mass (BM). It is known that abdominal obesity generates a state of inflammation in the body through the production of cytokines and chemokines, which is harmful to several organs, such as the pancreas, kidney, and liver, worsening glycemic control [44. Esser N, Legrand-Poels S, Piette J, Scheen AJ, Paquot N. Inflammation as a link between obesity, metabolic syndrome and type 2 diabetes. Diabetes Res Clin Pract. 2014;105(2):141-50. https://doi:10.1016/j.diabres.2014.04.006
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,55. Menon S, Venugopal R. A comparative study of lipid profile, body mass index, and waist circumference among Type 2 diabetes mellitus patients with poor and good metabolic control and normal age-matched control group. Natl J Physiol Pharm Pharmacol. 2018;8(2):239-43. https://doi.org/10.5455/njppp.2017.7.1040325102017
https://doi.org/https://doi.org/10.5455/...
].

Concerning food intake, a healthy diet and the consumption of foods such as nuts and oilseeds should be encouraged [66. Viguiliouk E, Kendall CWC, Mejia SB, Cozma AI, Ha V, Mirrahimi A, et al. Effect of tree nuts on glycemic control in diabetes: a systematic review and meta-analysis of randomized controlled dietary trials. PLos One. 2014;9(7):1-13. https://doi.org/10.1371/journal.pone.0109224
https://doi.org/https://doi.org/10.1371/...
]. Baru nuts, an edible native seed from the Cerrado biome, are rich in good-quality proteins, mono and polyunsaturated fats, dietary fibers, and micronutrients, such as zinc [77. Alves AM, Fernandes DC, Borges JF, Sousa AGO, Naves MMV. Oilseeds native to the Cerrado have fatty acid profile beneficial for cardiovascular health. Rev Nutr. 2016;29(6). https://doi.org/10.1590/1678-98652016000600010
https://doi.org/https://doi.org/10.1590/...
], which have important effects on glycemic control [22. DeFronzo AR. From the triumvirate to the ominous octet: a new paradigm for the treatment of Type 2 Diabetes Mellitus. Diabetes. 2009;58(4):773-95. https://doi:10.2337/db09-9028
https://doi.org/https://doi:10.2337/db09...
,66. Viguiliouk E, Kendall CWC, Mejia SB, Cozma AI, Ha V, Mirrahimi A, et al. Effect of tree nuts on glycemic control in diabetes: a systematic review and meta-analysis of randomized controlled dietary trials. PLos One. 2014;9(7):1-13. https://doi.org/10.1371/journal.pone.0109224
https://doi.org/https://doi.org/10.1371/...
,88. Schwingshackl L, Strasser B, Hoffmann G. Effects of monounsaturated fatty acids on glycaemic control in patients with abnormal glucose metabolism: a systematic review and meta-analysis. Ann Nutr Metab. 2011;58(4):290-6. https://doi:10.1159/000331214
https://doi.org/https://doi:10.1159/0003...
]. The antioxidant action of phytic acid and other phenolic compounds [99. Siqueira EMA, Marin AMF, Cunha MSB, Fustinoni AM, Sant’ana LP, Arruda SF. Consumption of baru seeds [Dipteryx alata Vog.], a Brazilian savanna nut, prevents iron-induced oxidative stress in rats. ood Res Int. 2012;45(1):427-33. https://doi.org/10.1016/j.foodres.2011.11.005
https://doi.org/https://doi.org/10.1016/...
], and a reduction in total cholesterol and LDL-cholesterol [1010. Bento AP, Cominetti C, Simões Filho A, Naves MM. Baru almond improves lipid profile in mildly hypercholesterolemic subjects: a randomized, controlled, crossover study. Nutr Metab Cardiovasc Dis. 2014;24(12):1330-6. https://doi:10.1016/j.numecd.2014.07.002
https://doi.org/https://doi:10.1016/j.nu...
] can be mentioned among the benefits of this seed already described in the literature.

Given the possible effects of baru nuts on the improvement of clinical and biochemical manifestations of T2D and, to date, no publications evaluating their action on this disease have been found, the objective of this study was to evaluate the effect of baru nut supplementation on the body composition and metabolic profile in adults with T2D.

