HerbalEGram: Volume 16, Issue 5, May 2019

By Hannah Bauman^a and Jamie Moser, MS^b

^a HerbalGram Associate Editor

^b ABC Dietetics Intern (Texas State University, 2019)

Editor’s Note: Each month, HerbalEGram highlights a conventional food and briefly explores its history, traditional uses, nutritional profile, and modern medicinal research. We also feature a nutritious recipe for an easy-to-prepare dish with each article to encourage readers to experience the extensive benefits of these whole foods. With this series, we hope our readers will gain a new appreciation for the foods they see at the supermarket and frequently include in their diets.

The basic materials for this series were compiled by dietetic interns from Texas State University in San Marcos and the University of Texas at Austin through the American Botanical Council’s (ABC’s) Dietetic Internship Program, led by ABC Education Coordinator Jenny Perez. We would like to acknowledge Perez and ABC Chief Science Officer Stefan Gafner, PhD, for their contributions to this project.

Overview

The Brazil nut (Bertholletia excelsa) is the only known species in the genus Bertholletia and is a large tropical forest tree in the Lecythidaceae family. The tree commonly grows throughout Brazil, the Guianas, Venezuela, eastern Colombia, eastern Peru, and eastern Bolivia.^1,2 It is among the largest in the Amazon rainforest and reaches more than 48 meters (160 feet) in height. The species often is found scattered in large forests on the banks of the Amazon River, Rio Negro, and Orinoco River.

The Brazil nut tree has co-evolved with the help of the euglossine bee, also called orchid bee or long-tongued bee, which pollinates its heavy-lidded flowers. Once pollinated, the flower can then develop into a full fruit.³ Each mature tree can produce up to 300 fruit pods in a season, which ripen at the end of the tree’s thick branches and take approximately 14 months to mature.^3,4 The large fruit pods are roughly the size of a baseball and can weigh up to two kilograms (4.5 pounds). Each fruit pod has a hard, woody shell that contains eight to 24 triangular seeds that are up to two centimeters (3/4 inch) wide and five centimeters (two inches) long. The seed, or nut kernel, is white and covered with dark brown skin.³

Production of Brazil nuts increased from 3,557 tons in 1944 to approximately 95,000 tons in 2014.⁴ Brazil nuts are harvested almost entirely from wild trees during the six-month rainy season (January through June). Once harvested, the pods are sent downriver for processing. Brazil nut production consists of processing (cleaning, drying and soaking, peeling the nuts, drying the peeled nuts), sorting (by size, specific gravity, color, or damage), and packaging.

Historical and Commercial Uses

For centuries, the indigenous tribes of the Amazon have relied on the nut and other parts of the Brazil nut tree as a staple of their diet and trading commodity.⁴ Indigenous tribes commonly used a bark infusion to ease liver ailments and chronic diseases. Traditionally, the nuts were eaten raw, grated with the thorny stilt roots of Socratea palm (Socratea exorrhiza, Arecaceae) into a white mush known as leite de castanha (“Brazil nut milk”), or stirred into cassava (Manihot esculenta, Euphorbiaceae) flour. These calorie-dense, high-protein, high-fat, high-fiber preparations are a valuable source of nutrition for rural communities.

In addition to its value as a nutrition source, the Brazil nut is an important economic plant for Brazil, Bolivia, Peru, and the Ivory Coast. It is exported primarily to England, France, the United States, and Germany.¹ In an effort to maximize the yield of the Brazil nut tree, unsellable remnants of processed nuts are used in food products, such as mixed nut blends, cereal bars, and chocolate, and ground for use as a flour. The pod and shell have been formulated into a fuel source, as well as processed to produce recycled wood and handcrafted items. The oil pressed from the Brazil nut is clear or yellowish and is sweet smelling and tasting. Composed mainly of palmitic, oleic, linoleic, and alpha-linolenic acids, this oil is used in the cosmetic industry for its emollient properties and as a culinary ingredient.⁴

