Randomised controlled trialindependent cross-checkabstract checked I-GUT-118 in-depth review
Chewing affects how much fat is released from nuts
Effect of mastication on lipid bioaccessibility of almonds in a randomized human study and its implications for digestion kinetics, metabolizable energy, and postprandial lipemia.
Overview
Grundy MM et al.. Am J Clin Nutr 2015 · PMID 25527747 · DOI 10.3945/ajcn.114.088328
After chewing almonds, most cells stayed intact and only about a tenth of the fat was released for digestion.
Does the study support the specific claim? Partly · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Measure effect of chewing on nutrient release.
- How was the study done?
Randomised crossover lab study.
- How many people, animals or samples were studied?
17 healthy adults.
- What was actually found?
Most almond cells survived chewing; ~10% fat released.
- How large was the observed effect?
8.5-11.3% lipid released.
- What do the results mean in everyday life?
Chewing well affects digestion of some foods.
- What are the study's limitations?
One food; no clinical outcome.
- What does it say about Elawady's specific claim?
Supports 'incomplete digestion', not 'obstruction'.
- Do the results apply to Germany and Europe?
Universal.
- What can explicitly not be concluded from this study?
Cannot show poor chewing causes blockages.
Scientific in-depth review
1. Full reference
- Authors
- Grundy MM et al.
- Journal
- Am J Clin Nutr
- Year
- 2015
- Identifier
- PMID 25527747 DOI 10.3945/ajcn.114.088328
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref 2026-10-26
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
BBSRC (UK public funding)
2. Research question
How does chewing affect particle size and lipid release (bioaccessibility) from almonds?
3. Study design and population
- Study design
- Randomised controlled trial – Randomised, subject-blind crossover mastication study
- Population
17 healthy adults (15 completed)
- Country
UK
- Period
Published 2015
- Sample size
17
- Inclusion and exclusion criteria
Healthy adults
4. Methods and endpoints
- Exposure / intervention
Chewing natural or roasted almonds
- Comparator
Almond form; theoretical model
- Endpoints
Particle size of chewed boluses; predicted and measured lipid release
- Statistical methods
Laser diffraction, sieving, modelling
5. Actual results
- Results
35-40% of chewed almond particles were large (>500 um); only 8.5% (natural) and 11.3% (roasted) of lipid was released; most cells stayed intact after chewing.
- Absolute risks
Not applicable
- Authors' conclusion
Most almond lipid remains encapsulated after chewing, explaining lower metabolisable energy.
6. Strengths
- Randomised crossover with microscopy
7. Weaknesses
- One food
- Small
- Bioaccessibility, not clinical outcomes
8. Risk of bias
- Orienting tool
- RoB 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
Laboratory outcome; low risk.
9. Assessment of the statistical interpretation
Not applicable
10. Relevance to the specific claim
Supports the first half of C-GUT-09: chewing determines how much of some foods is digested; unreleased nutrients pass on to the colon rather than causing obstruction.
11. Independent contrary findings
No obstruction or harm observed.
12. Transferability to Germany and Europe
Universal.
13. Overall methodological judgement
Correct kernel: chewing affects digestion.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | low |
| Precision of results | low |
| Directness | indirect |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | consistent |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Effects for bread and staple foods.