MATERIALS AND METHODS

This is a randomized, placebo-controlled, crossover trial carried out between August 2017 and June 2018 in Brazabrantes and Santo Antônio de Goiás, cities in the state of Goiás, Brazil. This study was approved by the Research Ethics Committee of the Universidade Federal de Goiás (protocol n° 784.446/2014 and Certificate of Presentation for Ethical Appreciation n° 32847014.2.0000.5083) and registered in the Brazilian Registry of Clinical Trials (Registration Number: RBR-8zmmgm). All participants gave informed consent before participating in the study and signed the Terms of Free and Informed Consent.

The sample size calculation was performed in G*Power 3.1, considering the values of waist circumference (WC) of adult women supplemented with baru nuts [1111. Souza RGM, Gomes AC, Castro IA, Mota JF. A baru almond-enriched diet reduces abdominal obesity and improves HDL concentrations: a randomized, placebo-controlled trial. Nutrition. 2018;55:154-60. https://doi:10.1016/j.nut.2018.06.001
https://doi.org/https://doi:10.1016/j.nu...
]. A paired Student’s t-test and type of power analysis “a priori: compute required sample size - given α, power, and effect size” was performed, which resulted in a required sample of 13 individuals, with a power of 0.80 and effect size of 0.48. However, 37 adults were randomized and 30 were analyzed, with a power of 0.80 and an effect size of 0.31.

In total, 52 adults were recruited, all aged 20-59, with a diagnosis of T2D, attended by the public health service of the cities. The eligibility criteria included (1) adults; (2) not receiving insulin therapy; (3) with no clinical history of cardiovascular disease (heart attacks in the last six months, unstable angina, cardiac arrhythmia, and stroke), cancer, chronic lung disease, musculoskeletal disorders, and neurological deficit; (4) nuts intake < twice a month; (5) not participating in food education and/or a physical exercise programs; (6) individuals not allergic to nuts and/or edible seeds; (7) not pregnant and lactating; and (8) not taking hormone replacement therapy. Adults with some physical or cognitive disability that would compromise the data collection were excluded.

Of the 52 individuals assessed for eligibility, 37 were randomized into two groups (baru nuts group and placebo group), and 30 were analyzed (Figure 1).

Stratified randomization was performed by a volunteer researcher aiming to eliminate potential biases that could confuse the two groups [sex, age, Body Mass Index (BMI), WC, and fasting glucose]. The study was performed in two periods of 12 weeks each. Between the two periods, there was a 12-week washout to eliminate possible carryover effects of the first phase. In the first period of the study, the baru nuts group consumed a daily serving of 30 g of baru nuts with skin, and the placebo group consumed one capsule/day of placebo (containing 300 mg microcrystalline cellulose) for 12 weeks. In the second period, there was an inversion of the treatments. The duration of 12 weeks was considered given that it was a longer intervention compared to other studies that evaluated baru nut supplementation’s effects on the health parameters of adults [1010. Bento AP, Cominetti C, Simões Filho A, Naves MM. Baru almond improves lipid profile in mildly hypercholesterolemic subjects: a randomized, controlled, crossover study. Nutr Metab Cardiovasc Dis. 2014;24(12):1330-6. https://doi:10.1016/j.numecd.2014.07.002
https://doi.org/https://doi:10.1016/j.nu...
,1111. Souza RGM, Gomes AC, Castro IA, Mota JF. A baru almond-enriched diet reduces abdominal obesity and improves HDL concentrations: a randomized, placebo-controlled trial. Nutrition. 2018;55:154-60. https://doi:10.1016/j.nut.2018.06.001
https://doi.org/https://doi:10.1016/j.nu...
].