Phytochemicals and Constituents

Brazil nuts are a rich source of unsaturated fatty acids, protein, fiber, micronutrients, vitamins, and other phytochemicals. Their macronutrient composition is approximately 18% protein, 13% carbohydrates, and 69% fat.¹ Having one of the highest percentages of unsaturated fat of the tree nuts, Brazil nuts primarily are composed of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs).⁵ Sterols are also present in Brazil nuts in significant quantities. Plant sterols are lipids, which in humans can act to promote cardiovascular health by reducing low-density lipoprotein (LDL) cholesterol levels.⁶

Due to its high contents of alpha- and gamma-tocopherol, Brazil nuts are a rich source of antioxidants.³ Brazil nuts also have been found to contain the highest content of squalene compared to other tree nuts, which is an essential building block of steroid hormones.⁵ While providing four grams of protein per one-ounce serving, Brazil nuts have a lower protein content than other tree nuts.³ Of the proteins present, Brazil nuts are rich in sulfur-containing amino acids, including cysteine and methionine. Brazil nuts contain high concentrations of micronutrients, including selenium, magnesium, phosphorus, and thiamine (vitamin B₁). They also provide a substantial amount of niacin (vitamin B₃), vitamin E, pyridoxine (vitamin B₆), calcium, iron, potassium, zinc, copper, arginine, and flavonoids.⁷

Brazil nuts have been reported to contain the highest known level of selenium of any food.⁷ The selenium content of Brazil nuts has been found to vary from region to region, tree to tree, as well as seed to seed.¹ Selenium distribution is dependent on multiple factors, such as the selenium content of the soil, chemical form of selenium in the soil, presence of heavy metals, rain intensity, absorption ability of the tree’s root system, and tree maturity. The high selenium content observed in Brazil nuts may be the result of selenium’s chemical similarity to sulfur, which is often deficient in Amazon soils, thereby forcing many plants to use selenium instead of sulfur.²

Like other nuts, Brazil nuts are a good dietary source of phytochemicals such as phenolic acids, flavonoids, tocopherols, and phytosterols.³ Extracts of Brazil nuts show strong antioxidant and antiproliferative activities in vitro, with the strongest effects observed in the presence of selenium. Of the phytochemicals present in Brazil nuts, phenolic compounds are present in the highest concentration. The main compounds identified include gallic acid, ellagic acid, vanillic acid, protocatechuic acid, and catechin. Within the nut, the outer brown skin contains a higher concentration of phenolics compared to the nutmeat itself. Regarding other phytochemicals, flavan-3-ols are found in the highest concentration, with isoflavones, anthocyanins, and flavonols, as well as carotenoids present.

Modern Research

Selenium is an essential nutrient for human health, and its biological functions are mediated by the expression of 25 different selenoproteins, which are essential for thyroid hormone metabolism and act as potent antioxidants.^2,3 Selenium has been shown to be anti-aging, immune-stimulating, and important in thyroid health. It also has been shown to offer protection against heart disease, certain forms of cancer, viral infection, and progression of human immunodeficiency virus (HIV).² Selenium may protect the body from damage associated with heavy metals due to its ability to bind to these elements and convert them into biologically inert conjugates.^8,9 Research on selenium indicates it may reduce the rate of miscarriages and promote male fertility.⁸

Selenium deficiency is associated with a wide variety of health issues, including neurological, endocrine, muscle, and cardiovascular disorders, and it may contribute to Keshan disease (congestive cardiomyopathy) and Kashin-Beck disease (bone disease characterized by deformed growth).⁸ Consuming one Brazil nut daily has been shown to increase blood levels of selenium and the activity of various selenium-dependent enzymes.^8,10 Natural and food-derived forms of selenium may have beneficial effects not observed in supplemental forms of selenium due to the synergistic effects of selenium and other beneficial compounds present within the nut.

Glutathione peroxidase (GPx) and thioredoxin reductase (TrxR) are important selenium-containing enzymes that act to promote multiple health benefits possibly via their antioxidant properties.¹¹ GPx functions to prevent the oxidative modification of lipids, inhibit platelet aggregation, and modulate inflammation.¹² Normal GPx activity also has been found to be associated with reduced risk of prostate cancer, lung cancer, and colon cancer.⁸ In addition, GPx activity has been shown to play a role in thyroid health. In autoimmune thyroiditis, a dysregulation of thyroid hormone metabolism and/or thyroid tissue damage occurs. Incidence of autoimmune thyroiditis has been linked to the decrease of selenium-dependent GPx activity in thyroid cells. According to a meta-analysis conducted by Ventura et al., consumption of 200 mcg of selenium daily (approximately two brazil nuts per day) was found to be beneficial for modulating immune function in those living with autoimmune thyroiditis.¹³

