Effects of Regular Brazil Nut (Bertholletia excelsa H.B.K.) Consumption on Health: A Systematic Review of Clinical Trials

Abstract

The Brazil nut (BN) is a promising food due to its numerous health benefits, but it is still necessary to systematically review the scientific evidence on these benefits. Thus, we examined the effects of regular BN consumption on health markers in humans according to the health state (with specific diseases or not) of the subjects. PubMed, Embase^®, and Scielo databases were used to search for clinical trials. The PRISMA guideline was used to report the review, and the risk of bias for all studies was assessed. Twenty-four studies were included in the present review, of which fifteen were non-randomized. BNs were consumed in the context of a habitual free-living diet in all studies. Improvement in antioxidant status through increased levels of selenium and/or glutathione peroxidase activity in plasma, serum, whole blood, and/or erythrocytes was observed in all studies that evaluated antioxidant status, regardless of the health state of the sample. In addition, healthy subjects improved lipid markers and fasting glucose. Subjects with obesity had improvement in markers of lipid metabolism. Subjects with type 2 diabetes mellitus or dyslipidemia improved oxidative stress or DNA damage. Subjects undergoing hemodialysis benefited greatly from BN consumption, as they improved lipid profile markers, oxidative stress, inflammation, and thyroid function. Older adults with mild cognitive impairment improved verbal fluency and constructional praxis, and controversial results regarding the change in a marker of lipid peroxidation were observed in subjects with coronary artery disease. In conclusion, the benefits of BN consumption were found in different pathways of action and study populations.

Keywords: functional foods; metabolic risk factors; nutrition; nuts; oilseeds; selenium.

Figure 1

Flowchart of studies included in the systematic review.

Figure 2

Assessment of studies’ bias risk following the Joanna Briggs Institute (JBI) Reviewer’s Manual. (A) Risk of bias assessment of randomized clinical trials (n = 9); (B) Risk of bias assessment of non-randomized clinical trials (n = 15); (C) Total score.

Figure 3

Summary of the effects of Brazil nuts consumption on human health. The effects of regular BN consumption were grouped according to the health status of the subjects evaluated in the studies included in the review. These effects were then linked to a larger category of health markers.

Figure 4

Blood selenium levels (plasma or serum or total blood) before and after Brazil nut supplementation in (A). healthy subjects [14,18,24,34], (B). subjects with obesity [15,19,20,26,27], (C). subjects undergoing hemodialysis [25,28,29,30,31], and (D). subjects with type 2 diabetes mellitus (T2DM) or using statins or mild cognitive impairment (MCI) or with coronary artery disease (CAD). ?, not informed [16,17,21,22,35,36,37].