The proportion of baru nuts supplied was determined from a meta-analysis, which showed that the daily intake of 28 g or more of nuts is sufficient to reduce individuals’ fasting glycemia [66. Viguiliouk E, Kendall CWC, Mejia SB, Cozma AI, Ha V, Mirrahimi A, et al. Effect of tree nuts on glycemic control in diabetes: a systematic review and meta-analysis of randomized controlled dietary trials. PLos One. 2014;9(7):1-13. https://doi.org/10.1371/journal.pone.0109224
https://doi.org/https://doi.org/10.1371/...
]. The offered baru nuts were roasted at 140 ºC for 30 minutes [1212. Fernandes DC, Freitas JB, Czeder LP, Naves MMV. Nutritional composition and protein value of the baru (Dipteryx alata Vog.) almond from the Brazilian Savanna. J Sci Food Agric. 2010;90(10):1650-5. https://doi:10-1002/jsfa.3997
https://doi.org/https://doi:10-1002/jsfa...
] to inactivate antinutritional factors [1313. Togashi M, Sgarbieri VC. Caracterização química parcial do fruto do baru (Dipteryx alata, Vog.). Cien Tec Alimen. 1994;14(1):85-95.]. The portions of baru nuts were offered to the patients in packages containing 30 g of the almond, vacuum-packed (the portions were weighed and packed at the Laboratório de Nutrição Experimental / Universidade Federal de Goiás (Experimental Nutrition Laboratory / Federal University of Goiás/Brazil). Every 21 days, meetings were held with the participants to deliver baru nuts or placebo capsules and to assess their consumption during the period.

Figure 1.
CONSORT flow diagram of participants throughout the study.

Adherence to supplementation was monitored fortnightly by the researchers. During the intervention period, participants were advised not to modify their eating habits and physical activity. At the beginning and end of each 12-week intervention, a collection of data, including anthropometry, body composition, blood pressure, blood sampling, food intake, and physical activity was performed.

Data on age and sex were collected in a self-administered questionnaire. The BM (kg) was measured in a digital scale (Plenna, São Paulo, Brazil); the height (m) in a portable stadiometer (Sanny, São Paulo, Brazil); the waist circumference with an inextensible tape (Cescorf, Rio Grande do Sul, Brazil) at the midpoint between the lower portion of the last rib and the iliac crest [1414. World Health Organization. Physical status: the use of and interpretation of anthropometry, report of a WHO expert committee. Geneva: Organization; 1995 [cited 2018 Oct 20]. Available from: Available from: https://www.who.int/publications/i/item/9241208546
https://www.who.int/publications/i/item/...
]; and the body composition by a tetrapolar bioimpedance model Quantum II (RJL Systems, Michigan, United States of America).

The metabolic profile was characterized by the biochemical parameters and blood pressure. The systolic blood pressure and diastolic blood pressure were measured in a semiautomatic validated equipment (OMRON brand - HEM 705CP, Kyoto, Japan), following the protocol of the VII Brazilian Hypertension Guidelines of the Brazilian Society of Cardiology [1515. Malachias MVB, Souza WKSB, Plavnik FL, Rodrigues CIS, Brandão AA, Neves MFT, et al. VII Diretrizes Brasileiras de Hipertensão da Sociedade Brasileira de Cardiologia. Arq Bras Cardiol. 2016;107(Supl.3):1-83. https://doi:10.5935/abc.20160140
https://doi.org/https://doi:10.5935/abc....
].

The subjects’ blood, in a 12-hour fast, was drawn and analyzed for fasting glucose by enzymatic method (LABTEST® kit, Labmax® Plenno automatic analyzer); fasting insulin by chemiluminescence (Architect i1000 analyzer, Abbott Diagnostics®); total cholesterol and triglycerides by enzyme system (endpoint reaction); HDL per system for direct homogeneous determination (LABTEST® kit, Labmax® Plenno automatic analyzer); and C-Reactive Protein (CRP) (LABTEST® kit, Labmax® Plenno automatic analyzer) by the immunoturbidimetry method. The HOMA-IR was obtained by the equation [fasting glucose (nmol/L) x fasting insulin(µU/L)]/22.5, and LDL-c was calculated using the Friedewald equation [1616. Matthews DR, Hosker JP, Rudenski AS, Naylor BA, Treacher DF, Turner RC. Homeostasis model assessment: insulin resistance and beta-cell function from fasting plasma glucose and insulin concentrations in man. Diabetologia. 1985;28:412-19.,1717. Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1072;18;499-502.].