Selenium status has been shown to be associated with mild cognitive impairment (MCI).¹⁴ MCI commonly occurs in the elderly population, which is at risk for selenium deficiency related to increased nutrient requirements, metabolic changes, lower nutrient absorption, and changes in diet. In a randomized placebo-controlled study of 31 older adults with MCI, one Brazil nut daily for six months was enough to reverse selenium deficiency and resulted in some improvement of cognitive functions. These improvements are thought to be the result of both the selenium content of the nut as well as its high content of phenolic compounds, which allow for an increase in antioxidant activity and promote normal mitochondrial function, synaptic transmission, axonal transport, and inhibition of neuroinflammation.

Brazil nuts are a rich source of MUFAs and PUFAs and therefore have been shown to be beneficial for cardiovascular health. In a randomized crossover study, intake of either 20 g or 50 g of Brazil nuts daily by 10 healthy subjects was associated with increased high-density lipoprotein (HDL) cholesterol concentration and a reduction of LDL concentration.¹¹ Additionally, in a randomized placebo-controlled study of 17 obese female adolescents, it was observed that supplementation with three to five Brazil nuts per day (15-25 g per day) for 16 weeks positively influenced lipid profiles (total cholesterol, LDL, and glucose levels).⁵

Consumer Considerations

Despite the numerous potential health benefits provided by Brazil nuts, daily consumption should be limited. Selenium intakes above the Recommended Daily Allowance (RDA) of 55 mcg per day, or approximately one Brazil nut, can result in an accumulation of selenium as selenomethionine in tissues, which can lead to selenosis, with symptoms such as nail brittleness, hair loss, peripheral paresthesia, decreased cognitive function, and skin lesions.^1,15 Excessive Brazil nut intake can also lead to the accumulation of heavy metals such as barium and strontium and carcinogenic elements such as radium.^3,15 The presence of barium in Brazil nuts is thought to result from the presence of hollandite ore in soils of the Amazon region. While there is no evidence that strontium is toxic for adults, in children it may impair mineralization of the developing bones.

Brazil nuts are commonly contaminated by fungi and their metabolites (mycotoxins). Occasionally, aflatoxins present in Brazil nuts have been reported to exceed limits accepted by European legislation (4 μg/kg).³ In the United States, federally mandated Good Manufacturing Practices (GMPs) have been modified in an attempt to prevent contamination of tree nuts by aflatoxins. Such preventative measures include multiple rounds of sorting and screening of the nut during processing, as well as the disposal of damaged nuts that do not meet processing standards.¹ Despite these efforts to minimize fungal growth and mycotoxin production, contamination remains an ongoing challenge due to the hot and humid climatic conditions of the Amazon.

As with other tree nut allergies, allergic reactions to Brazil nuts are usually immunoglobulin E (IgE) mediated. While allergic reactions to Brazil nuts are fairly rare, immunological studies have found several proteins in the nut with potent antigenic components.³ Symptoms of an allergic reaction vary from swelling and itching around the mouth to acute and life-threatening anaphylaxis.¹⁶

Nutrient Profile¹⁷

Macronutrient Profile: (Per six Brazil nuts [approx. 1 oz])

185 calories
4.0 g protein
3.5 g carbohydrate
18.8 g fat

Secondary Metabolites: (Per six Brazil nuts [approx. 1 oz])

Excellent source of:

Selenium: 542 mcg (985% DV)
Magnesium: 106 mg (27% DV)
Copper: 0.5 mg (25% DV)
Phosphorus: 205 mg (20% DV)

Very good source of:

Manganese: 0.3 mg (17% DV)
Thiamin: 0.2 mg (12% DV)

Good source of:

Dietary Fiber: 2.1 g (8% DV)
Vitamin E: 1.6 mg (8% DV)
Zinc: 1.1 mg (8% DV)
Calcium: 45.2 mg (5% DV)
Potassium: 186 mg (5% DV)
Iron: 0.7 mg (4% DV)
Folate: 6.2 mcg (2% DV)

Also provides:

Pantothenic Acid: 0.1 mg
Betaine: 0.1 mg (no daily value established)
Choline: 8.1 mg (no daily value established)

DV = Daily Value as established by the US Food and Drug Administration, based on a 2,000-calorie diet.

