The Metabolizable Energy and Lipid Bioaccessibility of Tree Nuts and Peanuts: A Systematic Review with Narrative Synthesis of Human and In Vitro Studies.
Level 1 - systematic review of randomized trials
Systematic review of human feeding trials and in vitro bioaccessibility studies
PubMed 36934832 · doi:10.1016/j.advnut.2023.03.006
What was done
A systematic review (PROSPERO CRD42021252287) was conducted by searching PubMed, MEDLINE, CINAHL, Cochrane, and Embase through June 2021 to examine the metabolizable energy (ME) and lipid bioaccessibility of tree nuts and peanuts. The review included both in vitro models and human trials in adults (age ≥18 years) assessing fecal fat excretion or fat release. Data were synthesized narratively across nut form, processing, and dose.
What was found
Twenty-one studies were included covering almonds, cashews, hazelnuts, pistachios, walnuts, and peanuts. Measured ME was consistently lower than Atwater-predicted values across all investigated nut types. ME varied by nut type (ME = 22.6 kJ/g for pistachios vs. 18.5 kJ/g for raw almonds), physical form (flour > chopped > whole nuts), heat processing (butter > roasted > raw), and dose.
Why it matters
This helps explain the lack of weight gain observed with regular nut consumption despite high energy density, and indicates that current food composition databases and nutrition labels overestimate available calories from whole and minimally processed nuts.
Limits
The review could only perform a narrative synthesis due to methodological variation among studies. Carbohydrate and protein digestibility were not evaluated, which could affect total ME estimates. Human trial and in vitro data were combined, and participant sample sizes were not reported in the abstract.
Cited by
- partial Grinding peanuts into peanut butter increases available energy extraction by about 25% compared to consuming whole peanuts.