The intake of energy, carbohydrates, proteins, and lipids was estimated using three 24-hour dietary recalls on non-consecutive days, including one during the weekend, estimated in DietBox® software. The physical activity was evaluated through the International Physical Activity Questionnaire - Short Version, computed in continuous scores and expressed in metabolic equivalents (METS) (minutes/week) [1818. International Physical Activity Questionnaire. Guidelines for data processing and analysis of the International Physical Activity Questionnaire (IPAQ). Geneve: IPAQ; 2005 [cited 2018 June 1]. Available from: Available from: http://www.IPAQ.ki.se
http://www.IPAQ.ki.se...
], to monitor consumption and energy expenditure.

The data collection regarding food intake, anthropometry, body composition, blood pressure, and blood sampling occurred at the beginning and end of each of the two 12-week intervention periods.

Data were typed in double entry and analyzed in the R 3.5.2 and RStudio 1.1.463 programs. The discrepant values were excluded, and a Lilliefors test was performed to evaluate the normality of the data. The carryover evaluation was performed for all variables, and the means comparison test was by analysis of variance (factorial ANOVA). For data on anthropometry, body composition, blood pressure, biochemical parameters, food intake, and physical activity (METS), a factorial ANOVA test was performed. In addition, a paired Student’s t-test was performed to assess whether there were differences between the initial and final time for the two interventions (intra-group). The significance level of 5% was adopted for all tests.

RESULTS

Of the 30 adults who were analyzed, 18 were female and 12 were male. The mean age of participants was 49±7.24 years. The washout time was sufficient since no carryover effect was found between the two periods for all variables, and there were no initial differences between the two groups (p≥0.050). The 30 g intake of baru nuts resulted in a reduction in WC (p=0.032) in the baru nut group when compared to the placebo group, with no difference in blood pressure, glycemic profile, serum lipids, and CRP concentration (p≥0.050) (Tables 1,2). In the intra-group evaluation, a reduction of total cholesterol (p=0.012) and LDL-cholesterol (p=0.017) was observed at the end of the baru nuts treatment (Table 2). Energy and macronutrients intake and physical activity, expressed in METS, did not differ between groups during the intervention, identified by factorial ANOVA (p≥0.050) (Table 2).

Table 1.
Anthropometry, body composition, and blood pressure of participants at baseline and after 12 weeks of treatment with baru nuts and placebo (n=30).
Table 2.
Biochemical parameters, food intake, and physical activity of participants at baseline and after 12 weeks of treatment with baru nuts and placebo (n=30).

DISCUSSION

This is the first study that investigated the effect of baru nut supplementation in T2D adults. The present study showed that the daily ingestion of 30 g of baru nuts for 12 weeks reduced abdominal adiposity when compared to the placebo group.

Concerning the reduction of WC, regardless of the type of nut and edible seed, studies have related the ingestion of these foods with the decrease of adiposity in humans. Observational studies, such as cross-sectional research carried out with 34831 European women, observed that individuals with higher nut intake had a BMI of 2.4 kg/m2 and a WC 2.6 cm smaller compared to lower-consumption groups [1919. Brown RC, Gray AR, Tey SL, Chisholm A, Burley V, Greenwood DC, Cade J. Associations between nut consumption and health vary between omnivores, vegetarians, and vegans. Nutrients. 2017;9(11):E1219. https://doi:10.3390/nu9111219
https://doi.org/https://doi:10.3390/nu91...
]. In addition, a cohort of European countries, which evaluated 14535 people, found that individuals who consumed more than a 30 g portion of nuts per week for five years had a 10% lower BM gain when compared to those who ingested oilseeds with lower frequency [2020. Freisling H, Noh H, Slimani N, Chajès V, May AM, Peeters PH, et al. Nut intake and 5-year changes in body weight and obesity risk in adults: results from the EPIC-PANACEA study. Eur J Nutr. 2017;21. https://doi:10.1007/s00394-017-1513-0
https://doi.org/https://doi:10.1007/s003...
]. Clinical trials also presented similar results, as a study that offered 50 g of nuts for three months, associated with a hypocaloric diet, and observed a reduction in BMI and WC [2121. Abazarfard Z, Salehi M, Keshavarzi S. The effect of almonds on anthropometric measurements and lipid profile in overweight and obese females in a weight reduction program: A randomized controlled clinical trial. J Res Med Sci. 2014;19(5):457-64.]. Another example is the study with 214 women who ingested 42 g of nuts for a year and observed an 8.2% BM loss, while the group that had a restricted diet lost 6.5% [2222. Rock CL, Flatt SW, Pakiz B, Quintana EL, Heath DD, Rana BK, et al. Effects of diet composition on weight loss, metabolic factors and biomarkers in a 1-year weight loss intervention in obese women examined by baseline insulin resistance status. Metabolism. 2016;65(11):1605-13. https://doi:10.1016/j.metabol.2016.07.008
https://doi.org/https://doi:10.1016/j.me...
].