Image credits (top to bottom):

Brazil nut tree canopy. ©2019 Steven Foster.
Illustration of tropical fruits and nuts, including Brazil nut (bottom right), from A History of the Vegetable Kingdom by William Rhind. 1874.
Brazil nuts and their pods. ©2019 Steven Foster.

References

1. Freitas-Silva O, Venâncio A. Brazil nuts: Benefits and risks associated with contamination by fungi and mycotoxins. Food Res Int. 2011;44:1434-1440. 10.1016/j.foodres.2011.02.047.
2. Preedy V, Watson R, Patel V. Nuts and Seeds in Health and Disease Prevention. London, UK: Academic Press; 2011.
3. Cardoso BR, Duarte GBS, Reis BZ, Cozzolino SMF. Brazil nuts: Nutritional composition, health benefits and safety aspects. Food Res Int. 2017;100(Pt 2):9-18.
4. Taylor L. Brazil Nut. Tropical Plant Database website. 2005. Available at: www.rain-tree.com/brazilnu.htm. Accessed April 8, 2019.
5. Maranhão PA, Kraemer-Aguiar LG, De Oliveira CL, et al. Brazil nuts intake improves lipid profile, oxidative stress and microvascular function in obese adolescents: a randomized controlled trial. Nutr Metab (Lond). 2011;8(1):32.
6. Abumweis SS, Barake R, Jones PJ. Plant sterols/stanols as cholesterol lowering agents: A meta-analysis of randomized controlled trials. Food Nutr Res. 2008;52.
7. John JA, Shahidi F. Phenolic compounds and antioxidant activity of Brazil nut (Bertholletia excelsa). J Func Food. 2010;2:196-209. 10.1016/j.jff.2010.04.008.
8. Yang R, Liu Y, Zhou Z. Selenium and selenoproteins, from structure, function to food resource and nutrition. Food Science and Technology Research. 2017;23:363-373. 10.3136/fstr.23.363.
9. Zwolak I, Zaporowska H. Selenium interactions and toxicity: a review. Selenium interactions and toxicity. Cell Biol Toxicol. 2012;28(1):31-46.
10. Thomson CD, Chisholm A, Mclachlan SK, Campbell JM. Brazil nuts: an effective way to improve selenium status. Am J Clin Nutr. 2008;87(2):379-84.
11. Colpo E, Vilanova CD, Brenner Reetz LG, et al. A single consumption of high amounts of the Brazil nuts improves lipid profile of healthy volunteers. J Nutr Metab. 2013;2013:653185.
12. Cominetti C, De Bortoli MC, Purgatto E, et al. Associations between glutathione peroxidase-1 Pro198Leu polymorphism, selenium status, and DNA damage levels in obese women after consumption of Brazil nuts. Nutrition. 2011;27(9):891-896.
13. Ventura M, Melo M, Carrilho F. Selenium and thyroid disease: From pathophysiology to treatment. Int J Endocrinol. 2017;2017:1297658.
14. Cardoso BR, Apolinário D, Da Silva Bandeira V, et al. Effects of Brazil nut consumption on selenium status and cognitive performance in older adults with mild cognitive impairment: a randomized controlled pilot trial. Eur J Nutr. 2016;55(1):107-16.
15. Office of Dietary Supplements - Selenium. NIH Office of Dietary Supplements website. Available at: https://ods.od.nih.gov/factsheets/Selenium-HealthProfessional/. Accessed April 8, 2019.
16. Arshad SH, Malmberg E, Krapf K, Hide DW. Clinical and immunological characteristics of Brazil nut allergy. Clin Exp Allergy. 1991;21(3):373-6.
17. Basic report: 12078 Nuts, brazilnuts, dried, unblanched. National Nutrient Database for Standard Reference Legacy Release. United States Department of Agriculture website. April 2018. Available at: https://ndb.nal.usda.gov/ndb/foods/show/12078. Accessed May 14, 2019.