Several mechanisms have been proposed to justify the effect of nut intake on abdominal adiposity. One of them is associated with the low bioavailability of the nuts’ energy content. To access the nutrients of the nuts, the walls of their cells must be broken, which happens in the mechanical chewing process or enzymatic or microbial degradation. However, studies have revealed that this degradation is not completely efficient, since the cells of the nuts are not totally ruptured, and, consequently, their content is not absorbed but eliminated, which is evidenced by studies that show that, when consuming this food, a 10-15% increase of fat occurs in the fecal content [2323. Cassady BA, Hollis JH, Fulford AD, Considine RV, Mattes RD. Mastication of almonds: effects of lipid bioaccessibility, appetite, and hormone response. Am J Clin Nutr. 2009;89(3):794-800. https://doi:10.3945/ajcn.2008.26669
https://doi.org/https://doi:10.3945/ajcn...

24. Ellis PR, Kendall CW, Ren Y, Parker C, Pacy JF, Waldron KW, et al. Role of cell walls in the bioaccessibility of lipids in almond seeds. Am J Clin Nutr. 2004;80(3):604-13. https://doi:10.1093/ajcn/80.3.604
https://doi.org/https://doi:10.1093/ajcn...
-2525. Mattes RD, Dreher ML. Nuts and healthy body weight maintenance mechanisms. Asia Pac J Clin Nutr. 2010;19(1):137-41.]. Thus, the metabolizable energy of nuts is 5-21% lower than expected by the Atwater factors, which generically determine the metabolizable energy values from the consumption of carbohydrates, proteins, and lipids from food [2626. Baer DJ, Gebauer SK, Novotny JÁ. Walnuts Consumed by Healthy Adults Provide Less Available Energy than Predicted by the Atwater Factors. J Nutr. 2016;146(1):9-13. https://doi:10.3945/jn.115.217372
https://doi.org/https://doi:10.3945/jn.1...
].

Another mechanism is related to satiety after the ingestion of nuts, from the stimulation of secretion of the intestinal hormone glucagon like-peptide 1, cholecystokinin [2222. Rock CL, Flatt SW, Pakiz B, Quintana EL, Heath DD, Rana BK, et al. Effects of diet composition on weight loss, metabolic factors and biomarkers in a 1-year weight loss intervention in obese women examined by baseline insulin resistance status. Metabolism. 2016;65(11):1605-13. https://doi:10.1016/j.metabol.2016.07.008
https://doi.org/https://doi:10.1016/j.me...
], and peptide YY [2727. Pasman WJ, Heimerikx J, Rubingh CM, Van Den Berg R, O’Shea M, Gambelli L, et al. The effect of Korean pine nut oil on in vitro CCK release, on appetite sensations and on gut hormones in post-menopausal overweight women. Lipids Health Dis. 2008;20(7):10. https://doi:10.1186/1476-511X-7-10
https://doi.org/https://doi:10.1186/1476...
]. This effect seems to be induced by the high content of proteins and fats in nuts, and therefore, more satiety may be generated after a meal containing oleaginous foods [2727. Pasman WJ, Heimerikx J, Rubingh CM, Van Den Berg R, O’Shea M, Gambelli L, et al. The effect of Korean pine nut oil on in vitro CCK release, on appetite sensations and on gut hormones in post-menopausal overweight women. Lipids Health Dis. 2008;20(7):10. https://doi:10.1186/1476-511X-7-10
https://doi.org/https://doi:10.1186/1476...
,2828. Reis CE, Ribeiro DN, Costa NM, Bressan J, Alfenas RC, Mattes RD. Acute and second-meal effects of peanuts on glycaemic response and appetite in obese women with high type 2 diabetes risk: a randomised cross-over clinical trial. Br J Nutr. 2013;109(11):2015-23. https://doi:10.1017/S0007114512004217
https://doi.org/https://doi:10.1017/S000...
]. Yet another mechanism proposed the synergistic effect between nutrients and phytochemicals of nuts that generate satiety, and it is estimated that 55-75% of the energy supplied by this food is offset by a subsequent lower energy intake [2525. Mattes RD, Dreher ML. Nuts and healthy body weight maintenance mechanisms. Asia Pac J Clin Nutr. 2010;19(1):137-41.]. Furthermore, the dietary fiber content present in the nuts also generates satiety and reduces energy intake, as it delays gastric emptying and the intestines’ transit time [2929. Jenkins DJ, Kendall CW, Axelsen M, Augustin LS, Vuksan V. Viscous and nonviscous fibres, nonabsorbable and low glycaemic index carbohydrates, blood lipids and coronary heart disease. Curr Opin Lipidol. 2000;11:49-56.,3030. Tan SY, Dhillon J, Mattes RD. A review of the effects of nuts on appetite, food intake, metabolism, and body weight. Am J Clin Nutr. 2014;100:412S-422S. https://doi:10.3945/ajcn.113.071456
https://doi.org/https://doi:10.3945/ajcn...
].

Finally, like other nuts, the baru contains polyphenols such as tannins, which reduce oxidative stress, a condition observed in obese individuals and related to excess adiposity, which seems to exert a suppressing effect on energy intake [3131. Budriesi R, Vivarelli F, Canistro D, Aldini R, Babot Marquillas C, Corazza I, et al. Liver and intestinal protective effects of Castanea sativa Mill. bark extract in high-fat diet rats. PLos One. 2018;13(8):e0201540 https://doi:10.1371/journal.pone.0201540
https://doi.org/https://doi:10.1371/jour...
,3232. Lei F, Zhang XN, Wang W, Xing DM, Xie WD, Su H, et al. Evidence of anti-obesity effects of the pomegranate leaf extract in high-fat diet induced obese mice. Int J Obes. 2007;31(6):1023-9. https://doi:10.1038/sj.ijo.0803502
https://doi.org/https://doi:10.1038/sj.i...
]. Thus, the significant reduction in individuals’ WC in this study can be justified by the synergistic effect of baru nuts’ nutrients, directly or indirectly, on food intake and adiposity.

The present study did not find an effect of baru nut supplementation on the glycemic profile. However, the literature has shown a correlation between the reduction of abdominal adiposity and the prevention of T2D, such as the results reported in Chinese cohort studies which observed an association between the incidence of T2D and visceral and central obesity [3333. Bragg F, Tang K, Guo Y, Iona A, Du H, Holmes MV, et al. China Kadoorie Biobank (CKB) Collaborative Group. Associations of General and Central Adiposity with Incident Diabetes in Chinese Men and Women. Diabetes Care. 2018;41(3):494-502. https://doi:10.2337/dc17-1852
https://doi.org/https://doi:10.2337/dc17...
,3434. Chen P, Hou X, Hu G, Wei L, Jiao L, Wang H, et al. Abdominal subcutaneous adipose tissue: a favorable adipose depot for diabetes? Cardiovasc Diabetol. 2018;26;17(1):93. https://doi:10.1186/s12933-018-0734-8
https://doi.org/https://doi:10.1186/s129...
]. Another cohort study with adults aged 35-79 years in the United States found that the increase in adiposity led to a rise in the diabetes rate in that population in the period between 1988-2014 [3535. Stokes A, Preston SH. The contribution of rising adiposity to the increasing prevalence of diabetes in the United States. Prev Med. 2017;101:91-5. https://doi:10.1016/j.ypmed.2017.05.031
https://doi.org/https://doi:10.1016/j.yp...
].

The mechanisms by which overweight, especially abdominal adiposity, contributes to the development of T2D seem to be related to the chronic state of low-grade inflammation [3636. Hill JH, Solt C, Foster MT. Obesity associated disease risk: the role of inherent differences and location of adipose depots. Horm Mol Biol Clin Investig. 2018;16;33 (2). https://doi:10.1515/hmbci-2018-0012
https://doi.org/https://doi:10.1515/hmbc...
]. The generation of inflammation can occur from high energy intake, which promotes the expansion of adipose tissue, generating adipocyte dysfunction. With this dysfunction, adipocytes release adipokines such as tumor necrosis factor- α (TNF-α), interleukin-6 (IL-6), resistin, leptin, and monocyte chemoattractant protein-1 (MCP-1), which contribute to insulin resistance [3636. Hill JH, Solt C, Foster MT. Obesity associated disease risk: the role of inherent differences and location of adipose depots. Horm Mol Biol Clin Investig. 2018;16;33 (2). https://doi:10.1515/hmbci-2018-0012
https://doi.org/https://doi:10.1515/hmbc...

37. Huh JY, Park YJ, Ham M, Kim JB. Crosstalk between adipocytes and immune cells in adipose tissue inflammation and metabolic dysregulation in obesity. Mol Cells. 2014;37(5):365-71. https://doi:10.14348/molcells.2014.0074
https://doi.org/https://doi:10.14348/mol...
-3838. Seijkens T, Kusters P, Chatzigeorgiou A, Chavakis T, Lutgens E. Immune cell crosstalk in obesity: a key role for costimulation? Diabetes. 2014;63(12):3982-91. https://doi:10.2337/db14-0272
https://doi.org/https://doi:10.2337/db14...
].

Therefore, the reduction of WC in subjects who consumed baru nuts in this study may be considered an important factor in attenuating inflammation and insulin resistance, although an effect of baru nut supplementation was not observed on CRP, glucose, insulin, and HOMA-IR. The intervention period and/or the amount of baru nuts offered may not have been enough for an effect on these parameters. Moreover, further studies are needed to evaluate other biomarkers, such as glycated hemoglobin (HbA1c), TNF-α, IL-1, and IL-6, which is a limitation of this study. Another limitation of the study was the non-evaluation of the drugs used by the participants. However, the sample size, the length of intervention, and the study design can be considered a strength of this research.

CONCLUSION

In the present study, baru nut supplementation reduced the abdominal adiposity of adults with T2D without difference in blood pressure and biochemical parameters. Although it did not improve the glycemic profile, its consumption can contribute to a reduced cardiometabolic risk.

ACKNOWLEDGMENTS

We thank the City Health Department of Santo Antônio de Goiás and Brazabrantes, Goiás, Brazil, for allowing us to carry out the research.

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Editor

  • Eliane Fialho de Oliveira
  • Article elaborated from the dissertation of BAC CRUVINEL, entitled “Avaliação do consumo alimentar e efeito da amêndoa de baru em adultos com diabetes mellitus tipo 2”. Universidade Federal de Goiás; 2019.
  • How to cite this article: Cruvinel BAC, Alves AGP, Schincaglia RM, Silva MS. Baru nuts reduce abdominal adiposity in type 2 diabetic adults: a randomized, placebo-controlled, crossover trial. Rev Nutr. 2023;36:e220103. https://doi.org/10.1590/1678-9865202336e220103

Publication Dates

  • Publication in this collection
    24 Nov 2023
  • Date of issue
    2023

History

  • Received
    05 May 2022
  • Reviewed
    13 Feb 2023
  • Accepted
    07 Aug 2023
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